neovim

expressions.c (111238B)

---

/// Vimscript expression parser

// Planned incompatibilities (to be included into vim_diff.txt when this parser
// will be an actual part of Vimscript evaluation process):
//
// 1. Expressions are first fully parsed and only then executed.  This means
//    that while ":echo [system('touch abc')" will create file "abc" in Vim and
//    only then raise syntax error regarding missing comma in list in Neovim
//    trying to execute that will immediately raise syntax error regarding
//    missing list end without actually executing anything.
// 2. Expressions are first fully parsed, without considering any runtime
//    information.  This means things like that "d.a" does not change its
//    meaning depending on type of "d" (or whether Vim is currently executing or
//    skipping).  For compatibility reasons the dot thus may either be “concat
//    or subscript” operator or just “concat” operator.
// 3. Expressions parser is aware whether it is called for :echo or <C-r>=.
//    This means that while "<C-r>=1 | 2<CR>" is equivalent to "<C-r>=1<CR>"
//    because "| 2" part is left to be treated as a command separator and then
//    ignored in Neovim it is an error.
// 4. Expressions parser has generally better error reporting.  But for
//    compatibility reasons most errors have error code E15 while error messages
//    are significantly different from Vim’s E15.  Also some error codes were
//    retired because of being harder to emulate or because of them being
//    a result of differences in parsing process: e.g. with ":echo {a, b}" Vim
//    will attempt to parse expression as lambda, fail, check whether it is
//    a curly-braces-name, fail again, and evaluate that as a dictionary, giving
//    error regarding undefined variable "a" (or about missing colon).  Neovim
//    will not try to evaluate anything here: comma right after an argument name
//    means that expression may not be anything, but lambda, so the resulting
//    error message will never be about missing variable or colon: it will be
//    about missing arrow (or a continuation of argument list).
// 5. Failing to parse expression always gives exactly one error message: no
//    more stack of error messages like >
//
//        :echo [1,
//        E697: Missing end of List ']':
//        E15: Invalid expression: [1,
//
// <  , just exactly one E697 message.
// 6. Some expressions involving calling parenthesis which are treated
//    separately by Vim even when not separated by spaces are treated as one
//    expression by Neovim: e.g. ":echo (1)(1)" will yield runtime error after
//    failing to call "1", while Vim will echo "1 1". Reasoning is the same:
//    type of what is in the first expression is generally not known when
//    parsing, so to have separate expressions like this separate them with
//    spaces.
// 7. 'isident' no longer applies to environment variables, they always include
//    ASCII alphanumeric characters and underscore and nothing except this.

#include <assert.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "klib/kvec.h"
#include "nvim/ascii_defs.h"
#include "nvim/assert_defs.h"
#include "nvim/charset.h"
#include "nvim/eval.h"
#include "nvim/gettext_defs.h"
#include "nvim/keycodes.h"
#include "nvim/macros_defs.h"
#include "nvim/mbyte.h"
#include "nvim/memory.h"
#include "nvim/types_defs.h"
#include "nvim/viml/parser/expressions.h"
#include "nvim/viml/parser/parser.h"

typedef kvec_withinit_t(ExprASTNode **, 16) ExprASTStack;

/// Which nodes may be wanted
typedef enum {
 /// Operators: function call, subscripts, binary operators, …
 ///
 /// For unrestricted expressions.
 kENodeOperator,
 /// Values: literals, variables, nested expressions, unary operators.
 ///
 /// For unrestricted expressions as well, implies that top item in AST stack
 /// points to NULL.
 kENodeValue,
} ExprASTWantedNode;

/// Parse type: what is being parsed currently
typedef enum {
 /// Parsing regular Vimscript expression
 kEPTExpr = 0,
 /// Parsing lambda arguments
 ///
 /// Just like parsing function arguments, but it is valid to be ended with an
 /// arrow only.
 kEPTLambdaArguments,
 /// Assignment: parsing for :let
 kEPTAssignment,
 /// Single assignment: used when lists are not allowed (i.e. when nesting)
 kEPTSingleAssignment,
} ExprASTParseType;

typedef kvec_withinit_t(ExprASTParseType, 4) ExprASTParseTypeStack;

/// Operator priority level
typedef enum {
 kEOpLvlInvalid = 0,
 kEOpLvlComplexIdentifier,
 kEOpLvlParens,
 kEOpLvlAssignment,
 kEOpLvlArrow,
 kEOpLvlComma,
 kEOpLvlColon,
 kEOpLvlTernaryValue,
 kEOpLvlTernary,
 kEOpLvlOr,
 kEOpLvlAnd,
 kEOpLvlComparison,
 kEOpLvlAddition,  ///< Addition, subtraction and concatenation.
 kEOpLvlMultiplication,  ///< Multiplication, division and modulo.
 kEOpLvlUnary,  ///< Unary operations: not, minus, plus.
 kEOpLvlSubscript,  ///< Subscripts.
 kEOpLvlValue,  ///< Values: literals, variables, nested expressions, …
} ExprOpLvl;

/// Operator associativity
typedef enum {
 kEOpAssNo= 'n',  ///< Not associative / not applicable.
 kEOpAssLeft = 'l',  ///< Left associativity.
 kEOpAssRight = 'r',  ///< Right associativity.
} ExprOpAssociativity;

#include "viml/parser/expressions.c.generated.h"

/// Scale number by a given factor
///
/// Used to apply exponent to a number. Idea taken from uClibc.
///
/// @param[in]  num  Number to scale. Does not bother doing anything if it is
///                  zero.
/// @param[in]  base  Base, should be 10 since non-decimal floating-point
///                   numbers are not supported.
/// @param[in]  exponent  Exponent to scale by.
/// @param[in]  exponent_negative  True if exponent is negative.
static inline float_T scale_number(const float_T num, const uint8_t base,
                                  const uvarnumber_T exponent, const bool exponent_negative)
 FUNC_ATTR_ALWAYS_INLINE FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_CONST
{
 if (num == 0 || exponent == 0) {
   return num;
 }
 assert(base);
 uvarnumber_T exp = exponent;
 float_T p_base = (float_T)base;
 float_T ret = num;
 while (exp) {
   if (exp & 1) {
     if (exponent_negative) {
       ret /= p_base;
     } else {
       ret *= p_base;
     }
   }
   exp >>= 1;
   p_base *= p_base;
 }
 return ret;
}

/// Get next token for the Vimscript expression input
///
/// @param  pstate  Parser state.
/// @param[in]  flags  Flags, @see LexExprFlags.
///
/// @return Next token.
LexExprToken viml_pexpr_next_token(ParserState *const pstate, const int flags)
 FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
{
 LexExprToken ret = {
   .type = kExprLexInvalid,
   .start = pstate->pos,
 };
 ParserLine pline;
 if (!viml_parser_get_remaining_line(pstate, &pline)) {
   ret.type = kExprLexEOC;
   return ret;
 }
 if (pline.size <= 0) {
   ret.len = 0;
   ret.type = kExprLexEOC;
   goto viml_pexpr_next_token_adv_return;
 }
 ret.len = 1;
 const uint8_t schar = (uint8_t)pline.data[0];
#define GET_CCS(ret, pline) \
 do { \
   if (ret.len < pline.size \
       && strchr("?#", pline.data[ret.len]) != NULL) { \
     ret.data.cmp.ccs = \
       (ExprCaseCompareStrategy)pline.data[ret.len]; \
     ret.len++; \
   } else { \
     ret.data.cmp.ccs = kCCStrategyUseOption; \
   } \
 } while (0)
 switch (schar) {
 // Paired brackets.
#define BRACKET(typ, opning, clsing) \
 case opning: \
 case clsing: { \
     ret.type = typ; \
     ret.data.brc.closing = (schar == clsing); \
     break; \
 }
 BRACKET(kExprLexParenthesis, '(', ')')
 BRACKET(kExprLexBracket, '[', ']')
 BRACKET(kExprLexFigureBrace, '{', '}')
#undef BRACKET

 // Single character tokens without data.
#define CHAR(typ, ch) \
 case ch: { \
     ret.type = typ; \
     break; \
 }
 CHAR(kExprLexQuestion, '?')
 CHAR(kExprLexColon, ':')
 CHAR(kExprLexComma, ',')
#undef CHAR

 // Multiplication/division/modulo.
#define MUL(mul_type, ch) \
 case ch: { \
     ret.type = kExprLexMultiplication; \
     ret.data.mul.type = mul_type; \
     break; \
 }
 MUL(kExprLexMulMul, '*')
 MUL(kExprLexMulDiv, '/')
 MUL(kExprLexMulMod, '%')
#undef MUL

#define CHARREG(typ, cond) \
 do { \
   ret.type = typ; \
   for (; (ret.len < pline.size \
           && cond(pline.data[ret.len])) \
        ; ret.len++) { \
   } \
 } while (0)

 // Whitespace.
 case ' ':
 case TAB:
   CHARREG(kExprLexSpacing, ascii_iswhite);
   break;

 // Control character, except for NUL, NL and TAB.
 case Ctrl_A:
 case Ctrl_B:
 case Ctrl_C:
 case Ctrl_D:
 case Ctrl_E:
 case Ctrl_F:
 case Ctrl_G:
 case Ctrl_H:

 case Ctrl_K:
 case Ctrl_L:
 case Ctrl_M:
 case Ctrl_N:
 case Ctrl_O:
 case Ctrl_P:
 case Ctrl_Q:
 case Ctrl_R:
 case Ctrl_S:
 case Ctrl_T:
 case Ctrl_U:
 case Ctrl_V:
 case Ctrl_W:
 case Ctrl_X:
 case Ctrl_Y:
 case Ctrl_Z:
#define ISCTRL(schar) (schar < ' ')
   CHARREG(kExprLexInvalid, ISCTRL);
   ret.data.err.type = kExprLexSpacing;
   ret.data.err.msg =
     _("E15: Invalid control character present in input: %.*s");
   break;
#undef ISCTRL

 // Number.
 case '0':
 case '1':
 case '2':
 case '3':
 case '4':
 case '5':
 case '6':
 case '7':
 case '8':
 case '9': {
   ret.data.num.is_float = false;
   ret.data.num.base = 10;
   size_t frac_start = 0;
   size_t exp_start = 0;
   size_t frac_end = 0;
   bool exp_negative = false;
   CHARREG(kExprLexNumber, ascii_isdigit);
   if (flags & kELFlagAllowFloat) {
     const LexExprToken non_float_ret = ret;
     if (pline.size > ret.len + 1
         && pline.data[ret.len] == '.'
         && ascii_isdigit(pline.data[ret.len + 1])) {
       ret.len++;
       frac_start = ret.len;
       frac_end = ret.len;
       ret.data.num.is_float = true;
       for (; ret.len < pline.size && ascii_isdigit(pline.data[ret.len])
            ; ret.len++) {
         // A small optimization: trailing zeroes in fractional part do not
         // add anything to significand, so it is useless to include them in
         // frac_end.
         if (pline.data[ret.len] != '0') {
           frac_end = ret.len + 1;
         }
       }
       if (pline.size > ret.len + 1
           && (pline.data[ret.len] == 'e'
               || pline.data[ret.len] == 'E')
           && ((pline.size > ret.len + 2
                && (pline.data[ret.len + 1] == '+'
                    || pline.data[ret.len + 1] == '-')
                && ascii_isdigit(pline.data[ret.len + 2]))
               || ascii_isdigit(pline.data[ret.len + 1]))) {
         ret.len++;
         if (pline.data[ret.len] == '+'
             || (exp_negative = (pline.data[ret.len] == '-'))) {
           ret.len++;
         }
         exp_start = ret.len;
         CHARREG(kExprLexNumber, ascii_isdigit);
       }
     }
     if (pline.size > ret.len
         && (pline.data[ret.len] == '.'
             || ASCII_ISALPHA(pline.data[ret.len]))) {
       ret = non_float_ret;
     }
   }
   // TODO(ZyX-I): detect overflows
   if (ret.data.num.is_float) {
     // Vim used to use string2float here which in turn uses strtod(). There
     // are two problems with this approach:
     // 1. strtod() is locale-dependent. Not sure how it is worked around so
     //    that I do not see relevant bugs, but it still does not look like
     //    a good idea.
     // 2. strtod() does not accept length argument.
     //
     // The below variant of parsing floats was recognized as acceptable
     // because it is basically how uClibc does the thing: it generates
     // a number ignoring decimal point (but recording its position), then
     // uses recorded position to scale number down when processing exponent.
     float_T significand_part = 0;
     uvarnumber_T exp_part = 0;
     const size_t frac_size = frac_end - frac_start;
     for (size_t i = 0; i < frac_end; i++) {
       if (i == frac_start - 1) {
         continue;
       }
       significand_part = significand_part * 10 + (pline.data[i] - '0');
     }
     if (exp_start) {
       vim_str2nr(pline.data + exp_start, NULL, NULL, 0, NULL, &exp_part,
                  (int)(ret.len - exp_start), false, NULL);
     }
     if (exp_negative) {
       exp_part += frac_size;
     } else {
       if (exp_part < frac_size) {
         exp_negative = true;
         exp_part = frac_size - exp_part;
       } else {
         exp_part -= frac_size;
       }
     }
     ret.data.num.val.floating = scale_number(significand_part, 10, exp_part,
                                              exp_negative);
   } else {
     int len;
     int prep;
     vim_str2nr(pline.data, &prep, &len, STR2NR_ALL, NULL,
                &ret.data.num.val.integer, (int)pline.size, false, NULL);
     ret.len = (size_t)len;
     const uint8_t bases[] = {
       [0] = 10,
       ['0'] = 8,
       ['x'] = 16, ['X'] = 16,
       ['b'] = 2, ['B'] = 2,
     };
     ret.data.num.base = bases[prep];
   }
   break;
 }

#define ISWORD_OR_AUTOLOAD(x) \
 (ascii_isident(x) || (x) == AUTOLOAD_CHAR)

 // Environment variable.
 case '$':
   CHARREG(kExprLexEnv, ascii_isident);
   break;

 // Normal variable/function name.
 case 'a':
 case 'b':
 case 'c':
 case 'd':
 case 'e':
 case 'f':
 case 'g':
 case 'h':
 case 'i':
 case 'j':
 case 'k':
 case 'l':
 case 'm':
 case 'n':
 case 'o':
 case 'p':
 case 'q':
 case 'r':
 case 's':
 case 't':
 case 'u':
 case 'v':
 case 'w':
 case 'x':
 case 'y':
 case 'z':
 case 'A':
 case 'B':
 case 'C':
 case 'D':
 case 'E':
 case 'F':
 case 'G':
 case 'H':
 case 'I':
 case 'J':
 case 'K':
 case 'L':
 case 'M':
 case 'N':
 case 'O':
 case 'P':
 case 'Q':
 case 'R':
 case 'S':
 case 'T':
 case 'U':
 case 'V':
 case 'W':
 case 'X':
 case 'Y':
 case 'Z':
 case '_':
   ret.data.var.scope = 0;
   ret.data.var.autoload = false;
   CHARREG(kExprLexPlainIdentifier, ascii_isident);
   // "is" and "isnot" operators.
   if (!(flags & kELFlagIsNotCmp)
       && ((ret.len == 2 && memcmp(pline.data, "is", 2) == 0)
           || (ret.len == 5 && memcmp(pline.data, "isnot", 5) == 0))) {
     ret.type = kExprLexComparison;
     ret.data.cmp.type = kExprCmpIdentical;
     ret.data.cmp.inv = (ret.len == 5);
     GET_CCS(ret, pline);
     // Scope: `s:`, etc.
   } else if (ret.len == 1
              && pline.size > 1
              && memchr(EXPR_VAR_SCOPE_LIST, schar,
                        sizeof(EXPR_VAR_SCOPE_LIST)) != NULL
              && pline.data[ret.len] == ':'
              && !(flags & kELFlagForbidScope)) {
     ret.len++;
     ret.data.var.scope = (ExprVarScope)schar;
     CHARREG(kExprLexPlainIdentifier, ISWORD_OR_AUTOLOAD);
     ret.data.var.autoload = (
                              memchr(pline.data + 2, AUTOLOAD_CHAR, ret.len - 2)
                              != NULL);
     // Previous CHARREG stopped at autoload character in order to make it
     // possible to detect `is#`. Continue now with autoload characters
     // included.
     //
     // Warning: there is ambiguity for the lexer: `is#Foo(1)` is a call of
     // function `is#Foo()`, `1is#Foo(1)` is a comparison `1 is# Foo(1)`. This
     // needs to be resolved on the higher level where context is available.
   } else if (pline.size > ret.len
              && pline.data[ret.len] == AUTOLOAD_CHAR) {
     ret.data.var.autoload = true;
     CHARREG(kExprLexPlainIdentifier, ISWORD_OR_AUTOLOAD);
   }
   break;

#undef ISWORD_OR_AUTOLOAD
#undef CHARREG

 // Option.
 case '&': {
#define OPTNAMEMISS(ret) \
 do { \
   ret.type = kExprLexInvalid; \
   ret.data.err.type = kExprLexOption; \
   ret.data.err.msg = _("E112: Option name missing: %.*s"); \
 } while (0)
   if (pline.size > 1 && pline.data[1] == '&') {
     ret.type = kExprLexAnd;
     ret.len++;
     break;
   }
   if (pline.size == 1 || !ASCII_ISALPHA(pline.data[1])) {
     OPTNAMEMISS(ret);
     break;
   }
   ret.type = kExprLexOption;
   if (pline.size > 2
       && pline.data[2] == ':'
       && memchr(EXPR_OPT_SCOPE_LIST, pline.data[1],
                 sizeof(EXPR_OPT_SCOPE_LIST)) != NULL) {
     ret.len += 2;
     ret.data.opt.scope = (ExprOptScope)pline.data[1];
     ret.data.opt.name = pline.data + 3;
   } else {
     ret.data.opt.scope = kExprOptScopeUnspecified;
     ret.data.opt.name = pline.data + 1;
   }
   const char *p = ret.data.opt.name;
   const char *const e = pline.data + pline.size;
   if (e - p >= 4 && p[0] == 't' && p[1] == '_') {
     ret.data.opt.len = 4;
     ret.len += 4;
   } else {
     for (; p < e && ASCII_ISALPHA(*p); p++) {}
     ret.data.opt.len = (size_t)(p - ret.data.opt.name);
     if (ret.data.opt.len == 0) {
       OPTNAMEMISS(ret);
     } else {
       ret.len += ret.data.opt.len;
     }
   }
   break;
#undef OPTNAMEMISS
 }

 // Register.
 case '@':
   ret.type = kExprLexRegister;
   if (pline.size > 1) {
     ret.len++;
     ret.data.reg.name = (uint8_t)pline.data[1];
   } else {
     ret.data.reg.name = -1;
   }
   break;

 // Single quoted string.
 case '\'':
   ret.type = kExprLexSingleQuotedString;
   ret.data.str.closed = false;
   for (; ret.len < pline.size && !ret.data.str.closed; ret.len++) {
     if (pline.data[ret.len] == '\'') {
       if (ret.len + 1 < pline.size && pline.data[ret.len + 1] == '\'') {
         ret.len++;
       } else {
         ret.data.str.closed = true;
       }
     }
   }
   break;

 // Double quoted string.
 case '"':
   ret.type = kExprLexDoubleQuotedString;
   ret.data.str.closed = false;
   for (; ret.len < pline.size && !ret.data.str.closed; ret.len++) {
     if (pline.data[ret.len] == '\\') {
       if (ret.len + 1 < pline.size) {
         ret.len++;
       }
     } else if (pline.data[ret.len] == '"') {
       ret.data.str.closed = true;
     }
   }
   break;

 // Unary not, (un)equality and regex (not) match comparison operators.
 case '!':
 case '=':
   if (pline.size == 1) {
     ret.type = (schar == '!' ? kExprLexNot : kExprLexAssignment);
     ret.data.ass.type = kExprAsgnPlain;
     break;
   }
   ret.type = kExprLexComparison;
   ret.data.cmp.inv = (schar == '!');
   if (pline.data[1] == '=') {
     ret.data.cmp.type = kExprCmpEqual;
     ret.len++;
   } else if (pline.data[1] == '~') {
     ret.data.cmp.type = kExprCmpMatches;
     ret.len++;
   } else if (schar == '!') {
     ret.type = kExprLexNot;
   } else {
     ret.type = kExprLexAssignment;
     ret.data.ass.type = kExprAsgnPlain;
   }
   GET_CCS(ret, pline);
   break;

 // Less/greater [or equal to] comparison operators.
 case '>':
 case '<': {
   ret.type = kExprLexComparison;
   const bool haseqsign = (pline.size > 1 && pline.data[1] == '=');
   if (haseqsign) {
     ret.len++;
   }
   GET_CCS(ret, pline);
   ret.data.cmp.inv = (schar == '<');
   ret.data.cmp.type = ((ret.data.cmp.inv ^ haseqsign)
                        ? kExprCmpGreaterOrEqual
                        : kExprCmpGreater);
   break;
 }

 // Minus sign, arrow from lambdas or augmented assignment.
 case '-': {
   if (pline.size > 1 && pline.data[1] == '>') {
     ret.len++;
     ret.type = kExprLexArrow;
   } else if (pline.size > 1 && pline.data[1] == '=') {
     ret.len++;
     ret.type = kExprLexAssignment;
     ret.data.ass.type = kExprAsgnSubtract;
   } else {
     ret.type = kExprLexMinus;
   }
   break;
 }

   // Sign or augmented assignment.
#define CHAR_OR_ASSIGN(ch, ch_type, ass_type) \
 case ch: { \
     if (pline.size > 1 && pline.data[1] == '=') { \
       ret.len++; \
       ret.type = kExprLexAssignment; \
       ret.data.ass.type = ass_type; \
     } else { \
       ret.type = ch_type; \
     } \
     break; \
 }
   CHAR_OR_ASSIGN('+', kExprLexPlus, kExprAsgnAdd)
   CHAR_OR_ASSIGN('.', kExprLexDot, kExprAsgnConcat)
#undef CHAR_OR_ASSIGN

 // Expression end because Ex command ended.
 case NUL:
 case NL:
   if (flags & kELFlagForbidEOC) {
     ret.type = kExprLexInvalid;
     ret.data.err.msg = _("E15: Unexpected EOC character: %.*s");
     ret.data.err.type = kExprLexSpacing;
   } else {
     ret.type = kExprLexEOC;
   }
   break;

 case '|':
   if (pline.size >= 2 && pline.data[ret.len] == '|') {
     // "||" is or.
     ret.len++;
     ret.type = kExprLexOr;
   } else if (flags & kELFlagForbidEOC) {
     // Note: `<C-r>=1 | 2<CR>` actually yields 1 in Vim without any
     //       errors. This will be changed here.
     ret.type = kExprLexInvalid;
     ret.data.err.msg = _("E15: Unexpected EOC character: %.*s");
     ret.data.err.type = kExprLexOr;
   } else {
     ret.type = kExprLexEOC;
   }
   break;

 // Everything else is not valid.
 default:
   ret.len = (size_t)utfc_ptr2len_len(pline.data, (int)pline.size);
   ret.type = kExprLexInvalid;
   ret.data.err.type = kExprLexPlainIdentifier;
   ret.data.err.msg = _("E15: Unidentified character: %.*s");
   break;
 }
#undef GET_CCS
viml_pexpr_next_token_adv_return:
 if (!(flags & kELFlagPeek)) {
   viml_parser_advance(pstate, ret.len);
 }
 return ret;
}

static const char *const eltkn_type_tab[] = {
 [kExprLexInvalid] = "Invalid",
 [kExprLexMissing] = "Missing",
 [kExprLexSpacing] = "Spacing",
 [kExprLexEOC] = "EOC",

 [kExprLexQuestion] = "Question",
 [kExprLexColon] = "Colon",
 [kExprLexOr] = "Or",
 [kExprLexAnd] = "And",
 [kExprLexComparison] = "Comparison",
 [kExprLexPlus] = "Plus",
 [kExprLexMinus] = "Minus",
 [kExprLexDot] = "Dot",
 [kExprLexMultiplication] = "Multiplication",

 [kExprLexNot] = "Not",

 [kExprLexNumber] = "Number",
 [kExprLexSingleQuotedString] = "SingleQuotedString",
 [kExprLexDoubleQuotedString] = "DoubleQuotedString",
 [kExprLexOption] = "Option",
 [kExprLexRegister] = "Register",
 [kExprLexEnv] = "Env",
 [kExprLexPlainIdentifier] = "PlainIdentifier",

 [kExprLexBracket] = "Bracket",
 [kExprLexFigureBrace] = "FigureBrace",
 [kExprLexParenthesis] = "Parenthesis",
 [kExprLexComma] = "Comma",
 [kExprLexArrow] = "Arrow",
 [kExprLexAssignment] = "Assignment",
};

const char *const eltkn_cmp_type_tab[] = {
 [kExprCmpEqual] = "Equal",
 [kExprCmpMatches] = "Matches",
 [kExprCmpGreater] = "Greater",
 [kExprCmpGreaterOrEqual] = "GreaterOrEqual",
 [kExprCmpIdentical] = "Identical",
};

const char *const expr_asgn_type_tab[] = {
 [kExprAsgnPlain] = "Plain",
 [kExprAsgnAdd] = "Add",
 [kExprAsgnSubtract] = "Subtract",
 [kExprAsgnConcat] = "Concat",
};

const char *const ccs_tab[] = {
 [kCCStrategyUseOption] = "UseOption",
 [kCCStrategyMatchCase] = "MatchCase",
 [kCCStrategyIgnoreCase] = "IgnoreCase",
};

static const char *const eltkn_mul_type_tab[] = {
 [kExprLexMulMul] = "Mul",
 [kExprLexMulDiv] = "Div",
 [kExprLexMulMod] = "Mod",
};

static const char *const eltkn_opt_scope_tab[] = {
 [kExprOptScopeUnspecified] = "Unspecified",
 [kExprOptScopeGlobal] = "Global",
 [kExprOptScopeLocal] = "Local",
};

/// Represent token as a string
///
/// Intended for testing and debugging purposes.
///
/// @param[in]  pstate  Parser state, needed to get token string from it. May be
///                     NULL, in which case in place of obtaining part of the
///                     string represented by token only token length is
///                     returned.
/// @param[in]  token  Token to represent.
/// @param[out]  ret_size  Return string size, for cases like NULs inside
///                        a string. May be NULL.
///
/// @return Token represented in a string form, in a static buffer (overwritten
///         on each call).
const char *viml_pexpr_repr_token(const ParserState *const pstate, const LexExprToken token,
                                 size_t *const ret_size)
 FUNC_ATTR_WARN_UNUSED_RESULT
{
 static char ret[1024];
 char *p = ret;
 const char *const e = &ret[1024] - 1;
#define ADDSTR(...) \
 do { \
   p += snprintf(p, (size_t)(sizeof(ret) - (size_t)(p - ret)), __VA_ARGS__); \
   if (p >= e) { \
     goto viml_pexpr_repr_token_end; \
   } \
 } while (0)
 ADDSTR("%zu:%zu:%s", token.start.line, token.start.col,
        eltkn_type_tab[token.type]);
 switch (token.type) {
#define TKNARGS(tkn_type, ...) \
 case tkn_type: { \
     ADDSTR(__VA_ARGS__); \
     break; \
 }
 TKNARGS(kExprLexComparison, "(type=%s,ccs=%s,inv=%i)",
         eltkn_cmp_type_tab[token.data.cmp.type],
         ccs_tab[token.data.cmp.ccs],
         (int)token.data.cmp.inv)
 TKNARGS(kExprLexMultiplication, "(type=%s)",
         eltkn_mul_type_tab[token.data.mul.type])
 TKNARGS(kExprLexAssignment, "(type=%s)",
         expr_asgn_type_tab[token.data.ass.type])
 TKNARGS(kExprLexRegister, "(name=%s)", intchar2str(token.data.reg.name))
 case kExprLexDoubleQuotedString:
   TKNARGS(kExprLexSingleQuotedString, "(closed=%i)",
           (int)token.data.str.closed)
   TKNARGS(kExprLexOption, "(scope=%s,name=%.*s)",
           eltkn_opt_scope_tab[token.data.opt.scope],
           (int)token.data.opt.len, token.data.opt.name)
   TKNARGS(kExprLexPlainIdentifier, "(scope=%s,autoload=%i)",
           intchar2str((int)token.data.var.scope),
           (int)token.data.var.autoload)
   TKNARGS(kExprLexNumber, "(is_float=%i,base=%i,val=%lg)",
           (int)token.data.num.is_float,
           (int)token.data.num.base,
           (double)(token.data.num.is_float
                    ? (double)token.data.num.val.floating
                    : (double)token.data.num.val.integer))
   TKNARGS(kExprLexInvalid, "(msg=%s)", token.data.err.msg)
 default:
   // No additional arguments.
   break;
#undef TKNARGS
 }
 if (pstate == NULL) {
   ADDSTR("::%zu", token.len);
 } else {
   *p++ = ':';
   memmove(p, &pstate->reader.lines.items[token.start.line].data[token.start.col],
           token.len);
   p += token.len;
   *p = NUL;
 }
#undef ADDSTR
viml_pexpr_repr_token_end:
 if (ret_size != NULL) {
   *ret_size = (size_t)(p - ret);
 }
 return ret;
}

const char *const east_node_type_tab[] = {
 [kExprNodeMissing] = "Missing",
 [kExprNodeOpMissing] = "OpMissing",
 [kExprNodeTernary] = "Ternary",
 [kExprNodeTernaryValue] = "TernaryValue",
 [kExprNodeRegister] = "Register",
 [kExprNodeSubscript] = "Subscript",
 [kExprNodeListLiteral] = "ListLiteral",
 [kExprNodeUnaryPlus] = "UnaryPlus",
 [kExprNodeBinaryPlus] = "BinaryPlus",
 [kExprNodeNested] = "Nested",
 [kExprNodeCall] = "Call",
 [kExprNodePlainIdentifier] = "PlainIdentifier",
 [kExprNodePlainKey] = "PlainKey",
 [kExprNodeComplexIdentifier] = "ComplexIdentifier",
 [kExprNodeUnknownFigure] = "UnknownFigure",
 [kExprNodeLambda] = "Lambda",
 [kExprNodeDictLiteral] = "DictLiteral",
 [kExprNodeCurlyBracesIdentifier] = "CurlyBracesIdentifier",
 [kExprNodeComma] = "Comma",
 [kExprNodeColon] = "Colon",
 [kExprNodeArrow] = "Arrow",
 [kExprNodeComparison] = "Comparison",
 [kExprNodeConcat] = "Concat",
 [kExprNodeConcatOrSubscript] = "ConcatOrSubscript",
 [kExprNodeInteger] = "Integer",
 [kExprNodeFloat] = "Float",
 [kExprNodeSingleQuotedString] = "SingleQuotedString",
 [kExprNodeDoubleQuotedString] = "DoubleQuotedString",
 [kExprNodeOr] = "Or",
 [kExprNodeAnd] = "And",
 [kExprNodeUnaryMinus] = "UnaryMinus",
 [kExprNodeBinaryMinus] = "BinaryMinus",
 [kExprNodeNot] = "Not",
 [kExprNodeMultiplication] = "Multiplication",
 [kExprNodeDivision] = "Division",
 [kExprNodeMod] = "Mod",
 [kExprNodeOption] = "Option",
 [kExprNodeEnvironment] = "Environment",
 [kExprNodeAssignment] = "Assignment",
};

/// Represent `int` character as a string
///
/// Converts
/// - ASCII digits into '{digit}'
/// - ASCII printable characters into a single-character strings
/// - everything else to numbers.
///
/// @param[in]  ch  Character to convert.
///
/// @return Converted string, stored in a static buffer (overridden after each
///         call).
static const char *intchar2str(const int ch)
 FUNC_ATTR_WARN_UNUSED_RESULT
{
 static char buf[sizeof(int) * 3 + 1];
 if (' ' <= ch && ch < 0x7f) {
   if (ascii_isdigit(ch)) {
     buf[0] = '\'';
     buf[1] = (char)ch;
     buf[2] = '\'';
     buf[3] = NUL;
   } else {
     buf[0] = (char)ch;
     buf[1] = NUL;
   }
 } else {
   snprintf(buf, sizeof(buf), "%i", ch);
 }
 return buf;
}

#ifdef UNIT_TESTING

REAL_FATTR_UNUSED
static inline void viml_pexpr_debug_print_ast_node(const ExprASTNode *const *const eastnode_p,
                                                  const char *const prefix)
{
 if (*eastnode_p == NULL) {
   fprintf(stderr, "%s %p : NULL\n", prefix, (void *)eastnode_p);
 } else {
   fprintf(stderr, "%s %p : %p : %s : %zu:%zu:%zu\n",
           prefix, (void *)eastnode_p, (void *)(*eastnode_p),
           east_node_type_tab[(*eastnode_p)->type], (*eastnode_p)->start.line,
           (*eastnode_p)->start.col, (*eastnode_p)->len);
 }
}

REAL_FATTR_UNUSED
static inline void viml_pexpr_debug_print_ast_stack(const ExprASTStack *const ast_stack,
                                                   const char *const msg)
 FUNC_ATTR_NONNULL_ALL FUNC_ATTR_ALWAYS_INLINE
{
 fprintf(stderr, "\n%sstack: %zu:\n", msg, kv_size(*ast_stack));
 for (size_t i = 0; i < kv_size(*ast_stack); i++) {
   viml_pexpr_debug_print_ast_node((const ExprASTNode *const *)kv_A(*ast_stack, i),
                                   "-");
 }
}

REAL_FATTR_UNUSED
static inline void viml_pexpr_debug_print_token(const ParserState *const pstate,
                                               const LexExprToken token)
 FUNC_ATTR_ALWAYS_INLINE
{
 fprintf(stderr, "\ntkn: %s\n", viml_pexpr_repr_token(pstate, token, NULL));
}
# define PSTACK(msg) \
 viml_pexpr_debug_print_ast_stack(&ast_stack, #msg)
# define PSTACK_P(msg) \
 viml_pexpr_debug_print_ast_stack(ast_stack, #msg)
# define PNODE_P(eastnode_p, msg) \
 viml_pexpr_debug_print_ast_node((const ExprASTNode *const *)eastnode_p, \
                                 (#msg))
# define PTOKEN(tkn) \
 viml_pexpr_debug_print_token(pstate, tkn)
#endif

const uint8_t node_maxchildren[] = {
 [kExprNodeMissing] = 0,
 [kExprNodeOpMissing] = 2,
 [kExprNodeTernary] = 2,
 [kExprNodeTernaryValue] = 2,
 [kExprNodeRegister] = 0,
 [kExprNodeSubscript] = 2,
 [kExprNodeListLiteral] = 1,
 [kExprNodeUnaryPlus] = 1,
 [kExprNodeBinaryPlus] = 2,
 [kExprNodeNested] = 1,
 [kExprNodeCall] = 2,
 [kExprNodePlainIdentifier] = 0,
 [kExprNodePlainKey] = 0,
 [kExprNodeComplexIdentifier] = 2,
 [kExprNodeUnknownFigure] = 1,
 [kExprNodeLambda] = 2,
 [kExprNodeDictLiteral] = 1,
 [kExprNodeCurlyBracesIdentifier] = 1,
 [kExprNodeComma] = 2,
 [kExprNodeColon] = 2,
 [kExprNodeArrow] = 2,
 [kExprNodeComparison] = 2,
 [kExprNodeConcat] = 2,
 [kExprNodeConcatOrSubscript] = 2,
 [kExprNodeInteger] = 0,
 [kExprNodeFloat] = 0,
 [kExprNodeSingleQuotedString] = 0,
 [kExprNodeDoubleQuotedString] = 0,
 [kExprNodeOr] = 2,
 [kExprNodeAnd] = 2,
 [kExprNodeUnaryMinus] = 1,
 [kExprNodeBinaryMinus] = 2,
 [kExprNodeNot] = 1,
 [kExprNodeMultiplication] = 2,
 [kExprNodeDivision] = 2,
 [kExprNodeMod] = 2,
 [kExprNodeOption] = 0,
 [kExprNodeEnvironment] = 0,
 [kExprNodeAssignment] = 2,
};

/// Free memory occupied by AST
///
/// @param  ast  AST stack to free.
void viml_pexpr_free_ast(ExprAST ast)
{
 ExprASTStack ast_stack;
 kvi_init(ast_stack);
 kvi_push(ast_stack, &ast.root);
 while (kv_size(ast_stack)) {
   ExprASTNode **const cur_node = kv_last(ast_stack);
#ifndef NDEBUG
   // Explicitly check for AST recursiveness.
   for (size_t i = 0; i < kv_size(ast_stack) - 1; i++) {
     assert(*kv_A(ast_stack, i) != *cur_node);
   }
#endif
   if (*cur_node == NULL) {
     assert(kv_size(ast_stack) == 1);
     kv_drop(ast_stack, 1);
   } else if ((*cur_node)->children != NULL) {
#ifndef NDEBUG
     const uint8_t maxchildren = node_maxchildren[(*cur_node)->type];
     assert(maxchildren > 0);
     assert(maxchildren <= 2);
     assert(maxchildren == 1
            ? (*cur_node)->children->next == NULL
            : ((*cur_node)->children->next == NULL
               || (*cur_node)->children->next->next == NULL));
#endif
     kvi_push(ast_stack, &(*cur_node)->children);
   } else if ((*cur_node)->next != NULL) {
     kvi_push(ast_stack, &(*cur_node)->next);
   } else if (*cur_node != NULL) {
     kv_drop(ast_stack, 1);
     switch ((*cur_node)->type) {
     case kExprNodeDoubleQuotedString:
     case kExprNodeSingleQuotedString:
       xfree((*cur_node)->data.str.value);
       break;
     case kExprNodeMissing:
     case kExprNodeOpMissing:
     case kExprNodeTernary:
     case kExprNodeTernaryValue:
     case kExprNodeRegister:
     case kExprNodeSubscript:
     case kExprNodeListLiteral:
     case kExprNodeUnaryPlus:
     case kExprNodeBinaryPlus:
     case kExprNodeNested:
     case kExprNodeCall:
     case kExprNodePlainIdentifier:
     case kExprNodePlainKey:
     case kExprNodeComplexIdentifier:
     case kExprNodeUnknownFigure:
     case kExprNodeLambda:
     case kExprNodeDictLiteral:
     case kExprNodeCurlyBracesIdentifier:
     case kExprNodeAssignment:
     case kExprNodeComma:
     case kExprNodeColon:
     case kExprNodeArrow:
     case kExprNodeComparison:
     case kExprNodeConcat:
     case kExprNodeConcatOrSubscript:
     case kExprNodeInteger:
     case kExprNodeFloat:
     case kExprNodeOr:
     case kExprNodeAnd:
     case kExprNodeUnaryMinus:
     case kExprNodeBinaryMinus:
     case kExprNodeNot:
     case kExprNodeMultiplication:
     case kExprNodeDivision:
     case kExprNodeMod:
     case kExprNodeOption:
     case kExprNodeEnvironment:
       break;
     }
     xfree(*cur_node);
     *cur_node = NULL;
   }
 }
 kvi_destroy(ast_stack);
}

// Binary operator precedence and associativity:
//
// Operator | Precedence | Associativity
// ---------+------------+-----------------
// ||       | 2          | left
// &&       | 3          | left
// cmp*     | 4          | not associative
// + - .    | 5          | left
// * / %    | 6          | left
//
// * comparison operators:
//
// == ==# ==?  != !=# !=?
// =~ =~# =~?  !~ !~# !~?
//  >  >#  >?  <= <=# <=?
//  <  <#  <?  >= >=# >=?
// is is# is?  isnot isnot# isnot?

/// Allocate a new node and set some of the values
///
/// @param[in]  type  Node type to allocate.
/// @param[in]  level  Node level to allocate
static inline ExprASTNode *viml_pexpr_new_node(const ExprASTNodeType type)
 FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_MALLOC
{
 ExprASTNode *ret = xmalloc(sizeof(*ret));
 ret->type = type;
 ret->children = NULL;
 ret->next = NULL;
 return ret;
}

static struct {
 ExprOpLvl lvl;
 ExprOpAssociativity ass;
} node_type_to_node_props[] = {
 [kExprNodeMissing] = { kEOpLvlInvalid, kEOpAssNo, },
 [kExprNodeOpMissing] = { kEOpLvlMultiplication, kEOpAssNo },

 [kExprNodeNested] = { kEOpLvlParens, kEOpAssNo },
 // Note: below nodes are kEOpLvlSubscript for “binary operator” itself, but
 //       kEOpLvlParens when it comes to inside the parenthesis.
 [kExprNodeCall] = { kEOpLvlParens, kEOpAssNo },
 [kExprNodeSubscript] = { kEOpLvlParens, kEOpAssNo },

 [kExprNodeUnknownFigure] = { kEOpLvlParens, kEOpAssLeft },
 [kExprNodeLambda] = { kEOpLvlParens, kEOpAssNo },
 [kExprNodeDictLiteral] = { kEOpLvlParens, kEOpAssNo },
 [kExprNodeListLiteral] = { kEOpLvlParens, kEOpAssNo },

 [kExprNodeArrow] = { kEOpLvlArrow, kEOpAssNo },

 // Right associativity for comma because this means easier access to arguments
 // list, etc: for "[a, b, c, d]" you can access "a" in one step if it is
 // represented as "list(comma(a, comma(b, comma(c, d))))" then if it is
 // "list(comma(comma(comma(a, b), c), d))" in which case you will need to
 // traverse all three comma() structures. And with comma operator (including
 // actual comma operator from C which is not present in Vimscript) nobody cares
 // about associativity, only about order of execution.
 [kExprNodeComma] = { kEOpLvlComma, kEOpAssRight },

 // Colons are not eligible for chaining, so nobody cares about associativity.
 [kExprNodeColon] = { kEOpLvlColon, kEOpAssNo },

 [kExprNodeTernary] = { kEOpLvlTernary, kEOpAssRight },

 [kExprNodeOr] = { kEOpLvlOr, kEOpAssLeft },

 [kExprNodeAnd] = { kEOpLvlAnd, kEOpAssLeft },

 [kExprNodeTernaryValue] = { kEOpLvlTernaryValue, kEOpAssRight },

 [kExprNodeComparison] = { kEOpLvlComparison, kEOpAssRight },

 [kExprNodeBinaryPlus] = { kEOpLvlAddition, kEOpAssLeft },
 [kExprNodeBinaryMinus] = { kEOpLvlAddition, kEOpAssLeft },
 [kExprNodeConcat] = { kEOpLvlAddition, kEOpAssLeft },

 [kExprNodeMultiplication] = { kEOpLvlMultiplication, kEOpAssLeft },
 [kExprNodeDivision] = { kEOpLvlMultiplication, kEOpAssLeft },
 [kExprNodeMod] = { kEOpLvlMultiplication, kEOpAssLeft },

 [kExprNodeUnaryPlus] = { kEOpLvlUnary, kEOpAssNo },
 [kExprNodeUnaryMinus] = { kEOpLvlUnary, kEOpAssNo },
 [kExprNodeNot] = { kEOpLvlUnary, kEOpAssNo },

 [kExprNodeConcatOrSubscript] = { kEOpLvlSubscript, kEOpAssLeft },

 [kExprNodeCurlyBracesIdentifier] = { kEOpLvlComplexIdentifier, kEOpAssLeft },

 [kExprNodeAssignment] = { kEOpLvlAssignment, kEOpAssLeft },

 [kExprNodeComplexIdentifier] = { kEOpLvlValue, kEOpAssLeft },

 [kExprNodePlainIdentifier] = { kEOpLvlValue, kEOpAssNo },
 [kExprNodePlainKey] = { kEOpLvlValue, kEOpAssNo },
 [kExprNodeRegister] = { kEOpLvlValue, kEOpAssNo },
 [kExprNodeInteger] = { kEOpLvlValue, kEOpAssNo },
 [kExprNodeFloat] = { kEOpLvlValue, kEOpAssNo },
 [kExprNodeDoubleQuotedString] = { kEOpLvlValue, kEOpAssNo },
 [kExprNodeSingleQuotedString] = { kEOpLvlValue, kEOpAssNo },
 [kExprNodeOption] = { kEOpLvlValue, kEOpAssNo },
 [kExprNodeEnvironment] = { kEOpLvlValue, kEOpAssNo },
};

/// Get AST node priority level
///
/// Used primary to reduce line length, so keep the name short.
///
/// @param[in]  node  Node to get priority for.
///
/// @return Node priority level.
static inline ExprOpLvl node_lvl(const ExprASTNode node)
 FUNC_ATTR_ALWAYS_INLINE FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
{
 return node_type_to_node_props[node.type].lvl;
}

/// Get AST node associativity, to be used for operator nodes primary
///
/// Used primary to reduce line length, so keep the name short.
///
/// @param[in]  node  Node to get priority for.
///
/// @return Node associativity.
static inline ExprOpAssociativity node_ass(const ExprASTNode node)
 FUNC_ATTR_ALWAYS_INLINE FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
{
 return node_type_to_node_props[node.type].ass;
}

/// Handle binary operator
///
/// This function is responsible for handling priority levels as well.
///
/// @param[in]  pstate  Parser state, used for error reporting.
/// @param  ast_stack  AST stack. May be popped of some values and will
///                    definitely receive new ones.
/// @param  bop_node  New node to handle.
/// @param[out]  want_node_p  New value of want_node.
/// @param[out]  ast_err  Location where error is saved, if any.
///
/// @return True if no errors occurred, false otherwise.
static bool viml_pexpr_handle_bop(const ParserState *const pstate, ExprASTStack *const ast_stack,
                                 ExprASTNode *const bop_node, ExprASTWantedNode *const want_node_p,
                                 ExprASTError *const ast_err)
 FUNC_ATTR_NONNULL_ALL
{
 bool ret = true;
 ExprASTNode **top_node_p = NULL;
 ExprASTNode *top_node;
 ExprOpLvl top_node_lvl;
 ExprOpAssociativity top_node_ass;
 assert(kv_size(*ast_stack));
 const ExprOpLvl bop_node_lvl = ((bop_node->type == kExprNodeCall
                                  || bop_node->type == kExprNodeSubscript)
                                 ? kEOpLvlSubscript
                                 : node_lvl(*bop_node));
 do {
   ExprASTNode **new_top_node_p = kv_last(*ast_stack);
   ExprASTNode *new_top_node = *new_top_node_p;
   assert(new_top_node != NULL);
   const ExprOpLvl new_top_node_lvl = node_lvl(*new_top_node);
   const ExprOpAssociativity new_top_node_ass = node_ass(*new_top_node);
   if (top_node_p != NULL
       && ((bop_node_lvl > new_top_node_lvl
            || (bop_node_lvl == new_top_node_lvl
                && new_top_node_ass == kEOpAssNo)))) {
     break;
   }
   kv_drop(*ast_stack, 1);
   top_node_p = new_top_node_p;
   top_node = new_top_node;
   top_node_lvl = new_top_node_lvl;
   top_node_ass = new_top_node_ass;
   if (bop_node_lvl == top_node_lvl && top_node_ass == kEOpAssRight) {
     break;
   }
 } while (kv_size(*ast_stack));
 if (top_node_ass == kEOpAssLeft || top_node_lvl != bop_node_lvl) {
   // outer(op(x,y)) -> outer(new_op(op(x,y),*))
   //
   // Before: top_node_p = outer(*), points to op(x,y)
   //         Other stack elements unknown
   //
   // After: top_node_p = outer(*), points to new_op(op(x,y))
   //        &bop_node->children->next = new_op(op(x,y),*), points to NULL
   *top_node_p = bop_node;
   bop_node->children = top_node;
   assert(bop_node->children->next == NULL);
   kvi_push(*ast_stack, top_node_p);
   kvi_push(*ast_stack, &bop_node->children->next);
 } else {
   assert(top_node_lvl == bop_node_lvl && top_node_ass == kEOpAssRight);
   assert(top_node->children != NULL && top_node->children->next != NULL);
   // outer(op(x,y)) -> outer(op(x,new_op(y,*)))
   //
   // Before: top_node_p = outer(*), points to op(x,y)
   //         Other stack elements unknown
   //
   // After: top_node_p = outer(*), points to op(x,new_op(y))
   //        &top_node->children->next = op(x,*), points to new_op(y)
   //        &bop_node->children->next = new_op(y,*), points to NULL
   bop_node->children = top_node->children->next;
   top_node->children->next = bop_node;
   assert(bop_node->children->next == NULL);
   kvi_push(*ast_stack, top_node_p);
   kvi_push(*ast_stack, &top_node->children->next);
   kvi_push(*ast_stack, &bop_node->children->next);
   // TODO(ZyX-I): Make this not error, but treat like Python does
   if (bop_node->type == kExprNodeComparison) {
     east_set_error(pstate, ast_err,
                    _("E15: Operator is not associative: %.*s"),
                    bop_node->start);
     ret = false;
   }
 }
 *want_node_p = kENodeValue;
 return ret;
}

/// ParserPosition literal based on ParserPosition pos with columns shifted
///
/// Function does not check whether resulting position is valid.
///
/// @param[in]  pos  Position to shift.
/// @param[in]  shift  Number of bytes to shift.
///
/// @return Shifted position.
static inline ParserPosition shifted_pos(const ParserPosition pos, const size_t shift)
 FUNC_ATTR_CONST FUNC_ATTR_ALWAYS_INLINE FUNC_ATTR_WARN_UNUSED_RESULT
{
 return (ParserPosition) { .line = pos.line, .col = pos.col + shift };
}

/// ParserPosition literal based on ParserPosition pos with specified column
///
/// Function does not check whether remaining position is valid.
///
/// @param[in]  pos  Position to adjust.
/// @param[in]  new_col  New column.
///
/// @return Shifted position.
static inline ParserPosition recol_pos(const ParserPosition pos, const size_t new_col)
 FUNC_ATTR_CONST FUNC_ATTR_ALWAYS_INLINE FUNC_ATTR_WARN_UNUSED_RESULT
{
 return (ParserPosition) { .line = pos.line, .col = new_col };
}

/// Get highlight group name
#define HL(g) (is_invalid ? "NvimInvalid" #g : "Nvim" #g)

/// Highlight current token with the given group
#define HL_CUR_TOKEN(g) \
 viml_parser_highlight(pstate, cur_token.start, cur_token.len, \
                       HL(g))

/// Allocate new node, saving some values
#define NEW_NODE(type) \
 viml_pexpr_new_node(type)

/// Set position of the given node to position from the given token
///
/// @param  cur_node  Node to modify.
/// @param  cur_token  Token to set position from.
#define POS_FROM_TOKEN(cur_node, cur_token) \
 do { \
   (cur_node)->start = cur_token.start; \
   (cur_node)->len = cur_token.len; \
 } while (0)

/// Allocate new node and set its position from the current token
///
/// If previous token happened to contain spacing then it will be included.
///
/// @param  cur_node  Variable to save allocated node to.
/// @param  typ  Node type.
#define NEW_NODE_WITH_CUR_POS(cur_node, typ) \
 do { \
   (cur_node) = NEW_NODE(typ); \
   POS_FROM_TOKEN((cur_node), cur_token); \
   if (prev_token.type == kExprLexSpacing) { \
     (cur_node)->start = prev_token.start; \
     (cur_node)->len += prev_token.len; \
   } \
 } while (0)

/// Check whether it is possible to have next expression after current
///
/// For :echo: `:echo @a @a` is a valid expression. `:echo (@a @a)` is not.
#define MAY_HAVE_NEXT_EXPR \
 (kv_size(ast_stack) == 1)

/// Add operator node
///
/// @param[in]  cur_node  Node to add.
#define ADD_OP_NODE(cur_node) \
 is_invalid |= !viml_pexpr_handle_bop(pstate, &ast_stack, cur_node, \
                                      &want_node, &ast.err)

/// Record missing operator: for things like
///
///     :echo @a @a
///
/// (allowed) or
///
///     :echo (@a @a)
///
/// (parsed as OpMissing(@a, @a)).
#define OP_MISSING \
 do { \
   if (flags & kExprFlagsMulti && MAY_HAVE_NEXT_EXPR) { \
     /* Multiple expressions allowed, return without calling */ \
     /* viml_parser_advance(). */ \
     goto viml_pexpr_parse_end; \
   } else { \
     assert(*top_node_p != NULL); \
     ERROR_FROM_TOKEN_AND_MSG(cur_token, _("E15: Missing operator: %.*s")); \
     NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeOpMissing); \
     cur_node->len = 0; \
     ADD_OP_NODE(cur_node); \
     goto viml_pexpr_parse_process_token; \
   } \
 } while (0)

/// Record missing value: for things like "* 5"
///
/// @param[in]  msg  Error message.
#define ADD_VALUE_IF_MISSING(msg) \
 do { \
   if (want_node == kENodeValue) { \
     ERROR_FROM_TOKEN_AND_MSG(cur_token, (msg)); \
     NEW_NODE_WITH_CUR_POS((*top_node_p), kExprNodeMissing); \
     (*top_node_p)->len = 0; \
     want_node = kENodeOperator; \
   } \
 } while (0)

/// Set AST error, unless AST already is not correct
///
/// @param[out]  ret_ast  AST to set error in.
/// @param[in]  pstate  Parser state, used to get error message argument.
/// @param[in]  msg  Error message, assumed to be already translated and
///                  containing a single %token "%.*s".
/// @param[in]  start  Position at which error occurred.
static inline void east_set_error(const ParserState *const pstate, ExprASTError *const ret_ast_err,
                                 const char *const msg, const ParserPosition start)
 FUNC_ATTR_NONNULL_ALL FUNC_ATTR_ALWAYS_INLINE
{
 if (ret_ast_err->msg != NULL) {
   return;
 }
 const ParserLine pline = pstate->reader.lines.items[start.line];
 ret_ast_err->msg = msg;
 ret_ast_err->arg_len = (int)(pline.size - start.col);
 ret_ast_err->arg = pline.data ? pline.data + start.col : NULL;
}

/// Set error from the given token and given message
#define ERROR_FROM_TOKEN_AND_MSG(cur_token, msg) \
 do { \
   is_invalid = true; \
   east_set_error(pstate, &ast.err, msg, cur_token.start); \
 } while (0)

/// Like #ERROR_FROM_TOKEN_AND_MSG, but gets position from a node
#define ERROR_FROM_NODE_AND_MSG(node, msg) \
 do { \
   is_invalid = true; \
   east_set_error(pstate, &ast.err, msg, node->start); \
 } while (0)

/// Set error from the given kExprLexInvalid token
#define ERROR_FROM_TOKEN(cur_token) \
 ERROR_FROM_TOKEN_AND_MSG(cur_token, cur_token.data.err.msg)

/// Select figure brace type, altering highlighting as well if needed
///
/// @param[out]  node  Node to modify type.
/// @param[in]  new_type  New type, one of ExprASTNodeType values without
///                       kExprNode prefix.
/// @param[in]  hl  Corresponding highlighting, passed as an argument to #HL.
#define SELECT_FIGURE_BRACE_TYPE(node, new_type, hl) \
 do { \
   ExprASTNode *const node_ = (node); \
   assert(node_->type == kExprNodeUnknownFigure \
          || node_->type == kExprNode##new_type); \
   node_->type = kExprNode##new_type; \
   if (pstate->colors) { \
     kv_A(*pstate->colors, node_->data.fig.opening_hl_idx).group = \
       HL(hl); \
   } \
 } while (0)

/// Add identifier which should constitute complex identifier node
///
/// This one is to be called only in case want_node is kENodeOperator.
///
/// @param  new_ident_node_code  Code used to create a new identifier node and
///                              update want_node and ast_stack, without
///                              a trailing semicolon.
/// @param  hl  Highlighting name to use, passed as an argument to #HL.
#define ADD_IDENT(new_ident_node_code, hl) \
 do { \
   assert(want_node == kENodeOperator); \
   /* Operator: may only be curly braces name, but only under certain */ \
   /* conditions. */ \
   /* First condition is that there is no space before a part of complex */ \
   /* identifier. */ \
   if (prev_token.type == kExprLexSpacing) { \
     OP_MISSING; \
   } \
   switch ((*top_node_p)->type) { \
   /* Second is that previous node is one of the identifiers: */ \
   /* complex, plain, curly braces. */ \
   /* TODO(ZyX-I): Extend syntax to allow ${expr}. This is needed to */ \
   /* handle environment variables like those bash uses for */ \
   /* `export -f`: their names consist not only of alphanumeric */ \
   /* characters. */ \
   case kExprNodeComplexIdentifier: \
   case kExprNodePlainIdentifier: \
   case kExprNodeCurlyBracesIdentifier: { \
       NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeComplexIdentifier); \
       cur_node->len = 0; \
       cur_node->children = *top_node_p; \
       *top_node_p = cur_node; \
       kvi_push(ast_stack, &cur_node->children->next); \
       ExprASTNode **const new_top_node_p = kv_last(ast_stack); \
       assert(*new_top_node_p == NULL); \
       new_ident_node_code; \
       *new_top_node_p = cur_node; \
       HL_CUR_TOKEN(hl); \
       break; \
   } \
   default: { \
       OP_MISSING; \
       break; \
   } \
   } \
 } while (0)

/// Determine whether given parse type is an assignment
///
/// @param[in]  pt  Checked parse type.
///
/// @return true if parsing an assignment, false otherwise.
static inline bool pt_is_assignment(const ExprASTParseType pt)
 FUNC_ATTR_ALWAYS_INLINE FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
{
 return (pt == kEPTAssignment || pt == kEPTSingleAssignment);
}

/// Structure used to define “string shifts” necessary to map string
/// highlighting to actual strings.
typedef struct {
 size_t start;  ///< Where special character starts in original string.
 size_t orig_len;  ///< Length of orininal string (e.g. 4 for "\x80").
 size_t act_len;  ///< Length of resulting character(s) (e.g. 1 for "\x80").
 bool escape_not_known;  ///< True if escape sequence in original is not known.
} StringShift;

/// Parse and highlight single- or double-quoted string
///
/// Function is supposed to detect and highlight regular expressions (but does
/// not do now).
///
/// @param[out]  pstate  Parser state which also contains a place where
///                      highlighting is saved.
/// @param[out]  node  Node where string parsing results are saved.
/// @param[in]  token  Token to highlight.
/// @param[in]  ast_stack  Parser AST stack, used to detect whether current
///                        string is a regex.
/// @param[in]  is_invalid  Whether currently processed token is not valid.
static void parse_quoted_string(ParserState *const pstate, ExprASTNode *const node,
                               const LexExprToken token, const ExprASTStack *ast_stack,
                               const bool is_invalid)
 FUNC_ATTR_NONNULL_ALL
{
 const ParserLine pline = pstate->reader.lines.items[token.start.line];
 const char *const s = pline.data + token.start.col;
 const char *const e = s + token.len - token.data.str.closed;
 const char *p = s + 1;
 const bool is_double = (token.type == kExprLexDoubleQuotedString);
 size_t size = token.len - token.data.str.closed - 1;
 kvec_withinit_t(StringShift, 16) shifts;
 kvi_init(shifts);
 if (!is_double) {
   viml_parser_highlight(pstate, token.start, 1, HL(SingleQuote));
   while (p < e) {
     const char *const chunk_e = memchr(p, '\'', (size_t)(e - p));
     if (chunk_e == NULL) {
       break;
     }
     size--;
     p = chunk_e + 2;
     if (pstate->colors) {
       kvi_push(shifts, ((StringShift) {
         .start = token.start.col + (size_t)(chunk_e - s),
         .orig_len = 2,
         .act_len = 1,
         .escape_not_known = false,
       }));
     }
   }
   node->data.str.size = size;
   if (size == 0) {
     node->data.str.value = NULL;
   } else {
     char *v_p;
     v_p = node->data.str.value = xmallocz(size);
     p = s + 1;
     while (p < e) {
       const char *const chunk_e = memchr(p, '\'', (size_t)(e - p));
       if (chunk_e == NULL) {
         memcpy(v_p, p, (size_t)(e - p));
         break;
       }
       memcpy(v_p, p, (size_t)(chunk_e - p));
       v_p += (size_t)(chunk_e - p) + 1;
       v_p[-1] = '\'';
       p = chunk_e + 2;
     }
   }
 } else {
   viml_parser_highlight(pstate, token.start, 1, HL(DoubleQuote));
   for (p = s + 1; p < e; p++) {
     if (*p == '\\' && p + 1 < e) {
       p++;
       if (p + 1 == e) {
         size--;
         break;
       }
       switch (*p) {
       // A "\<x>" form occupies at least 4 characters, and produces up to
       // to 9 characters (6 for the char and 3 for a modifier):
       // reserve space for 5 extra, but do not compute actual length
       // just now, it would be costly.
       case '<':
         size += 5;
         break;
       // Hexadecimal, always single byte, but at least three bytes each.
       case 'x':
       case 'X':
         size--;
         if (ascii_isxdigit(p[1])) {
           size--;
           if (p + 2 < e && ascii_isxdigit(p[2])) {
             size--;
           }
         }
         break;
       // Unicode
       //
       // \uF takes 1 byte which is 2 bytes less then escape sequence.
       // \uFF: 2 bytes, 2 bytes less.
       // \uFFF: 3 bytes, 2 bytes less.
       // \uFFFF: 3 bytes, 3 bytes less.
       // \UFFFFF: 4 bytes, 3 bytes less.
       // \UFFFFFF: 5 bytes, 3 bytes less.
       // \UFFFFFFF: 6 bytes, 3 bytes less.
       // \U7FFFFFFF: 6 bytes, 4 bytes less.
       case 'u':
       case 'U': {
         const char *const esc_start = p;
         size_t n = (*p == 'u' ? 4 : 8);
         int nr = 0;
         p++;
         while (p + 1 < e && n-- && ascii_isxdigit(p[1])) {
           p++;
           nr = (nr << 4) + hex2nr(*p);
         }
         // Escape length: (esc_start - 1) points to "\\", esc_start to "u"
         // or "U", p to the byte after last byte. So escape sequence
         // occupies p - (esc_start - 1), but it stands for a utf_char2len
         // bytes.
         size -= (size_t)((p - (esc_start - 1)) - utf_char2len(nr));
         p--;
         break;
       }
       // Octal, always single byte, but at least two bytes each.
       case '0':
       case '1':
       case '2':
       case '3':
       case '4':
       case '5':
       case '6':
       case '7':
         size--;
         p++;
         if (*p >= '0' && *p <= '7') {
           size--;
           p++;
           if (p < e && *p >= '0' && *p <= '7') {
             size--;
             p++;
           }
         }
         break;
       default:
         size--;
         break;
       }
     }
   }
   if (size == 0) {
     node->data.str.value = NULL;
     node->data.str.size = 0;
   } else {
     char *v_p;
     v_p = node->data.str.value = xmalloc(size);
     p = s + 1;
     while (p < e) {
       const char *const chunk_e = memchr(p, '\\', (size_t)(e - p));
       if (chunk_e == NULL) {
         memcpy(v_p, p, (size_t)(e - p));
         v_p += e - p;
         break;
       }
       memcpy(v_p, p, (size_t)(chunk_e - p));
       v_p += (size_t)(chunk_e - p);
       p = chunk_e + 1;
       if (p == e) {
         *v_p++ = '\\';
         break;
       }
       bool is_unknown = false;
       const char *const v_p_start = v_p;
       switch (*p) {
#define SINGLE_CHAR_ESC(ch, real_ch) \
 case ch: { \
     *v_p++ = real_ch; \
     p++; \
     break; \
 }
       SINGLE_CHAR_ESC('b', BS)
       SINGLE_CHAR_ESC('e', ESC)
       SINGLE_CHAR_ESC('f', FF)
       SINGLE_CHAR_ESC('n', NL)
       SINGLE_CHAR_ESC('r', CAR)
       SINGLE_CHAR_ESC('t', TAB)
       SINGLE_CHAR_ESC('"', '"')
       SINGLE_CHAR_ESC('\\', '\\')
#undef SINGLE_CHAR_ESC

       // Hexadecimal or unicode.
       case 'X':
       case 'x':
       case 'u':
       case 'U':
         if (p + 1 < e && ascii_isxdigit(p[1])) {
           size_t n;
           int nr;
           bool is_hex = (*p == 'x' || *p == 'X');

           if (is_hex) {
             n = 2;
           } else if (*p == 'u') {
             n = 4;
           } else {
             n = 8;
           }
           nr = 0;
           while (p + 1 < e && n-- && ascii_isxdigit(p[1])) {
             p++;
             nr = (nr << 4) + hex2nr(*p);
           }
           p++;
           if (is_hex) {
             *v_p++ = (char)nr;
           } else {
             v_p += utf_char2bytes(nr, v_p);
           }
         } else {
           is_unknown = true;
           *v_p++ = *p;
           p++;
         }
         break;
       // Octal: "\1", "\12", "\123".
       case '0':
       case '1':
       case '2':
       case '3':
       case '4':
       case '5':
       case '6':
       case '7': {
         uint8_t ch = (uint8_t)(*p++ - '0');
         if (p < e && *p >= '0' && *p <= '7') {
           ch = (uint8_t)((ch << 3) + *p++ - '0');
           if (p < e && *p >= '0' && *p <= '7') {
             ch = (uint8_t)((ch << 3) + *p++ - '0');
           }
         }
         *v_p++ = (char)ch;
         break;
       }
       // Special key, e.g.: "\<C-W>"
       case '<': {
         int flags = FSK_KEYCODE | FSK_IN_STRING;

         if (p[1] != '*') {
           flags |= FSK_SIMPLIFY;
         }
         const size_t special_len = trans_special(&p, (size_t)(e - p),
                                                  v_p, flags, false, NULL);
         if (special_len != 0) {
           v_p += special_len;
         } else {
           is_unknown = true;
           mb_copy_char(&p, &v_p);
         }
         break;
       }
       default:
         is_unknown = true;
         mb_copy_char(&p, &v_p);
         break;
       }
       if (pstate->colors) {
         kvi_push(shifts, ((StringShift) {
           .start = token.start.col + (size_t)(chunk_e - s),
           .orig_len = (size_t)(p - chunk_e),
           .act_len = (size_t)(v_p - (char *)v_p_start),
           .escape_not_known = is_unknown,
         }));
       }
     }
     node->data.str.size = (size_t)(v_p - node->data.str.value);
   }
 }
 if (pstate->colors) {
   // TODO(ZyX-I): use ast_stack to determine and highlight regular expressions
   // TODO(ZyX-I): use ast_stack to determine and highlight printf format str
   // TODO(ZyX-I): use ast_stack to determine and highlight expression strings
   size_t next_col = token.start.col + 1;
   const char *const body_str = (is_double
                                 ? HL(DoubleQuotedBody)
                                 : HL(SingleQuotedBody));
   const char *const esc_str = (is_double
                                ? HL(DoubleQuotedEscape)
                                : HL(SingleQuotedQuote));
   const char *const ukn_esc_str = (is_double
                                    ? HL(DoubleQuotedUnknownEscape)
                                    : HL(SingleQuotedUnknownEscape));
   for (size_t i = 0; i < kv_size(shifts); i++) {
     const StringShift cur_shift = kv_A(shifts, i);
     if (cur_shift.start > next_col) {
       viml_parser_highlight(pstate, recol_pos(token.start, next_col),
                             cur_shift.start - next_col,
                             body_str);
     }
     viml_parser_highlight(pstate, recol_pos(token.start, cur_shift.start),
                           cur_shift.orig_len,
                           (cur_shift.escape_not_known
                            ? ukn_esc_str
                            : esc_str));
     next_col = cur_shift.start + cur_shift.orig_len;
   }
   if (next_col - token.start.col < token.len - token.data.str.closed) {
     viml_parser_highlight(pstate, recol_pos(token.start, next_col),
                           (token.start.col
                            + token.len
                            - token.data.str.closed
                            - next_col),
                           body_str);
   }
 }
 if (token.data.str.closed) {
   if (is_double) {
     viml_parser_highlight(pstate, shifted_pos(token.start, token.len - 1),
                           1, HL(DoubleQuote));
   } else {
     viml_parser_highlight(pstate, shifted_pos(token.start, token.len - 1),
                           1, HL(SingleQuote));
   }
 }
 kvi_destroy(shifts);
}

/// Additional flags to pass to lexer depending on want_node
static const int want_node_to_lexer_flags[] = {
 [kENodeValue] = kELFlagIsNotCmp,
 [kENodeOperator] = kELFlagForbidScope,
};

/// Number of characters to highlight as NumberPrefix depending on the base
static const uint8_t base_to_prefix_length[] = {
 [2] = 2,
 [8] = 1,
 [10] = 0,
 [16] = 2,
};

/// Parse one Vimscript expression
///
/// @param  pstate  Parser state.
/// @param[in]  flags  Additional flags, see ExprParserFlags
///
/// @return Parsed AST.
ExprAST viml_pexpr_parse(ParserState *const pstate, const int flags)
 FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
{
 ExprAST ast = {
   .err = {
     .msg = NULL,
     .arg_len = 0,
     .arg = NULL,
   },
   .root = NULL,
 };
 // Expression stack contains current branch in AST tree: that is
 // - Stack item 0 contains root of the tree, i.e. &ast->root.
 // - Stack item i points to the previous stack items’ last child.
 //
 // When parser expects “value” node that is something like identifier or "["
 // (list start) last stack item contains NULL. Otherwise last stack item is
 // supposed to contain last “finished” value: e.g. "1" or "+(1, 1)" (node
 // representing "1+1").
 ExprASTStack ast_stack;
 kvi_init(ast_stack);
 kvi_push(ast_stack, &ast.root);
 ExprASTWantedNode want_node = kENodeValue;
 ExprASTParseTypeStack pt_stack;
 kvi_init(pt_stack);
 kvi_push(pt_stack, kEPTExpr);
 if (flags & kExprFlagsParseLet) {
   kvi_push(pt_stack, kEPTAssignment);
 }
 LexExprToken prev_token = { .type = kExprLexMissing };
 bool highlighted_prev_spacing = false;
 // Lambda node, valid when parsing lambda arguments only.
 ExprASTNode *lambda_node = NULL;
 size_t asgn_level = 0;
 do {
   const bool is_concat_or_subscript = (
                                        want_node == kENodeValue
                                        && kv_size(ast_stack) > 1
                                        && (*kv_Z(ast_stack,
                                                  1))->type == kExprNodeConcatOrSubscript);
   const int lexer_additional_flags = (
                                       kELFlagPeek
                                       | ((flags & kExprFlagsDisallowEOC) ? kELFlagForbidEOC : 0)
                                       | ((want_node == kENodeValue
                                           && (kv_size(ast_stack) == 1
                                               || ((*kv_Z(ast_stack, 1))->type != kExprNodeConcat
                                                   && ((*kv_Z(ast_stack, 1))->type
                                                       != kExprNodeConcatOrSubscript))))
                                          ? kELFlagAllowFloat
                                          : 0));
   LexExprToken cur_token = viml_pexpr_next_token(pstate,
                                                  want_node_to_lexer_flags[want_node] |
                                                  lexer_additional_flags);
   if (cur_token.type == kExprLexEOC) {
     break;
   }
   LexExprTokenType tok_type = cur_token.type;
   const bool token_invalid = (tok_type == kExprLexInvalid);
   bool is_invalid = token_invalid;
viml_pexpr_parse_process_token:
   // May use different flags this time.
   cur_token = viml_pexpr_next_token(pstate,
                                     want_node_to_lexer_flags[want_node] | lexer_additional_flags);
   if (tok_type == kExprLexSpacing) {
     if (is_invalid) {
       HL_CUR_TOKEN(Spacing);
     } else {
       // Do not do anything: let regular spacing be highlighted as normal.
       // This also allows later to highlight spacing as invalid.
     }
     goto viml_pexpr_parse_cycle_end;
   } else if (is_invalid && prev_token.type == kExprLexSpacing
              && !highlighted_prev_spacing) {
     viml_parser_highlight(pstate, prev_token.start, prev_token.len,
                           HL(Spacing));
     is_invalid = false;
     highlighted_prev_spacing = true;
   }
   const ParserLine pline = pstate->reader.lines.items[cur_token.start.line];
   ExprASTNode **const top_node_p = kv_last(ast_stack);
   assert(kv_size(ast_stack) >= 1);
   ExprASTNode *cur_node = NULL;
#ifndef NDEBUG
   const bool want_value = (want_node == kENodeValue);
   assert(want_value == (*top_node_p == NULL));
   assert(kv_A(ast_stack, 0) == &ast.root);
   // Check that stack item i + 1 points to stack items’ i *last* child.
   for (size_t i = 0; i + 1 < kv_size(ast_stack); i++) {
     const bool item_null = (want_value && i + 2 == kv_size(ast_stack));
     assert((&(*kv_A(ast_stack, i))->children == kv_A(ast_stack, i + 1)
             && (item_null
                 ? (*kv_A(ast_stack, i))->children == NULL
                 : (*kv_A(ast_stack, i))->children->next == NULL))
            || ((&(*kv_A(ast_stack, i))->children->next
                 == kv_A(ast_stack, i + 1))
                && (item_null
                    ? (*kv_A(ast_stack, i))->children->next == NULL
                    : (*kv_A(ast_stack, i))->children->next->next == NULL)));
   }
#endif
   // Note: in Vim whether expression "cond?d.a:2" is valid depends both on
   // "cond" and whether "d" is a dictionary: expression is valid if condition
   // is true and "d" is a dictionary (with "a" key or it will complain about
   // missing one, but this is not relevant); if any of the requirements is
   // broken then this thing is parsed as "d . a:2" yielding missing colon
   // error. This parser does not allow such ambiguity, especially because it
   // simply can’t: whether "d" is a dictionary is not known at the parsing
   // time.
   //
   // Here example will always contain a concat with "a:2" sucking colon,
   // making expression invalid both because there is no longer a spare colon
   // for ternary and because concatenating dictionary with anything is not
   // valid. There are more cases when this will make a difference though.
   const bool node_is_key = (
                             is_concat_or_subscript
                             && (cur_token.type == kExprLexPlainIdentifier
                                 ? (!cur_token.data.var.autoload
                                    && cur_token.data.var.scope == kExprVarScopeMissing)
                                 : (cur_token.type == kExprLexNumber))
                             && prev_token.type != kExprLexSpacing);
   if (is_concat_or_subscript && !node_is_key) {
     // Note: in Vim "d. a" (this is the reason behind `prev_token.type !=
     // kExprLexSpacing` part of the condition) as well as any other "d.{expr}"
     // where "{expr}" does not look like a key is invalid whenever "d" happens
     // to be a dictionary. Since parser has no idea whether preceding
     // expression is actually a dictionary it can’t outright reject anything,
     // so it turns kExprNodeConcatOrSubscript into kExprNodeConcat instead,
     // which will yield different errors then Vim does in a number of
     // circumstances, and in any case runtime and not parse time errors.
     (*kv_Z(ast_stack, 1))->type = kExprNodeConcat;
   }
   // Pop some stack pt_stack items in case of misplaced nodes.
   const bool is_single_assignment = kv_last(pt_stack) == kEPTSingleAssignment;
   switch (kv_last(pt_stack)) {
   case kEPTExpr:
     break;
   case kEPTLambdaArguments:
     if ((want_node == kENodeOperator
          && tok_type != kExprLexComma
          && tok_type != kExprLexArrow)
         || (want_node == kENodeValue
             && !(cur_token.type == kExprLexPlainIdentifier
                  && cur_token.data.var.scope == kExprVarScopeMissing
                  && !cur_token.data.var.autoload)
             && tok_type != kExprLexArrow)) {
       lambda_node->data.fig.type_guesses.allow_lambda = false;
       if (lambda_node->children != NULL
           && lambda_node->children->type == kExprNodeComma) {
         // If lambda has comma child this means that parser has already seen
         // at least "{arg1,", so node cannot possibly be anything, but
         // lambda.

         // Vim may give E121 or E720 in this case, but it does not look
         // right to have either because both are results of reevaluation
         // possibly-lambda node as a dictionary and here this is not going
         // to happen.
         ERROR_FROM_TOKEN_AND_MSG(cur_token,
                                  _("E15: Expected lambda arguments list or arrow: %.*s"));
       } else {
         // Else it may appear that possibly-lambda node is actually
         // a dictionary or curly-braces-name identifier.
         lambda_node = NULL;
         kv_drop(pt_stack, 1);
       }
     }
     break;
   case kEPTSingleAssignment:
   case kEPTAssignment:
     if (want_node == kENodeValue
         && tok_type != kExprLexBracket
         && tok_type != kExprLexPlainIdentifier
         && (tok_type != kExprLexFigureBrace || cur_token.data.brc.closing)
         && !(node_is_key && tok_type == kExprLexNumber)
         && tok_type != kExprLexEnv
         && tok_type != kExprLexOption
         && tok_type != kExprLexRegister) {
       ERROR_FROM_TOKEN_AND_MSG(cur_token,
                                _("E15: Expected value part of assignment lvalue: %.*s"));
       kv_drop(pt_stack, 1);
     } else if (want_node == kENodeOperator
                && tok_type != kExprLexBracket
                && (tok_type != kExprLexFigureBrace
                    || cur_token.data.brc.closing)
                && tok_type != kExprLexDot
                && (tok_type != kExprLexComma || !is_single_assignment)
                && tok_type != kExprLexAssignment
                // Curly brace identifiers: will contain plain identifier or
                // another curly brace in position where operator is wanted.
                && !((tok_type == kExprLexPlainIdentifier
                      || (tok_type == kExprLexFigureBrace
                          && !cur_token.data.brc.closing))
                     && prev_token.type != kExprLexSpacing)) {
       if (flags & kExprFlagsMulti && MAY_HAVE_NEXT_EXPR) {
         goto viml_pexpr_parse_end;
       }
       ERROR_FROM_TOKEN_AND_MSG(cur_token,
                                _("E15: Expected assignment operator or subscript: %.*s"));
       kv_drop(pt_stack, 1);
     }
     assert(kv_size(pt_stack));
     break;
   }
   assert(kv_size(pt_stack));
   const ExprASTParseType cur_pt = kv_last(pt_stack);
   assert(lambda_node == NULL || cur_pt == kEPTLambdaArguments);
#define SIMPLE_UB_OP(op) \
 case kExprLex##op: { \
     if (want_node == kENodeValue) { \
       /* Value level: assume unary operator. */ \
       NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeUnary##op); \
       *top_node_p = cur_node; \
       kvi_push(ast_stack, &cur_node->children); \
       HL_CUR_TOKEN(Unary##op); \
     } else { \
       NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeBinary##op); \
       ADD_OP_NODE(cur_node); \
       HL_CUR_TOKEN(Binary##op); \
     } \
     want_node = kENodeValue; \
     break; \
 }
   switch (tok_type) {
   case kExprLexMissing:
   case kExprLexSpacing:
   case kExprLexEOC:
     abort();
   case kExprLexInvalid:
     ERROR_FROM_TOKEN(cur_token);
     tok_type = cur_token.data.err.type;
     goto viml_pexpr_parse_process_token;
   case kExprLexRegister: {
     if (want_node == kENodeOperator) {
       // Register in operator position: e.g. @a @a
       OP_MISSING;
     }
     NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeRegister);
     cur_node->data.reg.name = cur_token.data.reg.name;
     *top_node_p = cur_node;
     want_node = kENodeOperator;
     HL_CUR_TOKEN(Register);
     break;
   }
     SIMPLE_UB_OP(Plus)
     SIMPLE_UB_OP(Minus)
#undef SIMPLE_UB_OP
#define SIMPLE_B_OP(op, msg) \
 case kExprLex##op: { \
     ADD_VALUE_IF_MISSING(_("E15: Unexpected " msg ": %.*s")); \
     NEW_NODE_WITH_CUR_POS(cur_node, kExprNode##op); \
     HL_CUR_TOKEN(op); \
     ADD_OP_NODE(cur_node); \
     break; \
 }
     SIMPLE_B_OP(Or, "or operator")
     SIMPLE_B_OP(And, "and operator")
#undef SIMPLE_B_OP
   case kExprLexMultiplication:
     ADD_VALUE_IF_MISSING(_("E15: Unexpected multiplication-like operator: %.*s"));
     switch (cur_token.data.mul.type) {
#define MUL_OP(lex_op_tail, node_op_tail) \
 case kExprLexMul##lex_op_tail: { \
     NEW_NODE_WITH_CUR_POS(cur_node, kExprNode##node_op_tail); \
     HL_CUR_TOKEN(node_op_tail); \
     break; \
 }
     MUL_OP(Mul, Multiplication)
     MUL_OP(Div, Division)
     MUL_OP(Mod, Mod)
#undef MUL_OP
     }
     ADD_OP_NODE(cur_node);
     break;
   case kExprLexOption: {
     if (want_node == kENodeOperator) {
       OP_MISSING;
     }
     NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeOption);
     if (cur_token.type == kExprLexInvalid) {
       assert(cur_token.len == 1
              || (cur_token.len == 3
                  && pline.data[cur_token.start.col + 2] == ':'));
       cur_node->data.opt.ident = (
                                   pline.data + cur_token.start.col + cur_token.len);
       cur_node->data.opt.ident_len = 0;
       cur_node->data.opt.scope = (
                                   cur_token.len == 3
                                   ? (ExprOptScope)pline.data[cur_token.start.col + 1]
                                   : kExprOptScopeUnspecified);
     } else {
       cur_node->data.opt.ident = cur_token.data.opt.name;
       cur_node->data.opt.ident_len = cur_token.data.opt.len;
       cur_node->data.opt.scope = cur_token.data.opt.scope;
     }
     *top_node_p = cur_node;
     want_node = kENodeOperator;
     viml_parser_highlight(pstate, cur_token.start, 1, HL(OptionSigil));
     const size_t scope_shift = (
                                 cur_token.data.opt.scope == kExprOptScopeUnspecified ? 0 : 2);
     if (scope_shift) {
       viml_parser_highlight(pstate, shifted_pos(cur_token.start, 1), 1,
                             HL(OptionScope));
       viml_parser_highlight(pstate, shifted_pos(cur_token.start, 2), 1,
                             HL(OptionScopeDelimiter));
     }
     viml_parser_highlight(pstate, shifted_pos(cur_token.start, scope_shift + 1),
                           cur_token.len - (scope_shift + 1), HL(OptionName));
     break;
   }
   case kExprLexEnv:
     if (want_node == kENodeOperator) {
       OP_MISSING;
     }
     NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeEnvironment);
     cur_node->data.env.ident = pline.data + cur_token.start.col + 1;
     cur_node->data.env.ident_len = cur_token.len - 1;
     if (cur_node->data.env.ident_len == 0) {
       ERROR_FROM_TOKEN_AND_MSG(cur_token,
                                _("E15: Environment variable name missing"));
     }
     *top_node_p = cur_node;
     want_node = kENodeOperator;
     viml_parser_highlight(pstate, cur_token.start, 1, HL(EnvironmentSigil));
     viml_parser_highlight(pstate, shifted_pos(cur_token.start, 1),
                           cur_token.len - 1, HL(EnvironmentName));
     break;
   case kExprLexNot:
     if (want_node == kENodeOperator) {
       OP_MISSING;
     }
     NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeNot);
     *top_node_p = cur_node;
     kvi_push(ast_stack, &cur_node->children);
     HL_CUR_TOKEN(Not);
     break;
   case kExprLexComparison:
     ADD_VALUE_IF_MISSING(_("E15: Expected value, got comparison operator: %.*s"));
     NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeComparison);
     if (cur_token.type == kExprLexInvalid) {
       cur_node->data.cmp.ccs = kCCStrategyUseOption;
       cur_node->data.cmp.type = kExprCmpEqual;
       cur_node->data.cmp.inv = false;
     } else {
       cur_node->data.cmp.ccs = cur_token.data.cmp.ccs;
       cur_node->data.cmp.type = cur_token.data.cmp.type;
       cur_node->data.cmp.inv = cur_token.data.cmp.inv;
     }
     ADD_OP_NODE(cur_node);
     if (cur_token.data.cmp.ccs != kCCStrategyUseOption) {
       viml_parser_highlight(pstate, cur_token.start, cur_token.len - 1,
                             HL(Comparison));
       viml_parser_highlight(pstate, shifted_pos(cur_token.start, cur_token.len - 1), 1,
                             HL(ComparisonModifier));
     } else {
       HL_CUR_TOKEN(Comparison);
     }
     want_node = kENodeValue;
     break;
   case kExprLexComma:
     assert(!(want_node == kENodeValue && cur_pt == kEPTLambdaArguments));
     if (want_node == kENodeValue) {
       // Value level: comma appearing here is not valid.
       // Note: in Vim string(,x) will give E116, this is not the case here.
       ERROR_FROM_TOKEN_AND_MSG(cur_token, _("E15: Expected value, got comma: %.*s"));
       NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeMissing);
       cur_node->len = 0;
       *top_node_p = cur_node;
       want_node = kENodeOperator;
     }
     if (cur_pt == kEPTLambdaArguments) {
       assert(lambda_node != NULL);
       assert(lambda_node->data.fig.type_guesses.allow_lambda);
       SELECT_FIGURE_BRACE_TYPE(lambda_node, Lambda, Lambda);
     }
     if (kv_size(ast_stack) < 2) {
       goto viml_pexpr_parse_invalid_comma;
     }
     for (size_t i = 1; i < kv_size(ast_stack); i++) {
       ExprASTNode *const *const eastnode_p =
         (ExprASTNode *const *)kv_Z(ast_stack, i);
       const ExprASTNodeType eastnode_type = (*eastnode_p)->type;
       const ExprOpLvl eastnode_lvl = node_lvl(**eastnode_p);
       if (eastnode_type == kExprNodeLambda) {
         assert(cur_pt == kEPTLambdaArguments
                && want_node == kENodeOperator);
         break;
       } else if (eastnode_type == kExprNodeDictLiteral
                  || eastnode_type == kExprNodeListLiteral
                  || eastnode_type == kExprNodeCall) {
         break;
       } else if (eastnode_type == kExprNodeComma
                  || eastnode_type == kExprNodeColon
                  || eastnode_lvl > kEOpLvlComma) {
         // Do nothing
       } else {
viml_pexpr_parse_invalid_comma:
         ERROR_FROM_TOKEN_AND_MSG(cur_token,
                                  _("E15: Comma outside of call, lambda or literal: %.*s"));
         break;
       }
       if (i == kv_size(ast_stack) - 1) {
         goto viml_pexpr_parse_invalid_comma;
       }
     }
     NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeComma);
     ADD_OP_NODE(cur_node);
     HL_CUR_TOKEN(Comma);
     break;
#define EXP_VAL_COLON "E15: Expected value, got colon: %.*s"
   case kExprLexColon: {
     bool is_ternary = false;
     if (kv_size(ast_stack) < 2) {
       goto viml_pexpr_parse_invalid_colon;
     }
     bool can_be_ternary = true;
     bool is_subscript = false;
     for (size_t i = 1; i < kv_size(ast_stack); i++) {
       ExprASTNode *const *const eastnode_p =
         (ExprASTNode *const *)kv_Z(ast_stack, i);
       const ExprASTNodeType eastnode_type = (*eastnode_p)->type;
       const ExprOpLvl eastnode_lvl = node_lvl(**eastnode_p);
       STATIC_ASSERT(kEOpLvlTernary > kEOpLvlComma,
                     "Unexpected operator priorities");
       if (can_be_ternary && eastnode_type == kExprNodeTernaryValue
           && !(*eastnode_p)->data.ter.got_colon) {
         kv_drop(ast_stack, i);
         (*eastnode_p)->start = cur_token.start;
         (*eastnode_p)->len = cur_token.len;
         if (prev_token.type == kExprLexSpacing) {
           (*eastnode_p)->start = prev_token.start;
           (*eastnode_p)->len += prev_token.len;
         }
         is_ternary = true;
         (*eastnode_p)->data.ter.got_colon = true;
         ADD_VALUE_IF_MISSING(_(EXP_VAL_COLON));
         assert((*eastnode_p)->children != NULL);
         assert((*eastnode_p)->children->next == NULL);
         kvi_push(ast_stack, &(*eastnode_p)->children->next);
         break;
       } else if (eastnode_type == kExprNodeUnknownFigure) {
         SELECT_FIGURE_BRACE_TYPE(*eastnode_p, DictLiteral, Dict);
         break;
       } else if (eastnode_type == kExprNodeDictLiteral) {
         break;
       } else if (eastnode_type == kExprNodeSubscript) {
         is_subscript = true;
         // can_be_ternary = false;
         assert(!is_ternary);
         break;
       } else if (eastnode_type == kExprNodeColon) {
         goto viml_pexpr_parse_invalid_colon;
       } else if (eastnode_lvl >= kEOpLvlTernaryValue) {
         // Do nothing
       } else if (eastnode_lvl >= kEOpLvlComma) {
         can_be_ternary = false;
       } else {
         goto viml_pexpr_parse_invalid_colon;
       }
       if (i == kv_size(ast_stack) - 1) {
         goto viml_pexpr_parse_invalid_colon;
       }
     }
     if (is_subscript) {
       assert(kv_size(ast_stack) > 1);
       // Colon immediately following subscript start: it is empty subscript
       // part like a[:2].
       if (want_node == kENodeValue
           && (*kv_Z(ast_stack, 1))->type == kExprNodeSubscript) {
         NEW_NODE_WITH_CUR_POS(*top_node_p, kExprNodeMissing);
         (*top_node_p)->len = 0;
         want_node = kENodeOperator;
       } else {
         ADD_VALUE_IF_MISSING(_(EXP_VAL_COLON));
       }
       NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeColon);
       ADD_OP_NODE(cur_node);
       HL_CUR_TOKEN(SubscriptColon);
     } else {
       goto viml_pexpr_parse_valid_colon;
viml_pexpr_parse_invalid_colon:
       ERROR_FROM_TOKEN_AND_MSG(cur_token,
                                _("E15: Colon outside of dictionary or ternary operator: %.*s"));
viml_pexpr_parse_valid_colon:
       ADD_VALUE_IF_MISSING(_(EXP_VAL_COLON));
       if (is_ternary) {
         HL_CUR_TOKEN(TernaryColon);
       } else {
         NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeColon);
         ADD_OP_NODE(cur_node);
         HL_CUR_TOKEN(Colon);
       }
     }
     want_node = kENodeValue;
     break;
   }
#undef EXP_VAL_COLON
   case kExprLexBracket:
     if (cur_token.data.brc.closing) {
       ExprASTNode **new_top_node_p = NULL;
       // Always drop the topmost value:
       //
       // 1. When want_node != kENodeValue topmost item on stack is
       //    a *finished* left operand, which may as well be "[@a]" which
       //    needs not be finished again.
       // 2. Otherwise it is pointing to NULL what nobody wants.
       kv_drop(ast_stack, 1);
       if (!kv_size(ast_stack)) {
         NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeListLiteral);
         cur_node->len = 0;
         if (want_node != kENodeValue) {
           cur_node->children = *top_node_p;
         }
         *top_node_p = cur_node;
         new_top_node_p = top_node_p;
         goto viml_pexpr_parse_bracket_closing_error;
       }
       if (want_node == kENodeValue) {
         // It is OK to want value if
         //
         // 1. It is empty list literal, in which case top node will be
         //    ListLiteral.
         // 2. It is list literal with trailing comma, in which case top node
         //    will be that comma.
         // 3. It is subscript with colon, but without one of the values:
         //    e.g. "a[:]", "a[1:]", top node will be colon in this case.
         if ((*kv_last(ast_stack))->type != kExprNodeListLiteral
             && (*kv_last(ast_stack))->type != kExprNodeComma
             && (*kv_last(ast_stack))->type != kExprNodeColon) {
           ERROR_FROM_TOKEN_AND_MSG(cur_token,
                                    _("E15: Expected value, got closing bracket: %.*s"));
         }
       }
       do {
         new_top_node_p = kv_pop(ast_stack);
       } while (kv_size(ast_stack)
                && (new_top_node_p == NULL
                    || ((*new_top_node_p)->type != kExprNodeListLiteral
                        && (*new_top_node_p)->type != kExprNodeSubscript)));
       ExprASTNode *new_top_node = *new_top_node_p;
       switch (new_top_node->type) {
       case kExprNodeListLiteral:
         if (pt_is_assignment(cur_pt) && new_top_node->children == NULL) {
           ERROR_FROM_TOKEN_AND_MSG(cur_token, _("E475: Unable to assign to empty list: %.*s"));
         }
         HL_CUR_TOKEN(List);
         break;
       case kExprNodeSubscript:
         HL_CUR_TOKEN(SubscriptBracket);
         break;
       default:
viml_pexpr_parse_bracket_closing_error:
         assert(!kv_size(ast_stack));
         ERROR_FROM_TOKEN_AND_MSG(cur_token, _("E15: Unexpected closing figure brace: %.*s"));
         HL_CUR_TOKEN(List);
         break;
       }
       kvi_push(ast_stack, new_top_node_p);
       want_node = kENodeOperator;
       if (kv_size(ast_stack) <= asgn_level) {
         assert(kv_size(ast_stack) == asgn_level);
         asgn_level = 0;
         if (cur_pt == kEPTAssignment) {
           assert(ast.err.msg);
         } else if (cur_pt == kEPTExpr
                    && kv_size(pt_stack) > 1
                    && pt_is_assignment(kv_Z(pt_stack, 1))) {
           kv_drop(pt_stack, 1);
         }
       }
       if (cur_pt == kEPTSingleAssignment && kv_size(ast_stack) == 1) {
         kv_drop(pt_stack, 1);
       }
     } else {
       if (want_node == kENodeValue) {
         // Value means list literal or list assignment.
         NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeListLiteral);
         *top_node_p = cur_node;
         kvi_push(ast_stack, &cur_node->children);
         if (cur_pt == kEPTAssignment) {
           // Additional assignment parse type allows to easily forbid nested
           // lists.
           kvi_push(pt_stack, kEPTSingleAssignment);
         } else if (cur_pt == kEPTSingleAssignment) {
           ERROR_FROM_TOKEN_AND_MSG(cur_token,
                                    _("E475: Nested lists not allowed when assigning: %.*s"));
         }
         HL_CUR_TOKEN(List);
       } else {
         // Operator means subscript, also in assignment. But in assignment
         // subscript may be pretty much any expression, so need to push
         // kEPTExpr.
         if (prev_token.type == kExprLexSpacing) {
           OP_MISSING;
         }
         NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeSubscript);
         ADD_OP_NODE(cur_node);
         HL_CUR_TOKEN(SubscriptBracket);
         if (pt_is_assignment(cur_pt)) {
           assert(want_node == kENodeValue);  // Subtract 1 for NULL at top.
           asgn_level = kv_size(ast_stack) - 1;
           kvi_push(pt_stack, kEPTExpr);
         }
       }
     }
     break;
   case kExprLexFigureBrace:
     if (cur_token.data.brc.closing) {
       ExprASTNode **new_top_node_p = NULL;
       // Always drop the topmost value:
       //
       // 1. When want_node != kENodeValue topmost item on stack is
       //    a *finished* left operand, which may as well be "{@a}" which
       //    needs not be finished again.
       // 2. Otherwise it is pointing to NULL what nobody wants.
       kv_drop(ast_stack, 1);
       if (!kv_size(ast_stack)) {
         NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeUnknownFigure);
         cur_node->data.fig.type_guesses.allow_lambda = false;
         cur_node->data.fig.type_guesses.allow_dict = false;
         cur_node->data.fig.type_guesses.allow_ident = false;
         cur_node->len = 0;
         if (want_node != kENodeValue) {
           cur_node->children = *top_node_p;
         }
         *top_node_p = cur_node;
         new_top_node_p = top_node_p;
         goto viml_pexpr_parse_figure_brace_closing_error;
       }
       if (want_node == kENodeValue) {
         if ((*kv_last(ast_stack))->type != kExprNodeUnknownFigure
             && (*kv_last(ast_stack))->type != kExprNodeComma) {
           // kv_last being UnknownFigure may occur for empty dictionary
           // literal, while Comma is expected in case of non-empty one.
           ERROR_FROM_TOKEN_AND_MSG(cur_token,
                                    _("E15: Expected value, got closing figure brace: %.*s"));
         }
       }
       do {
         new_top_node_p = kv_pop(ast_stack);
       } while (kv_size(ast_stack)
                && (new_top_node_p == NULL
                    || ((*new_top_node_p)->type != kExprNodeUnknownFigure
                        && (*new_top_node_p)->type != kExprNodeDictLiteral
                        && ((*new_top_node_p)->type
                            != kExprNodeCurlyBracesIdentifier)
                        && (*new_top_node_p)->type != kExprNodeLambda)));
       ExprASTNode *new_top_node = *new_top_node_p;
       switch (new_top_node->type) {
       case kExprNodeUnknownFigure:
         if (new_top_node->children == NULL) {
           // No children of curly braces node indicates empty dictionary.
           assert(want_node == kENodeValue);
           assert(new_top_node->data.fig.type_guesses.allow_dict);
           SELECT_FIGURE_BRACE_TYPE(new_top_node, DictLiteral, Dict);
           HL_CUR_TOKEN(Dict);
         } else if (new_top_node->data.fig.type_guesses.allow_ident) {
           SELECT_FIGURE_BRACE_TYPE(new_top_node, CurlyBracesIdentifier,
                                    Curly);
           HL_CUR_TOKEN(Curly);
         } else {
           // If by this time type of the node has not already been
           // guessed, but it definitely is not a curly braces name then
           // it is invalid for sure.
           ERROR_FROM_NODE_AND_MSG(new_top_node,
                                   _("E15: Don't know what figure brace means: %.*s"));
           if (pstate->colors) {
             // Will reset to NvimInvalidFigureBrace.
             kv_A(*pstate->colors,
                  new_top_node->data.fig.opening_hl_idx).group = (
                                                                  HL(FigureBrace));
           }
           HL_CUR_TOKEN(FigureBrace);
         }
         break;
       case kExprNodeDictLiteral:
         HL_CUR_TOKEN(Dict);
         break;
       case kExprNodeCurlyBracesIdentifier:
         HL_CUR_TOKEN(Curly);
         break;
       case kExprNodeLambda:
         HL_CUR_TOKEN(Lambda);
         break;
       default:
viml_pexpr_parse_figure_brace_closing_error:
         assert(!kv_size(ast_stack));
         ERROR_FROM_TOKEN_AND_MSG(cur_token, _("E15: Unexpected closing figure brace: %.*s"));
         HL_CUR_TOKEN(FigureBrace);
         break;
       }
       kvi_push(ast_stack, new_top_node_p);
       want_node = kENodeOperator;
       if (kv_size(ast_stack) <= asgn_level) {
         assert(kv_size(ast_stack) == asgn_level);
         if (cur_pt == kEPTExpr
             && kv_size(pt_stack) > 1
             && pt_is_assignment(kv_Z(pt_stack, 1))) {
           kv_drop(pt_stack, 1);
           asgn_level = 0;
         }
       }
     } else {
       if (want_node == kENodeValue) {
         HL_CUR_TOKEN(FigureBrace);
         // Value: may be any of lambda, dictionary literal and curly braces
         // name.

         // Though if we are in an assignment this may only be a curly braces
         // name.
         if (pt_is_assignment(cur_pt)) {
           NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeCurlyBracesIdentifier);
           cur_node->data.fig.type_guesses.allow_lambda = false;
           cur_node->data.fig.type_guesses.allow_dict = false;
           cur_node->data.fig.type_guesses.allow_ident = true;
           kvi_push(pt_stack, kEPTExpr);
         } else {
           NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeUnknownFigure);
           cur_node->data.fig.type_guesses.allow_lambda = true;
           cur_node->data.fig.type_guesses.allow_dict = true;
           cur_node->data.fig.type_guesses.allow_ident = true;
         }
         if (pstate->colors) {
           cur_node->data.fig.opening_hl_idx = kv_size(*pstate->colors) - 1;
         }
         *top_node_p = cur_node;
         kvi_push(ast_stack, &cur_node->children);
         kvi_push(pt_stack, kEPTLambdaArguments);
         lambda_node = cur_node;
       } else {
         // uncrustify:off
         ADD_IDENT(do {
           NEW_NODE_WITH_CUR_POS(cur_node,
                                 kExprNodeCurlyBracesIdentifier);
           if (pstate->colors) {
             cur_node->data.fig.opening_hl_idx = kv_size(*pstate->colors);
           }
           cur_node->data.fig.type_guesses.allow_lambda = false;
           cur_node->data.fig.type_guesses.allow_dict = false;
           cur_node->data.fig.type_guesses.allow_ident = true;
           kvi_push(ast_stack, &cur_node->children);
           if (pt_is_assignment(cur_pt)) {
             kvi_push(pt_stack, kEPTExpr);
           }
           want_node = kENodeValue;
         } while (0),
                   Curly);
         // uncrustify:on
       }
       if (pt_is_assignment(cur_pt)
           && !pt_is_assignment(kv_last(pt_stack))) {
         assert(want_node == kENodeValue);  // Subtract 1 for NULL at top.
         asgn_level = kv_size(ast_stack) - 1;
       }
     }
     break;
   case kExprLexArrow:
     if (cur_pt == kEPTLambdaArguments) {
       kv_drop(pt_stack, 1);
       assert(kv_size(pt_stack));
       if (want_node == kENodeValue) {
         // Wanting value means trailing comma and NULL at the top of the
         // stack.
         kv_drop(ast_stack, 1);
       }
       assert(kv_size(ast_stack) >= 1);
       while ((*kv_last(ast_stack))->type != kExprNodeLambda
              && (*kv_last(ast_stack))->type != kExprNodeUnknownFigure) {
         kv_drop(ast_stack, 1);
       }
       assert((*kv_last(ast_stack)) == lambda_node);
       SELECT_FIGURE_BRACE_TYPE(lambda_node, Lambda, Lambda);
       NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeArrow);
       if (lambda_node->children == NULL) {
         assert(want_node == kENodeValue);
         lambda_node->children = cur_node;
         kvi_push(ast_stack, &lambda_node->children);
       } else {
         assert(lambda_node->children->next == NULL);
         lambda_node->children->next = cur_node;
         kvi_push(ast_stack, &lambda_node->children->next);
       }
       kvi_push(ast_stack, &cur_node->children);
       lambda_node = NULL;
     } else {
       // Only first branch is valid.
       ADD_VALUE_IF_MISSING(_("E15: Unexpected arrow: %.*s"));
       ERROR_FROM_TOKEN_AND_MSG(cur_token, _("E15: Arrow outside of lambda: %.*s"));
       NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeArrow);
       ADD_OP_NODE(cur_node);
     }
     want_node = kENodeValue;
     HL_CUR_TOKEN(Arrow);
     break;
   case kExprLexPlainIdentifier: {
     const ExprVarScope scope = (cur_token.type == kExprLexInvalid
                                 ? kExprVarScopeMissing
                                 : cur_token.data.var.scope);
     if (want_node == kENodeValue) {
       want_node = kENodeOperator;
       NEW_NODE_WITH_CUR_POS(cur_node,
                             (node_is_key
                              ? kExprNodePlainKey
                              : kExprNodePlainIdentifier));
       cur_node->data.var.scope = scope;
       const size_t scope_shift = (scope == kExprVarScopeMissing ? 0 : 2);
       cur_node->data.var.ident = (pline.data + cur_token.start.col
                                   + scope_shift);
       cur_node->data.var.ident_len = cur_token.len - scope_shift;
       *top_node_p = cur_node;
       if (scope_shift) {
         assert(!node_is_key);
         viml_parser_highlight(pstate, cur_token.start, 1,
                               HL(IdentifierScope));
         viml_parser_highlight(pstate, shifted_pos(cur_token.start, 1), 1,
                               HL(IdentifierScopeDelimiter));
       }
       viml_parser_highlight(pstate, shifted_pos(cur_token.start,
                                                 scope_shift),
                             cur_token.len - scope_shift,
                             (node_is_key
                              ? HL(IdentifierKey)
                              : HL(IdentifierName)));
     } else {
       if (scope == kExprVarScopeMissing) {
         // uncrustify:off
         ADD_IDENT(do {
             NEW_NODE_WITH_CUR_POS(cur_node, kExprNodePlainIdentifier);
             cur_node->data.var.scope = scope;
             cur_node->data.var.ident = pline.data + cur_token.start.col;
             cur_node->data.var.ident_len = cur_token.len;
             want_node = kENodeOperator;
           } while (0),
                   IdentifierName);
         // uncrustify:on
       } else {
         OP_MISSING;
       }
     }
     break;
   }
   case kExprLexNumber:
     if (want_node != kENodeValue) {
       OP_MISSING;
     }
     if (node_is_key) {
       NEW_NODE_WITH_CUR_POS(cur_node, kExprNodePlainKey);
       cur_node->data.var.ident = pline.data + cur_token.start.col;
       cur_node->data.var.ident_len = cur_token.len;
       HL_CUR_TOKEN(IdentifierKey);
     } else if (cur_token.data.num.is_float) {
       NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeFloat);
       cur_node->data.flt.value = cur_token.data.num.val.floating;
       HL_CUR_TOKEN(Float);
     } else {
       NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeInteger);
       cur_node->data.num.value = cur_token.data.num.val.integer;
       const uint8_t prefix_length = base_to_prefix_length[
                                                           cur_token.data.num.base];
       viml_parser_highlight(pstate, cur_token.start, prefix_length,
                             HL(NumberPrefix));
       viml_parser_highlight(pstate, shifted_pos(cur_token.start, prefix_length),
                             cur_token.len - prefix_length, HL(Number));
     }
     want_node = kENodeOperator;
     *top_node_p = cur_node;
     break;
   case kExprLexDot:
     ADD_VALUE_IF_MISSING(_("E15: Unexpected dot: %.*s"));
     if (prev_token.type == kExprLexSpacing) {
       if (cur_pt == kEPTAssignment) {
         ERROR_FROM_TOKEN_AND_MSG(cur_token, _("E15: Cannot concatenate in assignments: %.*s"));
       }
       NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeConcat);
       HL_CUR_TOKEN(Concat);
     } else {
       NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeConcatOrSubscript);
       HL_CUR_TOKEN(ConcatOrSubscript);
     }
     ADD_OP_NODE(cur_node);
     break;
   case kExprLexParenthesis:
     if (cur_token.data.brc.closing) {
       if (want_node == kENodeValue) {
         if (kv_size(ast_stack) > 1) {
           const ExprASTNode *const prev_top_node = *kv_Z(ast_stack, 1);
           if (prev_top_node->type == kExprNodeCall) {
             // Function call without arguments, this is not an error.
             // But further code does not expect NULL nodes.
             kv_drop(ast_stack, 1);
             goto viml_pexpr_parse_no_paren_closing_error;
           }
         }
         ERROR_FROM_TOKEN_AND_MSG(cur_token, _("E15: Expected value, got parenthesis: %.*s"));
         NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeMissing);
         cur_node->len = 0;
         *top_node_p = cur_node;
       } else {
         // Always drop the topmost value: when want_node != kENodeValue
         // topmost item on stack is a *finished* left operand, which may as
         // well be "(@a)" which needs not be finished again.
         kv_drop(ast_stack, 1);
       }
viml_pexpr_parse_no_paren_closing_error: {}
       ExprASTNode **new_top_node_p = NULL;
       while (kv_size(ast_stack)
              && (new_top_node_p == NULL
                  || ((*new_top_node_p)->type != kExprNodeNested
                      && (*new_top_node_p)->type != kExprNodeCall))) {
         new_top_node_p = kv_pop(ast_stack);
       }
       if (new_top_node_p != NULL
           && ((*new_top_node_p)->type == kExprNodeNested
               || (*new_top_node_p)->type == kExprNodeCall)) {
         if ((*new_top_node_p)->type == kExprNodeNested) {
           HL_CUR_TOKEN(NestingParenthesis);
         } else {
           HL_CUR_TOKEN(CallingParenthesis);
         }
       } else {
         // “Always drop the topmost value” branch has got rid of the single
         // value stack had, so there is nothing known to enclose. Correct
         // this.
         if (new_top_node_p == NULL) {
           new_top_node_p = top_node_p;
         }
         ERROR_FROM_TOKEN_AND_MSG(cur_token, _("E15: Unexpected closing parenthesis: %.*s"));
         HL_CUR_TOKEN(NestingParenthesis);
         cur_node = NEW_NODE(kExprNodeNested);
         cur_node->start = cur_token.start;
         cur_node->len = 0;
         // Unexpected closing parenthesis, assume that it was wanted to
         // enclose everything in ().
         cur_node->children = *new_top_node_p;
         *new_top_node_p = cur_node;
         assert(cur_node->next == NULL);
       }
       kvi_push(ast_stack, new_top_node_p);
       want_node = kENodeOperator;
     } else {
       switch (want_node) {
       case kENodeValue:
         NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeNested);
         *top_node_p = cur_node;
         kvi_push(ast_stack, &cur_node->children);
         HL_CUR_TOKEN(NestingParenthesis);
         break;
       case kENodeOperator:
         if (prev_token.type == kExprLexSpacing) {
           // For some reason "function (args)" is a function call, but
           // "(funcref) (args)" is not. As far as I remember this somehow involves
           // compatibility and Bram was commenting that this is
           // intentionally inconsistent and he is not very happy with the
           // situation himself.
           if ((*top_node_p)->type != kExprNodePlainIdentifier
               && (*top_node_p)->type != kExprNodeComplexIdentifier
               && (*top_node_p)->type != kExprNodeCurlyBracesIdentifier) {
             OP_MISSING;
           }
         }
         NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeCall);
         ADD_OP_NODE(cur_node);
         HL_CUR_TOKEN(CallingParenthesis);
         break;
       }
       want_node = kENodeValue;
     }
     break;
   case kExprLexQuestion: {
     ADD_VALUE_IF_MISSING(_("E15: Expected value, got question mark: %.*s"));
     NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeTernary);
     ADD_OP_NODE(cur_node);
     HL_CUR_TOKEN(Ternary);
     ExprASTNode *ter_val_node;
     NEW_NODE_WITH_CUR_POS(ter_val_node, kExprNodeTernaryValue);
     ter_val_node->data.ter.got_colon = false;
     assert(cur_node->children != NULL);
     assert(cur_node->children->next == NULL);
     assert(kv_last(ast_stack) == &cur_node->children->next);
     *kv_last(ast_stack) = ter_val_node;
     kvi_push(ast_stack, &ter_val_node->children);
     break;
   }
   case kExprLexDoubleQuotedString:
   case kExprLexSingleQuotedString: {
     const bool is_double = (tok_type == kExprLexDoubleQuotedString);
     if (!cur_token.data.str.closed) {
       // It is weird, but Vim has two identical errors messages with
       // different error numbers: "E114: Missing quote" and
       // "E115: Missing quote".
       ERROR_FROM_TOKEN_AND_MSG(cur_token, (is_double
                                            ? _("E114: Missing double quote: %.*s")
                                            : _("E115: Missing single quote: %.*s")));
     }
     if (want_node == kENodeOperator) {
       OP_MISSING;
     }
     NEW_NODE_WITH_CUR_POS(cur_node, (is_double
                                      ? kExprNodeDoubleQuotedString
                                      : kExprNodeSingleQuotedString));
     *top_node_p = cur_node;
     parse_quoted_string(pstate, cur_node, cur_token, &ast_stack, is_invalid);
     want_node = kENodeOperator;
     break;
   }
   case kExprLexAssignment:
     if (cur_pt == kEPTAssignment) {
       kv_drop(pt_stack, 1);
     } else if (cur_pt == kEPTSingleAssignment) {
       kv_drop(pt_stack, 2);
       ERROR_FROM_TOKEN_AND_MSG(cur_token,
                                _("E475: Expected closing bracket to end list assignment "
                                  "lvalue: %.*s"));
     } else {
       ERROR_FROM_TOKEN_AND_MSG(cur_token, _("E15: Misplaced assignment: %.*s"));
     }
     assert(kv_size(pt_stack));
     assert(kv_last(pt_stack) == kEPTExpr);
     ADD_VALUE_IF_MISSING(_("E15: Unexpected assignment: %.*s"));
     NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeAssignment);
     cur_node->data.ass.type = cur_token.data.ass.type;
     switch (cur_token.data.ass.type) {
#define HL_ASGN(asgn, hl) \
 case kExprAsgn##asgn: { HL_CUR_TOKEN(hl); break; }
     HL_ASGN(Plain, PlainAssignment)
     HL_ASGN(Add, AssignmentWithAddition)
     HL_ASGN(Subtract, AssignmentWithSubtraction)
     HL_ASGN(Concat, AssignmentWithConcatenation)
#undef HL_ASGN
     }
     ADD_OP_NODE(cur_node);
     break;
   }
viml_pexpr_parse_cycle_end:
   prev_token = cur_token;
   highlighted_prev_spacing = false;
   viml_parser_advance(pstate, cur_token.len);
 } while (true);
viml_pexpr_parse_end:
 assert(kv_size(pt_stack));
 assert(kv_size(ast_stack));
 if (want_node == kENodeValue
     // Blacklist some parse type entries as their presence means better error
     // message in the other branch.
     && kv_last(pt_stack) != kEPTLambdaArguments) {
   east_set_error(pstate, &ast.err, _("E15: Expected value, got EOC: %.*s"),
                  pstate->pos);
 } else if (kv_size(ast_stack) != 1) {
   // Something may be wrong, check whether it really is.

   // Pointer to ast.root must never be dropped, so “!= 1” is expected to be
   // the same as “> 1”.
   assert(kv_size(ast_stack));
   // Topmost stack item must be a *finished* value, so it must not be
   // analyzed. E.g. it may contain an already finished nested expression.
   kv_drop(ast_stack, 1);
   while (ast.err.msg == NULL && kv_size(ast_stack)) {
     const ExprASTNode *const cur_node = (*kv_pop(ast_stack));
     // This should only happen when want_node == kENodeValue.
     assert(cur_node != NULL);
     // TODO(ZyX-I): Rehighlight as invalid?
     switch (cur_node->type) {
     case kExprNodeOpMissing:
     case kExprNodeMissing:
       // Error should’ve been already reported.
       break;
     case kExprNodeCall:
       east_set_error(pstate, &ast.err,
                      _("E116: Missing closing parenthesis for function call: %.*s"),
                      cur_node->start);
       break;
     case kExprNodeNested:
       east_set_error(pstate, &ast.err,
                      _("E110: Missing closing parenthesis for nested expression"
                        ": %.*s"),
                      cur_node->start);
       break;
     case kExprNodeListLiteral:
       // For whatever reason "[1" yields "E696: Missing comma in list" error
       // in Vim while "[1," yields E697.
       east_set_error(pstate, &ast.err,
                      _("E697: Missing end of List ']': %.*s"),
                      cur_node->start);
       break;
     case kExprNodeDictLiteral:
       // Same problem like with list literal with E722 (missing comma) vs
       // E723, but additionally just "{" yields only E15.
       east_set_error(pstate, &ast.err,
                      _("E723: Missing end of Dictionary '}': %.*s"),
                      cur_node->start);
       break;
     case kExprNodeUnknownFigure:
       east_set_error(pstate, &ast.err,
                      _("E15: Missing closing figure brace: %.*s"),
                      cur_node->start);
       break;
     case kExprNodeLambda:
       east_set_error(pstate, &ast.err,
                      _("E15: Missing closing figure brace for lambda: %.*s"),
                      cur_node->start);
       break;
     case kExprNodeCurlyBracesIdentifier:
       // Until trailing "}" it is impossible to distinguish curly braces
       // identifier and Dict, so it must not appear in the stack like this.
       abort();
     case kExprNodeInteger:
     case kExprNodeFloat:
     case kExprNodeSingleQuotedString:
     case kExprNodeDoubleQuotedString:
     case kExprNodeOption:
     case kExprNodeEnvironment:
     case kExprNodeRegister:
     case kExprNodePlainIdentifier:
     case kExprNodePlainKey:
       // These are plain values and not containers, for them it should only
       // be possible to show up in the topmost stack element, but it was
       // unconditionally popped at the start.
       abort();
     case kExprNodeComma:
     case kExprNodeColon:
     case kExprNodeArrow:
       // It is actually only valid inside something else, but everything
       // where one of the above is valid requires to be closed and thus is
       // to be caught later.
       break;
     case kExprNodeSubscript:
     case kExprNodeConcatOrSubscript:
     case kExprNodeComplexIdentifier:
     case kExprNodeAssignment:
     case kExprNodeMod:
     case kExprNodeDivision:
     case kExprNodeMultiplication:
     case kExprNodeNot:
     case kExprNodeAnd:
     case kExprNodeOr:
     case kExprNodeConcat:
     case kExprNodeComparison:
     case kExprNodeUnaryMinus:
     case kExprNodeUnaryPlus:
     case kExprNodeBinaryMinus:
     case kExprNodeTernary:
     case kExprNodeBinaryPlus:
       // It is OK to see these in the stack.
       break;
     case kExprNodeTernaryValue:
       if (!cur_node->data.ter.got_colon) {
         // Actually Vim throws E109 in more cases.
         east_set_error(pstate, &ast.err, _("E109: Missing ':' after '?': %.*s"),
                        cur_node->start);
       }
       break;
     }
   }
 }
 kvi_destroy(ast_stack);
 return ast;
}

#undef NEW_NODE
#undef HL