keymap: Do not use vim_isIDc in keymap.c

Note: there are three changes to ascii_isident. Reverting first two (in 
find_special_key and first in get_special_key_code) normally fails the new test 
with empty &isident, but reverting the third does not. Hence adding `>` to 
&isident.

Ref vim/vim#2389.

3 files changed, 19 insertions, 9 deletions

diff --git a/src/nvim/ascii.h b/src/nvim/ascii.h
index adde91f9ec..9ccb70764d 100644
--- a/src/nvim/ascii.h
+++ b/src/nvim/ascii.h
@@ -3,6 +3,7 @@
 
 #include <stdbool.h>
 
+#include "nvim/macros.h"
 #include "nvim/func_attr.h"
 #include "nvim/os/os_defs.h"
 
@@ -98,6 +99,10 @@ static inline bool ascii_isxdigit(int)
   REAL_FATTR_CONST
   REAL_FATTR_ALWAYS_INLINE;
 
+static inline bool ascii_isident(int)
+  REAL_FATTR_CONST
+  REAL_FATTR_ALWAYS_INLINE;
+
 static inline bool ascii_isbdigit(int)
   REAL_FATTR_CONST
   REAL_FATTR_ALWAYS_INLINE;
@@ -138,6 +143,14 @@ static inline bool ascii_isxdigit(int c)
          || (c >= 'A' && c <= 'F');
 }
 
+/// Checks if `c` is an “identifier” character
+///
+/// That is, whether it is alphanumeric character or underscore.
+static inline bool ascii_isident(const int c)
+{
+  return ASCII_ISALNUM(c) || c == '_';
+}
+
 /// Checks if `c` is a binary digit, that is, 0-1.
 ///
 /// @see {ascii_isdigit}
diff --git a/src/nvim/keymap.c b/src/nvim/keymap.c
index aca21c20a5..0eb5a41b1e 100644
--- a/src/nvim/keymap.c
+++ b/src/nvim/keymap.c
@@ -567,7 +567,7 @@ int find_special_key(const char_u **srcp, const size_t src_len, int *const modp,
 
   // Find end of modifier list
   last_dash = src;
-  for (bp = src + 1; bp <= end && (*bp == '-' || vim_isIDc(*bp)); bp++) {
+  for (bp = src + 1; bp <= end && (*bp == '-' || ascii_isident(*bp)); bp++) {
     if (*bp == '-') {
       last_dash = bp;
       if (bp + 1 <= end) {
@@ -721,12 +721,12 @@ int get_special_key_code(const char_u *name)
   for (int i = 0; key_names_table[i].name != NULL; i++) {
     const char *const table_name = key_names_table[i].name;
     int j;
-    for (j = 0; vim_isIDc(name[j]) && table_name[j] != NUL; j++) {
+    for (j = 0; ascii_isident(name[j]) && table_name[j] != NUL; j++) {
       if (TOLOWER_ASC(table_name[j]) != TOLOWER_ASC(name[j])) {
         break;
       }
     }
-    if (!vim_isIDc(name[j]) && table_name[j] == NUL) {
+    if (!ascii_isident(name[j]) && table_name[j] == NUL) {
       return key_names_table[i].key;
     }
   }
diff --git a/src/nvim/viml/parser/expressions.c b/src/nvim/viml/parser/expressions.c
index 9773e60bbd..cfcde6bb38 100644
--- a/src/nvim/viml/parser/expressions.c
+++ b/src/nvim/viml/parser/expressions.c
@@ -386,13 +386,11 @@ LexExprToken viml_pexpr_next_token(ParserState *const pstate, const int flags)
     }
 
 #define ISWORD_OR_AUTOLOAD(x) \
-      (ASCII_ISALNUM(x) || (x) == AUTOLOAD_CHAR || (x) == '_')
-#define ISWORD(x) \
-      (ASCII_ISALNUM(x) || (x) == '_')
+      (ascii_isident(x) || (x) == AUTOLOAD_CHAR)
 
     // Environment variable.
     case '$': {
-      CHARREG(kExprLexEnv, ISWORD);
+      CHARREG(kExprLexEnv, ascii_isident);
       break;
     }
 
@@ -408,7 +406,7 @@ LexExprToken viml_pexpr_next_token(ParserState *const pstate, const int flags)
     case '_': {
       ret.data.var.scope = 0;
       ret.data.var.autoload = false;
-      CHARREG(kExprLexPlainIdentifier, ISWORD);
+      CHARREG(kExprLexPlainIdentifier, ascii_isident);
       // "is" and "isnot" operators.
       if (!(flags & kELFlagIsNotCmp)
           && ((ret.len == 2 && memcmp(pline.data, "is", 2) == 0)
@@ -445,7 +443,6 @@ LexExprToken viml_pexpr_next_token(ParserState *const pstate, const int flags)
       break;
     }
 
-#undef ISWORD
 #undef ISWORD_OR_AUTOLOAD
 #undef CHARREG