A special state to track field selection is not necessary.

src/compiler/glslang.l

@@ -64,7 +64,6 @@ static int floatsuffix_check(TParseContext* context);
 %option noyywrap nounput never-interactive
 %option yylineno reentrant bison-bridge
 %option extra-type="TParseContext*"
-%x FIELDS
 
 D           [0-9]
 L           [a-zA-Z_]
@@ -342,7 +341,7 @@ O           [0-7]
 ")"             { return RIGHT_PAREN; }
 ("["|"<:")      { return LEFT_BRACKET; }
 ("]"|":>")      { return RIGHT_BRACKET; }
-"."             { BEGIN(FIELDS);  return DOT; }
+"."             { return DOT; }
 "!"             { return BANG; }
 "-"             { return DASH; }
 "~"             { return TILDE; }
@@ -357,16 +356,9 @@ O           [0-7]
 "&"             { return AMPERSAND; }
 "?"             { return QUESTION; }
 
-<FIELDS>{L}({L}|{D})* { 
-    BEGIN(INITIAL);
-    yylval->lex.string = NewPoolTString(yytext); 
-    return FIELD_SELECTION;
-}
-<FIELDS>[ \t\v\f\r] {}
-
 [ \t\v\n\f\r] { }
-<*><<EOF>>    { yyterminate(); }
-<*>.          { assert(false); return 0; }
+<<EOF>>       { yyterminate(); }
+.             { assert(false); return 0; }
 
 %%
 

src/compiler/glslang.y

@@ -268,7 +268,7 @@ postfix_expression
     | function_call {
         $$ = $1;
     }
-    | postfix_expression DOT FIELD_SELECTION {
+    | postfix_expression DOT identifier {
         $$ = context->addFieldSelectionExpression($1, $2.line, *$3.string, $3.line);
     }
     | postfix_expression INC_OP {
@@ -468,13 +468,6 @@ function_identifier
         TFunction *function = new TFunction($1.string, type);
         $$ = function;
     }
-    | FIELD_SELECTION {
-        if (context->reservedErrorCheck($1.line, *$1.string))
-            context->recover();
-        TType type(EbtVoid, EbpUndefined);
-        TFunction *function = new TFunction($1.string, type);
-        $$ = function;
-    }
     ;
 
 unary_expression