Replace identifierNotFUNCTION with identifier.

Closes https://github.com/dart-lang/sdk/pull/51675

GitOrigin-RevId: 420ce80ffed652776cc612aaa7209a81df4fe222
Change-Id: I870ffe0d63eb0bbcbfe8f5db6be940c6a470750d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/287667
Reviewed-by: Erik Ernst <eernst@google.com>
Commit-Queue: Erik Ernst <eernst@google.com>

tools/spec_parser/Dart.g

@@ -3,6 +3,8 @@
 // BSD-style license that can be found in the LICENSE file.
 
 // CHANGES:
+// v0.31 Inline `identifierNotFUNCTION` into `identifier`. Replace all
+// other references with `identifier` to match the spec.
 //
 // v0.30 Add support for the class modifiers `sealed`, `final`, `base`,
 // `interface`, and for `mixin class` declarations. Also add support for
@@ -280,7 +282,7 @@ initializedIdentifierList
     ;
 
 functionSignature
-    :    type? identifierNotFUNCTION formalParameterPart
+    :    type? identifier formalParameterPart
     ;
 
 functionBody
@@ -337,7 +339,7 @@ normalFormalParameterNoMetadata
 
 // NB: It is an anomaly that a functionFormalParameter cannot be FINAL.
 functionFormalParameter
-    :    COVARIANT? type? identifierNotFUNCTION formalParameterPart '?'?
+    :    COVARIANT? type? identifier formalParameterPart '?'?
     ;
 
 simpleFormalParameter
@@ -997,18 +999,13 @@ assignableSelector
     |    '?' '[' expression ']'
     ;
 
-identifierNotFUNCTION
+identifier
     :    IDENTIFIER
     |    builtInIdentifier
     |    otherIdentifier
     |    { asyncEtcPredicate(getCurrentToken().getType()) }? (AWAIT|YIELD)
     ;
 
-identifier
-    :    identifierNotFUNCTION
-    |    FUNCTION // Built-in identifier that can be used as a type.
-    ;
-
 qualifiedName
     :    typeIdentifier '.' identifierOrNew
     |    typeIdentifier '.' typeIdentifier '.' identifierOrNew