Renewed tests from built_in_identifier_prefix

The test language_2/built_in_identifier_prefix_test stated 'it is not
illegal to use a built-in identifier as a library prefix', which has
been untrue for quite a while, and then proceeded to check a number of
cases where said situation was used in practice. All of that is now
obsolete, so that test was split into several tests, each of which was
adjusted to test something which is relevant today.

The new tests include checks for the use of "known" identifiers (such
as `of`, `show`, `on` and a few more) which are mentioned explicitly
in the grammar, but which are neither built-in identifiers nor
reserved words.

The new tests gave rise to a number of status entries, including 25
crashes (so it is not just "expect `MissingCompileTimeError` here
because it's not strong mode").

Note that `Function` is considered to be a built-in identifier.
This makes no difference for the grammar, but it means that there
are no cases where `Function` is used as a library prefix.

If we insist that `Function` cannot be a built-in identifier then
we just need to add a few more grammar rules to all such things as
`import .. as Function;`, but I considered it less confusing to
include `Function` among the built-in identifiers and avoid adding
support for this.

Note that we haven't said anywhere that `Function` is a built-in
identifier, so we would need to adjust an informal/*.md file to say
that, to finish this off.

Change-Id: Ifa5bbd95022498480b7ee2e94605f81cd11d9696
Reviewed-on: https://dart-review.googlesource.com/21080
Reviewed-by: Lasse R.H. Nielsen <lrn@google.com>
Commit-Queue: Erik Ernst <eernst@google.com>

docs/language/Dart.g

@@ -189,7 +189,7 @@ topLevelDefinition
          EXTERNAL setterSignature ';'
     |    (getterSignature functionBodyPrefix) => getterSignature functionBody
     |    (type? SET identifier '(') => setterSignature functionBody
-    |    (type? identifierNotFunction typeParameters? '(') =>
+    |    (type? identifierNotFUNCTION typeParameters? '(') =>
          functionSignature functionBody
     |    (FINAL | CONST) type? staticFinalDeclarationList ';'
     |    topLevelVariableDeclaration ';'
@@ -223,7 +223,7 @@ initializedIdentifierList
     ;
 
 functionSignature
-    :    type? identifierNotFunction formalParameterPart
+    :    type? identifierNotFUNCTION formalParameterPart
     ;
 
 functionBodyPrefix
@@ -276,7 +276,7 @@ normalFormalParameter
     ;
 
 normalFormalParameterNoMetadata
-    :    (COVARIANT? type? identifierNotFunction formalParameterPart) =>
+    :    (COVARIANT? type? identifierNotFUNCTION formalParameterPart) =>
          functionFormalParameter
     |    (finalConstVarOrType? THIS) => fieldFormalParameter
     |    simpleFormalParameter
@@ -284,7 +284,7 @@ normalFormalParameterNoMetadata
 
 // NB: It is an anomaly that a functionFormalParameter cannot be FINAL.
 functionFormalParameter
-    :    COVARIANT? type? identifierNotFunction formalParameterPart
+    :    COVARIANT? type? identifierNotFUNCTION formalParameterPart
     ;
 
 simpleFormalParameter
@@ -329,7 +329,7 @@ classMemberDefinition
 methodSignature
     :    (constructorSignature ':') => constructorSignature initializers
     |    (FACTORY constructorName '(') => factoryConstructorSignature
-    |    (STATIC? type? identifierNotFunction typeParameters? '(') =>
+    |    (STATIC? type? identifierNotFUNCTION typeParameters? '(') =>
          STATIC? functionSignature
     |    (STATIC? type? GET) => STATIC? getterSignature
     |    (STATIC? type? SET) => STATIC? setterSignature
@@ -854,25 +854,25 @@ assignableSelector
     |    '?.' identifier
     ;
 
-identifierNotFunction
+identifierNotFUNCTION
     :    IDENTIFIER
-    |    ABSTRACT
-    |    AS
-    |    COVARIANT
-    |    DEFERRED
-    |    DYNAMIC
-    |    EXPORT
-    |    EXTERNAL
-    |    FACTORY
-    |    GET
-    |    IMPLEMENTS
-    |    IMPORT
-    |    LIBRARY
-    |    OPERATOR
-    |    PART
-    |    SET
-    |    STATIC
-    |    TYPEDEF
+    |    ABSTRACT // Built-in identifier.
+    |    AS // Built-in identifier.
+    |    COVARIANT // Built-in identifier.
+    |    DEFERRED // Built-in identifier.
+    |    DYNAMIC // Built-in identifier.
+    |    EXPORT // Built-in identifier.
+    |    EXTERNAL // Built-in identifier.
+    |    FACTORY // Built-in identifier.
+    |    GET // Built-in identifier.
+    |    IMPLEMENTS // Built-in identifier.
+    |    IMPORT // Built-in identifier.
+    |    LIBRARY // Built-in identifier.
+    |    OPERATOR // Built-in identifier.
+    |    PART // Built-in identifier.
+    |    SET // Built-in identifier.
+    |    STATIC // Built-in identifier.
+    |    TYPEDEF // Built-in identifier.
     |    HIDE // Not a built-in identifier.
     |    OF // Not a built-in identifier.
     |    ON // Not a built-in identifier.
@@ -882,8 +882,8 @@ identifierNotFunction
     ;
 
 identifier
-    :    identifierNotFunction
-    |    FUNCTION // Not a built-in identifier.
+    :    identifierNotFUNCTION
+    |    FUNCTION // Built-in identifier that can be used as a type.
     ;
 
 qualified
@@ -894,7 +894,7 @@ qualified
 
 typeIdentifier
     :    IDENTIFIER
-    |    DYNAMIC // The only built-in identifier that can be used as a type.
+    |    DYNAMIC // Built-in identifier that can be used as a type.
     |    HIDE // Not a built-in identifier.
     |    OF // Not a built-in identifier.
     |    ON // Not a built-in identifier.