Support `void` as generic argument.

pkg/front_end/lib/src/fasta/parser/parser.dart

Index: pkg/front_end/lib/src/fasta/parser/parser.dart
diff --git a/pkg/front_end/lib/src/fasta/parser/parser.dart b/pkg/front_end/lib/src/fasta/parser/parser.dart
index ce6741a54c27894336570acc8b8999bfa5f3b6d1..5b3c27de3bd4ac410a8c63304c375c11a027fa1c 100644
--- a/pkg/front_end/lib/src/fasta/parser/parser.dart
+++ b/pkg/front_end/lib/src/fasta/parser/parser.dart
@@ -401,7 +401,7 @@ class Parser {
       token = expect('=', token);
       token = parseType(token);
     } else {
-      token = parseReturnTypeOpt(token.next);
+      token = parseTypeOpt(token.next);
       token = parseIdentifier(token, IdentifierContext.typedefDeclaration);
       token = parseTypeVariablesOpt(token);
       token = parseFormalParameters(token);
@@ -419,19 +419,6 @@ class Parser {
     return token;
   }
 
-  Token parseReturnTypeOpt(Token token) {
-    if (identical(token.stringValue, 'void')) {
-      if (isGeneralizedFunctionType(token.next)) {
-        return parseType(token);
-      } else {
-        listener.handleVoidKeyword(token);
-        return token.next;
-      }
-    } else {
-      return parseTypeOpt(token);
-    }
-  }
-
   Token parseFormalParametersOpt(Token token) {
     if (optional('(', token)) {
       return parseFormalParameters(token);
@@ -522,7 +509,7 @@ class Parser {
         listener.handleNoName(token);
       }
     } else {
-      token = parseReturnTypeOpt(token);
+      token = parseTypeOpt(token);
       if (optional('this', token)) {
         thisKeyword = token;
         token = expect('.', token.next);
@@ -937,10 +924,6 @@ class Parser {
       // Push the non-existing return type first. The loop below will
       // generate the full type.
       listener.handleNoType(token);
-    } else if (identical(token.stringValue, 'void') &&
-        isGeneralizedFunctionType(token.next)) {
-      listener.handleVoidKeyword(token);
-      token = token.next;
     } else {
       if (isValidTypeReference(token)) {
         token = parseIdentifier(token, IdentifierContext.typeReference);
@@ -1198,13 +1181,6 @@ class Parser {
 
     if (!hasType) {
       listener.handleNoType(name);
-    } else if (optional('void', type) &&
-        !isGeneralizedFunctionType(type.next)) {
-      listener.handleNoType(name);
-      // TODO(ahe): This error is reported twice, second time is from
-      // [parseVariablesDeclarationMaybeSemicolon] via
-      // [PartialFieldListElement.parseNode].
-      reportRecoverableError(type, ErrorKind.InvalidVoid);
     } else {
       parseType(type);
       if (isVar) {
@@ -1259,7 +1235,7 @@ class Parser {
     if (type == null) {
       listener.handleNoType(name);
     } else {
-      parseReturnTypeOpt(type);
+      parseTypeOpt(type);
     }
     Token token =
         parseIdentifier(name, IdentifierContext.topLevelFunctionDeclaration);
@@ -1603,7 +1579,7 @@ class Parser {
    * If [token] is not the start of a type, null is returned.
    */
   Token peekAfterIfType(Token token) {
-    if (!optional('void', token) && !token.isIdentifier()) {
+    if (!token.isIdentifier()) {
       return null;
     }
     return peekAfterType(token);
@@ -1789,7 +1765,7 @@ class Parser {
     if (type == null) {
       listener.handleNoType(name);
     } else {
-      parseReturnTypeOpt(type);
+      parseTypeOpt(type);
     }
     Token token;
     if (optional('operator', name)) {
@@ -1885,7 +1861,7 @@ class Parser {
       token = parseOperatorName(token);
     } else {
       // <type>? <get>? <name>
-      token = parseReturnTypeOpt(token);
+      token = parseTypeOpt(token);
       if (identical(getOrSet, token)) {
         token = token.next;
       }
@@ -1937,7 +1913,7 @@ class Parser {
   Token parseFunctionExpression(Token token) {
     listener.beginFunction(token);
     listener.handleModifiers(0);
-    token = parseReturnTypeOpt(token);
+    token = parseTypeOpt(token);
     listener.beginFunctionName(token);
     token = parseIdentifier(token, IdentifierContext.functionExpressionName);
     listener.endFunctionName(token);
@@ -2143,8 +2119,6 @@ class Parser {
     } else if (identical(value, 'throw') && optional(';', token.next)) {
       // TODO(kasperl): Stop dealing with throw here.
       return parseRethrowStatement(token);
-    } else if (identical(value, 'void')) {
-      return parseExpressionStatementOrDeclaration(token);
     } else if (identical(value, 'while')) {
       return parseWhileStatement(token);
     } else if (identical(value, 'do')) {
@@ -2225,7 +2199,7 @@ class Parser {
   }
 
   Token parseExpressionStatementOrDeclaration(Token token) {
-    assert(token.isIdentifier() || identical(token.stringValue, 'void'));
+    assert(token.isIdentifier());
     Token identifier = peekIdentifierAfterType(token);
     if (identifier != null) {
       assert(identifier.isIdentifier());
@@ -2639,8 +2613,6 @@ class Parser {
         return parseNewExpression(token);
       } else if (value == 'const') {
         return parseConstExpression(token);
-      } else if (value == 'void') {
-        return parseFunctionExpression(token);
       } else if (asyncAwaitKeywordsEnabled &&
           (value == 'yield' || value == 'async')) {
         return expressionExpected(token);