Fix recovery when parsing complex type variables

This fixes parser recovery when the user has inserted a word before
a method declaration with a complex type arguments, such as

  foo Future<List<int>> bar() {}

Fix dart-lang/sdk#34850

Change-Id: Ic6d1767668bd34d75c6ab5f9973e5762bdd8f160
Reviewed-on: https://dart-review.googlesource.com/c/80780
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Dan Rubel <[email protected]>

pkg/analyzer/test/generated/parser_fasta_test.dart

@@ -927,7 +927,56 @@ class SimpleParserTest_Fasta extends FastaParserTestCase
  */
 @reflectiveTest
 class StatementParserTest_Fasta extends FastaParserTestCase
-    with StatementParserTestMixin {}
+    with StatementParserTestMixin {
+  void test_invalid_typeArg_34850() {
+    var unit = parseCompilationUnit('foo Future<List<int>> bar() {}', errors: [
+      expectedError(ParserErrorCode.EXPECTED_TOKEN, 11, 4),
+      expectedError(ParserErrorCode.MISSING_FUNCTION_PARAMETERS, 4, 6),
+      expectedError(ParserErrorCode.MISSING_FUNCTION_BODY, 22, 3),
+    ]);
+    // Validate that recovery has properly updated the token stream.
+    analyzer.Token token = unit.beginToken;
+    while (!token.isEof) {
+      expect(token.type, isNot(TokenType.GT_GT));
+      analyzer.Token next = token.next;
+      expect(next.previous, token);
+      token = next;
+    }
+  }
+
+  void test_partial_typeArg1_34850() {
+    var unit = parseCompilationUnit('<bar<', errors: [
+      expectedError(ParserErrorCode.EXPECTED_EXECUTABLE, 0, 1),
+      expectedError(ParserErrorCode.MISSING_IDENTIFIER, 5, 0),
+      expectedError(ParserErrorCode.MISSING_FUNCTION_PARAMETERS, 1, 3),
+      expectedError(ParserErrorCode.MISSING_FUNCTION_BODY, 5, 0),
+    ]);
+    // Validate that recovery has properly updated the token stream.
+    analyzer.Token token = unit.beginToken;
+    while (!token.isEof) {
+      expect(token.type, isNot(TokenType.GT_GT));
+      analyzer.Token next = token.next;
+      expect(next.previous, token);
+      token = next;
+    }
+  }
+
+  void test_partial_typeArg2_34850() {
+    var unit = parseCompilationUnit('foo <bar<', errors: [
+      expectedError(ParserErrorCode.EXPECTED_TOKEN, 5, 3),
+      expectedError(ParserErrorCode.MISSING_FUNCTION_PARAMETERS, 0, 3),
+      expectedError(ParserErrorCode.MISSING_FUNCTION_BODY, 9, 0),
+    ]);
+    // Validate that recovery has properly updated the token stream.
+    analyzer.Token token = unit.beginToken;
+    while (!token.isEof) {
+      expect(token.type, isNot(TokenType.GT_GT));
+      analyzer.Token next = token.next;
+      expect(next.previous, token);
+      token = next;
+    }
+  }
+}
 
 /**
  * Tests of the fasta parser based on [TopLevelParserTestMixin].

pkg/analyzer/test/generated/parser_test.dart

@@ -4215,15 +4215,11 @@ class Wrong<T> {
   }
 
   void test_method_invalidTypeParameters() {
-    // TODO(jmesserly): ideally we'd be better at parser recovery here.
-    // It doesn't try to advance past the invalid token `!` to find the
-    // valid `>`. If it did we'd get less cascading errors, at least for this
-    // particular example.
     createParser('void m<E, hello!>() {}');
     ClassMember member = parser.parseClassMember('C');
     expectNotNullIfNoErrors(member);
     listener.assertErrors(usingFastaParser
-        ? [expectedError(ParserErrorCode.UNEXPECTED_TOKEN, 15, 1)]
+        ? [expectedError(ParserErrorCode.EXPECTED_TOKEN, 10, 5)]
         : [
             expectedError(ParserErrorCode.EXPECTED_TOKEN, 0, 0) /*>*/,
             expectedError(ParserErrorCode.MISSING_IDENTIFIER, 0, 0),
@@ -6576,7 +6572,7 @@ abstract class ExpressionParserTestMixin implements AbstractParserTestCase {
   void test_parseFunctionExpression_functionInPlaceOfTypeName() {
     Expression expression = parseExpression('<test(' ', (){});>[0, 1, 2]',
         codes: usingFastaParser
-            ? [ParserErrorCode.UNEXPECTED_TOKEN]
+            ? [ParserErrorCode.EXPECTED_TOKEN]
             : [
                 ParserErrorCode.EXPECTED_TOKEN,
                 ParserErrorCode.MISSING_IDENTIFIER,
@@ -10632,7 +10628,10 @@ Map<Symbol, convertStringToSymbolMap(Map<String, dynamic> map) {
     result[new Symbol(name)] = value;
   });
   return result;
-}''', errors: [expectedError(ParserErrorCode.EXPECTED_TOKEN, 12, 24)]);
+}''', errors: [
+        expectedError(ParserErrorCode.EXPECTED_TOKEN, 12, 24),
+        expectedError(ParserErrorCode.MISSING_FUNCTION_PARAMETERS, 0, 3)
+      ]);
     }
   }
 

pkg/analyzer/test/src/dart/analysis/unlinked_api_signature_test.dart

@@ -758,7 +758,7 @@ foo
 Future<List<int>> bar() {}
 ''', r'''
 foo
-Future<List<int>> bar() async {}
+Future<List<int>> bar(int x) {}
 ''');
   }
 

pkg/analyzer/test/src/fasta/recovery/invalid_code_test.dart

@@ -40,7 +40,7 @@ const default = const Object();
 f() {
   return <g('')>[0, 1, 2];
 }
-''', [ParserErrorCode.UNEXPECTED_TOKEN], '''
+''', [ParserErrorCode.EXPECTED_TOKEN], '''
 f() {
   return <g>[0, 1, 2];
 }
@@ -53,7 +53,7 @@ f() {
 f() {
   return <test('', (){})>[0, 1, 2];
 }
-''', [ParserErrorCode.UNEXPECTED_TOKEN], '''
+''', [ParserErrorCode.EXPECTED_TOKEN], '''
 f() {
   return <test>[0, 1, 2];
 }

pkg/analyzer/test/src/fasta/recovery/paired_tokens_test.dart

@@ -41,15 +41,21 @@ f<T> > () => null;
   void test_typeParameters_funct() {
     testRecovery('''
 f<T extends Function()() => null;
-''', [ParserErrorCode.EXPECTED_TOKEN], '''
+''', [
+      ParserErrorCode.EXPECTED_TOKEN,
+      ParserErrorCode.MISSING_FUNCTION_PARAMETERS
+    ], '''
 f<T extends Function()>() => null;
 ''');
   }
 
   void test_typeParameters_funct2() {
     testRecovery('''
 f<T extends Function<X>()() => null;
-''', [ParserErrorCode.EXPECTED_TOKEN], '''
+''', [
+      ParserErrorCode.EXPECTED_TOKEN,
+      ParserErrorCode.MISSING_FUNCTION_PARAMETERS
+    ], '''
 f<T extends Function<X>()>() => null;
 ''');
   }
@@ -133,15 +139,21 @@ List<int, double> f;
   void test_typeParameters_last() {
     testRecovery('''
 f<T() => null;
-''', [ParserErrorCode.EXPECTED_TOKEN], '''
+''', [
+      ParserErrorCode.EXPECTED_TOKEN,
+      ParserErrorCode.MISSING_FUNCTION_PARAMETERS
+    ], '''
 f<T>() => null;
 ''');
   }
 
   void test_typeParameters_outer_last() {
     testRecovery('''
 f<T extends List<int>() => null;
-''', [ParserErrorCode.EXPECTED_TOKEN], '''
+''', [
+      ParserErrorCode.EXPECTED_TOKEN,
+      ParserErrorCode.MISSING_FUNCTION_PARAMETERS
+    ], '''
 f<T extends List<int>>() => null;
 ''');
   }