Issue 56355. Fix token cycle via 'previous'.

Bug: #56355
Change-Id: I1ee7f837dc8beed9bb2ed1f27c45108345e7cceb
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/392460
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Phil Quitslund <pquitslund@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/analyzer/lib/src/fasta/ast_builder.dart

@@ -3636,17 +3636,24 @@ class AstBuilder extends StackListener {
               var awaitToken = variable.name;
               if (awaitToken.type == Keyword.AWAIT ||
                   awaitToken.type == TokenType.IDENTIFIER) {
+                // We see `x.foo await;`, where `;` is synthetic.
+                // It is followed by `y.bar()`.
+                // Insert a new `;`, and (unfortunately) drop `await;`.
+                type.name2.setNext(semicolon.next!);
+                var semicolon2 = parser.rewriter.insertSyntheticToken(
+                  type.name2,
+                  TokenType.SEMICOLON,
+                );
                 push(
                   ExpressionStatementImpl(
                     expression: PrefixedIdentifierImpl(
                       prefix: SimpleIdentifierImpl(importPrefix.name),
                       period: importPrefix.period,
                       identifier: SimpleIdentifierImpl(type.name2),
                     ),
-                    semicolon: semicolon,
+                    semicolon: semicolon2,
                   ),
                 );
-                parser.rewriter.insertToken(semicolon, awaitToken);
                 return;
               }
             }

pkg/analyzer/test/src/dart/parser/top_level_function_test.dart

@@ -65,7 +65,7 @@ FunctionDeclaration
     // https://github.com/dart-lang/sdk/issues/56355
     var parseResult = parseStringWithErrors(r'''
 void get() {
-  http.Response response = http
+  http.Response response = http2
 }
 ''');
 
@@ -109,25 +109,13 @@ FunctionDeclaration
               identifier: SimpleIdentifier
                 token: T7 Response @20
                   previous: T6 |.|
-                  next: T8 |response|
-            semicolon: T9 ; @45 <synthetic>
-              previousX: T10 http @40
-                previousX: T11 = @38
-                  previous: T8 |response|
-                  next: T10 |http|
-                next: T9 |;|
-              next: T8 |response|
-          ExpressionStatement
-            expression: SimpleIdentifier
-              token: T8 response @29
-                previous: T9 |;|
-                next: T12 |;|
-            semicolon: T12 ; @45 <synthetic>
-              previous: T8 |response|
-              next: T13 |}|
-        rightBracket: T13 } @45
-          previous: T12 |;|
-          next: T14 ||
+                  next: T8 |;|
+            semicolon: T8 ; @46 <synthetic>
+              previous: T7 |Response|
+              next: T9 |}|
+        rightBracket: T9 } @46
+          previous: T8 |;|
+          next: T10 ||
 ''',
     );
   }

pkg/analyzer/test/src/dart/parser/variable_declaration_statement_test.dart

@@ -17,14 +17,14 @@ main() {
 class VariableDeclarationStatementParserTest extends ParserDiagnosticsTest {
   test_recovery_propertyAccess_beforeAwait_hasIdentifier() {
     var parseResult = parseStringWithErrors(r'''
-void f(x) async {
+void f() async {
   x.foo
-  await x.bar();
+  await y.bar();
 }
 ''');
     parseResult.assertErrors([
-      error(ParserErrorCode.ASYNC_KEYWORD_USED_AS_IDENTIFIER, 28, 5),
-      error(ParserErrorCode.EXPECTED_TOKEN, 28, 5),
+      error(ParserErrorCode.ASYNC_KEYWORD_USED_AS_IDENTIFIER, 27, 5),
+      error(ParserErrorCode.EXPECTED_TOKEN, 27, 5),
     ]);
 
     var node = parseResult.findNode.singleBlock;
@@ -41,31 +41,29 @@ Block
           token: foo
       semicolon: ; <synthetic>
     ExpressionStatement
-      expression: AwaitExpression
-        awaitKeyword: await
-        expression: MethodInvocation
-          target: SimpleIdentifier
-            token: x
-          operator: .
-          methodName: SimpleIdentifier
-            token: bar
-          argumentList: ArgumentList
-            leftParenthesis: (
-            rightParenthesis: )
+      expression: MethodInvocation
+        target: SimpleIdentifier
+          token: y
+        operator: .
+        methodName: SimpleIdentifier
+          token: bar
+        argumentList: ArgumentList
+          leftParenthesis: (
+          rightParenthesis: )
       semicolon: ;
   rightBracket: }
 ''');
   }
 
   test_recovery_propertyAccess_beforeAwait_noIdentifier() {
     var parseResult = parseStringWithErrors(r'''
-void f(x) async {
+void f() async {
   x.
-  await x.foo();
+  await y.foo();
 }
 ''');
     parseResult.assertErrors([
-      error(ParserErrorCode.EXPECTED_TOKEN, 31, 1),
+      error(ParserErrorCode.EXPECTED_TOKEN, 30, 1),
     ]);
 
     var node = parseResult.findNode.singleBlock;
@@ -86,7 +84,7 @@ Block
         awaitKeyword: await
         expression: MethodInvocation
           target: SimpleIdentifier
-            token: x
+            token: y
           operator: .
           methodName: SimpleIdentifier
             token: foo
@@ -100,13 +98,13 @@ Block
 
   test_recovery_propertyAccess_beforeIdentifier_hasIdentifier() {
     var parseResult = parseStringWithErrors(r'''
-void f(x) {
+void f() {
   x.foo
   bar();
 }
 ''');
     parseResult.assertErrors([
-      error(ParserErrorCode.EXPECTED_TOKEN, 22, 3),
+      error(ParserErrorCode.EXPECTED_TOKEN, 21, 3),
     ]);
 
     var node = parseResult.findNode.singleBlock;
@@ -123,12 +121,9 @@ Block
           token: foo
       semicolon: ; <synthetic>
     ExpressionStatement
-      expression: MethodInvocation
-        methodName: SimpleIdentifier
-          token: bar
-        argumentList: ArgumentList
-          leftParenthesis: (
-          rightParenthesis: )
+      expression: RecordLiteral
+        leftParenthesis: (
+        rightParenthesis: )
       semicolon: ;
   rightBracket: }
 ''');