[scanner] Fix infinite loop in error recovery

Fixes #60785

Change-Id: Ida0750115e7582ca44b2a49419ed7ab56295caf6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/433701
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Jens Johansen <[email protected]>

Author: jensjoha

pkg/_fe_analyzer_shared/lib/src/scanner/abstract_scanner.dart

@@ -439,7 +439,12 @@ abstract class AbstractScanner implements Scanner {
       if (previous.isA(TokenType.CLOSE_PAREN)) {
         Token closeParen = token.previous!;
         Token? candidate = closeParen.previous;
-        while (candidate != null && candidate.endGroup != closeParen) {
+        while (candidate != null) {
+          if (candidate.endGroup == closeParen) break;
+          if (candidate.isEof) break;
+          if (candidate.endGroup != null) {
+            if (candidate.endGroup!.offset > closeParen.offset) break;
+          }
           candidate = candidate.previous;
         }
         if (candidate?.endGroup == closeParen && candidate!.previous != null) {

pkg/front_end/parser_testcases/general/issue_60785.crash_dart

@@ -0,0 +1,8 @@
+void foo(String s) {
+  switch (s) {
+    case 'foo') {
+    print('foo');
+  } else {
+    print('bar');
+  }
+}

pkg/front_end/parser_testcases/general/issue_60785.crash_dart.expect

@@ -0,0 +1,114 @@
+Problems reported:
+
+parser/general/issue_60785.crash:3:15: Expected ':' before this.
+    case 'foo') {
+              ^
+
+parser/general/issue_60785.crash:3:15: Expected an identifier, but got ')'.
+    case 'foo') {
+              ^
+
+parser/general/issue_60785.crash:3:10: Expected ';' after this.
+    case 'foo') {
+         ^^^^^
+
+parser/general/issue_60785.crash:3:15: Unexpected token ')'.
+    case 'foo') {
+              ^
+
+parser/general/issue_60785.crash:5:5: Expected an identifier, but got 'else'.
+  } else {
+    ^^^^
+
+parser/general/issue_60785.crash:5:3: Expected ';' after this.
+  } else {
+  ^
+
+parser/general/issue_60785.crash:5:5: Unexpected token 'else'.
+  } else {
+    ^^^^
+
+parser/general/issue_60785.crash:2:14: Can't find '}' to match '{'.
+  switch (s) {
+             ^
+
+beginCompilationUnit(void)
+  beginMetadataStar(void)
+  endMetadataStar(0)
+  beginTopLevelMember(void)
+    beginTopLevelMethod(UnmatchedToken({), null, null)
+      handleVoidKeyword(void)
+      handleIdentifier(foo, topLevelFunctionDeclaration)
+      handleNoTypeVariables(()
+      beginFormalParameters((, MemberKind.TopLevelMethod)
+        beginMetadataStar(String)
+        endMetadataStar(0)
+        beginFormalParameter(String, MemberKind.TopLevelMethod, null, null, null)
+          handleIdentifier(String, typeReference)
+          handleNoTypeArguments(s)
+          handleType(String, null)
+          handleIdentifier(s, formalParameterDeclaration)
+          handleFormalParameterWithoutValue())
+        endFormalParameter(null, null, null, s, null, null, FormalParameterKind.requiredPositional, MemberKind.TopLevelMethod)
+      endFormalParameters(1, (, ), MemberKind.TopLevelMethod)
+      handleAsyncModifier(null, null)
+      beginBlockFunctionBody({)
+        beginSwitchStatement(switch)
+          handleIdentifier(s, expression)
+          handleNoTypeArguments())
+          handleNoArguments())
+          handleSend(s, s)
+          handleParenthesizedCondition((, null, null)
+          beginSwitchBlock({)
+            beginCaseExpression(case)
+              beginLiteralString('foo')
+              endLiteralString(0, ))
+              handleSwitchCaseNoWhenClause('foo')
+              handleRecoverableError(Message[ExpectedButGot, Expected ':' before this., null, {string: :}], ), ))
+            endCaseExpression(case, null, :)
+            beginSwitchCase(0, 1, case)
+              handleRecoverableError(Message[ExpectedIdentifier, Expected an identifier, but got ')'., Try inserting an identifier before ')'., {lexeme: )}], ), ))
+              handleIdentifier(, expression)
+              handleNoTypeArguments())
+              handleNoArguments())
+              handleSend(, )
+              handleRecoverableError(Message[ExpectedAfterButGot, Expected ';' after this., null, {string: ;}], 'foo', 'foo')
+              handleExpressionStatement(), ;)
+              handleRecoverableError(Message[UnexpectedToken, Unexpected token ')'., null, {lexeme: )}], ), ))
+              beginBlock({, BlockKind(statement))
+                handleIdentifier(print, expression)
+                handleNoTypeArguments(()
+                beginArguments(()
+                  beginLiteralString('foo')
+                  endLiteralString(0, ))
+                endArguments(1, (, ))
+                handleSend(print, ))
+                handleExpressionStatement(print, ;)
+              endBlock(1, {, }, BlockKind(statement))
+              handleRecoverableError(Message[ExpectedIdentifier, Expected an identifier, but got 'else'., Try inserting an identifier before 'else'., {lexeme: else}], else, else)
+              handleIdentifier(, expression)
+              handleNoTypeArguments(else)
+              handleNoArguments(else)
+              handleSend(, )
+              handleRecoverableError(Message[ExpectedAfterButGot, Expected ';' after this., null, {string: ;}], }, })
+              handleExpressionStatement(else, ;)
+              handleRecoverableError(Message[UnexpectedToken, Unexpected token 'else'., null, {lexeme: else}], else, else)
+              beginBlock({, BlockKind(statement))
+                handleIdentifier(print, expression)
+                handleNoTypeArguments(()
+                beginArguments(()
+                  beginLiteralString('bar')
+                  endLiteralString(0, ))
+                endArguments(1, (, ))
+                handleSend(print, ))
+                handleExpressionStatement(print, ;)
+              endBlock(1, {, }, BlockKind(statement))
+            endSwitchCase(0, 1, null, null, 4, case, })
+          endSwitchBlock(1, {, })
+        endSwitchStatement(switch, })
+      endBlockFunctionBody(1, {, })
+    endTopLevelMethod(void, null, })
+  endTopLevelDeclaration(})
+  handleErrorToken(UnmatchedToken({))
+  handleRecoverableError(Message[UnmatchedToken, Can't find '}' to match '{'., null, {string: }, lexeme: {}], UnmatchedToken({), UnmatchedToken({))
+endCompilationUnit(1, )