From 202b07570d025e710034f47d55e142e68e254bbf Mon Sep 17 00:00:00 2001
From: Konstantin Shcheglov <scheglov@google.com>
Date: Mon, 15 May 2023 20:50:06 +0000
Subject: [PATCH] [stable] It is not an error to use a void typed expression in
 SwitchExpressionCase.

Bug: https://github.com/dart-lang/sdk/issues/52191
Change-Id: I2cea3260ad63a0c59399f02dadb99bb09a944623
Cherry-pick: https://dart-review.googlesource.com/c/sdk/+/299200
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/302880
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Samuel Rawlins <srawlins@google.com>
---
 .../lib/src/generated/error_verifier.dart     |  6 ++
 .../resolution/switch_expression_test.dart    | 93 +++++++++++++++++++
 2 files changed, 99 insertions(+)

diff --git a/pkg/analyzer/lib/src/generated/error_verifier.dart b/pkg/analyzer/lib/src/generated/error_verifier.dart
index 98ef3cb18735..3eaf49c865a0 100644
--- a/pkg/analyzer/lib/src/generated/error_verifier.dart
+++ b/pkg/analyzer/lib/src/generated/error_verifier.dart
@@ -1252,6 +1252,12 @@ class ErrorVerifier extends RecursiveAstVisitor<void>
     });
   }
 
+  @override
+  void visitSwitchExpression(SwitchExpression node) {
+    checkForUseOfVoidResult(node.expression);
+    super.visitSwitchExpression(node);
+  }
+
   @override
   void visitSwitchPatternCase(SwitchPatternCase node) {
     _withHiddenElements(node.statements, () {
diff --git a/pkg/analyzer/test/src/dart/resolution/switch_expression_test.dart b/pkg/analyzer/test/src/dart/resolution/switch_expression_test.dart
index c09eeb11752f..43a603905d37 100644
--- a/pkg/analyzer/test/src/dart/resolution/switch_expression_test.dart
+++ b/pkg/analyzer/test/src/dart/resolution/switch_expression_test.dart
@@ -15,6 +15,62 @@ main() {
 
 @reflectiveTest
 class SwitchExpressionResolutionTest extends PubPackageResolutionTest {
+  test_case_expression_void() async {
+    await assertNoErrorsInCode(r'''
+void f(Object? x) {
+  (switch(x) {
+    0 => 0,
+    _ => g(),
+  });
+}
+
+void g() {}
+''');
+
+    final node = findNode.singleSwitchExpression;
+    assertResolvedNodeText(node, r'''
+SwitchExpression
+  switchKeyword: switch
+  leftParenthesis: (
+  expression: SimpleIdentifier
+    token: x
+    staticElement: self::@function::f::@parameter::x
+    staticType: Object?
+  rightParenthesis: )
+  leftBracket: {
+  cases
+    SwitchExpressionCase
+      guardedPattern: GuardedPattern
+        pattern: ConstantPattern
+          expression: IntegerLiteral
+            literal: 0
+            staticType: int
+          matchedValueType: Object?
+      arrow: =>
+      expression: IntegerLiteral
+        literal: 0
+        staticType: int
+    SwitchExpressionCase
+      guardedPattern: GuardedPattern
+        pattern: WildcardPattern
+          name: _
+          matchedValueType: Object?
+      arrow: =>
+      expression: MethodInvocation
+        methodName: SimpleIdentifier
+          token: g
+          staticElement: self::@function::g
+          staticType: void Function()
+        argumentList: ArgumentList
+          leftParenthesis: (
+          rightParenthesis: )
+        staticInvokeType: void Function()
+        staticType: void
+  rightBracket: }
+  staticType: void
+''');
+  }
+
   test_cases_empty() async {
     await assertErrorsInCode(r'''
 final a = switch (0) {};
@@ -85,6 +141,43 @@ SwitchExpression
 ''');
   }
 
+  test_expression_void() async {
+    await assertErrorsInCode('''
+void f(void x) {
+  (switch(x) {
+    _ => 0,
+  });
+}
+''', [
+      error(CompileTimeErrorCode.USE_OF_VOID_RESULT, 27, 1),
+    ]);
+
+    final node = findNode.singleSwitchExpression;
+    assertResolvedNodeText(node, r'''
+SwitchExpression
+  switchKeyword: switch
+  leftParenthesis: (
+  expression: SimpleIdentifier
+    token: x
+    staticElement: self::@function::f::@parameter::x
+    staticType: void
+  rightParenthesis: )
+  leftBracket: {
+  cases
+    SwitchExpressionCase
+      guardedPattern: GuardedPattern
+        pattern: WildcardPattern
+          name: _
+          matchedValueType: void
+      arrow: =>
+      expression: IntegerLiteral
+        literal: 0
+        staticType: int
+  rightBracket: }
+  staticType: int
+''');
+  }
+
   test_location_topLevel() async {
     await assertNoErrorsInCode(r'''
 num a = 0;