support converting to switch expressions when cases have no breaks

Fixes: #51826

(Note: a pass to refactor some shared logic to follow.)

Change-Id: If82854f0d5fa5f6596308a04248bd6f4e7231a0d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/290661
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Phil Quitslund <[email protected]>

Author: pq

pkg/analysis_server/lib/src/services/correction/dart/convert_to_switch_expression.dart

@@ -205,15 +205,15 @@ class ConvertToSwitchExpression extends CorrectionProducer {
       if (member is! SwitchPatternCase) return false;
       if (member.labels.isNotEmpty) return false;
       var statements = member.statements;
-
-      if (statements.length == 1 &&
-          statements.first.isThrowExpressionStatement) {
-        continue;
+      if (statements.length == 1) {
+        if (statements.first.isThrowExpressionStatement) continue;
+      } else if (statements.length == 2) {
+        if (statements[1] is! BreakStatement) return false;
+      } else {
+        return false;
       }
 
-      if (statements.length != 2) return false;
-      if (statements[1] is! BreakStatement) return false;
-      var s = statements[0];
+      var s = statements.first;
       if (s is! ExpressionStatement) return false;
       var expression = s.expression;
       if (expression is! MethodInvocation) return false;
@@ -234,15 +234,15 @@ class ConvertToSwitchExpression extends CorrectionProducer {
       if (member is! SwitchPatternCase) return false;
       if (member.labels.isNotEmpty) return false;
       var statements = member.statements;
-
-      if (statements.length == 1 &&
-          statements.first.isThrowExpressionStatement) {
-        continue;
+      if (statements.length == 1) {
+        if (statements.first.isThrowExpressionStatement) continue;
+      } else if (statements.length == 2) {
+        if (statements[1] is! BreakStatement) return false;
+      } else {
+        return false;
       }
 
-      if (statements.length != 2) return false;
-      if (statements[1] is! BreakStatement) return false;
-      var s = statements[0];
+      var s = statements.first;
       if (s is! ExpressionStatement) return false;
       var expression = s.expression;
       if (expression is! AssignmentExpression) return false;

pkg/analysis_server/test/src/services/correction/assist/convert_to_switch_expression_test.dart

@@ -48,6 +48,46 @@ enum Color {
   red, blue, green, yellow
 }
     
+void f(Color color) {
+  print(switch (color) {
+    Color.red => 'red', // Red.
+    Color.blue => 'blue',
+    // Not green.
+    Color.green => throw 'Green is bad',
+    Color.yellow => 
+      // Yellow is OK.
+      'yellow'
+  });
+}
+''');
+  }
+
+  Future<void> test_argument_switchExpression_noBreaks() async {
+    await resolveTestCode('''
+enum Color {
+  red, blue, green, yellow
+}
+    
+void f(Color color) {
+  switch (color) {
+    case Color.red:
+      print('red'); // Red.
+    case Color.blue:
+      print('blue');
+    // Not green.
+    case Color.green:
+      throw 'Green is bad';
+    case Color.yellow:
+      // Yellow is OK.
+      print('yellow');
+  }
+}
+''');
+    await assertHasAssistAt('(color)', '''
+enum Color {
+  red, blue, green, yellow
+}
+    
 void f(Color color) {
   print(switch (color) {
     Color.red => 'red', // Red.
@@ -93,6 +133,50 @@ enum Color {
   red, blue, green, yellow
 }
     
+String f(Color color) {
+  var name = '';
+  name = switch (color) {
+    Color.red => 'red',
+    Color.blue => 'blue', // Blue!
+    // Not green.
+    Color.green => throw 'Green is bad',
+    Color.yellow =>
+      // Yellow is OK.
+      'yellow'
+  };
+  return name;
+}
+''');
+  }
+
+  Future<void> test_assignment_switchExpression_noBreaks() async {
+    await resolveTestCode('''
+enum Color {
+  red, blue, green, yellow
+}
+    
+String f(Color color) {
+  var name = '';
+  switch (color) {
+    case Color.red:
+      name = 'red';
+    case Color.blue:
+      name = 'blue'; // Blue!
+    // Not green.
+    case Color.green:
+      throw 'Green is bad';
+    case Color.yellow:
+      // Yellow is OK.
+      name = 'yellow';
+  }
+  return name;
+}
+''');
+    await assertHasAssistAt('(color)', '''
+enum Color {
+  red, blue, green, yellow
+}
+    
 String f(Color color) {
   var name = '';
   name = switch (color) {