switch expressions: report bad result expression types

if they are not convertible to poly expression target type

java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/analysis/HighlightUtil.java

@@ -1437,6 +1437,25 @@ public class HighlightUtil extends HighlightUtilBase {
     return null;
   }
 
+  static Collection<HighlightInfo> checkSwitchExpressionReturnTypeCompatible(PsiSwitchExpression switchExpression) {
+    if (!PsiPolyExpressionUtil.isPolyExpression(switchExpression)) return null;
+    List<HighlightInfo> infos = new ArrayList<>();
+    PsiType switchExpressionType = switchExpression.getType();
+    if (switchExpressionType != null) {
+      for (PsiExpression expression : PsiUtil.getSwitchResultExpressions(switchExpression)) {
+        final PsiType expressionType = PsiResolveHelper.ourGraphGuard.doPreventingRecursion(expression, true, expression::getType);
+        if (expressionType != null && !switchExpressionType.isAssignableFrom(expressionType)) {
+          infos.add(HighlightInfo.newHighlightInfo(HighlightInfoType.ERROR)
+                      .range(expression)
+                      .descriptionAndTooltip("Bad type in switch expression: " + expressionType.getCanonicalText() + " cannot be converted to " + switchExpressionType.getCanonicalText())
+                      .create());
+        }
+      }
+    }
+
+    return infos;
+  }
+
   private enum SelectorKind { INT, ENUM, STRING }
 
   private static SelectorKind getSwitchSelectorKind(@NotNull PsiType type) {

java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/analysis/HighlightVisitorImpl.java

@@ -1607,6 +1607,7 @@ public class HighlightVisitorImpl extends JavaElementVisitor implements Highligh
     super.visitSwitchExpression(expression);
     if (!myHolder.hasErrorResults()) myHolder.add(checkFeature(expression, Feature.SWITCH_EXPRESSION));
     checkSwitchBlock(expression);
+    if (!myHolder.hasErrorResults()) myHolder.addAll(HighlightUtil.checkSwitchExpressionReturnTypeCompatible(expression));
   }
 
   private void checkSwitchBlock(PsiSwitchBlock switchBlock) {

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting12/SimpleInferenceCases.java

@@ -26,9 +26,15 @@ no instance(s) of type variable(s) exist so that Object conforms to String">foo(
     String s4 = foo(() -> switch (i) {default -> { break bar();}});
     String s5 = foo(<error descr="Incompatible types. Required String but 'foo' was inferred to T:
 no instance(s) of type variable(s) exist so that Integer conforms to String">() -> switch (i) {default -> { break 1;}}</error>);
+    String s6 = switch (i) {
+      case 1 -> <error descr="Bad type in switch expression: int cannot be converted to java.lang.String">2</error>;
+      default -> {
+        break <error descr="Bad type in switch expression: int cannot be converted to java.lang.String">1</error>;
+      }
+    };
     Supplier<String> stringSupplier = switch (i) {
             default -> {
-                break  () -> <error descr="Bad return type in lambda expression: int cannot be converted to String">1</error>;
+                break () -> <error descr="Bad return type in lambda expression: int cannot be converted to String">1</error>;
             }
         };
   }