explicit right to left side assignment failure when inference breaks on return type (IDEA-152677)

java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/InferenceSession.java

@@ -378,6 +378,7 @@ public class InferenceSession {
 
     myCheckApplicabilityPhase = false;
     if (properties != null && !properties.isApplicabilityCheck()) {
+      String expectedActualErrorMessage = null;
       final PsiMethod method = properties.getMethod();
       if (parent instanceof PsiCallExpression && PsiPolyExpressionUtil.isMethodCallPolyExpression((PsiExpression)parent, method)) {
         final PsiType returnType = method.getReturnType();
@@ -389,12 +390,17 @@ public class InferenceSession {
           }
 
           if (targetType != null && !PsiType.VOID.equals(targetType)) {
-            registerReturnTypeConstraints(PsiUtil.isRawSubstitutor(method, mySiteSubstitutor) ? returnType : mySiteSubstitutor.substitute(returnType), targetType);
+            PsiType actualType = PsiUtil.isRawSubstitutor(method, mySiteSubstitutor) ? returnType : mySiteSubstitutor.substitute(returnType);
+            registerReturnTypeConstraints(actualType, targetType);
+            expectedActualErrorMessage = "Incompatible types. Required " + targetType.getPresentableText() + " but '" + method.getName() + "' was inferred to " + actualType.getPresentableText() + ":";
           }
         }
       }
 
       if (!repeatInferencePhases()) {
+        if (expectedActualErrorMessage != null && myErrorMessages != null) {
+          myErrorMessages.add(0, expectedActualErrorMessage);
+        }
         resolveBounds(getInputInferenceVariablesFromTopLevelFunctionalExpressions(args, properties), initialSubstitutor);
         return;
       }

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/genericsHighlighting8/IDEA106964.java

@@ -7,7 +7,8 @@ abstract class Test {
     abstract <T> T test(Serializable type);
 
     private void call(){
-        String s = <error descr="no instance(s) of type variable(s)  exist so that String[] conforms to String
+        String s = <error descr="Incompatible types. Required String but 'test' was inferred to T:
+no instance(s) of type variable(s)  exist so that String[] conforms to String
 inference variable T has incompatible bounds:
  equality constraints: String[]
 upper bounds: Object, String">test(String[].class);</error>

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/newLambda/InferTypeParametersFromFunctionalInterfaceInputs.java

@@ -9,7 +9,8 @@ class A {
     <error descr="Missing return statement">}</error>);
 
 
-    Map<Integer, Integer> map = Stream.iterate(5, <error descr="no instance(s) of type variable(s) T exist so that Stream<T> conforms to Map<Integer, Integer>">t -> t + 5</error>);
+    Map<Integer, Integer> map = Stream.iterate(5, <error descr="Incompatible types. Required Map<Integer, Integer> but 'iterate' was inferred to Stream<T>:
+no instance(s) of type variable(s) T exist so that Stream<T> conforms to Map<Integer, Integer>">t -> t + 5</error>);
   }
 
 

java/java-tests/testSrc/com/intellij/codeInsight/daemon/lambda/GraphInferenceHighlightingTest.java

@@ -153,7 +153,7 @@ public class GraphInferenceHighlightingTest extends LightDaemonAnalyzerTestCase
 
     boolean found = false;
     for (String tooltip : tooltips) {
-      if (tooltip.contains("reason: no instance(s) of type variable(s) K, U exist so that Map<K, U> conforms to Function<U, V>")) {
+      if (tooltip.contains("no instance(s) of type variable(s) K, U exist so that Map<K, U> conforms to Function<U, V>")) {
         found = true;
         break;
       }