CANNOT_INFER_PARAMETER_TYPE reporting improvement

compiler/frontend/src/org/jetbrains/jet/lang/types/expressions/ClosureExpressionsTypingVisitor.java

@@ -23,6 +23,7 @@ import org.jetbrains.jet.lang.descriptors.*;
 import org.jetbrains.jet.lang.descriptors.annotations.AnnotationDescriptor;
 import org.jetbrains.jet.lang.psi.*;
 import org.jetbrains.jet.lang.resolve.*;
+import org.jetbrains.jet.lang.resolve.calls.CallResolverUtil;
 import org.jetbrains.jet.lang.resolve.name.Name;
 import org.jetbrains.jet.lang.resolve.scopes.JetScope;
 import org.jetbrains.jet.lang.types.*;
@@ -236,11 +237,13 @@ public class ClosureExpressionsTypingVisitor extends ExpressionTypingVisitor {
                     }
                 }
                 else {
+                    if (expectedType == null || expectedType == CallResolverUtil.DONT_CARE || expectedType == CallResolverUtil.CANT_INFER) {
+                        context.trace.report(CANNOT_INFER_PARAMETER_TYPE.on(declaredParameter));
+                    }
                     if (expectedType != null) {
                         type = expectedType;
                     }
                     else {
-                        context.trace.report(CANNOT_INFER_PARAMETER_TYPE.on(declaredParameter));
                         type = ErrorUtils.createErrorType("Cannot be inferred");
                     }
                 }

compiler/testData/diagnostics/tests/inference/reportingImprovements/cannotInferParameterTypeWithInference.kt

@@ -0,0 +1,16 @@
+package aa
+
+fun <T, R> foo(block: (T)-> R) = block
+
+fun test1() {
+    <!TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>foo<!> {
+        <!CANNOT_INFER_PARAMETER_TYPE!>x<!> ->  // here we have 'cannot infer parameter type' error
+        43
+    }
+}
+
+fun bar(<!UNUSED_PARAMETER!>f<!>: (<!UNRESOLVED_REFERENCE!>A<!>)->Unit) {}
+
+fun test2() {
+    bar { a -> } // here we don't have 'cannot infer parameter type' error
+}

compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java

@@ -2265,6 +2265,11 @@ public class JetDiagnosticsTestGenerated extends AbstractDiagnosticsTestWithEage
                     JetTestUtils.assertAllTestsPresentByMetadata(this.getClass(), "org.jetbrains.jet.generators.tests.GenerateTests", new File("compiler/testData/diagnostics/tests/inference/reportingImprovements"), "kt", true);
                 }
                 
+                @TestMetadata("cannotInferParameterTypeWithInference.kt")
+                public void testCannotInferParameterTypeWithInference() throws Exception {
+                    doTest("compiler/testData/diagnostics/tests/inference/reportingImprovements/cannotInferParameterTypeWithInference.kt");
+                }
+                
                 @TestMetadata("NoAmbiguityForDifferentFunctionTypes.kt")
                 public void testNoAmbiguityForDifferentFunctionTypes() throws Exception {
                     doTest("compiler/testData/diagnostics/tests/inference/reportingImprovements/NoAmbiguityForDifferentFunctionTypes.kt");