From 344379d2f443f336702f288f0304443a9ec97108 Mon Sep 17 00:00:00 2001
From: Anna Kozlova <anna.kozlova@jetbrains.com>
Date: Thu, 12 Feb 2015 21:12:10 +0100
Subject: [PATCH] lambda: accept? inference variables as target type for lambda
 expression during lambda constraint reduction (IDEA-136435)

---
 .../LambdaExpressionCompatibilityConstraint.java      |  3 +++
 ...NestedLambdaWithInferenceVariableAsTargetType.java | 11 +++++++++++
 .../daemon/lambda/NewLambdaHighlightingTest.java      |  4 ++++
 3 files changed, 18 insertions(+)
 create mode 100644 java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/newLambda/NestedLambdaWithInferenceVariableAsTargetType.java

diff --git a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/LambdaExpressionCompatibilityConstraint.java b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/LambdaExpressionCompatibilityConstraint.java
index 28f407f2efb0..9a5c2fa84e3c 100644
--- a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/LambdaExpressionCompatibilityConstraint.java
+++ b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/LambdaExpressionCompatibilityConstraint.java
@@ -22,6 +22,9 @@ public class LambdaExpressionCompatibilityConstraint implements ConstraintFormul
 
   @Override
   public boolean reduce(InferenceSession session, List<ConstraintFormula> constraints) {
+    if (session.getInferenceVariable(myT) != null) {
+      return true;
+    }
     if (!LambdaUtil.isFunctionalType(myT)) {
       return false;
     }
diff --git a/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/newLambda/NestedLambdaWithInferenceVariableAsTargetType.java b/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/newLambda/NestedLambdaWithInferenceVariableAsTargetType.java
new file mode 100644
index 000000000000..16d6da06f529
--- /dev/null
+++ b/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/newLambda/NestedLambdaWithInferenceVariableAsTargetType.java
@@ -0,0 +1,11 @@
+import java.util.function.Supplier;
+
+class Test {
+  {
+    Supplier<Runnable> x = foo(() -> () -> {});
+  }
+
+  static <T> Supplier<T> foo(Supplier<T> delegate) {
+    return null;
+  }
+}
diff --git a/java/java-tests/testSrc/com/intellij/codeInsight/daemon/lambda/NewLambdaHighlightingTest.java b/java/java-tests/testSrc/com/intellij/codeInsight/daemon/lambda/NewLambdaHighlightingTest.java
index cf5189bb567c..72b67b4d5440 100644
--- a/java/java-tests/testSrc/com/intellij/codeInsight/daemon/lambda/NewLambdaHighlightingTest.java
+++ b/java/java-tests/testSrc/com/intellij/codeInsight/daemon/lambda/NewLambdaHighlightingTest.java
@@ -99,6 +99,10 @@ public class NewLambdaHighlightingTest extends LightDaemonAnalyzerTestCase {
     doTest();
   }
 
+  public void testNestedLambdaWithInferenceVariableAsTargetType() throws Exception {
+    doTest();
+  }
+
   public void testIDEA127596() throws Exception {
     doTest();
   }