From 78095fd61d9d1320f2cc117a318841fd66e4ab0e Mon Sep 17 00:00:00 2001
From: Anna Kozlova <anna.kozlova@jetbrains.com>
Date: Tue, 14 May 2019 09:41:10 +0200
Subject: [PATCH] inference: check lower bounds assignability to upper bounds

lub may break some capture invariants

GitOrigin-RevId: c7857bf255c357471fd9f14fc161d2ca03769f4b
---
 .../graphInference/InferenceSession.java        | 17 +++++++++--------
 .../LowerBoundAssignabilityCheck.java           | 11 +++++++++++
 .../lambda/GenericsHighlighting8Test.java       |  1 +
 3 files changed, 21 insertions(+), 8 deletions(-)
 create mode 100644 java/java-tests/testData/codeInsight/daemonCodeAnalyzer/genericsHighlighting8/LowerBoundAssignabilityCheck.java

diff --git a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/InferenceSession.java b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/InferenceSession.java
index d88afe7ea6c7..fd149b5d3594 100644
--- a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/InferenceSession.java
+++ b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/InferenceSession.java
@@ -1205,17 +1205,18 @@ public class InferenceSession {
     else {
       for (PsiType upperType : var.getBounds(InferenceBound.UPPER)) {
         if (myErrorMessages == null && isProperType(upperType)) {
-          String incompatibleBoundsMessage = null;
           if (type != lowerBound && !TypeConversionUtil.isAssignable(upperType, type)) {
-            incompatibleBoundsMessage = incompatibleBoundsMessage(var, substitutor, InferenceBound.EQ, EQUALITY_CONSTRAINTS_PRESENTATION, InferenceBound.UPPER, UPPER_BOUNDS_PRESENTATION);
-          }
-          else if (type == lowerBound && !TypeConversionUtil.isAssignable(upperType, lowerBound)) {
-            incompatibleBoundsMessage = incompatibleBoundsMessage(var, substitutor, InferenceBound.LOWER, LOWER_BOUNDS_PRESENTATION, InferenceBound.UPPER, UPPER_BOUNDS_PRESENTATION);
-          }
-          if (incompatibleBoundsMessage != null) {
-            registerIncompatibleErrorMessage(incompatibleBoundsMessage);
+            registerIncompatibleErrorMessage(incompatibleBoundsMessage(var, substitutor, InferenceBound.EQ, EQUALITY_CONSTRAINTS_PRESENTATION, InferenceBound.UPPER, UPPER_BOUNDS_PRESENTATION));
             return PsiType.NULL;
           }
+          else if (type == lowerBound) {
+            for (PsiType lowerBoundConjunct : var.getBounds(InferenceBound.LOWER)) {
+              if (isProperType(lowerBoundConjunct) && !TypeConversionUtil.isAssignable(upperType, lowerBoundConjunct)) {
+                registerIncompatibleErrorMessage(incompatibleBoundsMessage(var, substitutor, InferenceBound.LOWER, LOWER_BOUNDS_PRESENTATION, InferenceBound.UPPER, UPPER_BOUNDS_PRESENTATION));
+                return PsiType.NULL;
+              }
+            }
+          }
         }
       }
     }
diff --git a/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/genericsHighlighting8/LowerBoundAssignabilityCheck.java b/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/genericsHighlighting8/LowerBoundAssignabilityCheck.java
new file mode 100644
index 000000000000..2d8ebc794eaf
--- /dev/null
+++ b/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/genericsHighlighting8/LowerBoundAssignabilityCheck.java
@@ -0,0 +1,11 @@
+class MyTest<T> {
+  static void m(Ref<? super String> commentRef) {
+    commentRef = coalesce(commentRef, commentRef);
+  }
+
+  static <T> T coalesce(T t1, T t2) {
+    return t1;
+  }
+
+  static class Ref<T> { }
+}
diff --git a/java/java-tests/testSrc/com/intellij/java/codeInsight/daemon/lambda/GenericsHighlighting8Test.java b/java/java-tests/testSrc/com/intellij/java/codeInsight/daemon/lambda/GenericsHighlighting8Test.java
index c6be10a3e868..3e214035245a 100644
--- a/java/java-tests/testSrc/com/intellij/java/codeInsight/daemon/lambda/GenericsHighlighting8Test.java
+++ b/java/java-tests/testSrc/com/intellij/java/codeInsight/daemon/lambda/GenericsHighlighting8Test.java
@@ -1043,5 +1043,6 @@ public class GenericsHighlighting8Test extends LightDaemonAnalyzerTestCase {
   public void testNestedWildcardsWithImplicitBounds() { doTest(); }
   public void testCallOnRawWithExplicitTypeArguments() { doTest(); }
   public void testNoCaptureConversionDuringDetectingSupertypesDeepInHierarchy() { doTest(); }
+  public void testLowerBoundAssignabilityCheck() { doTest(); }
   public void testIgnoreErasureForProperTypeBound() { doTest(); }
 }