From a5ae1b38b06bc352be3d50f7dfb2d69f20661367 Mon Sep 17 00:00:00 2001
From: Mikhail Zarechenskiy <mikhail.zarechenskiy@jetbrains.com>
Date: Tue, 23 Jun 2020 12:56:12 +0300
Subject: [PATCH] Don't skip constraints from equations with the kind equal

 The problem was that we didn't incorporate T == Foo into K <: Inv<out T>.
 It happened because of optimisation that isn't applicable here as we
 already have projection in the initial type

 #KT-39777 Fixed
---
 ...irOldFrontendDiagnosticsTestGenerated.java |  5 +++++
 .../components/ConstraintIncorporator.kt      |  7 ++++---
 ...alitySubstitutionInsideNonInvariantType.kt | 17 +++++++++++++++
 ...litySubstitutionInsideNonInvariantType.txt | 21 +++++++++++++++++++
 .../checkers/DiagnosticsTestGenerated.java    |  5 +++++
 .../DiagnosticsUsingJavacTestGenerated.java   |  5 +++++
 6 files changed, 57 insertions(+), 3 deletions(-)
 create mode 100644 compiler/testData/diagnostics/tests/inference/equalitySubstitutionInsideNonInvariantType.kt
 create mode 100644 compiler/testData/diagnostics/tests/inference/equalitySubstitutionInsideNonInvariantType.txt

diff --git a/compiler/fir/analysis-tests/tests/org/jetbrains/kotlin/fir/FirOldFrontendDiagnosticsTestGenerated.java b/compiler/fir/analysis-tests/tests/org/jetbrains/kotlin/fir/FirOldFrontendDiagnosticsTestGenerated.java
index 13fbfa7bc11..8f12187f6f6 100644
--- a/compiler/fir/analysis-tests/tests/org/jetbrains/kotlin/fir/FirOldFrontendDiagnosticsTestGenerated.java
+++ b/compiler/fir/analysis-tests/tests/org/jetbrains/kotlin/fir/FirOldFrontendDiagnosticsTestGenerated.java
@@ -10006,6 +10006,11 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirOldFronte
             runTest("compiler/testData/diagnostics/tests/inference/dependantOnVarianceNullable.kt");
         }
 
+        @TestMetadata("equalitySubstitutionInsideNonInvariantType.kt")
+        public void testEqualitySubstitutionInsideNonInvariantType() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/inference/equalitySubstitutionInsideNonInvariantType.kt");
+        }
+
         @TestMetadata("expectedTypeAdditionalTest.kt")
         public void testExpectedTypeAdditionalTest() throws Exception {
             runTest("compiler/testData/diagnostics/tests/inference/expectedTypeAdditionalTest.kt");
diff --git a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/inference/components/ConstraintIncorporator.kt b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/inference/components/ConstraintIncorporator.kt
index f51a414b39d..f2a6d3d739e 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/inference/components/ConstraintIncorporator.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/inference/components/ConstraintIncorporator.kt
@@ -221,9 +221,10 @@ class ConstraintIncorporator(
         val isFromVariableFixation = baseConstraint.position.from is FixVariableConstraintPosition
                 || otherConstraint.position.from is FixVariableConstraintPosition
 
-        if (!containsConstrainingTypeWithoutProjection(newConstraint, otherConstraint)
-            && !isUsefulForNullabilityConstraint
-            && !isFromVariableFixation
+        if (!otherConstraint.kind.isEqual() &&
+            !isUsefulForNullabilityConstraint &&
+            !isFromVariableFixation &&
+            !containsConstrainingTypeWithoutProjection(newConstraint, otherConstraint)
         ) return
 
         if (trivialConstraintTypeInferenceOracle.isGeneratedConstraintTrivial(
diff --git a/compiler/testData/diagnostics/tests/inference/equalitySubstitutionInsideNonInvariantType.kt b/compiler/testData/diagnostics/tests/inference/equalitySubstitutionInsideNonInvariantType.kt
new file mode 100644
index 00000000000..24d3caa0b53
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/inference/equalitySubstitutionInsideNonInvariantType.kt
@@ -0,0 +1,17 @@
+// FIR_IDENTICAL
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+fun <K> materialize(): K = TODO()
+
+class Foo
+class Inv<T>
+
+fun <T> test1(x: Inv<out T>) {}
+fun <T> test2(x: Inv<in T>) {}
+fun <T> test3(x: Inv<T>) {}
+
+fun main() {
+    test1<Foo>(materialize())
+    test2<Foo>(materialize())
+    test3<Foo>(materialize())
+}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/inference/equalitySubstitutionInsideNonInvariantType.txt b/compiler/testData/diagnostics/tests/inference/equalitySubstitutionInsideNonInvariantType.txt
new file mode 100644
index 00000000000..a8a004b5700
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/inference/equalitySubstitutionInsideNonInvariantType.txt
@@ -0,0 +1,21 @@
+package
+
+public fun main(): kotlin.Unit
+public fun </*0*/ K> materialize(): K
+public fun </*0*/ T> test1(/*0*/ x: Inv<out T>): kotlin.Unit
+public fun </*0*/ T> test2(/*0*/ x: Inv<in T>): kotlin.Unit
+public fun </*0*/ T> test3(/*0*/ x: Inv<T>): kotlin.Unit
+
+public final class Foo {
+    public constructor Foo()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class Inv</*0*/ T> {
+    public constructor Inv</*0*/ T>()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java
index d2fc13bede4..93e1de72a1a 100644
--- a/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java
@@ -10013,6 +10013,11 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTestWithFirVali
                 runTest("compiler/testData/diagnostics/tests/inference/dependantOnVarianceNullable.kt");
             }
 
+            @TestMetadata("equalitySubstitutionInsideNonInvariantType.kt")
+            public void testEqualitySubstitutionInsideNonInvariantType() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/inference/equalitySubstitutionInsideNonInvariantType.kt");
+            }
+
             @TestMetadata("expectedTypeAdditionalTest.kt")
             public void testExpectedTypeAdditionalTest() throws Exception {
                 runTest("compiler/testData/diagnostics/tests/inference/expectedTypeAdditionalTest.kt");
diff --git a/compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java
index 7abab81c5c7..cf78fd6d00b 100644
--- a/compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java
@@ -10008,6 +10008,11 @@ public class DiagnosticsUsingJavacTestGenerated extends AbstractDiagnosticsUsing
                 runTest("compiler/testData/diagnostics/tests/inference/dependantOnVarianceNullable.kt");
             }
 
+            @TestMetadata("equalitySubstitutionInsideNonInvariantType.kt")
+            public void testEqualitySubstitutionInsideNonInvariantType() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/inference/equalitySubstitutionInsideNonInvariantType.kt");
+            }
+
             @TestMetadata("expectedTypeAdditionalTest.kt")
             public void testExpectedTypeAdditionalTest() throws Exception {
                 runTest("compiler/testData/diagnostics/tests/inference/expectedTypeAdditionalTest.kt");