From aafe41cf7a01d1a7d276cb936336649f370a23ca Mon Sep 17 00:00:00 2001
From: Mikhail Zarechenskiy <mikhail.zarechenskiy@jetbrains.com>
Date: Tue, 11 Aug 2020 23:17:01 +0300
Subject: [PATCH] Do not force coercion to Unit for nullable lambda return type

 #KT-41005 Fixed
---
 .../ir/FirBlackBoxCodegenTestGenerated.java   | 10 +++++++++
 .../components/PostponedArgumentsAnalyzer.kt  |  3 ++-
 ...rLambdaReturnTypeWithFlexibleConstraint.kt | 22 +++++++++++++++++++
 ...oercionToUniForNullableLambdaReturnType.kt |  7 ++++++
 .../codegen/BlackBoxCodegenTestGenerated.java | 10 +++++++++
 .../LightAnalysisModeTestGenerated.java       | 10 +++++++++
 .../ir/IrBlackBoxCodegenTestGenerated.java    | 10 +++++++++
 .../IrJsCodegenBoxES6TestGenerated.java       |  5 +++++
 .../IrJsCodegenBoxTestGenerated.java          |  5 +++++
 .../semantics/JsCodegenBoxTestGenerated.java  |  5 +++++
 10 files changed, 86 insertions(+), 1 deletion(-)
 create mode 100644 compiler/testData/codegen/box/inference/coercionToUnitForLambdaReturnTypeWithFlexibleConstraint.kt
 create mode 100644 compiler/testData/codegen/box/inference/noCoercionToUniForNullableLambdaReturnType.kt

diff --git a/compiler/fir/fir2ir/tests/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java b/compiler/fir/fir2ir/tests/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java
index dabdf90aeea..3c2ee813f72 100644
--- a/compiler/fir/fir2ir/tests/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java
+++ b/compiler/fir/fir2ir/tests/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java
@@ -12469,6 +12469,11 @@ public class FirBlackBoxCodegenTestGenerated extends AbstractFirBlackBoxCodegenT
             runTest("compiler/testData/codegen/box/inference/capturedStarProjection.kt");
         }
 
+        @TestMetadata("coercionToUnitForLambdaReturnTypeWithFlexibleConstraint.kt")
+        public void testCoercionToUnitForLambdaReturnTypeWithFlexibleConstraint() throws Exception {
+            runTest("compiler/testData/codegen/box/inference/coercionToUnitForLambdaReturnTypeWithFlexibleConstraint.kt");
+        }
+
         @TestMetadata("coercionToUnitWithLastLambdaExpression.kt")
         public void testCoercionToUnitWithLastLambdaExpression() throws Exception {
             runTest("compiler/testData/codegen/box/inference/coercionToUnitWithLastLambdaExpression.kt");
@@ -12529,6 +12534,11 @@ public class FirBlackBoxCodegenTestGenerated extends AbstractFirBlackBoxCodegenT
             runTest("compiler/testData/codegen/box/inference/lastExpressionOfLambdaWithNothingConstraint.kt");
         }
 
+        @TestMetadata("noCoercionToUniForNullableLambdaReturnType.kt")
+        public void testNoCoercionToUniForNullableLambdaReturnType() throws Exception {
+            runTest("compiler/testData/codegen/box/inference/noCoercionToUniForNullableLambdaReturnType.kt");
+        }
+
         @TestMetadata("noNothingValueInsideSpecialCall.kt")
         public void testNoNothingValueInsideSpecialCall() throws Exception {
             runTest("compiler/testData/codegen/box/inference/noNothingValueInsideSpecialCall.kt");
diff --git a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/PostponedArgumentsAnalyzer.kt b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/PostponedArgumentsAnalyzer.kt
index 2a82e15663f..17ab0a172bc 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/PostponedArgumentsAnalyzer.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/PostponedArgumentsAnalyzer.kt
@@ -13,6 +13,7 @@ import org.jetbrains.kotlin.descriptors.annotations.Annotations
 import org.jetbrains.kotlin.descriptors.annotations.FilteredAnnotations
 import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemBuilder
 import org.jetbrains.kotlin.resolve.calls.inference.addSubsystemFromArgument
+import org.jetbrains.kotlin.resolve.calls.inference.components.NewTypeSubstitutorByConstructorMap
 import org.jetbrains.kotlin.resolve.calls.inference.model.ConstraintStorage
 import org.jetbrains.kotlin.resolve.calls.inference.model.CoroutinePosition
 import org.jetbrains.kotlin.resolve.calls.inference.model.LambdaArgumentConstraintPosition
@@ -122,7 +123,7 @@ class PostponedArgumentsAnalyzer(
             c.canBeProper(rawReturnType) -> substitute(rawReturnType)
 
             // For Unit-coercion
-            c.hasUpperOrEqualUnitConstraint(rawReturnType) -> builtIns.unitType
+            !rawReturnType.isMarkedNullable && c.hasUpperOrEqualUnitConstraint(rawReturnType) -> builtIns.unitType
 
             else -> null
         }
diff --git a/compiler/testData/codegen/box/inference/coercionToUnitForLambdaReturnTypeWithFlexibleConstraint.kt b/compiler/testData/codegen/box/inference/coercionToUnitForLambdaReturnTypeWithFlexibleConstraint.kt
new file mode 100644
index 00000000000..508097cad2a
--- /dev/null
+++ b/compiler/testData/codegen/box/inference/coercionToUnitForLambdaReturnTypeWithFlexibleConstraint.kt
@@ -0,0 +1,22 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+// TARGET_BACKEND: JVM
+
+// FILE: TestJ.java
+
+public class TestJ {
+    public static <T> In<T> materialize() {
+        return null;
+    }
+}
+
+// FILE: test.kt
+
+class In<in T>
+
+fun <T> inferred(e: In<T>?, l: () -> T): T = l()
+
+fun box(): String {
+    // coercion to Unit for T!
+    val inferred = (inferred(TestJ.materialize<Unit>(), { null })).toString()
+    return if (inferred == "kotlin.Unit") "OK" else "fail : $inferred"
+}
\ No newline at end of file
diff --git a/compiler/testData/codegen/box/inference/noCoercionToUniForNullableLambdaReturnType.kt b/compiler/testData/codegen/box/inference/noCoercionToUniForNullableLambdaReturnType.kt
new file mode 100644
index 00000000000..cfe86b99a58
--- /dev/null
+++ b/compiler/testData/codegen/box/inference/noCoercionToUniForNullableLambdaReturnType.kt
@@ -0,0 +1,7 @@
+fun <T> nullableK(m: () -> T?) = m()
+
+fun box(): String {
+    // no coercion to Unit for T?
+    val nullableK = (nullableK<Unit> { null }).toString()
+    return if (nullableK == "null") "OK" else  "fail: $nullableK"
+}
\ No newline at end of file
diff --git a/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
index f2026a05ad6..b2aca54122f 100644
--- a/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
@@ -13694,6 +13694,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             runTest("compiler/testData/codegen/box/inference/capturedStarProjection.kt");
         }
 
+        @TestMetadata("coercionToUnitForLambdaReturnTypeWithFlexibleConstraint.kt")
+        public void testCoercionToUnitForLambdaReturnTypeWithFlexibleConstraint() throws Exception {
+            runTest("compiler/testData/codegen/box/inference/coercionToUnitForLambdaReturnTypeWithFlexibleConstraint.kt");
+        }
+
         @TestMetadata("coercionToUnitWithLastLambdaExpression.kt")
         public void testCoercionToUnitWithLastLambdaExpression() throws Exception {
             runTest("compiler/testData/codegen/box/inference/coercionToUnitWithLastLambdaExpression.kt");
@@ -13754,6 +13759,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             runTest("compiler/testData/codegen/box/inference/lastExpressionOfLambdaWithNothingConstraint.kt");
         }
 
+        @TestMetadata("noCoercionToUniForNullableLambdaReturnType.kt")
+        public void testNoCoercionToUniForNullableLambdaReturnType() throws Exception {
+            runTest("compiler/testData/codegen/box/inference/noCoercionToUniForNullableLambdaReturnType.kt");
+        }
+
         @TestMetadata("noNothingValueInsideSpecialCall.kt")
         public void testNoNothingValueInsideSpecialCall() throws Exception {
             runTest("compiler/testData/codegen/box/inference/noNothingValueInsideSpecialCall.kt");
diff --git a/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
index 4e553f9cb2c..a8706a3e18c 100644
--- a/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
@@ -13694,6 +13694,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             runTest("compiler/testData/codegen/box/inference/capturedStarProjection.kt");
         }
 
+        @TestMetadata("coercionToUnitForLambdaReturnTypeWithFlexibleConstraint.kt")
+        public void testCoercionToUnitForLambdaReturnTypeWithFlexibleConstraint() throws Exception {
+            runTest("compiler/testData/codegen/box/inference/coercionToUnitForLambdaReturnTypeWithFlexibleConstraint.kt");
+        }
+
         @TestMetadata("coercionToUnitWithLastLambdaExpression.kt")
         public void testCoercionToUnitWithLastLambdaExpression() throws Exception {
             runTest("compiler/testData/codegen/box/inference/coercionToUnitWithLastLambdaExpression.kt");
@@ -13754,6 +13759,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             runTest("compiler/testData/codegen/box/inference/lastExpressionOfLambdaWithNothingConstraint.kt");
         }
 
+        @TestMetadata("noCoercionToUniForNullableLambdaReturnType.kt")
+        public void testNoCoercionToUniForNullableLambdaReturnType() throws Exception {
+            runTest("compiler/testData/codegen/box/inference/noCoercionToUniForNullableLambdaReturnType.kt");
+        }
+
         @TestMetadata("noNothingValueInsideSpecialCall.kt")
         public void testNoNothingValueInsideSpecialCall() throws Exception {
             runTest("compiler/testData/codegen/box/inference/noNothingValueInsideSpecialCall.kt");
diff --git a/compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java
index 467882ce3b5..1259ee15c24 100644
--- a/compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java
@@ -12469,6 +12469,11 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             runTest("compiler/testData/codegen/box/inference/capturedStarProjection.kt");
         }
 
+        @TestMetadata("coercionToUnitForLambdaReturnTypeWithFlexibleConstraint.kt")
+        public void testCoercionToUnitForLambdaReturnTypeWithFlexibleConstraint() throws Exception {
+            runTest("compiler/testData/codegen/box/inference/coercionToUnitForLambdaReturnTypeWithFlexibleConstraint.kt");
+        }
+
         @TestMetadata("coercionToUnitWithLastLambdaExpression.kt")
         public void testCoercionToUnitWithLastLambdaExpression() throws Exception {
             runTest("compiler/testData/codegen/box/inference/coercionToUnitWithLastLambdaExpression.kt");
@@ -12529,6 +12534,11 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             runTest("compiler/testData/codegen/box/inference/lastExpressionOfLambdaWithNothingConstraint.kt");
         }
 
+        @TestMetadata("noCoercionToUniForNullableLambdaReturnType.kt")
+        public void testNoCoercionToUniForNullableLambdaReturnType() throws Exception {
+            runTest("compiler/testData/codegen/box/inference/noCoercionToUniForNullableLambdaReturnType.kt");
+        }
+
         @TestMetadata("noNothingValueInsideSpecialCall.kt")
         public void testNoNothingValueInsideSpecialCall() throws Exception {
             runTest("compiler/testData/codegen/box/inference/noNothingValueInsideSpecialCall.kt");
diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/es6/semantics/IrJsCodegenBoxES6TestGenerated.java b/js/js.tests/test/org/jetbrains/kotlin/js/test/es6/semantics/IrJsCodegenBoxES6TestGenerated.java
index af7ec258d8b..d8da68b5abc 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/js/test/es6/semantics/IrJsCodegenBoxES6TestGenerated.java
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/es6/semantics/IrJsCodegenBoxES6TestGenerated.java
@@ -10784,6 +10784,11 @@ public class IrJsCodegenBoxES6TestGenerated extends AbstractIrJsCodegenBoxES6Tes
             runTest("compiler/testData/codegen/box/inference/lastExpressionOfLambdaWithNothingConstraint.kt");
         }
 
+        @TestMetadata("noCoercionToUniForNullableLambdaReturnType.kt")
+        public void testNoCoercionToUniForNullableLambdaReturnType() throws Exception {
+            runTest("compiler/testData/codegen/box/inference/noCoercionToUniForNullableLambdaReturnType.kt");
+        }
+
         @TestMetadata("plusAssignInsideLambda.kt")
         public void testPlusAssignInsideLambda() throws Exception {
             runTest("compiler/testData/codegen/box/inference/plusAssignInsideLambda.kt");
diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/ir/semantics/IrJsCodegenBoxTestGenerated.java b/js/js.tests/test/org/jetbrains/kotlin/js/test/ir/semantics/IrJsCodegenBoxTestGenerated.java
index 4c4ba8c4223..57700872b9d 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/js/test/ir/semantics/IrJsCodegenBoxTestGenerated.java
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/ir/semantics/IrJsCodegenBoxTestGenerated.java
@@ -10784,6 +10784,11 @@ public class IrJsCodegenBoxTestGenerated extends AbstractIrJsCodegenBoxTest {
             runTest("compiler/testData/codegen/box/inference/lastExpressionOfLambdaWithNothingConstraint.kt");
         }
 
+        @TestMetadata("noCoercionToUniForNullableLambdaReturnType.kt")
+        public void testNoCoercionToUniForNullableLambdaReturnType() throws Exception {
+            runTest("compiler/testData/codegen/box/inference/noCoercionToUniForNullableLambdaReturnType.kt");
+        }
+
         @TestMetadata("plusAssignInsideLambda.kt")
         public void testPlusAssignInsideLambda() throws Exception {
             runTest("compiler/testData/codegen/box/inference/plusAssignInsideLambda.kt");
diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java b/js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java
index b714de2082a..471823fa815 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java
@@ -10849,6 +10849,11 @@ public class JsCodegenBoxTestGenerated extends AbstractJsCodegenBoxTest {
             runTest("compiler/testData/codegen/box/inference/lastExpressionOfLambdaWithNothingConstraint.kt");
         }
 
+        @TestMetadata("noCoercionToUniForNullableLambdaReturnType.kt")
+        public void testNoCoercionToUniForNullableLambdaReturnType() throws Exception {
+            runTest("compiler/testData/codegen/box/inference/noCoercionToUniForNullableLambdaReturnType.kt");
+        }
+
         @TestMetadata("plusAssignInsideLambda.kt")
         public void testPlusAssignInsideLambda() throws Exception {
             runTest("compiler/testData/codegen/box/inference/plusAssignInsideLambda.kt");