From 295f7d7500ccece1c450ad38653874fb778cd71d Mon Sep 17 00:00:00 2001
From: Denis Zharkov <denis.zharkov@jetbrains.com>
Date: Tue, 12 May 2020 17:41:34 +0300
Subject: [PATCH] FIR: Do not add trivial constraints

---
 ...CreateFreshTypeVariableSubstitutorStage.kt | 24 ++++++++++++++-----
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/CreateFreshTypeVariableSubstitutorStage.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/CreateFreshTypeVariableSubstitutorStage.kt
index ee1cdc30d8d..404e6d14482 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/CreateFreshTypeVariableSubstitutorStage.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/CreateFreshTypeVariableSubstitutorStage.kt
@@ -5,14 +5,14 @@
 
 package org.jetbrains.kotlin.fir.resolve.calls
 
-import org.jetbrains.kotlin.fir.declarations.FirTypeParameterRefsOwner
-import org.jetbrains.kotlin.fir.declarations.FirTypeParameter
+import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.declarations.FirTypeParameterRef
-import org.jetbrains.kotlin.fir.declarations.FirTypeParametersOwner
+import org.jetbrains.kotlin.fir.declarations.FirTypeParameterRefsOwner
 import org.jetbrains.kotlin.fir.renderWithType
 import org.jetbrains.kotlin.fir.resolve.inference.TypeParameterBasedTypeVariable
 import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutor
 import org.jetbrains.kotlin.fir.resolve.substitution.substitutorByMap
+import org.jetbrains.kotlin.fir.symbols.StandardClassIds
 import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.fir.types.impl.FirTypePlaceholderProjection
@@ -30,7 +30,8 @@ internal object CreateFreshTypeVariableSubstitutorStage : ResolutionStage() {
             return
         }
         val csBuilder = candidate.system.getBuilder()
-        val (substitutor, freshVariables) = createToFreshVariableSubstitutorAndAddInitialConstraints(declaration, candidate, csBuilder)
+        val (substitutor, freshVariables) =
+            createToFreshVariableSubstitutorAndAddInitialConstraints(declaration, candidate, csBuilder, callInfo.session)
         candidate.substitutor = substitutor
         candidate.freshVariables = freshVariables
 
@@ -113,7 +114,8 @@ internal object CreateFreshTypeVariableSubstitutorStage : ResolutionStage() {
 fun createToFreshVariableSubstitutorAndAddInitialConstraints(
     declaration: FirTypeParameterRefsOwner,
     candidate: Candidate,
-    csBuilder: ConstraintSystemOperation
+    csBuilder: ConstraintSystemOperation,
+    session: FirSession
 ): Pair<ConeSubstitutor, List<ConeTypeVariable>> {
 
     val typeParameters = declaration.typeParameters
@@ -130,7 +132,17 @@ fun createToFreshVariableSubstitutorAndAddInitialConstraints(
         upperBound: ConeKotlinType//,
         //position: DeclaredUpperBoundConstraintPosition
     ) {
-        csBuilder.addSubtypeConstraint(defaultType, toFreshVariables.substituteOrSelf(upperBound), FirDeclaredUpperBoundConstraintPosition())
+        if ((upperBound.lowerBoundIfFlexible() as? ConeClassLikeType)?.lookupTag?.classId == StandardClassIds.Any &&
+            upperBound.upperBoundIfFlexible().isMarkedNullable
+        ) {
+            return
+        }
+
+        csBuilder.addSubtypeConstraint(
+            defaultType,
+            toFreshVariables.substituteOrSelf(upperBound),
+            FirDeclaredUpperBoundConstraintPosition()
+        )
     }
 
     for (index in typeParameters.indices) {