From 915ac32bfbd84fbf62e5387902b1946d6a865519 Mon Sep 17 00:00:00 2001
From: Stanislav Erokhin <Stanislav.Erokhin@jetbrains.com>
Date: Fri, 9 Jun 2017 15:59:12 +0300
Subject: [PATCH] [NI] Improve type inference for T vs Captured(in Smt)

If we has Inv<T> <: Inv<Captured(in Foo)> then we should get:
- T <: Captured(in Foo)
- Captured(in Foo) <: T

Before this commit we got: T <: Foo instead first constraint.
---
 .../TypeCheckerContextForConstraintSystem.kt          |  7 +++++--
 .../kotlin/types/checker/NewKotlinTypeChecker.kt      | 11 +++++------
 .../kotlin/types/checker/TypeCheckerContext.kt        |  8 +++++++-
 3 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/inference/components/TypeCheckerContextForConstraintSystem.kt b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/inference/components/TypeCheckerContextForConstraintSystem.kt
index ac50e77b753..973b4d06796 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/inference/components/TypeCheckerContextForConstraintSystem.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/inference/components/TypeCheckerContextForConstraintSystem.kt
@@ -29,8 +29,11 @@ abstract class TypeCheckerContextForConstraintSystem : TypeCheckerContext(errorT
     abstract fun addUpperConstraint(typeVariable: TypeConstructor, superType: UnwrappedType)
     abstract fun addLowerConstraint(typeVariable: TypeConstructor, subType: UnwrappedType)
 
-    override fun shouldCheckOnlyLowerBoundForCapturedType(subType: SimpleType, superType: NewCapturedType) =
-            subType.contains { it.anyBound(this::isMyTypeVariable) }
+    override fun getLowerCapturedTypePolicy(subType: SimpleType, superType: NewCapturedType) = when {
+        isMyTypeVariable(subType) -> LowerCapturedTypePolicy.SKIP_LOWER
+        subType.contains { it.anyBound(this::isMyTypeVariable) } -> LowerCapturedTypePolicy.CHECK_ONLY_LOWER
+        else -> LowerCapturedTypePolicy.CHECK_SUBTYPE_AND_LOWER
+    }
 
     /**
      * todo: possible we should override this method, because otherwise OR in subtyping transformed to AND in constraint system
diff --git a/core/descriptors/src/org/jetbrains/kotlin/types/checker/NewKotlinTypeChecker.kt b/core/descriptors/src/org/jetbrains/kotlin/types/checker/NewKotlinTypeChecker.kt
index 257763f1d52..ef9ad3c67af 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/types/checker/NewKotlinTypeChecker.kt
+++ b/core/descriptors/src/org/jetbrains/kotlin/types/checker/NewKotlinTypeChecker.kt
@@ -23,6 +23,7 @@ import org.jetbrains.kotlin.resolve.calls.inference.CapturedType
 import org.jetbrains.kotlin.resolve.calls.inference.CapturedTypeConstructor
 import org.jetbrains.kotlin.resolve.constants.IntegerValueTypeConstructor
 import org.jetbrains.kotlin.types.*
+import org.jetbrains.kotlin.types.checker.TypeCheckerContext.LowerCapturedTypePolicy.*
 import org.jetbrains.kotlin.types.checker.TypeCheckerContext.SeveralSupertypesWithSameConstructorPolicy.*
 import org.jetbrains.kotlin.types.checker.TypeCheckerContext.SupertypesPolicy
 import org.jetbrains.kotlin.types.typeUtil.asTypeProjection
@@ -160,12 +161,10 @@ object NewKotlinTypeChecker : KotlinTypeChecker {
         }
 
         if (superType is NewCapturedType && superType.lowerType != null) {
-            val subtypeOfLowerType = isSubtypeOf(subType, superType.lowerType)
-            if (shouldCheckOnlyLowerBoundForCapturedType(subType, superType)) {
-                return subtypeOfLowerType
-            }
-            else if (subtypeOfLowerType) {
-                return true
+            when (getLowerCapturedTypePolicy(subType, superType)) {
+                CHECK_ONLY_LOWER -> return isSubtypeOf(subType, superType.lowerType)
+                CHECK_SUBTYPE_AND_LOWER -> if(isSubtypeOf(subType, superType.lowerType)) return true
+                SKIP_LOWER -> { /*do nothing*/ }
             }
         }
 
diff --git a/core/descriptors/src/org/jetbrains/kotlin/types/checker/TypeCheckerContext.kt b/core/descriptors/src/org/jetbrains/kotlin/types/checker/TypeCheckerContext.kt
index 4d6b239becd..d089e17a892 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/types/checker/TypeCheckerContext.kt
+++ b/core/descriptors/src/org/jetbrains/kotlin/types/checker/TypeCheckerContext.kt
@@ -33,7 +33,7 @@ open class TypeCheckerContext(val errorTypeEqualsToAnything: Boolean, val allowe
         return a == b
     }
 
-    open fun shouldCheckOnlyLowerBoundForCapturedType(subType: SimpleType, superType: NewCapturedType): Boolean = false
+    open fun getLowerCapturedTypePolicy(subType: SimpleType, superType: NewCapturedType) = LowerCapturedTypePolicy.CHECK_SUBTYPE_AND_LOWER
     open val sameConstructorPolicy get() = SeveralSupertypesWithSameConstructorPolicy.INTERSECT_ARGUMENTS_AND_CHECK_AGAIN
 
     internal inline fun <T> runWithArgumentsSettings(subArgument: UnwrappedType, f: TypeCheckerContext.() -> T): T {
@@ -127,5 +127,11 @@ open class TypeCheckerContext(val errorTypeEqualsToAnything: Boolean, val allowe
         INTERSECT_ARGUMENTS_AND_CHECK_AGAIN
     }
 
+    enum class LowerCapturedTypePolicy {
+        CHECK_ONLY_LOWER,
+        CHECK_SUBTYPE_AND_LOWER,
+        SKIP_LOWER
+    }
+
     val UnwrappedType.isAllowedTypeVariable: Boolean get() = allowedTypeVariable && constructor is NewTypeVariableConstructor
 }
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