FIR inference: implement simple constraint system properly

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/OverloadConflictResolver.kt

@@ -8,7 +8,10 @@ package org.jetbrains.kotlin.fir.resolve.calls
 import org.jetbrains.kotlin.fir.declarations.FirCallableDeclaration
 import org.jetbrains.kotlin.fir.declarations.FirConstructor
 import org.jetbrains.kotlin.fir.declarations.FirNamedFunction
+import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutorByMap
 import org.jetbrains.kotlin.fir.resolve.transformers.firUnsafe
+import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
+import org.jetbrains.kotlin.fir.types.ConeKotlinType
 import org.jetbrains.kotlin.fir.types.coneTypeUnsafe
 import org.jetbrains.kotlin.resolve.OverloadabilitySpecificityCallbacks
 import org.jetbrains.kotlin.resolve.calls.inference.model.NewConstraintSystemImpl
@@ -21,6 +24,7 @@ import org.jetbrains.kotlin.types.model.KotlinTypeMarker
 import org.jetbrains.kotlin.types.model.TypeParameterMarker
 import org.jetbrains.kotlin.types.model.TypeSubstitutorMarker
 import org.jetbrains.kotlin.types.model.TypeSystemInferenceExtensionContext
+import org.jetbrains.kotlin.utils.addToStdlib.cast
 
 class ConeOverloadConflictResolver(
     val specificityComparator: TypeSpecificityComparator,
@@ -73,7 +77,8 @@ class ConeOverloadConflictResolver(
         return FlatSignature(
             call,
             function.typeParameters.map { it.symbol },
-            call.argumentMapping!!.map { it.value.returnTypeRef.coneTypeUnsafe() },
+            listOfNotNull<ConeKotlinType>(function.receiverTypeRef?.coneTypeUnsafe()) +
+                    call.argumentMapping!!.map { it.value.returnTypeRef.coneTypeUnsafe() },
             function.receiverTypeRef != null,
             function.valueParameters.any { it.isVararg },
             function.valueParameters.count { it.defaultValue != null },
@@ -199,8 +204,24 @@ class ConeOverloadConflictResolver(
 object NoSubstitutor : TypeSubstitutorMarker
 
 class ConeSimpleConstraintSystemImpl(val system: NewConstraintSystemImpl) : SimpleConstraintSystem {
-    override fun registerTypeVariables(typeParameters: Collection<TypeParameterMarker>): TypeSubstitutorMarker {
+    override fun registerTypeVariables(typeParameters: Collection<TypeParameterMarker>): TypeSubstitutorMarker = with(context) {
-        return NoSubstitutor
+        val csBuilder = system.getBuilder()
+        val substitutionMap = typeParameters.associate {
+            require(it is FirTypeParameterSymbol)
+            val variable = TypeParameterBasedTypeVariable(it)
+            csBuilder.registerVariable(variable)
+
+
+            it to variable.defaultType
+        }
+        val substitutor = ConeSubstitutorByMap(substitutionMap.cast())
+        for (typeParameter in typeParameters) {
+            require(typeParameter is FirTypeParameterSymbol)
+            for (upperBound in typeParameter.fir.bounds) {
+                addSubtypeConstraint(substitutionMap[typeParameter]!!, substitutor.substituteOrSelf(upperBound.coneTypeUnsafe()))
+            }
+        }
+        return substitutor
     }
 
     override fun addSubtypeConstraint(subType: KotlinTypeMarker, superType: KotlinTypeMarker) {
@@ -209,6 +230,9 @@ class ConeSimpleConstraintSystemImpl(val system: NewConstraintSystemImpl) : Simp
 
     override fun hasContradiction(): Boolean = system.hasContradiction
 
+    override val captureFromArgument: Boolean
+        get() = true
+
     override val context: TypeSystemInferenceExtensionContext
         get() = system
 

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/substitution/ConeSubstitutor.kt

@@ -10,9 +10,10 @@ import org.jetbrains.kotlin.fir.symbols.ConeTypeParameterSymbol
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.fir.types.impl.ConeAbbreviatedTypeImpl
 import org.jetbrains.kotlin.fir.types.impl.ConeClassTypeImpl
+import org.jetbrains.kotlin.types.model.TypeSubstitutorMarker
 
 
-interface ConeSubstitutor {
+interface ConeSubstitutor : TypeSubstitutorMarker {
     fun substituteOrSelf(type: ConeKotlinType): ConeKotlinType
     fun substituteOrNull(type: ConeKotlinType): ConeKotlinType?
 

compiler/fir/resolve/testData/resolve/stdlib/components.txt

@@ -28,9 +28,9 @@ FILE: components.kt
             lval y: R|kotlin/String| = R|<local>/<destruct>|.R|/D.component2|()
         }
 
-        lval <destruct>: <ERROR TYPE REF: Ambiguity: first, [kotlin/collections/first, kotlin/collections/first]> = R|<local>/list|.<Ambiguity: first, [kotlin/collections/first, kotlin/collections/first]>#()
+        lval <destruct>: R|D| = R|<local>/list|.R|kotlin/collections/first|<R|D|>()
-        lval x: <ERROR TYPE REF: Ambiguity: component1, [kotlin/collections/component1, kotlin/collections/component1, kotlin/collections/component1, kotlin/collections/component1, kotlin/collections/component1, kotlin/collections/component1, kotlin/collections/component1, kotlin/collections/component1, kotlin/collections/component1, kotlin/collections/component1, kotlin/collections/component1, kotlin/collections/component1, kotlin/collections/component1, kotlin/collections/component1, kotlin/collections/component1]> = R|<local>/<destruct>|.component1()
+        lval x: R|kotlin/Int| = R|<local>/<destruct>|.R|/D.component1|()
-        lval y: <ERROR TYPE REF: Ambiguity: component2, [kotlin/collections/component2, kotlin/collections/component2, kotlin/collections/component2, kotlin/collections/component2, kotlin/collections/component2, kotlin/collections/component2, kotlin/collections/component2, kotlin/collections/component2, kotlin/collections/component2, kotlin/collections/component2, kotlin/collections/component2, kotlin/collections/component2, kotlin/collections/component2, kotlin/collections/component2, kotlin/collections/component2]> = R|<local>/<destruct>|.component2()
+        lval y: R|kotlin/String| = R|<local>/<destruct>|.R|/D.component2|()
         R|<local>/list|.R|kotlin/collections/forEach|<R|D|>(<L> = forEach@fun <anonymous>(<destruct>: R|D|): R|kotlin/Unit| {
             lval x: R|kotlin/Int| = R|<local>/<destruct>|.R|/D.component1|()
             lval y: R|kotlin/String| = R|<local>/<destruct>|.R|/D.component2|()