FIR: Make synthetic type variables fix to self-stub type if no info

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/AbstractManyCandidatesInferenceSession.kt

@@ -11,13 +11,19 @@ import org.jetbrains.kotlin.fir.resolve.BodyResolveComponents
 import org.jetbrains.kotlin.fir.resolve.calls.Candidate
 import org.jetbrains.kotlin.fir.resolve.calls.ResolutionContext
 import org.jetbrains.kotlin.fir.resolve.calls.candidate
+import org.jetbrains.kotlin.resolve.calls.inference.components.ConstraintSystemCompletionContext
 import org.jetbrains.kotlin.types.model.StubTypeMarker
 import org.jetbrains.kotlin.types.model.TypeVariableMarker
 
 abstract class AbstractManyCandidatesInferenceSession(
     protected val resolutionContext: ResolutionContext
 ) : FirInferenceSession() {
-    private val errorCalls: MutableList<FirResolvable> = mutableListOf()
+    override fun fixSyntheticTypeVariableWithNotEnoughInformation(
+        typeVariable: TypeVariableMarker,
+        completionContext: ConstraintSystemCompletionContext
+    ) {
+    }
+
     protected val partiallyResolvedCalls: MutableList<Pair<FirResolvable, Candidate>> = mutableListOf()
     private val completedCalls: MutableSet<FirResolvable> = mutableSetOf()
 

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/ConstraintSystemCompleter.kt

@@ -226,9 +226,13 @@ class ConstraintSystemCompleter(private val components: BodyResolveComponents, p
 
             val variableWithConstraints = notFixedTypeVariables.getValue(variableForFixation.variable)
 
-            if (variableForFixation.hasProperConstraint || context.inferenceSession.isSyntheticTypeVariable(variableWithConstraints.typeVariable)) {
+            if (variableForFixation.hasProperConstraint) {
                 fixVariable(asConstraintSystemCompletionContext(), topLevelType, variableWithConstraints, postponedArguments)
                 return true
+            } else if (context.inferenceSession.isSyntheticTypeVariable(variableWithConstraints.typeVariable)) {
+                val variable = variableWithConstraints.typeVariable as ConeTypeVariable
+                context.inferenceSession.fixSyntheticTypeVariableWithNotEnoughInformation(variable, asConstraintSystemCompletionContext())
+                return true
             } else {
                 processVariableWhenNotEnoughInformation(this, variableWithConstraints, topLevelAtoms)
             }

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/FirDelegatedPropertyInferenceSession.kt

@@ -9,12 +9,14 @@ import org.jetbrains.kotlin.fir.declarations.FirProperty
 import org.jetbrains.kotlin.fir.expressions.FirResolvable
 import org.jetbrains.kotlin.fir.expressions.FirStatement
 import org.jetbrains.kotlin.fir.resolve.calls.*
+import org.jetbrains.kotlin.fir.resolve.inference.model.ConeFixVariableConstraintPosition
 import org.jetbrains.kotlin.fir.resolve.substitution.AbstractConeSubstitutor
 import org.jetbrains.kotlin.fir.resolve.substitution.ChainedSubstitutor
 import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutor
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.resolve.calls.inference.NewConstraintSystem
 import org.jetbrains.kotlin.resolve.calls.inference.buildAbstractResultingSubstitutor
+import org.jetbrains.kotlin.resolve.calls.inference.components.ConstraintSystemCompletionContext
 import org.jetbrains.kotlin.resolve.calls.inference.components.ConstraintSystemCompletionMode
 import org.jetbrains.kotlin.resolve.calls.inference.model.*
 import org.jetbrains.kotlin.types.model.*
@@ -162,6 +164,17 @@ class FirDelegatedPropertyInferenceSession(
         return typeVariable in syntheticTypeVariableByTypeVariable.values
     }
 
+    override fun fixSyntheticTypeVariableWithNotEnoughInformation(
+        typeVariable: TypeVariableMarker,
+        completionContext: ConstraintSystemCompletionContext
+    ) {
+        completionContext.fixVariable(
+            typeVariable,
+            stubTypeBySyntheticTypeVariable[typeVariable]!!,
+            ConeFixVariableConstraintPosition(typeVariable)
+        )
+    }
+
     fun completeCandidates(): List<FirResolvable> {
         @Suppress("UNCHECKED_CAST")
         val notCompletedCalls = partiallyResolvedCalls.mapNotNull { partiallyResolvedCall ->

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/FirInferenceSession.kt

@@ -11,6 +11,7 @@ import org.jetbrains.kotlin.fir.resolve.calls.Candidate
 import org.jetbrains.kotlin.fir.types.ConeKotlinType
 import org.jetbrains.kotlin.fir.types.ConeStubType
 import org.jetbrains.kotlin.fir.types.ConeTypeVariableTypeConstructor
+import org.jetbrains.kotlin.resolve.calls.inference.components.ConstraintSystemCompletionContext
 import org.jetbrains.kotlin.resolve.calls.inference.components.ConstraintSystemCompletionMode
 import org.jetbrains.kotlin.resolve.calls.inference.model.ConstraintStorage
 import org.jetbrains.kotlin.resolve.calls.inference.model.NewConstraintSystemImpl
@@ -33,6 +34,10 @@ abstract class FirInferenceSession {
     abstract fun registerStubTypes(map: Map<TypeVariableMarker, StubTypeMarker>)
 
     abstract fun isSyntheticTypeVariable(typeVariable: TypeVariableMarker): Boolean
+    abstract fun fixSyntheticTypeVariableWithNotEnoughInformation(
+        typeVariable: TypeVariableMarker,
+        completionContext: ConstraintSystemCompletionContext
+    )
 
     abstract fun inferPostponedVariables(
         lambda: ResolvedLambdaAtom,
@@ -64,6 +69,10 @@ abstract class FirStubInferenceSession : FirInferenceSession() {
     override fun registerStubTypes(map: Map<TypeVariableMarker, StubTypeMarker>) {}
 
     override fun isSyntheticTypeVariable(typeVariable: TypeVariableMarker): Boolean = false
+    override fun fixSyntheticTypeVariableWithNotEnoughInformation(
+        typeVariable: TypeVariableMarker,
+        completionContext: ConstraintSystemCompletionContext
+    ) {}
 
     override fun createSyntheticStubTypes(system: NewConstraintSystemImpl): Map<TypeConstructorMarker, ConeStubType> = emptyMap()