Add check already fixed variables in PostponedArgumentInputTypesResolver during adding constraints on them and using inside a functional type

^KT-42374 Fixed

compiler/fir/analysis-tests/tests/org/jetbrains/kotlin/fir/FirOldFrontendDiagnosticsTestGenerated.java

@@ -11085,6 +11085,11 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirOldFronte
                     runTest("compiler/testData/diagnostics/tests/inference/completion/postponedArgumentsAnalysis/callableReferences.kt");
                 }
 
+                @TestMetadata("fixingVariableDuringAddingConstraintForFirstPosponedArgument.kt")
+                public void testFixingVariableDuringAddingConstraintForFirstPosponedArgument() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/inference/completion/postponedArgumentsAnalysis/fixingVariableDuringAddingConstraintForFirstPosponedArgument.kt");
+                }
+
                 @TestMetadata("lackOfDeepIncorporation.kt")
                 public void testLackOfDeepIncorporation() throws Exception {
                     runTest("compiler/testData/diagnostics/tests/inference/completion/postponedArgumentsAnalysis/lackOfDeepIncorporation.kt");

compiler/resolution.common/src/org/jetbrains/kotlin/resolve/calls/inference/components/ConstraintSystemCompletionContext.kt

@@ -16,6 +16,7 @@ import org.jetbrains.kotlin.types.model.TypeVariableMarker
 interface ConstraintSystemCompletionContext : VariableFixationFinder.Context, ResultTypeResolver.Context {
     val allTypeVariables: Map<TypeConstructorMarker, TypeVariableMarker>
     override val notFixedTypeVariables: Map<TypeConstructorMarker, VariableWithConstraints>
+    override val fixedTypeVariables: Map<TypeConstructorMarker, KotlinTypeMarker>
     override val postponedTypeVariables: List<TypeVariableMarker>
 
     fun getBuilder(): ConstraintSystemBuilder

compiler/resolution.common/src/org/jetbrains/kotlin/resolve/calls/inference/components/VariableFixationFinder.kt

@@ -20,6 +20,7 @@ class VariableFixationFinder(
 ) {
     interface Context : TypeSystemInferenceExtensionContext {
         val notFixedTypeVariables: Map<TypeConstructorMarker, VariableWithConstraints>
+        val fixedTypeVariables: Map<TypeConstructorMarker, KotlinTypeMarker>
         val postponedTypeVariables: List<TypeVariableMarker>
         fun isReified(variable: TypeVariableMarker): Boolean
     }

compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/inference/components/PostponedArgumentInputTypesResolver.kt

@@ -220,9 +220,12 @@ class PostponedArgumentInputTypesResolver(
 
         return allGroupedParameterTypes.mapIndexed { index, types ->
             val parameterTypeVariable = createTypeVariableForParameterType(argument, index)
+            val typeVariableConstructor = parameterTypeVariable.freshTypeConstructor
 
             for (typeWithKind in types) {
+                if (typeVariableConstructor in fixedTypeVariables) break
                 if (typeWithKind == null) continue
+
                 when (typeWithKind.direction) {
                     ConstraintKind.EQUALITY -> csBuilder.addEqualityConstraint(
                         parameterTypeVariable.defaultType, typeWithKind.type, ArgumentConstraintPositionImpl(atom)
@@ -236,7 +239,13 @@ class PostponedArgumentInputTypesResolver(
                 }
             }
 
-            parameterTypeVariable.defaultType.asTypeProjection()
+            val resultType = if (typeVariableConstructor in fixedTypeVariables) {
+                fixedTypeVariables[typeVariableConstructor] as KotlinType
+            } else {
+                parameterTypeVariable.defaultType
+            }
+
+            resultType.asTypeProjection()
         }
     }
 

compiler/testData/diagnostics/tests/inference/completion/postponedArgumentsAnalysis/fixingVariableDuringAddingConstraintForFirstPosponedArgument.kt

@@ -0,0 +1,8 @@
+// FIR_IDENTICAL
+// !DIAGNOSTICS: -UNUSED_PARAMETER -UNUSED_ANONYMOUS_PARAMETER
+
+fun f(p: (Int) -> (String) -> Unit) {}
+
+fun g(cond: Boolean) {
+    f(if (cond) { i -> { } } else { i -> { } })
+}

compiler/testData/diagnostics/tests/inference/completion/postponedArgumentsAnalysis/fixingVariableDuringAddingConstraintForFirstPosponedArgument.txt

@@ -0,0 +1,4 @@
+package
+
+public fun f(/*0*/ p: (kotlin.Int) -> (kotlin.String) -> kotlin.Unit): kotlin.Unit
+public fun g(/*0*/ cond: kotlin.Boolean): kotlin.Unit

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -11092,6 +11092,11 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTestWithFirVali
                         runTest("compiler/testData/diagnostics/tests/inference/completion/postponedArgumentsAnalysis/callableReferences.kt");
                     }
 
+                    @TestMetadata("fixingVariableDuringAddingConstraintForFirstPosponedArgument.kt")
+                    public void testFixingVariableDuringAddingConstraintForFirstPosponedArgument() throws Exception {
+                        runTest("compiler/testData/diagnostics/tests/inference/completion/postponedArgumentsAnalysis/fixingVariableDuringAddingConstraintForFirstPosponedArgument.kt");
+                    }
+
                     @TestMetadata("lackOfDeepIncorporation.kt")
                     public void testLackOfDeepIncorporation() throws Exception {
                         runTest("compiler/testData/diagnostics/tests/inference/completion/postponedArgumentsAnalysis/lackOfDeepIncorporation.kt");

compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java

@@ -11087,6 +11087,11 @@ public class DiagnosticsUsingJavacTestGenerated extends AbstractDiagnosticsUsing
                         runTest("compiler/testData/diagnostics/tests/inference/completion/postponedArgumentsAnalysis/callableReferences.kt");
                     }
 
+                    @TestMetadata("fixingVariableDuringAddingConstraintForFirstPosponedArgument.kt")
+                    public void testFixingVariableDuringAddingConstraintForFirstPosponedArgument() throws Exception {
+                        runTest("compiler/testData/diagnostics/tests/inference/completion/postponedArgumentsAnalysis/fixingVariableDuringAddingConstraintForFirstPosponedArgument.kt");
+                    }
+
                     @TestMetadata("lackOfDeepIncorporation.kt")
                     public void testLackOfDeepIncorporation() throws Exception {
                         runTest("compiler/testData/diagnostics/tests/inference/completion/postponedArgumentsAnalysis/lackOfDeepIncorporation.kt");