Use type substitution when matching header-impl members

Previously, type substitution, which is critical for matching generic
header/impl members with each other, was only performed when
checkImplementationHasHeaderDeclaration was called for impl class
(areCompatibleClassifiers creates the correct substitutor). This was
done in areCompatibleClassifiers: a substitutor which maps type
parameters of the header class to type parameters of the impl class was
created.

Now we create the same substitutor when
checkImplementationHasHeaderDeclaration is called for an impl member of
an impl class as well, manually.

 #KT-15230 Fixed

compiler/frontend/src/org/jetbrains/kotlin/resolve/checkers/HeaderImplDeclarationChecker.kt

@@ -119,9 +119,18 @@ class HeaderImplDeclarationChecker(val moduleToCheck: ModuleDescriptor? = null)
                     else -> return // do not report anything for incorrect code, e.g. 'impl' local function
                 }
                 candidates.any { declaration ->
+                    // TODO: optimize by caching this per impl-header class pair, do not create a new substitutor for each impl member
+                    val substitutor =
+                            if (container is ClassDescriptor) {
+                                val headerClass = declaration.containingDeclaration as ClassDescriptor
+                                // TODO: this might not work for members of inner generic classes
+                                Substitutor(headerClass.declaredTypeParameters, container.declaredTypeParameters)
+                            }
+                            else null
+
                     descriptor != declaration &&
                     declaration.isHeader &&
-                    areCompatibleCallables(declaration, descriptor, checkImpl = false) == Compatible
+                    areCompatibleCallables(declaration, descriptor, checkImpl = false, parentSubstitutor = substitutor) == Compatible
                 }
             }
             is ClassifierDescriptorWithTypeParameters -> descriptor.findDeclarationForClass() != null
@@ -342,12 +351,11 @@ class HeaderImplDeclarationChecker(val moduleToCheck: ModuleDescriptor? = null)
         val bTypeParams = b.declaredTypeParameters
         if (aTypeParams.size != bTypeParams.size) return Incompatible.TypeParameterCount
 
-        val substitutor = Substitutor(aTypeParams, bTypeParams, parentSubstitutor)
-
         if (a.modality != b.modality && !(a.modality == Modality.FINAL && b.modality == Modality.OPEN)) return Incompatible.Modality
 
         if (a.visibility != b.visibility) return Incompatible.Visibility
 
+        val substitutor = Substitutor(aTypeParams, bTypeParams, parentSubstitutor)
         areCompatibleTypeParameters(aTypeParams, bTypeParams, substitutor).let { if (it != Compatible) return it }
 
         // Subtract kotlin.Any from supertypes because it's implicitly added if no explicit supertype is specified,