Fix name resolution errors around alias ancestor types

`StructTypeImpl.parent` was not being resolved correctly when the
relevant ancestor was a type alias.
This was because we did an `instanceof StructTypeImpl` check, which is
incompatible with the generated type alias impl classes introduced in
b3b14dd.

CHANGELOG.md

@@ -21,6 +21,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- Name resolution errors around alias ancestor types.
 - Parsing errors around partial `asm` blocks blocks in conditional branches.
 - False positives around case items with multiple values in `CaseStatementSize`.
 

delphi-frontend/src/main/java/au/com/integradev/delphi/type/factory/StructTypeImpl.java

@@ -70,7 +70,7 @@ private void setAncestors(Set<Type> ancestorList) {
     } else {
       this.parent =
           this.ancestorList.stream()
-              .filter(StructTypeImpl.class::isInstance)
+              .filter(Type::isStruct)
               .filter(not(Type::isInterface))
               .findFirst()
               .orElse(TypeFactory.unknownType());