Here’s a clean PR description you can use:

🛠️ Fix ImmutablesBuilderProvider superclass handling and nested type resolution

Summary

This PR fixes incorrect superclass traversal and improves the resolution of Immutables-generated types in ImmutablesBuilderProvider. It also corrects issues in constructing qualified names for nested types when resolving Immutable implementations.

🔧 Changes

1. Fixed superclass lookup logic

• TypeElement.getSuperclass() returns a TypeMirror, not a TypeElement

• Added safe handling for:

  • TypeKind.NONE (e.g. java.lang.Object)
  • DeclaredType casting before recursion

• Prevents incorrect or unsafe recursive calls in findBuilderInfo

2. Fixed immutable type resolution for nested classes

• Improved asImmutableElement() to correctly handle nested types
• Replaced fragile single-level enclosing element handling with a safe hierarchy traversal
• Properly constructs fully qualified name using $ for nested classes

3. Fixed getTypeElement usage

• Ensured elementUtils.getTypeElement() is called with String (toString() result), not StringBuilder

🧪 Impact

• Correctly detects builder information for Immutables-generated implementations
• Fixes failures when working with nested classes or interfaces
• Prevents incorrect superclass traversal in type hierarchy resolution
• Improves robustness of annotation processing phase in MapStruct

⚠️ Notes

• No functional changes to public APIs
• Only affects annotation processing internals
• Safe for backward compatibility

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