[SAY-5]

Named as: targets were classified as IDENT without enabling conversion, so cast shims ignored their using: serializer. Pointer shims could generate invalid expressions such as &field.MarshalMsg(...). Enable conversion locally for named cast shims; primitive shims, ordinary aliases, and mode:convert retain their existing behavior.

Fixes #439. The regression generates a named map serializer and checks wire bytes, all five methods, zero-value decoding, nil pointers, container fields, and decode errors. The same valid fixture fails to compile with the upstream generator.

Validation on Go 1.26.2 / macOS ARM64:

• 824 top-level tests, 1,055 passing test/subtest outcomes across the generator, runtime, setof, and generated fixtures.
• go vet, gofmt, and CI-pinned golangci-lint 2.5.0 (./...) pass.
• TinyGo, TestConv32, TestConv64, TestReadIntfRecursion, TestSkipRecursion, fuzzing, and benchmarks were not run locally.

AI assistance: Codex assisted with the implementation, tests, and description. A separate agent reviewed the change.

[klauspost]

lgtm