slachiewicz opened a new pull request, #3812:
URL: https://github.com/apache/thrift/pull/3812
## Summary
A typedef of a struct was emitted as a **defined type** (`type Alias
Struct`). In Go a defined type is a distinct type with its own (empty) method
set. Because Thrift structs are always used through a pointer, the declared
type was actually `type Alias *Inner`, meaning:
- The alias had no `Read`/`Write`/`Equals` methods (`*Inner` methods were
not promoted).
- Every field access required a double pointer.
- The `-remote` stub called `NewAlias()` instead of the struct's own
`NewInner()`, which didn't exist.
**Fix:** emit a Go **type alias** (`type Alias = Struct`) when the typedef's
resolved type is a struct or exception. A Go alias shares the named type's
identity and method set entirely — which is exactly the Thrift typedef
semantics.
A secondary bug is also fixed: the forward-typedef unwrapping used a single
`if` that jumped directly to the true type, silently replacing user-declared
typedef names in field types with their underlying types. The fix changes it to
a `while` loop that stops at the first non-forward typedef.
## Root causes closed by this PR
| Ticket | Description |
|---|---|
| THRIFT-3037 | Go: typedef of struct from included file broken |
| THRIFT-3491 | Go: typedef of struct in service signature broken |
| THRIFT-4901 | Go: typedef of struct generates wrong type |
| THRIFT-5489 | Go: forward typedef loses declared name |
| THRIFT-5601 | Go: forward typedef fix (reverted in THRIFT-5685 due to side
effects now addressed here) |
| THRIFT-5685 | Revert of THRIFT-5601 |
## Changes
- **`compiler/cpp/src/thrift/generate/t_go_generator.cc`**
- `generate_typedef`: emit `= Struct` alias for struct/exception typedefs.
- `type_to_go_type_with_opt`: forward-typedef unwrapping changed from `if`
to `while` (stop at first declared typedef); struct typedefs now return
`*TypeName` as fields expect.
- `generate_service_remote`: use the resolved struct's name/module for
constructor; skip the typedef-conversion cast for struct typedefs (alias = same
type).
- **`lib/go/test/TypedefStructTest.thrift`** — new: covers forward typedef,
typedef of struct, typedef of typedef, typedef of exception, service with
typedef'd parameter/return.
- **`lib/go/test/TypedefIncludeTest.thrift`** — new: covers typedef of a
struct from an included file.
- **`lib/go/test/tests/typedef_struct_test.go`** — new: compile-time
alias-identity assertions + round-trip tests over binary/compact/JSON for each
shape.
- **`lib/go/test/Makefile.am`** — registers the two new Thrift files.
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