bug - Method-call decorators emit invalid Rust for static/class receivers

[dannymeijer]

Thanks for reporting! Please include a minimal reproduction when possible.

Area

• Compiler (frontend/backend/codegen)

Summary

Expected: method-call decorators should lower using the same receiver/member-call rules as ordinary checked Incan code. A class static method decorator such as @Registry::add("col") should emit a Rust associated function call, and a static registry instance decorator such as @FUNCTIONS.add("col") should access the static cell value before invoking the instance method.

Actual: both forms typecheck, but generated Rust is invalid. This blocks using a registry API where registry.add(...) is the decorator factory for function catalog registration.

Reproduction steps

1. Create repro_static_method.incn:

class Registry:
    pub names: list[str]

    @staticmethod
    def new() -> Self:
        return Registry(names=[])

    @staticmethod
    def add[F](name: str) -> (F) -> F:
        FUNCTIONS.names.append(name)
        return (func) => func


static FUNCTIONS: Registry = Registry.new()


@Registry::add("col")
def col(name: str) -> str:
    return name


def main() -> None:
    println(col("amount"))
    println(len(FUNCTIONS.names))

2. Run incan --check repro_static_method.incn.
3. Run incan build repro_static_method.incn.
4. Create repro_static_receiver.incn:

class Registry:
    pub names: list[str]

    @staticmethod
    def new() -> Self:
        return Registry(names=[])

    def add[F](mut self, name: str) -> (F) -> F:
        self.names.append(name)
        return (func) => func


static FUNCTIONS: Registry = Registry.new()


@FUNCTIONS.add("col")
def col(name: str) -> str:
    return name


def main() -> None:
    println(col("amount"))
    println(len(FUNCTIONS.names))

5. Run incan --check repro_static_receiver.incn.
6. Run incan build repro_static_receiver.incn.

Output / logs

$ incan --check repro_static_method.incn
✓ Type check passed!

$ incan build repro_static_method.incn
error[E0423]: expected value, found struct `Registry`
  --> src/main.rs:49:5
   |
49 |     Registry.add("col".into())(__incan_original_col),
   |     ^^^^^^^^
   |
help: use the path separator to refer to an item
   |
49 -     Registry.add("col".into())(__incan_original_col),
49 +     Registry::add("col".into())(__incan_original_col),
   |

$ incan --check repro_static_receiver.incn
✓ Type check passed!

$ incan build repro_static_receiver.incn
error[E0599]: no method named `add` found for struct `LazyLock<StaticCell<Registry>>` in the current scope
  --> src/main.rs:54:15
   |
54 |     FUNCTIONS.add("col".to_string())(__incan_original_col),
   |               ^^^ method not found in `LazyLock<StaticCell<Registry>>`

Environment

OS: macOS
Rust: rustc 1.96.0-nightly (362211dc2 2026-03-24)
Incan: 0.3.0-rc10 on release/v0.3
Command: incan --check repro_static_method.incn, incan build repro_static_method.incn, incan --check repro_static_receiver.incn, incan build repro_static_receiver.incn

Related context: discovered while implementing InQL RFC 014 function registry decorators. The desired API is a registry-owned add decorator factory with all function metadata supplied in the decorator call.

[dannymeijer]

Fixed on release/v0.3 in 903a5dad6fc8b3320995c3b9de98669ca9ce8998.

What changed:

• synthetic default-span decorator expressions now recover metadata-backed identifier classification during lowering, so class/static decorator receivers lower through the same type/static rules as checked source expressions;
• call emission now wraps storage-rooted method-call callees only when they are used as call targets, preserving existing static-storage statement emission while allowing @FUNCTIONS.add(...) to produce valid Rust;
• added an e2e regression covering both @Registry::add_static(...) and @FUNCTIONS.add(...) decorator factories;
• updated the v0.3 release notes to include bug - Method-call decorators emit invalid Rust for static/class receivers #645.

Verification:

• cargo test e2e_method_call_decorator_factories_use_checked_receiver_lowering -- --nocapture
• cargo test test_rfc052_pub_static_codegen
• cargo test test_rfc052_module_static_storage_codegen
• direct CLI repro build for the bug - Method-call decorators emit invalid Rust for static/class receivers #645 minimized project
• git diff --check
• make pre-commit
• release PR Release/v0.3 #618 CI run 799 completed successfully: https://github.com/dannys-code-corner/incan/actions/runs/26341518630