using cleanup on all exit paths + warning W3301

using cleanup on all exit paths + warning W3301

The :service profile’s using statement (SPEC-019 §3.5) now guarantees that the resource’s cleanup method runs on every exit path out of the block — not just on fall-through.

All-exit-path cleanup

Cleanup (close() / deinit()) now fires on early return, try error propagation, break, continue, and panic paths:

using file := try open("data.txt") do
    let header := try read_header(file)  // on error: file.close() runs, then the error propagates
    if header.empty() do
        return                           // file.close() runs before the return
    end
    process(file)
end  // fall-through: file.close() runs as before

Before this release, cleanup on error and early-return paths was silently skipped — the file stayed open. This is now fixed.

Warning W3301 — using resource without a cleanup method

A using resource’s type must provide a cleanup method (close() or deinit()). As of this release, when the resource’s type is inferred (no explicit annotation) and resolves to a named struct with no cleanup method, the compiler emits warning W3301 instead of silently falling back to a runtime no-op:

warning: W3301: `using` resource of type 'Config' has no cleanup method (close/deinit); cleanup is a no-op

The full diagnostic behavior:

Shape	Diagnostic
using x: T := … (annotated) with no cleanup method	E3301 hard error (unchanged)
Inferred named struct with no cleanup method	W3301 warning (new)
Inferred primitive resource (using f := open() where open() i64)	silent by design — primitives cannot have methods, so a diagnostic would be a false positive

Fix: add a close() or deinit() method to the struct, or don’t wrap the value in using if no cleanup is needed.