fix: emit $__() instead of $__i18n._() in useLingui transform

[cpruijsen]

Fixes #275

Inside a useLingui scope, t calls now compile to $__(...) instead of $__i18n._(...), the same shape @lingui/babel-plugin-lingui-macro emits:

// before
const { i18n: $__i18n, _: $__ } = $_useLingui();
$__i18n._(/*i18n*/ { id: "...", message: "Hello" });

// after
const { _: $__ } = $_useLingui();
$__(/*i18n*/ { id: "...", message: "Hello" });

The old output bound $__ but never called it. With @lingui/solid, i18n is an accessor, so $__i18n._ is undefined and the app crashes with TypeError: $__i18n._ is not a function. With React Compiler, a [t] dependency compiled to [$__] while the call went through $__i18n, so the compiler could not preserve the manual memoization.

Changes

• handle_use_lingui (lib.rs): drop the t prop from the rewritten pattern instead of replacing it with i18n: $__i18n. A user-written i18n in the pattern is kept.
• create_i18n_fn_call (js_macro_folder.rs): inside a useLingui scope, emit $__(...), tracked by a new optional RuntimeIdents::use_lingui_t set only on the per-function context clone. t(customI18n) still emits customI18n._(...), and calls outside a useLingui scope still emit $_i18n._(...), so those snapshots do not change.

Tests

• Updated use_lingui and lingui_directive insta snapshots and the native-tools transform.spec.ts inline snapshot. Added work_with_custom_i18n_instance for t(i18n) inside a useLingui scope.
• cargo test --workspace, cargo clippy --all-targets --all-features -- -D warnings, cargo fmt --check, and vitest in packages/native-tools pass. With the source reverted, 12 Rust snapshots and the vitest inline snapshot fail.
• Not tested against a real @lingui/solid app.

Open question

Core-macro calls such as plural from @lingui/core/macro inside a useLingui scope also go through $__ now, because they used the hook's $__i18n before. Routing them to the global i18n import instead is a one-branch change in create_i18n_fn_call if you prefer that.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.44%. Comparing base (9a1ae84) to head (dfa7bca).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #280      +/-   ##
==========================================
+ Coverage   94.41%   94.44%   +0.02%     
==========================================
  Files          11       11              
  Lines        2507     2518      +11     
==========================================
+ Hits         2367     2378      +11     
  Misses        140      140              

Flag	Coverage Δ
unittests	94.44% <100.00%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
crates/lingui_macro/src/js_macro_folder.rs	98.69% <100.00%> (+0.07%)	⬆️
crates/lingui_macro/src/lib.rs	91.47% <100.00%> (-0.07%)	⬇️
crates/lingui_macro/src/macro_utils.rs	91.88% <100.00%> (+0.02%)	⬆️

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[andrii-bodnar]

@cpruijsen thank you!

[andrii-bodnar]

Core-macro calls such as plural from @lingui/core/macro inside a useLingui scope also go through $__ now [...] Routing them to the global i18n import instead is a one-branch change if you prefer that.

Let's leave them on $__. They used the hook's $__i18n._ before, so this keeps the same i18n instance and only changes the call shape. Switching them to the global i18n would be a separate behavior change.