Add trybuild test for Captured::state lifetime correctness (#314)

[leynos]

Summary

Closes #314

Adds the trybuild scaffolding the issue specifies:

1. tests/compile_fail_tests.rs with captured_state_lifetime_tests running both UI cases.
2. tests/ui/captured_state_outlives_captured.rs — holds a &State beyond the owning Captured; rejected by the borrow checker (E0597, "captured does not live long enough").
3. tests/ui/captured_state_within_scope.rs — uses captured.state() only within the owning Captured's lifetime; compiles.
4. trybuild = { version = "1", features = ["diff"] } dev-dependency.
5. Expected .stderr recorded once with TRYBUILD=overwrite and committed.

Acceptance checks: fd -e rs . tests/ui | wc -l → 2; rg trybuild Cargo.toml → the new dev-dependency.

Validation

• make check-fmt / make lint / make test — pass (38 suites, including the new compile-fail target)

🤖 Generated with Claude Code

Summary by Sourcery

Add compile-time UI tests to validate the lifetime correctness of Captured::state() using trybuild.

Build:

• Add trybuild as a dev-dependency with the diff feature enabled.

Tests:

• Introduce a trybuild-based compile-fail test suite covering Captured::state() lifetime behavior, including a failing outlives case and a passing well-scoped case.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch issue-314-trybuild-captured-lifetime

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[sourcery-ai]

Reviewer's Guide

Adds trybuild-based UI tests to pin the borrow-checker guarantees around Captured::state() lifetimes, by introducing compile-fail and pass cases plus the required dev-dependency wiring.

Sequence diagram for trybuild-based Captured::state lifetime tests

sequenceDiagram
    actor Developer
    participant compile_fail_tests as compile_fail_tests_rs
    participant TestCases as trybuild_TestCases
    participant rustc

    Developer->>compile_fail_tests: run captured_state_lifetime_tests
    compile_fail_tests->>TestCases: new()

    compile_fail_tests->>TestCases: compile_fail("tests/ui/captured_state_outlives_captured.rs")
    TestCases->>rustc: compile captured_state_outlives_captured.rs
    rustc-->>TestCases: E0597 matches captured_state_outlives_captured.stderr

    compile_fail_tests->>TestCases: pass("tests/ui/captured_state_within_scope.rs")
    TestCases->>rustc: compile captured_state_within_scope.rs
    rustc-->>TestCases: success (no diagnostics)

Loading

File-Level Changes

Change	Details	Files
Introduce trybuild-based compile-time tests for Captured::state() lifetime behavior.	Add a new test harness that runs a failing UI test and a passing UI test via trybuild Create a UI test that intentionally lets a &State outlive its Captured owner and must fail to compile Create a UI test that uses Captured::state() only within the Captured's lifetime and must compile Record the expected compiler stderr for the failing UI test	tests/compile_fail_tests.rs tests/ui/captured_state_outlives_captured.rs tests/ui/captured_state_within_scope.rs tests/ui/captured_state_outlives_captured.stderr
Wire up the trybuild test framework as a dev-dependency.	Add trybuild with the diff feature to dev-dependencies so UI tests can be compiled and compared	Cargo.toml Cargo.lock

Assessment against linked issues

Issue	Objective	Addressed	Explanation
#314	Add trybuild compile-time test scaffolding, including tests/compile_fail_tests.rs with a captured_state_lifetime_tests function that runs a failing UI test for captured_state_outlives_captured.rs and a passing UI test for captured_state_within_scope.rs, and add trybuild as a dev-dependency in Cargo.toml.	✅
#314	Create tests/ui/captured_state_outlives_captured.rs that attempts to hold a &State reference beyond the lifetime of the owning Captured and is rejected by the borrow checker, and record the corresponding expected stderr file tests/ui/captured_state_outlives_captured.stderr.	✅
#314	Create tests/ui/captured_state_within_scope.rs that uses Captured::state() only within the lifetime of the owning Captured and compiles successfully.	✅

Possibly linked issues

• Add trybuild compile-time test for Captured::state() lifetime correctness #314: The PR implements the requested trybuild UI tests, files, and dev-dependency for Captured::state() lifetimes.

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