Update design for PR rust-lang#16180: feat(rwlock_atomic): add new lints for using RwLock with atomic types

Author: gauravagerwala

pr-analysis-16180.md

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+# PR #16180: Workflow Design Impact Analysis
+
+[PR #16180](https://github.com/rust-lang/rust-clippy/pull/16180)
+
+## Affected Workflows
+
+- **lint-development**: This workflow is impacted because the PR modifies key files involved in lint creation and integration, including a new lint implementation in `clippy_lints/src/rwlock_atomic.rs`, updates to `clippy_lints/src/lib.rs` for module inclusion and pass registration, generated updates to `clippy_lints/src/declared_lints.rs` for lint metadata registration, and new UI tests in `tests/ui/`. These align directly with the relevant files listed in `.exp/workflows.json` for lint development.
+
+- **testing**: The addition of new UI test files (`tests/ui/rwlock_atomic.rs`, `.stderr`, `.fixed`) extends the test suite, which is a core component of the testing workflow as per `.exp/workflows.json` relevant files (`tests/`, `ui/`, `tests/ui-*`).
+
+Other workflows like `clippy-driver` and `cargo-clippy` indirectly include `clippy_lints/src/` as relevant files, but the changes are confined to adding new lint logic without altering driver invocation, registration mechanisms, or CLI handling.
+
+## lint-development Analysis
+
+### Summary of design changes
+
+The PR implements two new restriction lints (`rwlock_atomic` and `rwlock_integer`) in a single `LateLintPass` (`RwLock`) within `clippy_lints/src/rwlock_atomic.rs`. These lints detect `RwLock` usage for types amenable to atomic operations (e.g., integers, bools, `*mut T`), suggesting replacements with `Atomic*` types for better performance. The pass checks static items and local bindings during HIR analysis, using `clippy_utils` for type queries and suggestions, including handling type ascriptions and multipart fixes.
+
+This adheres strictly to the existing design:
+- Lint declarations via `declare_clippy_lint!` macro for metadata (name, level=restrict, category, docs).
+- Implementation as standard late pass with `check_item` and `check_local` hooks.
+- Automatic integration via `update_lints` tool, evidenced by additions to `lib.rs` (mod and pass registration) and `declared_lints.rs` (added to `LINTS` array).
+- UI tests for validation and fix verification.
+- Documentation updates (CHANGELOG.md links, README.md and book/src/README.md lint counts) consistent with tool-generated refreshes.
+
+No new components, steps, or interactions introduced. The scaffolding sequence (new lint file, tests, update tools) and integration sequence (registration in driver via `LINTS` and passes) remain unchanged. Benefits include enhanced detection of inefficient concurrency patterns with actionable fixes; implications are minimal as it's additive.
+
+No Mermaid diagrams require updates, as the PR exemplifies rather than modifies the documented sequences.
+
+## testing Analysis
+
+### Summary of design changes
+
+New files in `tests/ui/rwlock_atomic/` provide test cases demonstrating lint triggers, expected diagnostics, and auto-fix outputs for the new lints. These UI tests simulate `RwLock` misuse scenarios, ensuring correct emission of warnings, suggestion messages, and replacement code.
+
+The changes conform to the testing design:
+- Standard UI test structure: `.rs` input, `.stderr` for diagnostic matching, `.fixed` for rustfix validation.
+- Integrated into `cargo test` via `compile-test.rs` and `ui_test` framework, which will compile these with Clippy and verify outputs.
+- No modifications to test execution, blessing (`cargo bless`), categories, or utilities like `check-fmt.rs`.
+
+No alterations to components (e.g., dogfooding, config checks) or sequences (UI test loop of spawning driver, comparing outputs). Benefits: Validates new lints prevent regressions; ensures fixes are correct. No broader implications.
+
+No Mermaid diagrams require updates, as test file additions fit within the existing "FS" (file system test files) in the UI and dogfooding sequences without changing flows.
+
+## Overall Impact
+
+The PR enhances Clippy's lint capabilities without disrupting or evolving the documented workflows' designs. It demonstrates effective use of the lint-development and testing processes. No updates to `.exp` design documents are necessary. All existing Mermaid diagrams remain accurate representations post-merge.