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Clean up some comments on lint implementation
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‎compiler/rustc_lint/src/builtin.rs‎

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@@ -4,21 +4,14 @@
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//! AST visitor. Also see `rustc_session::lint::builtin`, which contains the
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//! definitions of lints that are emitted directly inside the main compiler.
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//!
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//! To add a new lint to rustc, declare it here using `declare_lint!()`.
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//! To add a new lint to rustc, declare it here using [`declare_lint!`].
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//! Then add code to emit the new lint in the appropriate circumstances.
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//! You can do that in an existing `LintPass` if it makes sense, or in a
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//! new `LintPass`, or using `Session::add_lint` elsewhere in the
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//! compiler. Only do the latter if the check can't be written cleanly as a
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//! `LintPass` (also, note that such lints will need to be defined in
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//! `rustc_session::lint::builtin`, not here).
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//!
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//! If you define a new `EarlyLintPass`, you will also need to add it to the
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//! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
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//! `lib.rs`. Use the former for unit-like structs and the latter for structs
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//! with a `pub fn new()`.
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//! If you define a new [`EarlyLintPass`], you will also need to add it to the
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//! [`crate::early_lint_methods!`] invocation in `lib.rs`.
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//!
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//! If you define a new `LateLintPass`, you will also need to add it to the
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//! `late_lint_methods!` invocation in `lib.rs`.
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//! If you define a new [`LateLintPass`], you will also need to add it to the
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//! [`crate::late_lint_methods!`] invocation in `lib.rs`.
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use std::fmt::Write;
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‎compiler/rustc_lint/src/context.rs‎

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//! Implementation of lint checking.
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//! Basic types for managing and implementing lints.
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//!
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//! The lint checking is mostly consolidated into one pass which runs
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//! after all other analyses. Throughout compilation, lint warnings
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//! can be added via the `add_lint` method on the Session structure. This
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//! requires a span and an ID of the node that the lint is being added to. The
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//! lint isn't actually emitted at that time because it is unknown what the
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//! actual lint level at that location is.
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//!
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//! To actually emit lint warnings/errors, a separate pass is used.
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//! A context keeps track of the current state of all lint levels.
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//! Upon entering a node of the ast which can modify the lint settings, the
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//! previous lint state is pushed onto a stack and the ast is then recursed
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//! upon. As the ast is traversed, this keeps track of the current lint level
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//! for all lint attributes.
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//! See <https://rustc-dev-guide.rust-lang.org/diagnostics.html> for an
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//! overview of how lints are implemented.
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use std::cell::Cell;
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use std::{iter, slice};
@@ -52,9 +41,6 @@ type LateLintPassFactory =
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dyn for<'tcx> Fn(TyCtxt<'tcx>) -> LateLintPassObject<'tcx> + sync::DynSend + sync::DynSync;
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/// Information about the registered lints.
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///
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/// This is basically the subset of `Context` that we can
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/// build early in the compile pipeline.
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pub struct LintStore {
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/// Registered lints.
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lints: Vec<&'static Lint>,

‎compiler/rustc_lint/src/early.rs‎

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//! Implementation of lint checking.
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//! Implementation of the early lint pass.
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//!
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//! The lint checking is mostly consolidated into one pass which runs
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//! after all other analyses. Throughout compilation, lint warnings
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//! can be added via the `add_lint` method on the Session structure. This
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//! requires a span and an ID of the node that the lint is being added to. The
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//! lint isn't actually emitted at that time because it is unknown what the
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//! actual lint level at that location is.
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//!
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//! To actually emit lint warnings/errors, a separate pass is used.
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//! A context keeps track of the current state of all lint levels.
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//! Upon entering a node of the ast which can modify the lint settings, the
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//! previous lint state is pushed onto a stack and the ast is then recursed
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//! upon. As the ast is traversed, this keeps track of the current lint level
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//! for all lint attributes.
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//! The early lint pass works on AST nodes after macro expansion and name
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//! resolution, just before AST lowering. These lints are for purely
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//! syntactical lints.
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use rustc_ast::ptr::P;
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use rustc_ast::visit::{self as ast_visit, Visitor, walk_list};

‎compiler/rustc_lint/src/late.rs‎

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//! Implementation of lint checking.
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//! Implementation of the late lint pass.
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//!
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//! The lint checking is mostly consolidated into one pass which runs
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//! after all other analyses. Throughout compilation, lint warnings
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//! can be added via the `add_lint` method on the Session structure. This
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//! requires a span and an ID of the node that the lint is being added to. The
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//! lint isn't actually emitted at that time because it is unknown what the
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//! actual lint level at that location is.
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//!
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//! To actually emit lint warnings/errors, a separate pass is used.
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//! A context keeps track of the current state of all lint levels.
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//! Upon entering a node of the ast which can modify the lint settings, the
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//! previous lint state is pushed onto a stack and the ast is then recursed
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//! upon. As the ast is traversed, this keeps track of the current lint level
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//! for all lint attributes.
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//! The late lint pass Works on HIR nodes, towards the end of analysis (after
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//! borrow checking, etc.). These lints have full type information available.
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use std::any::Any;
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use std::cell::Cell;

‎compiler/rustc_lint/src/lib.rs‎

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//! other phases of the compiler, which are generally required to hold in order
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//! to compile the program at all.
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//!
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//! Most lints can be written as [LintPass] instances. These run after
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//! Most lints can be written as [`LintPass`] instances. These run after
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//! all other analyses. The `LintPass`es built into rustc are defined
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//! within [rustc_session::lint::builtin],
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//! which has further comments on how to add such a lint.
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//! rustc can also load external lint plugins, as is done for Clippy.
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//!
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//! Some of rustc's lints are defined elsewhere in the compiler and work by
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//! calling `add_lint()` on the overall `Session` object. This works when
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//! it happens before the main lint pass, which emits the lints stored by
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//! `add_lint()`. To emit lints after the main lint pass (from codegen, for
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//! example) requires more effort. See `emit_lint` and `GatherNodeLevels`
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//! in `context.rs`.
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//!
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//! Some code also exists in [rustc_session::lint], [rustc_middle::lint].
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//! See <https://rustc-dev-guide.rust-lang.org/diagnostics.html> for an
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//! overview of how lints are implemented.
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//!
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//! ## Note
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//!

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