63 lines
2.0 KiB
Rust
63 lines
2.0 KiB
Rust
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use if_chain::if_chain;
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use rustc::declare_lint_pass;
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use rustc::hir::*;
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use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc_session::declare_tool_lint;
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use crate::utils::{is_must_use_func_call, is_must_use_ty, span_help_and_lint};
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declare_clippy_lint! {
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/// **What it does:** Checks for `let _ = <expr>`
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/// where expr is #[must_use]
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///
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/// **Why is this bad?** It's better to explicitly
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/// handle the value of a #[must_use] expr
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// fn f() -> Result<u32, u32> {
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/// Ok(0)
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/// }
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///
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/// let _ = f();
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/// // is_ok() is marked #[must_use]
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/// let _ = f().is_ok();
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/// ```
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pub LET_UNDERSCORE_MUST_USE,
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restriction,
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"non-binding let on a #[must_use] expression"
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}
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declare_lint_pass!(LetUnderscore => [LET_UNDERSCORE_MUST_USE]);
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetUnderscore {
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fn check_stmt(&mut self, cx: &LateContext<'_, '_>, stmt: &Stmt) {
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if_chain! {
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if let StmtKind::Local(ref local) = stmt.kind;
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if let PatKind::Wild = local.pat.kind;
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if let Some(ref init) = local.init;
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then {
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if is_must_use_ty(cx, cx.tables.expr_ty(init)) {
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span_help_and_lint(
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cx,
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LET_UNDERSCORE_MUST_USE,
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stmt.span,
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"non-binding let on an expression with #[must_use] type",
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"consider explicitly using expression value"
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)
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} else if is_must_use_func_call(cx, init) {
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span_help_and_lint(
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cx,
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LET_UNDERSCORE_MUST_USE,
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stmt.span,
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"non-binding let on a result of a #[must_use] function",
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"consider explicitly using function result"
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)
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}
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}
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}
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}
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}
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