44 lines
1.4 KiB
Rust
44 lines
1.4 KiB
Rust
use clippy_utils::diagnostics::span_lint;
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use clippy_utils::is_adjusted;
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use rustc_hir::{Expr, ExprKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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declare_clippy_lint! {
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/// **What it does:** Checks for construction of a structure or tuple just to
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/// assign a value in it.
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///
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/// **Why is this bad?** Readability. If the structure is only created to be
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/// updated, why not write the structure you want in the first place?
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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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/// (0, 0).0 = 1
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/// ```
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pub TEMPORARY_ASSIGNMENT,
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complexity,
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"assignments to temporaries"
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}
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fn is_temporary(expr: &Expr<'_>) -> bool {
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matches!(&expr.kind, ExprKind::Struct(..) | ExprKind::Tup(..))
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}
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declare_lint_pass!(TemporaryAssignment => [TEMPORARY_ASSIGNMENT]);
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impl<'tcx> LateLintPass<'tcx> for TemporaryAssignment {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if let ExprKind::Assign(target, ..) = &expr.kind {
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let mut base = target;
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while let ExprKind::Field(f, _) | ExprKind::Index(f, _) = &base.kind {
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base = f;
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}
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if is_temporary(base) && !is_adjusted(cx, base) {
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span_lint(cx, TEMPORARY_ASSIGNMENT, expr.span, "assignment to temporary");
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}
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}
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}
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}
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