54 lines
1.7 KiB
Rust
54 lines
1.7 KiB
Rust
use crate::utils::{is_adjusted, span_lint};
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use rustc_hir::def::{DefKind, Res};
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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(cx: &LateContext<'_, '_>, expr: &Expr<'_>) -> bool {
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match &expr.kind {
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ExprKind::Struct(..) | ExprKind::Tup(..) => true,
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ExprKind::Path(qpath) => {
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if let Res::Def(DefKind::Const, ..) = cx.tables.qpath_res(qpath, expr.hir_id) {
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true
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} else {
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false
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}
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},
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_ => false,
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}
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}
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declare_lint_pass!(TemporaryAssignment => [TEMPORARY_ASSIGNMENT]);
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TemporaryAssignment {
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fn check_expr(&mut self, cx: &LateContext<'a, '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(cx, 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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