55 lines
1.5 KiB
Rust
55 lines
1.5 KiB
Rust
use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::hir::{Expr, ExprAssign, ExprField, ExprStruct, ExprTup, ExprTupField};
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use utils::is_adjusted;
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use utils::span_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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declare_lint! {
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pub TEMPORARY_ASSIGNMENT,
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Warn,
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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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match expr.node {
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ExprStruct(..) | ExprTup(..) => true,
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_ => false,
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}
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}
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#[derive(Copy, Clone)]
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pub struct Pass;
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impl LintPass for Pass {
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fn get_lints(&self) -> LintArray {
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lint_array!(TEMPORARY_ASSIGNMENT)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
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if let ExprAssign(ref target, _) = expr.node {
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match target.node {
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ExprField(ref base, _) |
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ExprTupField(ref base, _) => {
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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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}
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}
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}
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