| use crate::utils::is_adjusted; |
| use crate::utils::span_lint; |
| use rustc::hir::def::Def; |
| use rustc::hir::{Expr, ExprKind}; |
| use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; |
| use rustc::{declare_tool_lint, lint_array}; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for construction of a structure or tuple just to |
| /// assign a value in it. |
| /// |
| /// **Why is this bad?** Readability. If the structure is only created to be |
| /// updated, why not write the structure you want in the first place? |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// (0, 0).0 = 1 |
| /// ``` |
| pub TEMPORARY_ASSIGNMENT, |
| complexity, |
| "assignments to temporaries" |
| } |
| |
| fn is_temporary(cx: &LateContext<'_, '_>, expr: &Expr) -> bool { |
| match &expr.node { |
| ExprKind::Struct(..) | ExprKind::Tup(..) => true, |
| ExprKind::Path(qpath) => { |
| if let Def::Const(..) = cx.tables.qpath_def(qpath, expr.hir_id) { |
| true |
| } else { |
| false |
| } |
| }, |
| _ => false, |
| } |
| } |
| |
| #[derive(Copy, Clone)] |
| pub struct Pass; |
| |
| impl LintPass for Pass { |
| fn get_lints(&self) -> LintArray { |
| lint_array!(TEMPORARY_ASSIGNMENT) |
| } |
| |
| fn name(&self) -> &'static str { |
| "TemporaryAssignment" |
| } |
| } |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass { |
| fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) { |
| if let ExprKind::Assign(target, _) = &expr.node { |
| let mut base = target; |
| while let ExprKind::Field(f, _) | ExprKind::Index(f, _) = &base.node { |
| base = f; |
| } |
| if is_temporary(cx, base) && !is_adjusted(cx, base) { |
| span_lint(cx, TEMPORARY_ASSIGNMENT, expr.span, "assignment to temporary"); |
| } |
| } |
| } |
| } |