clippy: support `QPath::LangItem`

[rust.git] / clippy_lints / src / temporary_assignment.rs

diff --git a/clippy_lints/src/temporary_assignment.rs b/clippy_lints/src/temporary_assignment.rs
index 56e705ad0a7217143029d42ff29015f1d4a80ceb..1aeff1baa362e24a2362263c07a946e412abde46 100644 (file)
--- a/clippy_lints/src/temporary_assignment.rs
+++ b/clippy_lints/src/temporary_assignment.rs
@@ -1,50 +1,46 @@
-use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use rustc::{declare_lint, lint_array};
-use rustc::hir::{Expr, ExprKind};
-use crate::utils::is_adjusted;
-use crate::utils::span_lint;
+use crate::utils::{is_adjusted, span_lint};
+use rustc_hir::def::{DefKind, Res};
+use rustc_hir::{Expr, ExprKind};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_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
-/// ```
 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(expr: &Expr) -> bool {
-    match expr.node {
+fn is_temporary(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
+    match &expr.kind {
         ExprKind::Struct(..) | ExprKind::Tup(..) => true,
+        ExprKind::Path(qpath) => matches!(cx.qpath_res(qpath, expr.hir_id), Res::Def(DefKind::Const, ..)),
         _ => false,
     }
 }
 
-#[derive(Copy, Clone)]
-pub struct Pass;
+declare_lint_pass!(TemporaryAssignment => [TEMPORARY_ASSIGNMENT]);
 
-impl LintPass for Pass {
-    fn get_lints(&self) -> LintArray {
-        lint_array!(TEMPORARY_ASSIGNMENT)
-    }
-}
-
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
-    fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
-        if let ExprKind::Assign(ref target, _) = expr.node {
-            if let ExprKind::Field(ref base, _) = target.node {
-                if is_temporary(base) && !is_adjusted(cx, base) {
-                    span_lint(cx, TEMPORARY_ASSIGNMENT, expr.span, "assignment to temporary");
-                }
+impl<'tcx> LateLintPass<'tcx> for TemporaryAssignment {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+        if let ExprKind::Assign(target, ..) = &expr.kind {
+            let mut base = target;
+            while let ExprKind::Field(f, _) | ExprKind::Index(f, _) = &base.kind {
+                base = f;
+            }
+            if is_temporary(cx, base) && !is_adjusted(cx, base) {
+                span_lint(cx, TEMPORARY_ASSIGNMENT, expr.span, "assignment to temporary");
             }
         }
     }