Auto merge of #3946 - rchaser53:issue-3920, r=flip1995

[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 cd13ab0d51ff1da86370bd7232b5eeaecab3bd63..a6126f37282872afc0af76a808751e49131dda80 100644 (file)
--- a/clippy_lints/src/temporary_assignment.rs
+++ b/clippy_lints/src/temporary_assignment.rs
@@ -1,29 +1,38 @@
-use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use rustc::hir::{Expr, ExprAssign, ExprField, ExprStruct, ExprTup};
 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};
 
-/// **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 {
-        ExprStruct(..) | ExprTup(..) => true,
+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,
     }
 }
@@ -35,15 +44,21 @@ 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 ExprAssign(ref target, _) = expr.node {
-            if let ExprField(ref base, _) = target.node {
-                if is_temporary(base) && !is_adjusted(cx, base) {
-                    span_lint(cx, TEMPORARY_ASSIGNMENT, expr.span, "assignment to temporary");
-                }
+        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");
             }
         }
     }