modify code

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

diff --git a/clippy_lints/src/neg_multiply.rs b/clippy_lints/src/neg_multiply.rs
index fa36d8fb1b30f3f50ee2793d5a9db68b9d70edc9..0d05c83ffe45ee05804556515df1ce330e118152 100644 (file)
--- a/clippy_lints/src/neg_multiply.rs
+++ b/clippy_lints/src/neg_multiply.rs
@@ -1,6 +1,8 @@
 use clippy_utils::consts::{self, Constant};
-use clippy_utils::diagnostics::span_lint;
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::source::snippet_with_applicability;
 use if_chain::if_chain;
+use rustc_errors::Applicability;
 use rustc_hir::{BinOpKind, Expr, ExprKind, UnOp};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
@@ -18,11 +20,16 @@
     ///
     /// ### Example
     /// ```ignore
-    /// x * -1
+    /// // Bad
+    /// let a = x * -1;
+    ///
+    /// // Good
+    /// let b = -x;
     /// ```
+    #[clippy::version = "pre 1.29.0"]
     pub NEG_MULTIPLY,
     style,
-    "multiplying integers with `-1`"
+    "multiplying integers by `-1`"
 }
 
 declare_lint_pass!(NegMultiply => [NEG_MULTIPLY]);
@@ -46,10 +53,21 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
 fn check_mul(cx: &LateContext<'_>, span: Span, lit: &Expr<'_>, exp: &Expr<'_>) {
     if_chain! {
         if let ExprKind::Lit(ref l) = lit.kind;
-        if let Constant::Int(1) = consts::lit_to_constant(&l.node, cx.typeck_results().expr_ty_opt(lit));
+        if consts::lit_to_constant(&l.node, cx.typeck_results().expr_ty_opt(lit)) == Constant::Int(1);
         if cx.typeck_results().expr_ty(exp).is_integral();
+
         then {
-            span_lint(cx, NEG_MULTIPLY, span, "negation by multiplying with `-1`");
+            let mut applicability = Applicability::MachineApplicable;
+            let suggestion = format!("-{}", snippet_with_applicability(cx, exp.span, "..", &mut applicability));
+            span_lint_and_sugg(
+                    cx,
+                    NEG_MULTIPLY,
+                    span,
+                    "this multiplication by -1 can be written more succinctly",
+                    "consider using",
+                    suggestion,
+                    applicability,
+                );
         }
     }
 }