Merge pull request #1465 from Manishearth/1464

Use `span_suggestion` in the `precedence` lint

Author: llogiq

clippy_lints/src/precedence.rs

@@ -1,7 +1,7 @@
 use rustc::lint::*;
 use syntax::ast::*;
 use syntax::codemap::Spanned;
-use utils::{span_lint, snippet};
+use utils::{span_lint_and_then, snippet};
 
 /// **What it does:** Checks for operations where precedence may be unclear
 /// and suggests to add parentheses. Currently it catches the following:
@@ -36,41 +36,39 @@ impl LintPass for Precedence {
 impl EarlyLintPass for Precedence {
     fn check_expr(&mut self, cx: &EarlyContext, expr: &Expr) {
         if let ExprKind::Binary(Spanned { node: op, .. }, ref left, ref right) = expr.node {
+            let span_sugg =
+                |expr: &Expr, sugg| {
+                    span_lint_and_then(cx, PRECEDENCE, expr.span, "operator precedence can trip the unwary", |db| {
+                        db.span_suggestion(expr.span, "consider parenthesizing your expression", sugg);
+                    });
+                };
+
             if !is_bit_op(op) {
                 return;
             }
             match (is_arith_expr(left), is_arith_expr(right)) {
                 (true, true) => {
-                    span_lint(cx,
-                              PRECEDENCE,
-                              expr.span,
-                              &format!("operator precedence can trip the unwary. Consider parenthesizing your \
-                                        expression:`({}) {} ({})`",
+                    let sugg = format!("({}) {} ({})",
                                        snippet(cx, left.span, ".."),
                                        op.to_string(),
-                                       snippet(cx, right.span, "..")));
+                                       snippet(cx, right.span, ".."));
+                    span_sugg(expr, sugg);
                 },
                 (true, false) => {
-                    span_lint(cx,
-                              PRECEDENCE,
-                              expr.span,
-                              &format!("operator precedence can trip the unwary. Consider parenthesizing your \
-                                        expression:`({}) {} {}`",
+                    let sugg = format!("({}) {} {}",
                                        snippet(cx, left.span, ".."),
                                        op.to_string(),
-                                       snippet(cx, right.span, "..")));
+                                       snippet(cx, right.span, ".."));
+                    span_sugg(expr, sugg);
                 },
                 (false, true) => {
-                    span_lint(cx,
-                              PRECEDENCE,
-                              expr.span,
-                              &format!("operator precedence can trip the unwary. Consider parenthesizing your \
-                                        expression:`{} {} ({})`",
+                    let sugg = format!("{} {} ({})",
                                        snippet(cx, left.span, ".."),
                                        op.to_string(),
-                                       snippet(cx, right.span, "..")));
+                                       snippet(cx, right.span, ".."));
+                    span_sugg(expr, sugg);
                 },
-                _ => (),
+                (false, false) => (),
             }
         }
 
@@ -82,12 +80,15 @@ impl EarlyLintPass for Precedence {
                             LitKind::Int(..) |
                             LitKind::Float(..) |
                             LitKind::FloatUnsuffixed(..) => {
-                                span_lint(cx,
-                                          PRECEDENCE,
-                                          expr.span,
-                                          &format!("unary minus has lower precedence than method call. Consider \
-                                                    adding parentheses to clarify your intent: -({})",
-                                                   snippet(cx, rhs.span, "..")));
+                                span_lint_and_then(cx,
+                                                   PRECEDENCE,
+                                                   expr.span,
+                                                   "unary minus has lower precedence than method call",
+                                                   |db| {
+                                    db.span_suggestion(expr.span,
+                                                       "consider adding parentheses to clarify your intent",
+                                                       format!("-({})", snippet(cx, rhs.span, "..")));
+                                });
                             },
                             _ => (),
                         }

tests/compile-fail/precedence.rs

@@ -5,16 +5,34 @@
 #[allow(identity_op)]
 #[allow(eq_op)]
 fn main() {
-    format!("{} vs. {}", 1 << 2 + 3, (1 << 2) + 3); //~ERROR operator precedence can trip
-    format!("{} vs. {}", 1 + 2 << 3, 1 + (2 << 3)); //~ERROR operator precedence can trip
-    format!("{} vs. {}", 4 >> 1 + 1, (4 >> 1) + 1); //~ERROR operator precedence can trip
-    format!("{} vs. {}", 1 + 3 >> 2, 1 + (3 >> 2)); //~ERROR operator precedence can trip
-    format!("{} vs. {}", 1 ^ 1 - 1, (1 ^ 1) - 1);   //~ERROR operator precedence can trip
-    format!("{} vs. {}", 3 | 2 - 1, (3 | 2) - 1);   //~ERROR operator precedence can trip
-    format!("{} vs. {}", 3 & 5 - 2, (3 & 5) - 2);   //~ERROR operator precedence can trip
+    1 << 2 + 3;
+    //~^ ERROR operator precedence can trip
+    //~| SUGGESTION 1 << (2 + 3)
+    1 + 2 << 3;
+    //~^ERROR operator precedence can trip
+    //~| SUGGESTION (1 + 2) << 3
+    4 >> 1 + 1;
+    //~^ERROR operator precedence can trip
+    //~| SUGGESTION 4 >> (1 + 1)
+    1 + 3 >> 2;
+    //~^ERROR operator precedence can trip
+    //~| SUGGESTION (1 + 3) >> 2
+    1 ^ 1 - 1;
+    //~^ERROR operator precedence can trip
+    //~| SUGGESTION 1 ^ (1 - 1)
+    3 | 2 - 1;
+    //~^ERROR operator precedence can trip
+    //~| SUGGESTION 3 | (2 - 1)
+    3 & 5 - 2;
+    //~^ERROR operator precedence can trip
+    //~| SUGGESTION 3 & (5 - 2)
 
-    format!("{} vs. {}", -1i32.abs(), (-1i32).abs()); //~ERROR unary minus has lower precedence
-    format!("{} vs. {}", -1f32.abs(), (-1f32).abs()); //~ERROR unary minus has lower precedence
+    -1i32.abs();
+    //~^ERROR unary minus has lower precedence
+    //~| SUGGESTION -(1i32.abs())
+    -1f32.abs();
+    //~^ERROR unary minus has lower precedence
+    //~| SUGGESTION -(1f32.abs())
 
     // These should not trigger an error
     let _ = (-1i32).abs();