Rustup to syntax::errors changes

[rust.git] / src / precedence.rs

diff --git a/src/precedence.rs b/src/precedence.rs
index b659bd647a7c527062023c257223780b2cc03eab..91ff0680b3e2f8834fa70e8b331c143e328e76cc 100644 (file)
--- a/src/precedence.rs
+++ b/src/precedence.rs
@@ -1,10 +1,20 @@
 use rustc::lint::*;
 use syntax::codemap::Spanned;
 use syntax::ast::*;
-use syntax::ast_util::binop_to_string;
 
 use utils::{span_lint, snippet};
 
+/// **What it does:** This lint checks for operations where precedence may be unclear and `Warn`s about them by default, suggesting to add parentheses. Currently it catches the following:
+/// * mixed usage of arithmetic and bit shifting/combining operators without parentheses
+/// * a "negative" numeric literal (which is really a unary `-` followed by a numeric literal) followed by a method call
+///
+/// **Why is this bad?** Because not everyone knows the precedence of those operators by heart, so expressions like these may trip others trying to reason about the code.
+///
+/// **Known problems:** None
+///
+/// **Examples:**
+/// * `1 << 2 + 3` equals 32, while `(1 << 2) + 3` equals 7
+/// * `-1i32.abs()` equals -1, while `(-1i32).abs()` equals 1
 declare_lint!(pub PRECEDENCE, Warn,
               "catches operations where precedence may be unclear. See the wiki for a \
                list of cases caught");
@@ -23,21 +33,27 @@ fn check_expr(&mut self, cx: &EarlyContext, expr: &Expr) {
         if let ExprBinary(Spanned { node: op, ..}, ref left, ref right) = expr.node {
             if !is_bit_op(op) { return; }
             match (is_arith_expr(left), is_arith_expr(right)) {
-                (true, true) =>  span_lint(cx, PRECEDENCE, expr.span, 
+                (true, true) => {
+                    span_lint(cx, PRECEDENCE, expr.span, 
                     &format!("operator precedence can trip the unwary. \
                          Consider parenthesizing your expression:\
                          `({}) {} ({})`", snippet(cx, left.span, ".."),
-                         binop_to_string(op), snippet(cx, right.span, ".."))),
-                (true, false) => span_lint(cx, PRECEDENCE, expr.span, 
+                         op.to_string(), snippet(cx, right.span, "..")));
+                },
+                (true, false) => {
+                    span_lint(cx, PRECEDENCE, expr.span, 
                     &format!("operator precedence can trip the unwary. \
                          Consider parenthesizing your expression:\
                          `({}) {} {}`", snippet(cx, left.span, ".."),
-                         binop_to_string(op), snippet(cx, right.span, ".."))),
-                (false, true) => span_lint(cx, PRECEDENCE, expr.span, 
+                         op.to_string(), snippet(cx, right.span, "..")));
+                },
+                (false, true) => {
+                    span_lint(cx, PRECEDENCE, expr.span, 
                     &format!("operator precedence can trip the unwary. \
                          Consider parenthesizing your expression:\
                          `{} {} ({})`", snippet(cx, left.span, ".."),
-                         binop_to_string(op), snippet(cx, right.span, ".."))),
+                         op.to_string(), snippet(cx, right.span, "..")));
+                },
                 _ => (),
             }
         }
@@ -47,12 +63,13 @@ fn check_expr(&mut self, cx: &EarlyContext, expr: &Expr) {
                 if let Some(slf) = args.first() {
                     if let ExprLit(ref lit) = slf.node {
                         match lit.node {
-                            LitInt(..) | LitFloat(..) | LitFloatUnsuffixed(..) =>
+                            LitInt(..) | LitFloat(..) | LitFloatUnsuffixed(..) => {
                                 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, ".."))),
+                                     snippet(cx, rhs.span, "..")));
+                            }
                             _ => ()
                         }
                     }