Rustup to syntax::errors changes

[rust.git] / src / precedence.rs

diff --git a/src/precedence.rs b/src/precedence.rs
index 31c28146e1e597d5d7beb4972281fd3e463f54ce..91ff0680b3e2f8834fa70e8b331c143e328e76cc 100644 (file)
--- a/src/precedence.rs
+++ b/src/precedence.rs
@@ -1,9 +1,20 @@
 use rustc::lint::*;
-use rustc_front::hir::*;
 use syntax::codemap::Spanned;
+use syntax::ast::*;
 
-use utils::span_lint;
+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");
@@ -15,13 +26,35 @@ impl LintPass for Precedence {
     fn get_lints(&self) -> LintArray {
         lint_array!(PRECEDENCE)
     }
+}
 
-    fn check_expr(&mut self, cx: &Context, expr: &Expr) {
+impl EarlyLintPass for Precedence {
+    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) && (is_arith_expr(left) || is_arith_expr(right)) {
-                span_lint(cx, PRECEDENCE, expr.span,
-                    "operator precedence can trip the unwary. Consider adding parentheses \
-                     to the subexpression");
+            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:\
+                         `({}) {} ({})`", snippet(cx, left.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, ".."),
+                         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, ".."),
+                         op.to_string(), snippet(cx, right.span, "..")));
+                },
+                _ => (),
             }
         }
 
@@ -30,11 +63,14 @@ fn check_expr(&mut self, cx: &Context, expr: &Expr) {
                 if let Some(slf) = args.first() {
                     if let ExprLit(ref lit) = slf.node {
                         match lit.node {
-                            LitInt(..) | LitFloat(..) | LitFloatUnsuffixed(..) =>
-                                span_lint(cx, PRECEDENCE, expr.span,
-                                    "unary minus has lower precedence than method call. Consider \
-                                     adding parentheses to clarify your intent"),
-                                _ => ()
+                            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, "..")));
+                            }
+                            _ => ()
                         }
                     }
                 }
@@ -43,21 +79,21 @@ fn check_expr(&mut self, cx: &Context, expr: &Expr) {
     }
 }
 
-fn is_arith_expr(expr : &Expr) -> bool {
+fn is_arith_expr(expr: &Expr) -> bool {
     match expr.node {
         ExprBinary(Spanned { node: op, ..}, _, _) => is_arith_op(op),
         _ => false
     }
 }
 
-fn is_bit_op(op : BinOp_) -> bool {
+fn is_bit_op(op: BinOp_) -> bool {
     match op {
         BiBitXor | BiBitAnd | BiBitOr | BiShl | BiShr => true,
         _ => false
     }
 }
 
-fn is_arith_op(op : BinOp_) -> bool {
+fn is_arith_op(op: BinOp_) -> bool {
     match op {
         BiAdd | BiSub | BiMul | BiDiv | BiRem => true,
         _ => false