Implement #507

[rust.git] / src / misc.rs

diff --git a/src/misc.rs b/src/misc.rs
index 44d044a4384c2c482cfce6440282003e2dc03474..139dfde36815a71e82e1d2ba39445ff15482cc24 100644 (file)
--- a/src/misc.rs
+++ b/src/misc.rs
@@ -3,16 +3,15 @@
 use rustc_front::hir::*;
 use reexport::*;
 use rustc_front::util::{is_comparison_binop, binop_to_string};
-use syntax::codemap::{Span, Spanned};
+use syntax::codemap::{Span, Spanned, ExpnFormat};
 use rustc_front::intravisit::FnKind;
 use rustc::middle::ty;
 use rustc::middle::const_eval::ConstVal::Float;
 use rustc::middle::const_eval::eval_const_expr_partial;
 use rustc::middle::const_eval::EvalHint::ExprTypeChecked;
 
-use utils::{get_item_name, match_path, snippet, get_parent_expr, span_lint, walk_ptrs_ty,
-            is_integer_literal};
-use utils::span_help_and_lint;
+use utils::{get_item_name, match_path, snippet, get_parent_expr, span_lint};
+use utils::{span_help_and_lint, walk_ptrs_ty, is_integer_literal};
 
 /// **What it does:** This lint checks for function arguments and let bindings denoted as `ref`. It is `Warn` by default.
 ///
@@ -346,6 +345,9 @@ fn get_lints(&self) -> LintArray {
 
 impl LateLintPass for UsedUnderscoreBinding {
     fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
+        if in_attributes_expansion(cx, expr) { // Don't lint things expanded by #[derive(...)], etc
+            return;
+        }
         let needs_lint = match expr.node {
             ExprPath(_, ref path) => {
                 let ident = path.segments.last()
@@ -353,7 +355,7 @@ fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
                                 .identifier;
                 ident.name.as_str().chars().next() == Some('_') //starts with '_'
                 && ident.name.as_str().chars().skip(1).next() != Some('_') //doesn't start with "__"
-                && ident.name != ident.unhygienic_name //not in macro
+                && ident.name != ident.unhygienic_name //not in bang macro
                 && is_used(cx, expr)
             },
             ExprField(_, spanned) => {
@@ -371,6 +373,8 @@ fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
     }
 }
 
+/// Heuristic to see if an expression is used. Should be compatible with `unused_variables`'s idea
+/// of what it means for an expression to be "used".
 fn is_used(cx: &LateContext, expr: &Expr) -> bool {
     if let Some(ref parent) = get_parent_expr(cx, expr) {
         match parent.node {
@@ -383,3 +387,16 @@ fn is_used(cx: &LateContext, expr: &Expr) -> bool {
         true
     }
 }
+
+/// Test whether an expression is in a macro expansion (e.g. something generated by #[derive(...)]
+/// or the like)
+fn in_attributes_expansion(cx: &LateContext, expr: &Expr) -> bool {
+    cx.sess().codemap().with_expn_info(expr.span.expn_id, |info_opt| {
+        info_opt.map_or(false, |info| {
+            match info.callee.format {
+                ExpnFormat::MacroAttribute(_) => true,
+                _ => false,
+            }
+        })
+    })
+}