check item name for eq, fixes #268

src/misc.rs

@@ -4,6 +4,7 @@ use syntax::ast::*;
 use syntax::ast_util::{is_comparison_binop, binop_to_string};
 use syntax::codemap::{Span, Spanned};
 use syntax::visit::FnKind;
+use rustc::ast_map::Node::*;
 use rustc::middle::ty;
 
 use utils::{match_path, snippet, span_lint, walk_ptrs_ty};
@@ -91,6 +92,17 @@ impl LintPass for FloatCmp {
                         false, |c| c.0.as_float().map_or(false, |f| f == 0.0)) {
                     return;
                 }
+                let parent_id = cx.tcx.map.get_parent(expr.id);
+                match cx.tcx.map.find(parent_id) {
+                    Some(NodeItem(&Item{ ref ident, .. })) |
+                    Some(NodeTraitItem(&TraitItem{ id: _, ref ident, .. })) |
+                    Some(NodeImplItem(&ImplItem{ id: _, ref ident, .. })) => {
+                        let name = ident.name.as_str();
+                        if &*name == "eq" || name.starts_with("eq_") ||
+                                name.ends_with("_eq") { return; }
+                    },
+                    _ => (),
+                }
                 span_lint(cx, FLOAT_CMP, expr.span, &format!(
                     "{}-comparison of f32 or f64 detected. Consider changing this to \
                      `abs({} - {}) < epsilon` for some suitable value of epsilon",

tests/compile-fail/float_cmp.rs

@@ -1,6 +1,9 @@
 #![feature(plugin)]
 #![plugin(clippy)]
 
+#![deny(float_cmp)]
+#![allow(unused)]
+
 use std::ops::Add;
 
 const ZERO : f32 = 0.0;
@@ -10,8 +13,26 @@ fn twice<T>(x : T) -> T where T : Add<T, Output = T>, T : Copy {
     x + x
 }
 
-#[deny(float_cmp)]
-#[allow(unused)]
+fn eq_fl(x: f32, y: f32) -> bool {
+    if x.is_nan() { y.is_nan() } else { x == y } // no error, inside "eq" fn
+}
+
+fn fl_eq(x: f32, y: f32) -> bool {
+    if x.is_nan() { y.is_nan() } else { x == y } // no error, inside "eq" fn
+}
+
+struct X { val: f32 }
+
+impl PartialEq for X {
+    fn eq(&self, o: &X) -> bool {
+        if self.val.is_nan() {
+            o.val.is_nan()
+        } else {
+            self.val == o.val // no error, inside "eq" fn
+        }
+    }
+}
+
 fn main() {
     ZERO == 0f32; //no error, comparison with zero is ok
     ZERO == 0.0; //no error, comparison with zero is ok