From de9a80cd102021c05ad0352369abe5bdf38ab57d Mon Sep 17 00:00:00 2001
From: mcarton <cartonmartin+git@gmail.com>
Date: Wed, 20 Apr 2016 21:09:38 +0200
Subject: [PATCH] Check type for `SINGLE_CHAR_PATTERN`
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It’d be nicer to actually check for `Pattern` bounds but in the meantime
this needs to be fixed.
---
 src/methods.rs                | 20 +++++++++++++-------
 tests/compile-fail/methods.rs |  4 ++++
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/src/methods.rs b/src/methods.rs
index 4a31a564a..73f6a7aa4 100644
--- a/src/methods.rs
+++ b/src/methods.rs
@@ -365,16 +365,23 @@ impl LateLintPass for MethodsPass {
                     lint_cstring_as_ptr(cx, expr, &arglists[0][0], &arglists[1][0]);
                 }
 
-
                 lint_or_fun_call(cx, expr, &name.node.as_str(), &args);
+
+                let self_ty = cx.tcx.expr_ty_adjusted(&args[0]);
                 if args.len() == 1 && name.node.as_str() == "clone" {
                     lint_clone_on_copy(cx, expr);
-                    lint_clone_double_ref(cx, expr, &args[0]);
+                    lint_clone_double_ref(cx, expr, &args[0], self_ty);
                 }
-                for &(method, pos) in &PATTERN_METHODS {
-                    if name.node.as_str() == method && args.len() > pos {
-                        lint_single_char_pattern(cx, expr, &args[pos]);
+
+                match self_ty.sty {
+                    ty::TyRef(_, ty) if ty.ty.sty == ty::TyStr => {
+                        for &(method, pos) in &PATTERN_METHODS {
+                            if name.node.as_str() == method && args.len() > pos {
+                                lint_single_char_pattern(cx, expr, &args[pos]);
+                            }
+                        }
                     }
+                    _ => (),
                 }
             }
             ExprBinary(op, ref lhs, ref rhs) if op.node == BiEq || op.node == BiNe => {
@@ -552,8 +559,7 @@ fn lint_clone_on_copy(cx: &LateContext, expr: &Expr) {
 }
 
 /// Checks for the `CLONE_DOUBLE_REF` lint.
-fn lint_clone_double_ref(cx: &LateContext, expr: &Expr, arg: &Expr) {
-    let ty = cx.tcx.expr_ty(arg);
+fn lint_clone_double_ref(cx: &LateContext, expr: &Expr, arg: &Expr, ty: ty::Ty) {
     if let ty::TyRef(_, ty::TypeAndMut { ty: ref inner, .. }) = ty.sty {
         if let ty::TyRef(..) = inner.sty {
             let mut db = span_lint(cx,
diff --git a/tests/compile-fail/methods.rs b/tests/compile-fail/methods.rs
index 1869fd12a..7503cb507 100644
--- a/tests/compile-fail/methods.rs
+++ b/tests/compile-fail/methods.rs
@@ -6,6 +6,7 @@
 
 use std::collections::BTreeMap;
 use std::collections::HashMap;
+use std::collections::HashSet;
 use std::ops::Mul;
 
 struct T;
@@ -469,6 +470,9 @@ fn single_char_pattern() {
     //~^ ERROR single-character string constant used as pattern
     //~| HELP try using a char instead:
     //~| SUGGESTION x.trim_right_matches('x');
+
+    let h = HashSet::<String>::new();
+    h.contains("X"); // should not warn
 }
 
 #[allow(result_unwrap_used)]