---

yaml
---
r: 273266
b: refs/heads/beta
c: 9cc5ee3
h: refs/heads/master

Author: eddyb

[refs]

@@ -23,7 +23,7 @@ refs/tags/0.9: 36870b185fc5f5486636d4515f0e22677493f225
 refs/tags/0.10: ac33f2b15782272ae348dbd7b14b8257b2148b5a
 refs/tags/0.11.0: e1247cb1d0d681be034adb4b558b5a0c0d5720f9
 refs/tags/0.12.0: f0c419429ef30723ceaf6b42f9b5a2aeb5d2e2d1
-refs/heads/beta: ccc5e0732a95861de755cf14bec05d873bfa7481
+refs/heads/beta: 9cc5ee359a27b096d4945c672eb1383f4490fbf1
 refs/tags/1.0.0-alpha: e42bd6d93a1d3433c486200587f8f9e12590a4d7
 refs/heads/tmp: e06d2ad9fcd5027bcaac5b08fc9aa39a49d0ecd3
 refs/tags/1.0.0-alpha.2: 4c705f6bc559886632d3871b04f58aab093bfa2f

branches/beta/src/librustc/middle/ty/sty.rs

@@ -948,7 +948,7 @@ impl<'tcx> TyS<'tcx> {
         }
     }
 
-    fn is_slice(&self) -> bool {
+    pub fn is_slice(&self) -> bool {
         match self.sty {
             TyRawPtr(mt) | TyRef(_, mt) => match mt.ty.sty {
                 TySlice(_) | TyStr => true,

branches/beta/src/librustc_mir/build/matches/test.rs

@@ -175,9 +175,28 @@ impl<'a,'tcx> Builder<'a,'tcx> {
             }
 
             TestKind::Eq { ref value, ty } => {
-                let expect = self.literal_operand(test.span, ty.clone(), Literal::Value {
-                    value: value.clone()
-                });
+                // If we're matching against &[u8] with b"...", we need to insert
+                // an unsizing coercion, as the byte string has type &[u8; N].
+                let expect = match *value {
+                    ConstVal::ByteStr(ref bytes) if ty.is_slice() => {
+                        let tcx = self.hir.tcx();
+                        let array_ty = tcx.mk_array(tcx.types.u8, bytes.len());
+                        let ref_ty = tcx.mk_imm_ref(tcx.mk_region(ty::ReStatic), array_ty);
+                        let array = self.literal_operand(test.span, ref_ty, Literal::Value {
+                            value: value.clone()
+                        });
+
+                        let sliced = self.temp(ty);
+                        self.cfg.push_assign(block, test.span, &sliced,
+                                             Rvalue::Cast(CastKind::Unsize, array, ty));
+                        Operand::Consume(sliced)
+                    }
+                    _ => {
+                        self.literal_operand(test.span, ty, Literal::Value {
+                            value: value.clone()
+                        })
+                    }
+                };
                 let val = Operand::Consume(lvalue.clone());
                 let fail = self.cfg.start_new_block();
                 let block = self.compare(block, fail, test.span, BinOp::Eq, expect, val.clone());