auto merge of #5046 : sanxiyn/rust/struct-match, r=catamorphism

Previously check always succeeded because struct type was derived from the matched expression, not the matched pattern.

Fix #4849.

Author: bors

src/librustc/middle/ty.rs

@@ -2823,7 +2823,7 @@ pub pure fn ty_fn_ret(fty: t) -> t {
     }
 }
 
-fn is_fn_ty(fty: t) -> bool {
+pub fn is_fn_ty(fty: t) -> bool {
     match get(fty).sty {
         ty_bare_fn(_) => true,
         ty_closure(_) => true,

src/librustc/middle/typeck/check/_match.rs

@@ -92,7 +92,7 @@ pub fn check_pat_variant(pcx: pat_ctxt, pat: @ast::pat, path: @ast::path,
     match structure_of(pcx.fcx, pat.span, expected) {
         ty::ty_enum(_, ref expected_substs) => {
             // Lookup the enum and variant def ids:
-            let v_def = lookup_def(pcx.fcx, path.span, pat.id);
+            let v_def = lookup_def(pcx.fcx, pat.span, pat.id);
             let v_def_ids = ast_util::variant_def_ids(v_def);
 
             // Assign the pattern the type of the *enum*, not the variant.
@@ -125,8 +125,17 @@ pub fn check_pat_variant(pcx: pat_ctxt, pat: @ast::pat, path: @ast::path,
             kind_name = "variant";
         }
         ty::ty_struct(struct_def_id, ref expected_substs) => {
+            // Lookup the struct ctor def id
+            let s_def = lookup_def(pcx.fcx, pat.span, pat.id);
+            let s_def_id = ast_util::def_id_of_def(s_def);
+
             // Assign the pattern the type of the struct.
-            let struct_tpt = ty::lookup_item_type(tcx, struct_def_id);
+            let ctor_tpt = ty::lookup_item_type(tcx, s_def_id);
+            let struct_tpt = if ty::is_fn_ty(ctor_tpt.ty) {
+                {ty: ty::ty_fn_ret(ctor_tpt.ty), ..ctor_tpt}
+            } else {
+                ctor_tpt
+            };
             instantiate_path(pcx.fcx, path, struct_tpt, pat.span, pat.id,
                              pcx.block_region);
 

src/test/compile-fail/match-struct.rs

@@ -0,0 +1,11 @@
+// error-pattern: mismatched types
+
+struct S { a: int }
+enum E { C(int) }
+
+fn main() {
+    match S { a: 1 } {
+        C(_) => (),
+        _ => ()
+    }
+}