gc: Better typechecks and errors in switches.

Allow any type in switch on interface value.
Statically check typeswitch early.

Fixes #2423.
Fixes #2424.

R=rsc, dsymonds
CC=golang-dev
https://golang.org/cl/5339045

diff --git a/src/cmd/gc/swt.c b/src/cmd/gc/swt.c
index 97874e264ad88762cbee50d9f83a07ba6ad93678..4d07970c71a975cf02cab774cfb8dbf52ee341fa 100644 (file)
--- a/src/cmd/gc/swt.c
+++ b/src/cmd/gc/swt.c
@@ -810,8 +810,8 @@ walkswitch(Node *sw)
 void
 typecheckswitch(Node *n)
 {
-       int top, lno;
-       Type *t;
+       int top, lno, ptr;
+       Type *t, *missing, *have;
        NodeList *l, *ll;
        Node *ncase, *nvar;
        Node *def;
@@ -854,21 +854,35 @@ typecheckswitch(Node *n)
                                typecheck(&ll->n, Erv | Etype);
                                if(ll->n->type == T || t == T)
                                        continue;
+                               setlineno(ncase);
                                switch(top) {
                                case Erv:       // expression switch
                                        defaultlit(&ll->n, t);
                                        if(ll->n->op == OTYPE)
                                                yyerror("type %T is not an expression", ll->n->type);
-                                       else if(ll->n->type != T && !eqtype(ll->n->type, t))
-                                               yyerror("case %lN in %T switch", ll->n, t);
+                                       else if(ll->n->type != T && !assignop(ll->n->type, t, nil) && !assignop(t, ll->n->type, nil)) {
+                                               if(n->ntest)
+                                                       yyerror("invalid case %N in switch on %N (mismatched types %T and %T)", ll->n, n->ntest, ll->n->type, t);
+                                               else
+                                                       yyerror("invalid case %N in switch (mismatched types %T and bool)", ll->n, n->ntest, ll->n->type, t);
+                                       }
                                        break;
                                case Etype:     // type switch
                                        if(ll->n->op == OLITERAL && istype(ll->n->type, TNIL)) {
                                                ;
-                                       } else if(ll->n->op != OTYPE && ll->n->type != T) {
+                                       } else if(ll->n->op != OTYPE && ll->n->type != T) {  // should this be ||?
                                                yyerror("%lN is not a type", ll->n);
                                                // reset to original type
                                                ll->n = n->ntest->right;
+                                       } else if(!implements(ll->n->type, t, &missing, &have, &ptr)) {
+                                               if(have && !missing->broke && !have->broke)
+                                                       yyerror("impossible type switch case: %lN cannot have dynamic type %T"
+                                                               " (wrong type for %S method)\n\thave %S%hT\n\twant %S%hT",
+                                                               n->ntest->right, ll->n->type, missing->sym, have->sym, have->type,
+                                                               missing->sym, missing->type);
+                                               else if(!missing->broke)
+                                                       yyerror("impossible type switch case: %lN cannot have dynamic type %T"
+                                                               " (missing %S method)", n->ntest->right, ll->n->type, missing->sym);
                                        }
                                        break;
                                }

diff --git a/test/fixedbugs/bug270.go b/test/fixedbugs/bug270.go
deleted file mode 100644 (file)
index a9cda7b..0000000
--- a/test/fixedbugs/bug270.go
+++ /dev/null
@@ -1,21 +0,0 @@
-// $G $D/$F.go
-
-// Copyright 2010 The Go Authors.  All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// http://code.google.com/p/go/issues/detail?id=746
-
-package main
-
-type I interface { F() }
-
-type T struct{}
-
-func (T) F() {}
-
-func main() {
-       switch I(T{}).(type) {
-       case interface{}:
-       }
-}

diff --git a/test/fixedbugs/bug340.go b/test/fixedbugs/bug340.go
index 37731aad67628e42090bae0f6d4efcaa21adc796..34cc013151f992ac2377042c43b2b6c3ef9341f7 100644 (file)
--- a/test/fixedbugs/bug340.go
+++ b/test/fixedbugs/bug340.go
@@ -10,8 +10,8 @@ package main
 
 func main() {
        var x interface{}
-       switch t := x.(type) { // GC_ERROR "is not a type"
-       case 0:         // GCCGO_ERROR "expected type"
+       switch t := x.(type) {
+       case 0:         // ERROR "type"
                t.x = 1 // ERROR "type interface \{\}|reference to undefined field or method"
        }
 }

diff --git a/test/fixedbugs/bug375.go b/test/fixedbugs/bug375.go
new file mode 100644 (file)
index 0000000..5273585
--- /dev/null
+++ b/test/fixedbugs/bug375.go
@@ -0,0 +1,19 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out || echo BUG: bug375
+
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Issue 2423
+
+package main
+
+func main() {
+       var x interface{} = "hello"
+
+       switch x {
+       case "hello":
+       default:
+               println("FAIL")
+       }
+}

diff --git a/test/switch3.go b/test/switch3.go
new file mode 100644 (file)
index 0000000..95ff6ec
--- /dev/null
+++ b/test/switch3.go
@@ -0,0 +1,38 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+
+type I interface {
+       M()
+}
+
+func bad() {
+       var i I
+       var s string
+
+       switch i {
+       case s:  // ERROR "mismatched types string and I"
+       }
+
+       switch s {
+       case i:  // ERROR "mismatched types I and string"
+       }
+}
+
+func good() {
+       var i interface{}
+       var s string
+
+       switch i {
+       case s:
+       }
+
+       switch s {
+       case i:
+       }
+}

diff --git a/test/typeswitch3.go b/test/typeswitch3.go
new file mode 100644 (file)
index 0000000..99d08a2
--- /dev/null
+++ b/test/typeswitch3.go
@@ -0,0 +1,20 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+
+type I interface {
+       M()
+}
+
+func main(){
+       var x I
+       switch x.(type) {
+       case string:    // ERROR "impossible"
+               println("FAIL")
+       }
+}