update reflect for upcoming interface representation change.

test case for new change.

both work with the current compiler too.

R=r
DELTA=150  (145 added, 2 deleted, 3 changed)
OCL=28703
CL=28715

src/lib/reflect/value.go

@@ -782,7 +782,16 @@ type interfaceValueStruct struct {
 }
 
 func (v *interfaceValueStruct) Get() interface{} {
+	// There are two different representations of interface values,
+	// one if the interface type has methods and one if it doesn't.
+	// These two representations require different expressions
+	// to extract correctly.
+	if v.Type().(InterfaceType).Len() == 0 {
+		// Extract as interface value without methods.
 		return *(*interface{})(v.addr)
+	}
+	// Extract from v.addr as interface value with methods.
+	return *(*interface{ m() })(v.addr)
 }
 
 func (v *interfaceValueStruct) Value() Value {

test/interface11.go

@@ -0,0 +1,140 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2009 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.
+
+// Check uses of all the different interface
+// conversion runtime functions.
+
+package main
+
+type Stringer interface { String() string }
+type StringLengther interface { String() string; Length() int }
+type Empty interface { }
+
+type T string
+func (t T) String() string {
+	return string(t);
+}
+func (t T) Length() int {
+	return len(t);
+}
+
+type U string
+func (u U) String() string {
+	return string(u);
+}
+
+var t = T("hello")
+var u = U("goodbye")
+var e Empty
+var s Stringer = t
+var sl StringLengther = t
+var i int
+var ok bool
+
+func hello(s string) {
+	if s != "hello" {
+		panic("not hello: ", s);
+	}
+}
+
+func five(i int) {
+	if i != 5 {
+		panic("not 5: ", i);
+	}
+}
+
+func true(ok bool) {
+	if !ok {
+		panic("not true");
+	}
+}
+
+func false(ok bool) {
+	if ok {
+		panic("not false");
+	}
+}
+
+func main() {
+	// T2I
+	s = t;
+	hello(s.String());
+
+	// I2T
+	t = s.(T);
+	hello(t.String());
+
+	// T2E
+	e = t;
+
+	// E2T
+	t = e.(T);
+	hello(t.String());
+
+	// T2I again
+	sl = t;
+	hello(sl.String());
+	five(sl.Length());
+
+	// I2I static
+	s = sl;
+	hello(s.String());
+
+	// I2I dynamic
+	sl = s.(StringLengther);
+	hello(sl.String());
+	five(sl.Length());
+
+	// I2E (and E2T)
+	e = s;
+	hello(e.(T).String());
+
+	// E2I
+	s = e.(Stringer);
+	hello(s.String());
+
+	// I2T2 true
+	t, ok = s.(T);
+	true(ok);
+	hello(t.String());
+
+	// I2T2 false
+	var u1 U;
+	u1, ok = s.(U);
+	false(ok);
+
+	// I2I2 true
+	sl, ok = s.(StringLengther);
+	true(ok);
+	hello(sl.String());
+	five(sl.Length());
+
+	// I2I2 false (and T2I)
+	s = u;
+	sl, ok = s.(StringLengther);
+	false(ok);
+
+	// E2T2 true
+	t, ok = e.(T);
+	true(ok);
+	hello(t.String());
+
+	// E2T2 false
+	i, ok = e.(int);
+	false(ok);
+
+	// E2I2 true
+	sl, ok = e.(StringLengther);
+	true(ok);
+	hello(sl.String());
+	five(sl.Length());
+
+	// E2I2 false (and T2E)
+	e = u;
+	sl, ok = e.(StringLengther);
+	false(ok);
+}
+

test/interface4.go

@@ -9,8 +9,6 @@
 
 package main
 
-import "os"
-
 type I interface { M() int64 }
 
 type BigPtr struct { a, b, c, d int64 }
@@ -72,6 +70,6 @@ func main() {
 	nonptrs();
 
 	if bad {
-		os.Exit(1)
+		println("BUG: interface4");
 	}
 }