gc, spec, tests: no auto-indirect of pointer to interface value

Implies no embedding of pointer to interface value either.

R=gri, iant, ken2, r, r2
CC=golang-dev
https://golang.org/cl/2289041

doc/go_spec.html

@@ -879,9 +879,10 @@ struct {
 </pre>
 
 <p>
-A field declared with a type but no explicit field name is an <i>anonymous field</i>.
+A field declared with a type but no explicit field name is an <i>anonymous field</i>
+(colloquially called an embedded field).
 Such a field type must be specified as
-a type name <code>T</code> or as a pointer to a type name <code>*T</code>,
+a type name <code>T</code> or as a pointer to a non-interface type name <code>*T</code>,
 and <code>T</code> itself may not be
 a pointer type. The unqualified type name acts as the field name.
 </p>
@@ -2214,8 +2215,7 @@ x.f
 
 <p>
 denotes the field or method <code>f</code> of the value denoted by <code>x</code>
-(or of <code>*x</code> if
-<code>x</code> is of pointer type). The identifier <code>f</code>
+(or sometimes <code>*x</code>; see below). The identifier <code>f</code>
 is called the (field or method)
 <i>selector</i>; it must not be the <a href="#Blank_identifier">blank identifier</a>.
 The type of the expression is the type of <code>f</code>.
@@ -2258,16 +2258,13 @@ In all other cases, <code>x.f</code> is illegal.
 </li>
 </ol>
 <p>
-Selectors automatically dereference pointers.
-If <code>x</code> is of pointer type, <code>x.y</code>
-is shorthand for <code>(*x).y</code>; if <code>y</code>
-is also of pointer type, <code>x.y.z</code> is shorthand
+Selectors automatically dereference pointers to structs.
+If <code>x</code> is a pointer to a struct, <code>x.y</code>
+is shorthand for <code>(*x).y</code>; if the field <code>y</code>
+is also a pointer to a struct, <code>x.y.z</code> is shorthand
 for <code>(*(*x).y).z</code>, and so on.
-If <code>*x</code> is of pointer type, dereferencing
-must be explicit;
-only one level of automatic dereferencing is provided.
-For an <code>x</code> of type <code>T</code> containing an
-anonymous field declared as <code>*A</code>,
+If <code>x</code> contains an anonymous field of type <code>*A</code>,
+where <code>A</code> is also a struct type,
 <code>x.f</code> is a shortcut for <code>(*x.A).f</code>.
 </p>
 <p>

src/cmd/gc/dcl.c

@@ -729,8 +729,11 @@ stotype(NodeList *l, int et, Type **t)
 				n->right = N;
 				if(n->embedded && n->type != T) {
 					t1 = n->type;
-					if(t1->sym == S && isptr[t1->etype])
+					if(t1->sym == S && isptr[t1->etype]) {
 						t1 = t1->type;
+						if(t1->etype == TINTER)
+							yyerror("embedded type cannot be a pointer to interface");
+					}
 					if(isptr[t1->etype])
 						yyerror("embedded type cannot be a pointer");
 					else if(t1->etype == TFORW && t1->embedlineno == 0)

src/cmd/gc/reflect.c

@@ -286,15 +286,6 @@ imethods(Type *t)
 				oldlist = pc;
 			genwrapper(t, f, isym, 0);
 		}
-		
-		// Generate wrapper for pointer to interface type.
-		isym = methodsym(method, ptrto(t), 0);
-		if(!(isym->flags & SymSiggen)) {
-			isym->flags |= SymSiggen;
-			if(oldlist == nil)
-				oldlist = pc;
-			genwrapper(ptrto(t), f, isym, 0);
-		}
 	}
 
 	if(oldlist) {

src/cmd/gc/typecheck.c

@@ -520,7 +520,7 @@ reswitch:
 			ok = Erv;
 			goto ret;
 		}
-		if(isptr[t->etype]) {
+		if(isptr[t->etype] && t->type->etype != TINTER) {
 			t = t->type;
 			if(t == T)
 				goto error;

test/hashmap.go

@@ -21,7 +21,7 @@ func ASSERT(p bool) {
 
 type KeyType interface {
 	Hash() uint32
-	Match(other *KeyType) bool
+	Match(other KeyType) bool
 }
 
 
@@ -31,8 +31,8 @@ type ValueType interface {
 
 
 type Entry struct {
-	key *KeyType
-	value *ValueType
+	key KeyType
+	value ValueType
 }
 
 
@@ -68,7 +68,7 @@ func (m *HashMap) Initialize (initial_log2_capacity uint32) {
 }
 
 
-func (m *HashMap) Probe (key *KeyType) *Entry {
+func (m *HashMap) Probe (key KeyType) *Entry {
 	ASSERT(key != nil)
 
 	var i uint32 = key.Hash() % m.capacity()
@@ -86,7 +86,7 @@ func (m *HashMap) Probe (key *KeyType) *Entry {
 }
 
 
-func (m *HashMap) Lookup (key *KeyType, insert bool) *Entry {
+func (m *HashMap) Lookup (key KeyType, insert bool) *Entry {
 	// Find a matching entry.
 	var p *Entry = m.Probe(key)
 		if p.key != nil {
@@ -145,7 +145,7 @@ func (n *Number) Hash() uint32 {
 }
 
 
-func (n *Number) Match(other *KeyType) bool {
+func (n *Number) Match(other KeyType) bool {
 	// var y *Number = other
 	// return n.x == y.x
 	return false

test/interface/embed.go

@@ -4,7 +4,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Check methods derived from embedded interface and *interface values.
+// Check methods derived from embedded interface values.
 
 package main
 
@@ -19,18 +19,12 @@ func (t T) M() int64 { return int64(t) }
 var t = T(Value)
 var pt = &t
 var ti Inter = t
-var pti = &ti
 
 type S struct { Inter }
 var s = S{ ti }
 var ps = &s
 
-type SP struct { *Inter }
-var sp = SP{ &ti }
-var psp = &sp
-
 var i Inter
-var pi = &i
 
 var ok = true
 
@@ -45,35 +39,20 @@ func main() {
 	check("t.M()", t.M())
 	check("pt.M()", pt.M())
 	check("ti.M()", ti.M())
-	check("pti.M()", pti.M())
 	check("s.M()", s.M())
 	check("ps.M()", ps.M())
-	check("sp.M()", sp.M())
-	check("psp.M()", psp.M())
 
 	i = t
 	check("i = t; i.M()", i.M())
-	check("i = t; pi.M()", pi.M())
 
 	i = pt
 	check("i = pt; i.M()", i.M())
-	check("i = pt; pi.M()", pi.M())
 
 	i = s
 	check("i = s; i.M()", i.M())
-	check("i = s; pi.M()", pi.M())
 
 	i = ps
 	check("i = ps; i.M()", i.M())
-	check("i = ps; pi.M()", pi.M())
-
-	i = sp
-	check("i = sp; i.M()", i.M())
-	check("i = sp; pi.M()", pi.M())
-
-	i = psp
-	check("i = psp; i.M()", i.M())
-	check("i = psp; pi.M()", pi.M())
 
 	if !ok {
 		println("BUG: interface10")

test/interface/embed2.go

@@ -0,0 +1,70 @@
+// errchk $G -e $D/$F.go
+
+// 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 methods derived from embedded interface and *interface values.
+
+package main
+
+import "os"
+
+const Value = 1e12
+
+type Inter interface { M() int64 }
+
+type T int64
+func (t T) M() int64 { return int64(t) }
+var t = T(Value)
+var pt = &t
+var ti Inter = t
+var pti = &ti
+
+type S struct { Inter }
+var s = S{ ti }
+var ps = &s
+
+type SP struct { *Inter }	// ERROR "interface"
+
+var i Inter
+var pi = &i
+
+var ok = true
+
+func check(s string, v int64) {
+	if v != Value {
+		println(s, v)
+		ok = false
+	}
+}
+
+func main() {
+	check("t.M()", t.M())
+	check("pt.M()", pt.M())
+	check("ti.M()", ti.M())
+	check("pti.M()", pti.M())	// ERROR "method"
+	check("s.M()", s.M())
+	check("ps.M()", ps.M())
+
+	i = t
+	check("i = t; i.M()", i.M())
+	check("i = t; pi.M()", pi.M())	// ERROR "method"
+
+	i = pt
+	check("i = pt; i.M()", i.M())
+	check("i = pt; pi.M()", pi.M())	// ERROR "method"
+
+	i = s
+	check("i = s; i.M()", i.M())
+	check("i = s; pi.M()", pi.M())	// ERROR "method"
+
+	i = ps
+	check("i = ps; i.M()", i.M())
+	check("i = ps; pi.M()", pi.M())	// ERROR "method"
+
+	if !ok {
+		println("BUG: interface10")
+		os.Exit(1)
+	}
+}

test/method.go

@@ -124,9 +124,4 @@ func main() {
 		println("Val.val(v):", Val.val(v))
 		panic("fail")
 	}
-	pv := &v
-	if pv.val() != 3 {
-		println("pv.val():", pv.val())
-		panic("fail")
-	}
 }

test/method2.go

@@ -20,3 +20,8 @@ type Val interface {
 }
 
 var _ = (*Val).val // ERROR "method"
+
+var v Val
+var pv = &v
+
+var _ = pv.val()	// ERROR "method"