gc: new typechecking rules

* Code for assignment, conversions now mirrors spec.
* Changed some snprint -> smprint.
* Renamed runtime functions to separate
  interface conversions from type assertions:
  convT2I, assertI2T, etc.
* Correct checking of \U sequences.

Fixes issue 840.
Fixes issue 830.
Fixes issue 778.

R=ken2
CC=golang-dev
http://codereview.appspot.com/1303042

3 files changed, 74 insertions, 54 deletions

diff --git a/test/interface/explicit.go b/test/interface/explicit.go
index bd1bd19a9..797cec80e 100644
--- a/test/interface/explicit.go
+++ b/test/interface/explicit.go
@@ -8,34 +8,45 @@
 
 package main
 
-type T struct { a int }
+type T struct {
+	a int
+}
+
 var t *T
 
-type I interface { M() }
+type I interface {
+	M()
+}
+
 var i I
 
-type I2 interface { M(); N(); }
+type I2 interface {
+	M()
+	N()
+}
+
 var i2 I2
 
-type E interface { }
+type E interface{}
+
 var e E
 
 func main() {
-	e = t;	// ok
-	t = e;	// ERROR "need explicit|need type assertion"
+	e = t // ok
+	t = e // ERROR "need explicit|need type assertion"
 
 	// neither of these can work,
 	// because i has an extra method
 	// that t does not, so i cannot contain a t.
-	i = t;	// ERROR "missing|incompatible|is not"
-	t = i;	// ERROR "missing|incompatible|is not"
+	i = t // ERROR "incompatible|missing M method"
+	t = i // ERROR "incompatible|need type assertion"
+
+	i = i2 // ok
+	i2 = i // ERROR "missing N method"
 
-	i = i2;	// ok
-	i2 = i;	// ERROR "need explicit|need type assertion"
-	
-	i = I(i2);	// ok
-	i2 = I2(i);	// ERROR "need explicit|need type assertion"
+	i = I(i2)  // ok
+	i2 = I2(i) // ERROR "missing N method"
 
-	e = E(t);	// ok
-	t = T(e);	// ERROR "need explicit|need type assertion|incompatible"
+	e = E(t) // ok
+	t = T(e) // ERROR "need explicit|need type assertion|incompatible"
 }
diff --git a/test/interface/pointer.go b/test/interface/pointer.go
index be24952ff..e628b558e 100644
--- a/test/interface/pointer.go
+++ b/test/interface/pointer.go
@@ -9,28 +9,28 @@
 package main
 
 type Inst interface {
-	Next()	*Inst;
+	Next() *Inst
 }
 
 type Regexp struct {
-	code []Inst;
-	start	Inst;
+	code  []Inst
+	start Inst
 }
 
 type Start struct {
-	foo	*Inst;
+	foo *Inst
 }
 
 func (start *Start) Next() *Inst { return nil }
 
 
 func AddInst(Inst) *Inst {
-	print("ok in addinst\n");
+	print("ok in addinst\n")
 	return nil
 }
 
 func main() {
-	print("call addinst\n");
-	var x Inst = AddInst(new(Start));	// ERROR "illegal|incompatible|is not"
-	print("return from  addinst\n");
+	print("call addinst\n")
+	var x Inst = AddInst(new(Start)) // ERROR "pointer to interface"
+	print("return from  addinst\n")
 }
diff --git a/test/interface/receiver1.go b/test/interface/receiver1.go
index 8ce96424e..51312d000 100644
--- a/test/interface/receiver1.go
+++ b/test/interface/receiver1.go
@@ -9,41 +9,50 @@
 package main
 
 type T int
+
 func (t T) V()
 func (t *T) P()
 
-type V interface { V() }
-type P interface { P(); V() }
+type V interface {
+	V()
+}
+type P interface {
+	P()
+	V()
+}
 
-type S struct { T; }
-type SP struct { *T; }
+type S struct {
+	T
+}
+type SP struct {
+	*T
+}
 
 func main() {
-	var t T;
-	var v V;
-	var p P;
-	var s S;
-	var sp SP;
-
-	v = t;
-	p = t;	// ERROR "is not|requires a pointer"
-	_, _= v, p;
-	v = &t;
-	p = &t;
-	_, _= v, p;
-
-	v = s;
-	p = s;	// ERROR "is not|requires a pointer"
-	_, _= v, p;
-	v = &s;
-	p = &s;
-	_, _= v, p;
-
-	v = sp;
-	p = sp;	// no error!
-	_, _= v, p;
-	v = &sp;
-	p = &sp;
-	_, _= v, p;
+	var t T
+	var v V
+	var p P
+	var s S
+	var sp SP
+
+	v = t
+	p = t // ERROR "does not implement|requires a pointer"
+	_, _ = v, p
+	v = &t
+	p = &t
+	_, _ = v, p
+
+	v = s
+	p = s // ERROR "does not implement|requires a pointer"
+	_, _ = v, p
+	v = &s
+	p = &s
+	_, _ = v, p
+
+	v = sp
+	p = sp // no error!
+	_, _ = v, p
+	v = &sp
+	p = &sp
+	_, _ = v, p
 }
-