gc: preserve uint8 and byte distinction in errors, import data

There is no semantic change here, just better errors.
If a function says it takes a byte, and you pass it an int,
the compiler error now says that you need a byte, not
that you need a uint8.

Groundwork for rune.

R=ken2
CC=golang-dev
https://golang.org/cl/5300042

src/cmd/gc/builtin.c.boot

 char *runtimeimport =
 	"package runtime\n"
 	"import runtime \"runtime\"\n"
-	"func @\"\".new (typ *uint8) *any\n"
+	"func @\"\".new (typ *byte) *any\n"
 	"func @\"\".panicindex ()\n"
 	"func @\"\".panicslice ()\n"
 	"func @\"\".throwreturn ()\n"
@@ -24,67 +24,67 @@ char *runtimeimport =
 	"func @\"\".goprintf ()\n"
 	"func @\"\".concatstring ()\n"
 	"func @\"\".append ()\n"
-	"func @\"\".appendslice (typ *uint8, x any, y []any) any\n"
-	"func @\"\".appendstr (typ *uint8, x []uint8, y string) []uint8\n"
+	"func @\"\".appendslice (typ *byte, x any, y []any) any\n"
+	"func @\"\".appendstr (typ *byte, x []byte, y string) []byte\n"
 	"func @\"\".cmpstring (? string, ? string) int\n"
 	"func @\"\".slicestring (? string, ? int, ? int) string\n"
 	"func @\"\".slicestring1 (? string, ? int) string\n"
 	"func @\"\".intstring (? int64) string\n"
-	"func @\"\".slicebytetostring (? []uint8) string\n"
+	"func @\"\".slicebytetostring (? []byte) string\n"
 	"func @\"\".sliceinttostring (? []int) string\n"
-	"func @\"\".stringtoslicebyte (? string) []uint8\n"
+	"func @\"\".stringtoslicebyte (? string) []byte\n"
 	"func @\"\".stringtosliceint (? string) []int\n"
 	"func @\"\".stringiter (? string, ? int) int\n"
 	"func @\"\".stringiter2 (? string, ? int) (retk int, retv int)\n"
 	"func @\"\".slicecopy (to any, fr any, wid uint32) int\n"
 	"func @\"\".slicestringcopy (to any, fr any) int\n"
 	"func @\"\".convI2E (elem any) any\n"
-	"func @\"\".convI2I (typ *uint8, elem any) any\n"
-	"func @\"\".convT2E (typ *uint8, elem any) any\n"
-	"func @\"\".convT2I (typ *uint8, typ2 *uint8, elem any) any\n"
-	"func @\"\".assertE2E (typ *uint8, iface any) any\n"
-	"func @\"\".assertE2E2 (typ *uint8, iface any) (ret any, ok bool)\n"
-	"func @\"\".assertE2I (typ *uint8, iface any) any\n"
-	"func @\"\".assertE2I2 (typ *uint8, iface any) (ret any, ok bool)\n"
-	"func @\"\".assertE2T (typ *uint8, iface any) any\n"
-	"func @\"\".assertE2T2 (typ *uint8, iface any) (ret any, ok bool)\n"
-	"func @\"\".assertI2E (typ *uint8, iface any) any\n"
-	"func @\"\".assertI2E2 (typ *uint8, iface any) (ret any, ok bool)\n"
-	"func @\"\".assertI2I (typ *uint8, iface any) any\n"
-	"func @\"\".assertI2I2 (typ *uint8, iface any) (ret any, ok bool)\n"
-	"func @\"\".assertI2T (typ *uint8, iface any) any\n"
-	"func @\"\".assertI2T2 (typ *uint8, iface any) (ret any, ok bool)\n"
+	"func @\"\".convI2I (typ *byte, elem any) any\n"
+	"func @\"\".convT2E (typ *byte, elem any) any\n"
+	"func @\"\".convT2I (typ *byte, typ2 *byte, elem any) any\n"
+	"func @\"\".assertE2E (typ *byte, iface any) any\n"
+	"func @\"\".assertE2E2 (typ *byte, iface any) (ret any, ok bool)\n"
+	"func @\"\".assertE2I (typ *byte, iface any) any\n"
+	"func @\"\".assertE2I2 (typ *byte, iface any) (ret any, ok bool)\n"
+	"func @\"\".assertE2T (typ *byte, iface any) any\n"
+	"func @\"\".assertE2T2 (typ *byte, iface any) (ret any, ok bool)\n"
+	"func @\"\".assertI2E (typ *byte, iface any) any\n"
+	"func @\"\".assertI2E2 (typ *byte, iface any) (ret any, ok bool)\n"
+	"func @\"\".assertI2I (typ *byte, iface any) any\n"
+	"func @\"\".assertI2I2 (typ *byte, iface any) (ret any, ok bool)\n"
+	"func @\"\".assertI2T (typ *byte, iface any) any\n"
+	"func @\"\".assertI2T2 (typ *byte, iface any) (ret any, ok bool)\n"
 	"func @\"\".ifaceeq (i1 any, i2 any) bool\n"
 	"func @\"\".efaceeq (i1 any, i2 any) bool\n"
 	"func @\"\".ifacethash (i1 any) uint32\n"
 	"func @\"\".efacethash (i1 any) uint32\n"
-	"func @\"\".makemap (mapType *uint8, hint int64) map[any] any\n"
-	"func @\"\".mapaccess1 (mapType *uint8, hmap map[any] any, key any) any\n"
-	"func @\"\".mapaccess2 (mapType *uint8, hmap map[any] any, key any) (val any, pres bool)\n"
-	"func @\"\".mapassign1 (mapType *uint8, hmap map[any] any, key any, val any)\n"
-	"func @\"\".mapassign2 (mapType *uint8, hmap map[any] any, key any, val any, pres bool)\n"
-	"func @\"\".mapiterinit (mapType *uint8, hmap map[any] any, hiter *any)\n"
-	"func @\"\".mapdelete (mapType *uint8, hmap map[any] any, key any)\n"
+	"func @\"\".makemap (mapType *byte, hint int64) map[any] any\n"
+	"func @\"\".mapaccess1 (mapType *byte, hmap map[any] any, key any) any\n"
+	"func @\"\".mapaccess2 (mapType *byte, hmap map[any] any, key any) (val any, pres bool)\n"
+	"func @\"\".mapassign1 (mapType *byte, hmap map[any] any, key any, val any)\n"
+	"func @\"\".mapassign2 (mapType *byte, hmap map[any] any, key any, val any, pres bool)\n"
+	"func @\"\".mapiterinit (mapType *byte, hmap map[any] any, hiter *any)\n"
+	"func @\"\".mapdelete (mapType *byte, hmap map[any] any, key any)\n"
 	"func @\"\".mapiternext (hiter *any)\n"
 	"func @\"\".mapiter1 (hiter *any) any\n"
 	"func @\"\".mapiter2 (hiter *any) (key any, val any)\n"
-	"func @\"\".makechan (chanType *uint8, hint int64) chan any\n"
-	"func @\"\".chanrecv1 (chanType *uint8, hchan <-chan any) any\n"
-	"func @\"\".chanrecv2 (chanType *uint8, hchan <-chan any) (elem any, received bool)\n"
-	"func @\"\".chansend1 (chanType *uint8, hchan chan<- any, elem any)\n"
+	"func @\"\".makechan (chanType *byte, hint int64) chan any\n"
+	"func @\"\".chanrecv1 (chanType *byte, hchan <-chan any) any\n"
+	"func @\"\".chanrecv2 (chanType *byte, hchan <-chan any) (elem any, received bool)\n"
+	"func @\"\".chansend1 (chanType *byte, hchan chan<- any, elem any)\n"
 	"func @\"\".closechan (hchan any)\n"
-	"func @\"\".selectnbsend (chanType *uint8, hchan chan<- any, elem any) bool\n"
-	"func @\"\".selectnbrecv (chanType *uint8, elem *any, hchan <-chan any) bool\n"
-	"func @\"\".selectnbrecv2 (chanType *uint8, elem *any, received *bool, hchan <-chan any) bool\n"
-	"func @\"\".newselect (size int) *uint8\n"
-	"func @\"\".selectsend (sel *uint8, hchan chan<- any, elem *any) bool\n"
-	"func @\"\".selectrecv (sel *uint8, hchan <-chan any, elem *any) bool\n"
-	"func @\"\".selectrecv2 (sel *uint8, hchan <-chan any, elem *any, received *bool) bool\n"
-	"func @\"\".selectdefault (sel *uint8) bool\n"
-	"func @\"\".selectgo (sel *uint8)\n"
+	"func @\"\".selectnbsend (chanType *byte, hchan chan<- any, elem any) bool\n"
+	"func @\"\".selectnbrecv (chanType *byte, elem *any, hchan <-chan any) bool\n"
+	"func @\"\".selectnbrecv2 (chanType *byte, elem *any, received *bool, hchan <-chan any) bool\n"
+	"func @\"\".newselect (size int) *byte\n"
+	"func @\"\".selectsend (sel *byte, hchan chan<- any, elem *any) bool\n"
+	"func @\"\".selectrecv (sel *byte, hchan <-chan any, elem *any) bool\n"
+	"func @\"\".selectrecv2 (sel *byte, hchan <-chan any, elem *any, received *bool) bool\n"
+	"func @\"\".selectdefault (sel *byte) bool\n"
+	"func @\"\".selectgo (sel *byte)\n"
 	"func @\"\".block ()\n"
-	"func @\"\".makeslice (typ *uint8, nel int64, cap int64) []any\n"
-	"func @\"\".growslice (typ *uint8, old []any, n int64) []any\n"
+	"func @\"\".makeslice (typ *byte, nel int64, cap int64) []any\n"
+	"func @\"\".growslice (typ *byte, old []any, n int64) []any\n"
 	"func @\"\".sliceslice1 (old []any, lb uint64, width uint64) []any\n"
 	"func @\"\".sliceslice (old []any, lb uint64, hb uint64, width uint64) []any\n"
 	"func @\"\".slicearray (old *any, nel uint64, lb uint64, hb uint64, width uint64) []any\n"

src/cmd/gc/export.c

@@ -94,7 +94,7 @@ dumpprereq(Type *t)
 	if(t == T)
 		return;
 
-	if(t->printed || t == types[t->etype])
+	if(t->printed || t == types[t->etype] || t == bytetype)
 		return;
 	t->printed = 1;
 

src/cmd/gc/go.h

@@ -784,6 +784,7 @@ EXTERN	Idir*	idirs;
 EXTERN	Type*	types[NTYPE];
 EXTERN	Type*	idealstring;
 EXTERN	Type*	idealbool;
+EXTERN	Type*	bytetype;
 EXTERN	uchar	simtype[NTYPE];
 EXTERN	uchar	isptr[NTYPE];
 EXTERN	uchar	isforw[NTYPE];

src/cmd/gc/lex.c

@@ -19,6 +19,7 @@ int yyprev;
 int yylast;
 
 static void	lexinit(void);
+static void	lexinit1(void);
 static void	lexfini(void);
 static void	yytinit(void);
 static int	getc(void);
@@ -211,6 +212,7 @@ main(int argc, char *argv[])
 
 	lexinit();
 	typeinit();
+	lexinit1();
 	yytinit();
 
 	blockgen = 1;
@@ -1588,7 +1590,6 @@ static	struct
 	"complex128",	LNAME,		TCOMPLEX128,	OXXX,
 
 	"bool",		LNAME,		TBOOL,		OXXX,
-	"byte",		LNAME,		TUINT8,		OXXX,
 	"string",	LNAME,		TSTRING,	OXXX,
 
 	"any",		LNAME,		TANY,		OXXX,
@@ -1706,6 +1707,21 @@ lexinit(void)
 	nblank = s->def;
 }
 
+static void
+lexinit1(void)
+{
+	Sym *s, *s1;
+
+	// byte alias
+	s = lookup("byte");
+	s->lexical = LNAME;
+	bytetype = typ(TUINT8);
+	bytetype->sym = s;
+	s1 = pkglookup("byte", builtinpkg);
+	s1->lexical = LNAME;
+	s1->def = typenod(bytetype);
+}
+
 static void
 lexfini(void)
 {
@@ -1741,6 +1757,10 @@ lexfini(void)
 
 	// there's only so much table-driven we can handle.
 	// these are special cases.
+	s = lookup("byte");
+	if(s->def == N)
+		s->def = typenod(bytetype);
+
 	types[TNIL] = typ(TNIL);
 	s = lookup("nil");
 	if(s->def == N) {

src/cmd/gc/reflect.c

@@ -692,7 +692,7 @@ dtypesym(Type *t)
 		tbase = t->type;
 	dupok = tbase->sym == S;
 
-	if(compiling_runtime && tbase == types[tbase->etype])	// int, float, etc
+	if(compiling_runtime && (tbase == types[tbase->etype] || tbase == bytetype))	// int, float, etc
 		goto ok;
 
 	// named types from other files are defined only by those files

src/cmd/gc/subr.c

@@ -1280,12 +1280,18 @@ Tpretty(Fmt *fp, Type *t)
 		debug['r'] = 1;
 		return 0;
 	}
+	
+	if(noargnames) {
+		// called from typesym
+		if(t == bytetype)
+			t = types[bytetype->etype];
+	}
 
 	if(t->etype != TFIELD
 	&& t->sym != S
 	&& !(fp->flags&FmtLong)) {
 		s = t->sym;
-		if(t == types[t->etype] && t->etype != TUNSAFEPTR)
+		if((t == types[t->etype] && t->etype != TUNSAFEPTR) || t == bytetype)
 			return fmtprint(fp, "%s", s->name);
 		if(exporting) {
 			if(fp->flags & FmtShort)
@@ -1859,8 +1865,19 @@ eqtype(Type *t1, Type *t2)
 {
 	if(t1 == t2)
 		return 1;
-	if(t1 == T || t2 == T || t1->etype != t2->etype || t1->sym || t2->sym)
+	if(t1 == T || t2 == T || t1->etype != t2->etype)
+		return 0;
+	if(t1->sym || t2->sym) {
+		// Special case: we keep byte and uint8 separate
+		// for error messages.  Treat them as equal.
+		switch(t1->etype) {
+		case TUINT8:
+			if((t1 == types[TUINT8] || t1 == bytetype) && (t2 == types[TUINT8] || t2 == bytetype))
+				return 1;
+			break;
+		}
 		return 0;
+	}
 
 	switch(t1->etype) {
 	case TINTER:
@@ -2088,24 +2105,20 @@ convertop(Type *src, Type *dst, char **why)
 	if(isint[src->etype] && dst->etype == TSTRING)
 		return ORUNESTR;
 
-	if(isslice(src) && src->sym == nil &&  src->type == types[src->type->etype] && dst->etype == TSTRING) {
-		switch(src->type->etype) {
-		case TUINT8:
+	if(isslice(src) && src->sym == nil && dst->etype == TSTRING) {
+		if(eqtype(src->type, bytetype))
 			return OARRAYBYTESTR;
-		case TINT:
+		if(eqtype(src->type, types[TINT]))
 			return OARRAYRUNESTR;
-		}
 	}
 	
 	// 7. src is a string and dst is []byte or []int.
 	// String to slice.
-	if(src->etype == TSTRING && isslice(dst) && dst->sym == nil && dst->type == types[dst->type->etype]) {
-		switch(dst->type->etype) {
-		case TUINT8:
+	if(src->etype == TSTRING && isslice(dst) && dst->sym == nil) {
+		if(eqtype(dst->type, bytetype))
 			return OSTRARRAYBYTE;
-		case TINT:
+		if(eqtype(dst->type, types[TINT]))
 			return OSTRARRAYRUNE;
-		}
 	}
 	
 	// 8. src is a pointer or uintptr and dst is unsafe.Pointer.

src/cmd/gc/typecheck.c

@@ -1040,7 +1040,7 @@ reswitch:
 				yyerror("too many arguments to append");
 				goto error;
 			}
-			if(istype(t->type, TUINT8) &&  istype(args->next->n->type, TSTRING)) {
+			if(istype(t->type, TUINT8) && istype(args->next->n->type, TSTRING)) {
 				defaultlit(&args->next->n, types[TSTRING]);
 				goto ret;
 			}
@@ -1078,7 +1078,7 @@ reswitch:
 
 		// copy([]byte, string)
 		if(isslice(n->left->type) && n->right->type->etype == TSTRING) {
-			if(n->left->type->type == types[TUINT8])
+			if(eqtype(n->left->type->type, bytetype))
 				goto ret;
 			yyerror("arguments to copy have different element types: %lT and string", n->left->type);
 			goto error;

test/alias.go

+// 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
+
+// Test that error messages say what the source file says
+// (uint8 vs byte).
+
+func f(byte) {}
+func g(uint8) {}
+
+func main() {
+	var x int
+	f(x)  // ERROR "byte"
+	g(x)  // ERROR "uint8"
+}