diff --git a/src/cmd/gc/align.c b/src/cmd/gc/align.c
index 15738435f6..703182c0b1 100644
--- a/src/cmd/gc/align.c
+++ b/src/cmd/gc/align.c
@@ -237,7 +237,7 @@ typeinit(void)
 {
 	int i, etype, sameas;
 	Type *t;
-	Sym *s;
+	Sym *s, *s1;
 
 	if(widthptr == 0)
 		fatal("typeinit before betypeinit");
@@ -403,6 +403,7 @@ typeinit(void)
 	/* pick up the backend typedefs */
 	for(i=0; typedefs[i].name; i++) {
 		s = lookup(typedefs[i].name);
+		s1 = pkglookup(typedefs[i].name, "/builtin/");
 
 		etype = typedefs[i].etype;
 		if(etype < 0 || etype >= nelem(types))
@@ -425,7 +426,7 @@ typeinit(void)
 
 		dowidth(t);
 		types[etype] = t;
-		s->def = typenod(t);
+		s1->def = typenod(t);
 	}
 
 	Array_array = rnd(0, widthptr);
diff --git a/src/cmd/gc/const.c b/src/cmd/gc/const.c
index 59bd9a3887..16daab043e 100644
--- a/src/cmd/gc/const.c
+++ b/src/cmd/gc/const.c
@@ -722,6 +722,10 @@ defaultlit(Node **np, Type *t)
 		n->type = t;
 		return;
 	default:
+		if(n->left == N) {
+			dump("defaultlit", n);
+			fatal("defaultlit");
+		}
 		defaultlit(&n->left, t);
 		defaultlit(&n->right, t);
 		n->type = n->left->type;
diff --git a/src/cmd/gc/dcl.c b/src/cmd/gc/dcl.c
index 456e2e4eae..8e6c171845 100644
--- a/src/cmd/gc/dcl.c
+++ b/src/cmd/gc/dcl.c
@@ -417,10 +417,6 @@ dclname(Sym *s)
 	// referred to, in which case s->def is already
 	// set to an ONONAME.
 	if(dclcontext == PEXTERN && s->block <= 1) {
-		// toss predefined name like "close"
-		// TODO(rsc): put close in at the end.
-		if(s->def != N && s->def->etype)
-			s->def = N;
 		if(s->def == N)
 			oldname(s);
 		if(s->def->op == ONONAME)
@@ -971,11 +967,8 @@ checkarglist(NodeList *all)
 			t = n;
 			n = N;
 		}
-		if(n != N) {
-			if(n->op == ONONAME && n->sym->def == n)
-				n->sym->def = N;
+		if(n != N)
 			n = newname(n->sym);
-		}
 		n = nod(ODCLFIELD, n, t);
 		if(l->next != nil && n->right != N && n->right->op == OTYPE && isddd(n->right->type))
 			yyerror("only last argument can have type ...");
diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h
index c933357c46..7b743fd958 100644
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -356,6 +356,7 @@ enum
 	ORECV,
 	ORUNESTR,
 	OSELRECV,
+	OIOTA,
 
 	// stmts
 	OBLOCK,
diff --git a/src/cmd/gc/go.y b/src/cmd/gc/go.y
index bb8a5882d5..f784c862ab 100644
--- a/src/cmd/gc/go.y
+++ b/src/cmd/gc/go.y
@@ -1582,8 +1582,9 @@ hidden_type1:
 |	LNAME
 	{
 		// predefined name like uint8
+		$1 = pkglookup($1->name, "/builtin/");
 		if($1->def == N || $1->def->op != OTYPE) {
-			yyerror("%S is not a type", $1);
+			yyerror("%s is not a type", $1->name);
 			$$ = T;
 		} else
 			$$ = $1->def->type;
@@ -1660,11 +1661,15 @@ hidden_structdcl:
 	}
 |	'?' hidden_type oliteral
 	{
-		if(isptr[$2->etype]) {
-			$$ = embedded($2->type->sym);
-			$$->right = nod(OIND, $$->right, N);
-		} else
-			$$ = embedded($2->sym);
+		Sym *s;
+
+		s = $2->sym;
+		if(s == S && isptr[$2->etype])
+			s = $2->type->sym;
+		if(s && strcmp(s->package, "/builtin/") == 0)
+			s = lookup(s->name);
+		$$ = embedded(s);
+		$$->right = typenod($2);
 		$$->val = $3;
 	}
 
@@ -1709,9 +1714,9 @@ hidden_constant:
 			yyerror("bad negated constant");
 		}
 	}
-|	name
+|	sym
 	{
-		$$ = $1;
+		$$ = oldname(pkglookup($1->name, "/builtin/"));
 		if($$->op != OLITERAL)
 			yyerror("bad constant %S", $$->sym);
 	}
diff --git a/src/cmd/gc/lex.c b/src/cmd/gc/lex.c
index 42bbe04d79..fd78e446aa 100644
--- a/src/cmd/gc/lex.c
+++ b/src/cmd/gc/lex.c
@@ -8,8 +8,8 @@
 #include <ar.h>
 
 extern int yychar;
-Sym *anysym;
 char nopackage[] = "____";
+void lexfini(void);
 
 #define	DBG	if(!debug['x']);else print
 enum
@@ -96,8 +96,8 @@ main(int argc, char *argv[])
 		if(curio.bin != nil)
 			Bterm(curio.bin);
 	}
-
 	testdclstack();
+	lexfini();
 
 	typecheckok = 1;
 	if(debug['f'])
@@ -278,9 +278,6 @@ importfile(Val *f)
 		return;
 	}
 
-	if(!debug['A'])
-		anysym->def = typenod(types[TANY]);
-
 	if(!findpkg(f->u.sval))
 		fatal("can't find import: %Z", f->u.sval);
 	imp = Bopen(namebuf, OREAD);
@@ -337,9 +334,6 @@ unimportfile(void)
 {
 	linehist(nil, 0, 0);
 
-	if(!debug['A'])
-		anysym->def = nil;
-
 	if(curio.bin != nil) {
 		Bterm(curio.bin);
 		curio.bin = nil;
@@ -354,9 +348,6 @@ unimportfile(void)
 void
 cannedimports(char *file, char *cp)
 {
-	if(!debug['A'])
-		anysym->def = typenod(types[TANY]);
-
 	lexlineno++;		// if sys.6 is included on line 1,
 	linehist(file, 0, 0);	// the debugger gets confused
 
@@ -1274,10 +1265,9 @@ void
 lexinit(void)
 {
 	int i, lex;
-	Sym *s;
+	Sym *s, *s1;
 	Type *t;
 	int etype;
-	Val v;
 
 	/*
 	 * initialize basic types array
@@ -1287,7 +1277,6 @@ lexinit(void)
 		lex = syms[i].lexical;
 		s = lookup(syms[i].name);
 		s->lexical = lex;
-		s->package = package;
 
 		etype = syms[i].etype;
 		if(etype != Txxx) {
@@ -1302,48 +1291,26 @@ lexinit(void)
 					dowidth(t);
 				types[etype] = t;
 			}
-			s->def = typenod(t);
-			if(etype == TANY) {
-				anysym = s;
-				if(!debug['A'])
-					s->def = nil;
-			}
-			continue;
-		}
-
-		etype = syms[i].op;
-		if(etype != OXXX) {
-			s->def = nod(ONAME, N, N);
-			s->def->sym = s;
-			s->def->etype = etype;
-			s->def->builtin = 1;
+			s1 = pkglookup(syms[i].name, "/builtin/");	// impossible pkg name for builtins
+			s1->lexical = LNAME;
+			s1->def = typenod(t);
 			continue;
 		}
 	}
 
-	// there's only so much table-driven we can handle.
-	// these are special cases.
-	types[TNIL] = typ(TNIL);
-	s = lookup("nil");
-	v.ctype = CTNIL;
-	s->def = nodlit(v);
-	s->def->sym = s;
-	s->block = -1;	// above top level
-
-	s = lookup("true");
-	s->def = nodbool(1);
-	s->def->sym = s;
-	s->block = -1;	// above top level
-
-	s = lookup("false");
-	s->def = nodbool(0);
-	s->def->sym = s;
-	s->block = -1;	// above top level
-
 	s = lookup("iota");
-	s->def = nodintconst(iota);
-	s->def->iota = 1;	// flag to reevaluate on copy
-	s->block = -1;	// above top level
+	s->def = nod(ONONAME, N, N);
+	s->def->iota = 1;
+	s->def->sym = s;
+	
+	s = pkglookup("true", "/builtin/");
+	s->def = nodbool(1);
+	s->def->sym = lookup("true");
+
+	s = pkglookup("false", "/builtin/");
+	s->def = nodbool(0);
+	s->def->sym = lookup("false");
+
 
 	// logically, the type of a string literal.
 	// types[TSTRING] is the named type string
@@ -1362,6 +1329,63 @@ lexinit(void)
 	nblank = s->def;
 }
 
+void
+lexfini(void)
+{
+	Sym *s;
+	int lex, etype, i;
+	Val v;
+
+	for(i=0; i<nelem(syms); i++) {
+		lex = syms[i].lexical;
+		if(lex != LNAME)
+			continue;
+		s = lookup(syms[i].name);
+		s->lexical = lex;
+
+		etype = syms[i].etype;
+		if(etype != Txxx && (etype != TANY || debug['A']))
+		if(s->def != N && s->def->op == ONONAME)
+			*s->def = *typenod(types[etype]);
+
+		etype = syms[i].op;
+		if(etype != OXXX && s->def != N && s->def->op == ONONAME) {
+			s->def->op = ONAME;
+			s->def->sym = s;
+			s->def->etype = etype;
+			s->def->builtin = 1;
+		}
+	}
+
+	for(i=0; typedefs[i].name; i++) {
+		s = lookup(typedefs[i].name);
+		if(s->def != N && s->def->op == ONONAME)
+			*s->def = *typenod(types[typedefs[i].etype]);
+	}
+
+	// there's only so much table-driven we can handle.
+	// these are special cases.
+	types[TNIL] = typ(TNIL);
+	s = lookup("nil");
+	if(s->def != N && s->def->op == ONONAME) {
+		v.ctype = CTNIL;
+		*s->def = *nodlit(v);
+		s->def->sym = s;
+	}
+
+	s = lookup("true");
+	if(s->def != N && s->def->op == ONONAME) {
+		*s->def = *nodbool(1);
+		s->def->sym = s;
+	}
+
+	s = lookup("false");
+	if(s->def != N && s->def->op == ONONAME) {
+		*s->def = *nodbool(0);
+		s->def->sym = s;
+	}
+}
+
 struct
 {
 	int	lex;
@@ -1422,16 +1446,6 @@ lexname(int lex)
 	return buf;
 }
 
-int
-specialsym(Sym *s)
-{
-	if(strcmp(s->name, "byte") == 0 && s->def->sym == lookup("uint8"))
-		return 1;
-	if(strcmp(s->name, "iota") == 0 && s->def->sym == S)
-		return 1;
-	return 0;
-}
-
 void
 mkpackage(char* pkg)
 {
@@ -1459,10 +1473,13 @@ mkpackage(char* pkg)
 				if(s->def->op == OPACK) {
 					// throw away top-level package name leftover
 					// from previous file.
+					// TODO(rsc): remember that there was a package
+					// name, so that the name cannot be redeclared
+					// as a non-package in other files.
 					s->def = N;
 					continue;
 				}
-				if(s->def->sym != s && !specialsym(s)) {
+				if(s->def->sym != s) {
 					// throw away top-level name left over
 					// from previous import . "x"
 					s->def = N;
diff --git a/src/cmd/gc/subr.c b/src/cmd/gc/subr.c
index bfd91cf143..f2da5c003d 100644
--- a/src/cmd/gc/subr.c
+++ b/src/cmd/gc/subr.c
@@ -1324,13 +1324,13 @@ treecopy(Node *n)
 			abort();
 		break;
 
-	case OLITERAL:
+	case ONONAME:
 		if(n->iota) {
-			m = nodintconst(iota);
+			m = nod(OIOTA, n, nodintconst(iota));
 			break;
 		}
 		// fall through
-	case ONONAME:
+	case OLITERAL:
 	case ONAME:
 	case OTYPE:
 		m = n;
diff --git a/src/cmd/gc/typecheck.c b/src/cmd/gc/typecheck.c
index e83646f53a..7665cbf3c4 100644
--- a/src/cmd/gc/typecheck.c
+++ b/src/cmd/gc/typecheck.c
@@ -63,14 +63,25 @@ typecheck(Node **np, int top)
 		return N;
 	
 	// Skip typecheck if already done.
-	// But re-typecheck ONAME node in case context has changed.
-	if(n->typecheck == 1 && n->op != ONAME)
-		return n;
+	// But re-typecheck ONAME/OTYPE/OLITERAL/OPACK node in case context has changed.
+	if(n->typecheck == 1) {
+		switch(n->op) {
+		case ONAME:
+		case OTYPE:
+		case OLITERAL:
+		case OPACK:
+			break;
+		default:
+			return n;
+		}
+	}
+
 	if(n->typecheck == 2)
 		fatal("typecheck loop");
 	n->typecheck = 2;
 
-	if(n->sym && n->walkdef != 1)
+redo:
+	if(n->sym)
 		walkdef(n);
 
 	lno = setlineno(n);
@@ -88,10 +99,6 @@ reswitch:
 	 */
 	case OLITERAL:
 		ok |= Erv;
-		if(n->iota && !(top & Eiota)) {
-			yyerror("use of iota not in constant initializer");
-			goto error;
-		}
 		if(n->val.ctype == CTSTR)
 			n->type = idealstring;
 		goto ret;
@@ -116,6 +123,15 @@ reswitch:
 		yyerror("use of package %S not in selector", n->sym);
 		goto error;
 
+	case OIOTA:
+		// looked like iota during parsing but might
+		// have been redefined.  decide.
+		if(n->left->op != ONONAME)
+			n = n->left;
+		else
+			n = n->right;
+		goto redo;
+
 	/*
 	 * types (OIND is with exprs)
 	 */
@@ -1025,8 +1041,6 @@ error:
 out:
 	lineno = lno;
 	n->typecheck = 1;
-	if(n->iota)
-		n->typecheck = 0;
 	*np = n;
 	return n;
 }
@@ -1592,7 +1606,7 @@ typecheckcomplit(Node **np)
 				len = i;
 				if(t->bound >= 0 && len > t->bound) {
 					setlineno(l);
-					yyerror("array index out of bounds");
+					yyerror("array index %d out of bounds [0:%d]", len, t->bound);
 					t->bound = -1;	// no more errors
 				}
 			}
diff --git a/src/cmd/gc/walk.c b/src/cmd/gc/walk.c
index a8af6db49a..18c88867ae 100644
--- a/src/cmd/gc/walk.c
+++ b/src/cmd/gc/walk.c
@@ -161,7 +161,7 @@ walkdef(Node *n)
 			yyerror("xxx");
 		}
 		typecheck(&e, Erv | Eiota);
-		if(e->op != OLITERAL) {
+		if(e->type != T && e->op != OLITERAL) {
 			yyerror("const initializer must be constant");
 			goto ret;
 		}
diff --git a/src/pkg/big/arith.go b/src/pkg/big/arith.go
index d75f37ac12..e995192ecf 100644
--- a/src/pkg/big/arith.go
+++ b/src/pkg/big/arith.go
@@ -13,7 +13,7 @@ import "unsafe"
 type Word uintptr
 
 const (
-	_S = uintptr(unsafe.Sizeof(Word));  // TODO(gri) should Sizeof return a uintptr?
+	_S = uintptr(unsafe.Sizeof(Word(0)));  // TODO(gri) should Sizeof return a uintptr?
 	_W = _S*8;
 	_B = 1<<_W;
 	_M = _B-1;
diff --git a/test/fixedbugs/bug186.go b/test/fixedbugs/bug186.go
index a54934e2bd..dde794a5d7 100644
--- a/test/fixedbugs/bug186.go
+++ b/test/fixedbugs/bug186.go
@@ -12,7 +12,6 @@ func f(x int) { }
 
 func main() {
 	f(X);
-	f(iota);	// ERROR "iota.*initializer"
+	f(iota);	// ERROR "iota"
 	f(X);
-	f(iota);	// ERROR "iota.*initializer"
 }
diff --git a/test/bugs/bug194.go b/test/fixedbugs/bug194.go
similarity index 100%
rename from test/bugs/bug194.go
rename to test/fixedbugs/bug194.go
diff --git a/test/golden.out b/test/golden.out
index a5eb85bb3b..148471660a 100644
--- a/test/golden.out
+++ b/test/golden.out
@@ -163,10 +163,6 @@ BUG: should compile
 =========== bugs/bug193.go
 BUG: errchk: bugs/bug193.go:14: missing expected error: 'shift'
 
-=========== bugs/bug194.go
-bugs/bug194.go:15: array index must be non-negative integer constant
-BUG should compile and run
-
 =========== bugs/bug196.go
 too many calls: 5
 panic PC=xxx
diff --git a/test/rename.go b/test/rename.go
new file mode 100644
index 0000000000..8d5441375c
--- /dev/null
+++ b/test/rename.go
@@ -0,0 +1,75 @@
+// $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.
+
+package main
+
+import "fmt"
+
+func main() {
+	n :=
+		bool +
+		byte +
+		float +
+		float32 +
+		float64 + 
+		int +
+		int8 +
+		int16 +
+		int32 +
+		int64 +
+		uint +
+		uint8 +
+		uint16 +
+		uint32 +
+		uint64 +
+		uintptr +
+		true +
+		false +
+		iota +
+		nil + 
+		cap +
+		len +
+		make +
+		new +
+		panic +
+		panicln +
+		print +
+		println;
+	if n != 28*29/2 {
+		fmt.Println("BUG: wrong n", n, 28*29/2)
+	}
+}
+
+const (
+	bool = 1;
+	byte = 2;
+	float = 3;
+	float32 = 4;
+	float64 = 5;
+	int = 6;
+	int8 = 7;
+	int16 = 8;
+	int32 = 9;
+	int64 = 10;
+	uint = 11;
+	uint8 = 12;
+	uint16 = 13;
+	uint32 = 14;
+	uint64 = 15;
+	uintptr = 16;
+	true = 17;
+	false = 18;
+	iota = 19;
+	nil = 20;
+	cap = 21;
+	len = 22;
+	make = 23;
+	new = 24;
+	panic = 25;
+	panicln = 26;
+	print = 27;
+	println = 28;
+)
diff --git a/test/rename1.go b/test/rename1.go
new file mode 100644
index 0000000000..eb98e7accf
--- /dev/null
+++ b/test/rename1.go
@@ -0,0 +1,48 @@
+// 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.
+
+package main
+
+func main() {
+	var n byte;	// ERROR "not a type"
+	var y = float(0);	// ERROR "cannot call"
+	const (
+		a = 1+iota;	// ERROR "string"
+	)
+
+}
+
+const (
+	bool = 1;
+	byte = 2;
+	float = 3;
+	float32 = 4;
+	float64 = 5;
+	int = 6;
+	int8 = 7;
+	int16 = 8;
+	int32 = 9;
+	int64 = 10;
+	uint = 11;
+	uint8 = 12;
+	uint16 = 13;
+	uint32 = 14;
+	uint64 = 15;
+	uintptr = 16;
+	true = 17;
+	false = 18;
+	iota = "abc";
+	nil = 20;
+	cap = 21;
+	len = 22;
+	make = 23;
+	new = 24;
+	panic = 25;
+	panicln = 26;
+	print = 27;
+	println = 28;
+)
+