cmd/gc: fix type checking loop

CL 4313064 fixed its test case but did not address a
general enough problem:

type T1 struct { F *T2 }
type T2 T1
type T3 T2

could still end up copying the definition of T1 for T2
before T1 was done being evaluated, or T3 before T2
was done.

In order to propagate the updates correctly,
record a copy of an incomplete type for re-execution
once the type is completed. Roll back CL 4313064.

Fixes #3709.

R=ken2
CC=golang-dev, lstoakes
https://golang.org/cl/6301059

src/cmd/gc/go.h

@@ -182,6 +182,9 @@ struct	Type
 
 	int32	maplineno;	// first use of TFORW as map key
 	int32	embedlineno;	// first use of TFORW as embedded type
+	
+	// for TFORW, where to copy the eventual value to
+	NodeList	*copyto;
 };
 #define	T	((Type*)0)
 
@@ -1250,9 +1253,7 @@ int	islvalue(Node *n);
 Node*	typecheck(Node **np, int top);
 void	typechecklist(NodeList *l, int top);
 Node*	typecheckdef(Node *n);
-void	resumetypecopy(void);
 void	copytype(Node *n, Type *t);
-void	defertypecopy(Node *n, Type *t);
 void	queuemethod(Node *n);
 
 /*

src/cmd/gc/lex.c

@@ -349,7 +349,6 @@ main(int argc, char *argv[])
 	for(l=xtop; l; l=l->next)
 		if(l->n->op == ODCL || l->n->op == OAS)
 			typecheck(&l->n, Etop);
-	resumetypecopy();
 	resumecheckwidth();
 
 	// Phase 3: Type check function bodies.

src/cmd/gc/typecheck.c

@@ -31,7 +31,6 @@ static void	checkassign(Node*);
 static void	checkassignlist(NodeList*);
 static void	stringtoarraylit(Node**);
 static Node*	resolve(Node*);
-static Type*	getforwtype(Node*);
 
 static	NodeList*	typecheckdefstack;
 
@@ -237,7 +236,7 @@ typecheck1(Node **np, int top)
 	Node *n, *l, *r;
 	NodeList *args;
 	int ok, ntop;
-	Type *t, *tp, *ft, *missing, *have, *badtype;
+	Type *t, *tp, *missing, *have, *badtype;
 	Val v;
 	char *why;
 	
@@ -249,10 +248,6 @@ typecheck1(Node **np, int top)
 			goto error;
 		}
 
-		// a dance to handle forward-declared recursive pointer types.
-		if(n->op == OTYPE && (ft = getforwtype(n->ntype)) != T)
-			defertypecopy(n, ft);
-
 		typecheckdef(n);
 		n->realtype = n->type;
 		if(n->op == ONONAME)
@@ -2616,26 +2611,6 @@ stringtoarraylit(Node **np)
 	*np = nn;
 }
 
-static Type*
-getforwtype(Node *n)
-{
-	Node *f1, *f2;
-
-	for(f2=n; ; n=n->ntype) {
-		if((n = resolve(n)) == N || n->op != OTYPE)
-			return T;
-
-		if(n->type != T && n->type->etype == TFORW)
-			return n->type;
-
-		// Check for ntype cycle.
-		if((f2 = resolve(f2)) != N && (f1 = resolve(f2->ntype)) != N) {
-			f2 = resolve(f1->ntype);
-			if(f1 == n || f2 == n)
-				return T;
-		}
-	}
-}
 
 static int ntypecheckdeftype;
 static NodeList *methodqueue;
@@ -2673,49 +2648,24 @@ domethod(Node *n)
 	checkwidth(n->type);
 }
 
-typedef struct NodeTypeList NodeTypeList;
-struct NodeTypeList {
-	Node *n;
-	Type *t;
-	NodeTypeList *next;
-};
-
-static	NodeTypeList	*dntq;
-static	NodeTypeList	*dntend;
-
-void
-defertypecopy(Node *n, Type *t)
-{
-	NodeTypeList *ntl;
-
-	if(n == N || t == T)
-		return;
-
-	ntl = mal(sizeof *ntl);
-	ntl->n = n;
-	ntl->t = t;
-	ntl->next = nil;
-
-	if(dntq == nil)
-		dntq = ntl;
-	else
-		dntend->next = ntl;
-
-	dntend = ntl;
-}
-
-void
-resumetypecopy(void)
-{
-	NodeTypeList *l;
-
-	for(l=dntq; l; l=l->next)
-		copytype(l->n, l->t);
-}
+static NodeList *mapqueue;
 
 void
 copytype(Node *n, Type *t)
 {
+	int maplineno, embedlineno, lno;
+	NodeList *l;
+
+	if(t->etype == TFORW) {
+		// This type isn't computed yet; when it is, update n.
+		t->copyto = list(t->copyto, n);
+		return;
+	}
+
+	maplineno = n->type->maplineno;
+	embedlineno = n->type->embedlineno;
+
+	l = n->type->copyto;
 	*n->type = *t;
 
 	t = n->type;
@@ -2728,12 +2678,32 @@ copytype(Node *n, Type *t)
 	t->nod = N;
 	t->printed = 0;
 	t->deferwidth = 0;
+	t->copyto = nil;
+	
+	// Update nodes waiting on this type.
+	for(; l; l=l->next)
+		copytype(l->n, t);
+
+	// Double-check use of type as embedded type.
+	lno = lineno;
+	if(embedlineno) {
+		lineno = embedlineno;
+		if(isptr[t->etype])
+			yyerror("embedded type cannot be a pointer");
+	}
+	lineno = lno;
+	
+	// Queue check for map until all the types are done settling.
+	if(maplineno) {
+		t->maplineno = maplineno;
+		mapqueue = list(mapqueue, n);
+	}
 }
 
 static void
 typecheckdeftype(Node *n)
 {
-	int maplineno, embedlineno, lno;
+	int lno;
 	Type *t;
 	NodeList *l;
 
@@ -2752,26 +2722,12 @@ typecheckdeftype(Node *n)
 		goto ret;
 	}
 
-	maplineno = n->type->maplineno;
-	embedlineno = n->type->embedlineno;
-
 	// copy new type and clear fields
 	// that don't come along.
 	// anything zeroed here must be zeroed in
 	// typedcl2 too.
 	copytype(n, t);
 
-	// double-check use of type as map key.
-	if(maplineno) {
-		lineno = maplineno;
-		maptype(n->type, types[TBOOL]);
-	}
-	if(embedlineno) {
-		lineno = embedlineno;
-		if(isptr[t->etype])
-			yyerror("embedded type cannot be a pointer");
-	}
-
 ret:
 	lineno = lno;
 
@@ -2784,6 +2740,11 @@ ret:
 			for(; l; l=l->next)
 				domethod(l->n);
 		}
+		for(l=mapqueue; l; l=l->next) {
+			lineno = l->n->type->maplineno;
+			maptype(l->n->type, types[TBOOL]);
+		}
+		lineno = lno;
 	}
 	ntypecheckdeftype--;
 }

test/fixedbugs/bug443.go

@@ -0,0 +1,17 @@
+// compile
+
+// Copyright 2012 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.
+
+// Was failing to compile with 'invalid receiver' due to
+// incomplete type definition evaluation.  Issue 3709.
+
+package p
+
+type T1 struct { F *T2 }
+type T2 T1
+
+type T3 T2
+func (*T3) M()  // was invalid receiver
+

test/map1.go

@@ -41,4 +41,22 @@ var (
 	_ map[[]int]v       // ERROR "invalid map key"
 	_ map[func()]v      // ERROR "invalid map key"
 	_ map[map[int]int]v // ERROR "invalid map key"
+	_ map[T1]v    // ERROR "invalid map key"
+	_ map[T2]v    // ERROR "invalid map key"
+	_ map[T3]v    // ERROR "invalid map key"
+	_ map[T4]v    // ERROR "invalid map key"
+	_ map[T5]v
+	_ map[T6]v
+	_ map[T7]v
+	_ map[T8]v
 )
+
+type T1 []int
+type T2 struct { F T1 }
+type T3 []T4
+type T4 struct { F T3 }
+
+type T5 *int
+type T6 struct { F T5 }
+type T7 *T4
+type T8 struct { F *T7 }