gc: keep track of real actual type of identifiers.

R=rsc
CC=golang-dev
https://golang.org/cl/2519042

src/cmd/gc/go.h

@@ -218,6 +218,7 @@ struct	Node
 	Node*	left;
 	Node*	right;
 	Type*	type;
+	Type*	realtype;	// as determined by typecheck
 	NodeList*	list;
 	NodeList*	rlist;
 

src/cmd/gc/subr.c

@@ -3607,10 +3607,11 @@ umagic(Magic *m)
 Sym*
 ngotype(Node *n)
 {
-	if(n->sym != S && strncmp(n->sym->name, "autotmp_", 8) != 0)
-	if(n->type->etype != TFUNC || n->type->thistuple == 0)
-	if(n->type->etype != TSTRUCT || n->type->funarg == 0)
-		return typename(n->type)->left->sym;
+	if(n->sym != S && n->realtype != T)
+	if(strncmp(n->sym->name, "autotmp_", 8) != 0)
+	if(strncmp(n->sym->name, "statictmp_", 8) != 0)
+		return typename(n->realtype)->left->sym;
+
 	return S;
 }
 
@@ -3684,4 +3685,3 @@ strlit(char *s)
 	t->len = strlen(s);
 	return t;
 }
-

src/cmd/gc/typecheck.c

@@ -112,6 +112,7 @@ typecheck(Node **np, int top)
 			goto error;
 		}
 		walkdef(n);
+		n->realtype = n->type;
 		if(n->op == ONONAME)
 			goto error;
 	}