cmd/go: racewalk: fix nested struct handling

Fixes #4424.
Fixes #4425.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6849093

src/cmd/gc/racewalk.c

@@ -430,6 +430,11 @@ callinstr(Node **np, NodeList **init, int wr, int skip)
 				n = treecopy(n);
 				f = nod(OXDOT, n, newname(t1->sym));
 				f->type = t1;
+<<<<<<< local
+				if(f->type->etype == TFIELD)
+					f->type = f->type->type;
+=======
+>>>>>>> other
 				if(callinstr(&f, init, wr, 0)) {
 					typecheck(&f, Erv);
 					res = 1;