Issue 3723

This code worked on 1.053, fails to compile on 1.054, and on D2.
I suspect this was caused by the fix to bug 3611.
-----
FwdEnum this_fails;
enum :int
{
 E1 = 2
}
enum FwdEnum: int
{
 E2 = E1
}
-----
bug.d(10): Error: undefined identifier E1

The regression is caused by this addition to Type *TypeEnum::toBasetype().
Knowing this doesn't necessarily help in fixing the problem, though.
Type *TypeEnum::toBasetype()
{
+ if (sym->scope)
+ {
+	sym->semantic(NULL);	// attempt to resolve forward reference
+ }

I've fixed this by changing the code in mtype.c, line 5984:
Type *TypeEnum::toBasetype()
{
 if (sym->scope)
 {
- sym->semantic(NULL); // attempt to resolve forward reference
+ sym->trySemantic(NULL); // attempt to resolve forward reference
 }
and adding this code to enum.c:
void EnumDeclaration::trySemantic(Scope *sc)
{
 unsigned errors = global.errors;
 global.gag++;
 DsymbolTable *savetable = symtab;
 semantic(sc);
 global.gag--;
 if (errors != global.errors)
 { 
	global.errors = errors;
	symtab = savetable;
 }
}

Changeset 353

fixed dmd 1.056 and 2.040