4303 – __traits(compiles) returns wrong result when used recursively

compiling this code:
///
template foo()
if (__traits(compiles,undefined))
{
	enum foo = false;
}
template foo()
if (true)
{
	enum foo = true;
}
pragma(msg,__traits(compiles,foo!()));
const bool bar = foo!();
/////
compiles, but outputs:
false
This is caused by __traits(compiles) not restoring the global error count in recursive calls (more specifically: when the error output is gagged before evaluating __traits).
Here's the patch:
Index: traits.c
===================================================================
--- traits.c	(revision 532)
+++ traits.c	(working copy)
@@ -397,8 +397,8 @@
 
 global.gag--;
 if (errors != global.errors)
- { if (global.gag == 0)
- global.errors = errors;
+ {
+ global.errors = errors;
 goto Lfalse;
 }
 }
Issue 3448 seems similar, but this patch does not help there.

http://www.dsource.org/projects/dmd/changeset/565