libiberty: Demangle variadic template lambdas

Now we have templated lambdas, we can have variadic template lambdas,
and this leads to lambda signatures containing parameter packs.  But
just like 'auto' inside such a signature, we don't have a containing
template, and thus fail.  The fix is to check is_lambda_arg, just as
for a template parameter.  This allows us to demangle g++'s manglings
of such lambdas.

It's not a totally accurate demangling, because we don't mangle the
template head (that's a separate issue), but it is better than failing
to demangle.

Due to the way we print subexprs, we add an unnecessary parens around
the argument of the pack.  That's an orthogonal problem, for which the
solution is to have better knowledge of operator precedence.

	libiberty/
	* cp-demangle.c (d_print_comp_inner): Allow parameter packs
	in a lambda signature.
	* testsuite/demangle-expected: Add tests.

1 files changed, 17 insertions, 13 deletions

diff --git a/libiberty/cp-demangle.c b/libiberty/cp-demangle.c
index 7ff225e..303bfbf 100644
--- a/libiberty/cp-demangle.c
+++ b/libiberty/cp-demangle.c
@@ -348,7 +348,7 @@ struct d_print_info
      be bigger than MAX_RECURSION_COUNT.  */
   int recursion;
   /* Non-zero if we're printing a lambda argument.  A template
-     parameter reference actually means 'auto'.  */
+     parameter reference actually means 'auto', a pack expansion means T...  */
   int is_lambda_arg;
   /* The current index into any template argument packs we are using
      for printing, or -1 to print the whole pack.  */
@@ -5930,9 +5930,10 @@ d_print_comp_inner (struct d_print_info *dpi, int options,
 
     case DEMANGLE_COMPONENT_PACK_EXPANSION:
       {
-	int len;
-	int i;
-	struct demangle_component *a = d_find_pack (dpi, d_left (dc));
+	struct demangle_component *a = NULL;
+
+	if (!dpi->is_lambda_arg)
+	  a = d_find_pack (dpi, d_left (dc));
 	if (a == NULL)
 	  {
 	    /* d_find_pack won't find anything if the only packs involved
@@ -5940,17 +5941,20 @@ d_print_comp_inner (struct d_print_info *dpi, int options,
 	       case, just print the pattern and "...".  */
 	    d_print_subexpr (dpi, options, d_left (dc));
 	    d_append_string (dpi, "...");
-	    return;
 	  }
-
-	len = d_pack_length (a);
-	dc = d_left (dc);
-	for (i = 0; i < len; ++i)
+	else
 	  {
-	    dpi->pack_index = i;
-	    d_print_comp (dpi, options, dc);
-	    if (i < len-1)
-	      d_append_string (dpi, ", ");
+	    int len = d_pack_length (a);
+	    int i;
+
+	    dc = d_left (dc);
+	    for (i = 0; i < len; ++i)
+	      {
+		if (i)
+		  d_append_string (dpi, ", ");
+		dpi->pack_index = i;
+		d_print_comp (dpi, options, dc);
+	      }
 	  }
       }
       return;