c++: QT overload regression with attribute [PR94946]

Jason's fix for 90570 & 79585 was a bit overzealous.  Dependent attribs should still
attach to a parameter decl.

	* decl.c (grokdeclarator): Don't splice template attributes in
	parm context -- they can apply to the parm.

gcc/cp/ChangeLog

+2020-05-06  Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/94946
+	* decl.c (grokdeclarator): Don't splice template attributes in
+	parm context -- they can apply to the parm.
+
 2020-04-30  Jason Merrill  <jason@redhat.com>
 	    Nathan Sidwell  <nathan@acm.org>
 

gcc/cp/decl.c

@@ -11937,9 +11937,12 @@ grokdeclarator (const cp_declarator *declarator,
 	    attr_flags |= (int) ATTR_FLAG_FUNCTION_NEXT;
 	  if (declarator->kind == cdk_array)
 	    attr_flags |= (int) ATTR_FLAG_ARRAY_NEXT;
-	  /* Assume that any attributes that get applied late to templates will
-	     DTRT when applied to the declaration as a whole.  */
-	  tree late_attrs = splice_template_attributes (&attrs, type);
+	  tree late_attrs = NULL_TREE;
+	  if (decl_context != PARM)
+	    /* Assume that any attributes that get applied late to
+	       templates will DTRT when applied to the declaration
+	       as a whole.  */
+	    late_attrs = splice_template_attributes (&attrs, type);
 	  returned_attrs = decl_attributes (&type,
 					    chainon (returned_attrs, attrs),
 					    attr_flags);

gcc/testsuite/g++.dg/ext/attr-parm-1.C

+// { dg-do compile { target { i?86-*-* x86_64-*-* } } }
+// { dg-options -m32 }
+// PR 94946
+class a {
+  template <typename b> a(b (*)());
+  template <typename b> a(b(__attribute__((fastcall)) *c)());
+};