d: Fix ICE using non-local variable: internal compiler error: Segmentation fault

Moves no frame access error to own function, adding use of it for both
when get_framedecl() cannot find a path to the outer function frame, and
guarding get_decl_tree() from recursively calling itself.

gcc/d/ChangeLog:

	PR d/96254
	* d-codegen.cc (error_no_frame_access): New.
	(get_frame_for_symbol): Use fdparent name in error message.
	(get_framedecl): Replace call to assert with error.
	* d-tree.h (error_no_frame_access): Declare.
	* decl.cc (get_decl_tree): Detect recursion and error.

gcc/testsuite/ChangeLog:

	PR d/96254
	* gdc.dg/pr96254a.d: New test.
	* gdc.dg/pr96254b.d: New test.

2 files changed, 52 insertions, 0 deletions

diff --git a/gcc/testsuite/gdc.dg/pr96254a.d b/gcc/testsuite/gdc.dg/pr96254a.d
new file mode 100644
index 0000000..e5dd124
--- /dev/null
+++ b/gcc/testsuite/gdc.dg/pr96254a.d
@@ -0,0 +1,28 @@
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96254
+// { dg-do compile }
+struct map(alias fun)
+{
+    @property run()
+    {
+    }
+}
+
+struct Task(Args)
+{
+    Args _args;
+}
+
+template reduce(functions...)
+{
+    auto reduce(Args)(Args args)
+    {
+        alias RTask = Task!(typeof(args));
+        auto task = RTask();
+    }
+}
+
+void main() // { dg-error "'D main' is a nested function and cannot be accessed" }
+{
+    immutable delta = 1;
+    reduce!"a + b"(map!({ immutable x = delta; })());
+}
diff --git a/gcc/testsuite/gdc.dg/pr96254b.d b/gcc/testsuite/gdc.dg/pr96254b.d
new file mode 100644
index 0000000..02e3c48
--- /dev/null
+++ b/gcc/testsuite/gdc.dg/pr96254b.d
@@ -0,0 +1,24 @@
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96254
+// { dg-do compile }
+mixin template test()
+{
+    int next;
+}
+
+void foo(alias l)()
+{
+    l.next = 0; // { dg-error "cannot get frame pointer to 'D main'" }
+}
+
+void bar(alias l, alias t)()
+{
+    l.next = 0; // { dg-error "cannot get frame pointer to 'D main'" }
+}
+
+void main()
+{
+    mixin test l1;
+    mixin test l2;
+    foo!(l1);
+    bar!(l1,l2);
+}