gccrs: Add guards against getting data from an empty vector

gcc/rust/ChangeLog:

	* typecheck/rust-tyctx.cc (TypeCheckContext::pop_return_type): Add
	guards around `std::vector<T>.pop_back()`.
	(TypeCheckContext::peek_context): Likewise for `std::vector<T>.back()`.

diff --git a/gcc/rust/typecheck/rust-tyctx.cc b/gcc/rust/typecheck/rust-tyctx.cc
index ad5f67c..af86b06 100644 (file)
--- a/gcc/rust/typecheck/rust-tyctx.cc
+++ b/gcc/rust/typecheck/rust-tyctx.cc
@@ -142,12 +142,14 @@ TypeCheckContext::push_return_type (TypeCheckContextItem item,
 void
 TypeCheckContext::pop_return_type ()
 {
+  rust_assert (!return_type_stack.empty ());
   return_type_stack.pop_back ();
 }
 
 TypeCheckContextItem &
 TypeCheckContext::peek_context ()
 {
+  rust_assert (!return_type_stack.empty ());
   return return_type_stack.back ().first;
 }