[gccrs COMMIT] gccrs: make fn trait return optional

[gerris.rs@gmail.com]

From: Philip Herron <herron.philip@googlemail.com>

This is just a basic patch to get past a crash in libcore we probably need
to default to unit-type somewhere later on.

gcc/rust/ChangeLog:

	* typecheck/rust-tyty-bounds.cc: handle assertion

Signed-off-by: Philip Herron <herron.philip@googlemail.com>
---
This change was merged into the gccrs repository and is posted here for
upstream visibility and potential drive-by review, as requested by GCC
release managers.
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Commit on github: https://github.com/Rust-GCC/gccrs/commit/7ce9f8446d5665ec49137fd7f9d325694ffb4e76

The commit has NOT been mentioned in any issue.

The commit has been mentioned in the following pull-request(s):
 - https://github.com/Rust-GCC/gccrs/pull/4831

 gcc/rust/typecheck/rust-tyty-bounds.cc | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/gcc/rust/typecheck/rust-tyty-bounds.cc b/gcc/rust/typecheck/rust-tyty-bounds.cc
index f72ee57f9..fca42d61a 100644
--- a/gcc/rust/typecheck/rust-tyty-bounds.cc
+++ b/gcc/rust/typecheck/rust-tyty-bounds.cc
@@ -332,11 +332,6 @@ TypeCheckBase::get_predicate_from_bound (
 	  std::make_unique<HIR::TupleType> (mapping, std::move (params_copy),
 					    final_seg.get_locus ()));
 
-	// resolve the fn_once_output type which assumes there must be an output
-	// set
-	rust_assert (fn.has_return_type ());
-	TypeCheckType::Resolve (fn.get_return_type ());
-
 	HIR::TraitItem *trait_item
 	  = mappings
 	      .lookup_trait_item_lang_item (LangItem::Kind::FN_ONCE_OUTPUT,
@@ -344,10 +339,16 @@ TypeCheckBase::get_predicate_from_bound (
 	      .value ();
 
 	std::vector<HIR::GenericArgsBinding> bindings;
-	location_t output_locus = fn.get_return_type ().get_locus ();
-	bindings.emplace_back (Identifier (trait_item->trait_identifier ()),
-			       fn.get_return_type ().clone_type (),
-			       output_locus);
+
+	if (fn.has_return_type ())
+	  {
+	    TypeCheckType::Resolve (fn.get_return_type ());
+
+	    location_t output_locus = fn.get_return_type ().get_locus ();
+	    bindings.emplace_back (Identifier (trait_item->trait_identifier ()),
+				   fn.get_return_type ().clone_type (),
+				   output_locus);
+	  }
 
 	args = HIR::GenericArgs ({} /* lifetimes */,
 				 std::move (inputs) /* type_args*/,

base-commit: a64ace613c317103e3a0e347aefd030906d6309b
-- 
2.55.0