rust-unreachable: Add specific behavior for rust_unreachable

As discussed during the community call, rust_unreachable() should
always trigger an internal compiler error and should not offer
the behavior of __builtin_unreachable when asserts are disabled, unlike
gcc_unreachable().

gcc/rust/ChangeLog:

	* rust-system.h (rust_unreachable): Change definition to fancy_abort
	* ast/rust-ast-collector.cc (TokenCollector::visit): Use rust_unreachable
	instead of gcc_unreachable.
	(get_delimiters): Likewise.
	* ast/rust-ast-dump.h: Likewise.
	* ast/rust-ast-formatting.cc (get_string_in_delims): Likewise.
	(get_mode_dump_desc): Likewise.
	* ast/rust-ast.cc (Visibility::as_string): Likewise.
	(UseTreeGlob::as_string): Likewise.
	* ast/rust-ast.h: Likewise.
	* ast/rust-macro.h: Likewise.
	* ast/rust-path.h: Likewise.
	* backend/rust-compile-expr.cc (sort_tuple_patterns): Likewise.
	(CompileExpr::visit): Likewise.
	(CompileExpr::generate_closure_fntype): Likewise.
	* backend/rust-compile-intrinsic.cc (op_with_overflow_inner): Likewise.
	* backend/rust-compile-pattern.cc (CompilePatternBindings::visit): Likewise.
	(CompilePatternLet::visit): Likewise.
	* backend/rust-constexpr.cc (base_field_constructor_elt): Likewise.
	(eval_array_reference): Likewise.
	(label_matches): Likewise.
	(eval_store_expression): Likewise.
	(eval_call_expression): Likewise.
	(build_data_member_initialization): Likewise.
	(array_index_cmp): Likewise.
	(get_array_or_vector_nelts): Likewise.
	(eval_bit_field_ref): Likewise.
	(eval_loop_expr): Likewise.
	(potential_constant_expression_1): Likewise.
	* backend/rust-mangle.cc (v0_simple_type_prefix): Likewise.
	(v0_type_prefix): Likewise.
	(v0_mangle_item): Likewise.
	(Mangler::mangle_item): Likewise.
	* backend/rust-tree.cc (convert_to_void): Likewise.
	(type_memfn_quals): Likewise.
	(rs_tree_equal): Likewise.
	(fold_offsetof): Likewise.
	(fold_builtin_source_location): Likewise.
	(lvalue_error): Likewise.
	* backend/rust-tree.h (struct named_decl_hash): Likewise.
	(struct named_label_hash): Likewise.
	* checks/errors/privacy/rust-visibility-resolver.cc
	(VisibilityResolver::resolve_visibility): Likewise.
	(VisibilityResolver::visit): Likewise.
	* checks/errors/rust-const-checker.cc (ConstChecker::ctx_to_str): Likewise.
	* checks/errors/rust-feature.cc (Feature::create): Likewise.
	* expand/rust-expand-visitor.cc (get_traits_to_derive): Likewise.
	(derive_item): Likewise.
	(expand_item_attribute): Likewise.
	(expand_stmt_attribute): Likewise.
	* expand/rust-macro-expand.cc (MacroExpander::match_matcher): Likewise.
	(MacroExpander::match_repetition): Likewise.
	(transcribe_context): Likewise.
	(MacroExpander::import_proc_macros): Likewise.
	(MacroExpander::parse_proc_macro_output): Likewise.
	* expand/rust-macro-expand.h: Likewise.
	* expand/rust-macro-invoc-lexer.h: Likewise.
	* expand/rust-macro-substitute-ctx.cc (SubstituteCtx::substitute_token): Likewise.
	* expand/rust-proc-macro-invoc-lexer.h: Likewise.
	* expand/rust-proc-macro.cc (load_macros): Likewise.
	* hir/rust-ast-lower-base.cc (ASTLoweringBase::lower_generic_args): Likewise.
	(ASTLoweringBase::lower_literal): Likewise.
	* hir/rust-ast-lower-expr.cc (ASTLoweringExpr::visit): Likewise.
	* hir/rust-ast-lower-pattern.cc (ASTLoweringPattern::visit): Likewise.
	* hir/rust-ast-lower-type.cc (ASTLoweringType::visit): Likewise.
	* hir/rust-hir-dump.cc (Dump::visit): Likewise.
	* hir/tree/rust-hir.cc (get_string_in_delims): Likewise.
	(Visibility::as_string): Likewise.
	(UseTreeGlob::as_string): Likewise.
	(CompoundAssignmentExpr::as_string): Likewise.
	(ArithmeticOrLogicalExpr::as_string): Likewise.
	* lex/rust-lex.cc (Lexer::parse_byte_string): Likewise.
	(Lexer::parse_string): Likewise.
	* lex/rust-token.cc (RS_TOKEN): Likewise.
	* parse/rust-parse-impl.h (Parser::parse_simple_path_segment): Likewise.
	(Parser::parse_path_ident_segment): Likewise.
	(Parser::parse_attr_input): Likewise.
	(Parser::parse_inherent_impl_item): Likewise.
	(Parser::parse_trait_impl_item): Likewise.
	(Parser::parse_type_path_segment): Likewise.
	(Parser::parse_reference_type): Likewise.
	(get_lbp_for_comparison_expr): Likewise.
	* parse/rust-parse.cc (peculiar_fragment_match_compatible): Likewise.
	* resolve/rust-ast-resolve-path.cc (ResolvePath::resolve_path): Likewise.
	* resolve/rust-ast-resolve-pattern.cc (PatternDeclaration::visit): Likewise.
	* resolve/rust-ast-resolve-type.cc (ResolveRelativeTypePath::go): Likewise.
	(ResolveTypeToCanonicalPath::visit): Likewise.
	(ResolveGenericArgs::resolve_disambiguated_generic): Likewise.
	* rust-gcc.cc (operator_to_tree_code): Likewise.
	(fetch_overflow_builtins): Likewise.
	(Gcc_backend::non_zero_size_type): Likewise.
	(Gcc_backend::convert_tree): Likewise.
	* rust-lang.cc (grs_langhook_type_for_mode): Likewise.
	(grs_langhook_global_bindings_p): Likewise.
	(grs_langhook_pushdecl): Likewise.
	(grs_langhook_getdecls): Likewise.
	(convert): Likewise.
	* typecheck/rust-autoderef.h: Likewise.
	* typecheck/rust-hir-path-probe.cc: Likewise.
	* typecheck/rust-hir-trait-reference.cc (TraitItemReference::get_tyty): Likewise.
	* typecheck/rust-hir-type-check-base.cc (TypeCheckBase::resolve_literal): Likewise.
	* typecheck/rust-hir-type-check-expr.cc: Likewise.
	* typecheck/rust-hir-type-check-expr.h: Likewise.
	* typecheck/rust-hir-type-check-implitem.cc (TypeCheckImplItem::visit): Likewise.
	* typecheck/rust-hir-type-check-pattern.cc (TypeCheckPattern::visit): Likewise.
	* typecheck/rust-hir-type-check-stmt.h: Likewise.
	* typecheck/rust-hir-type-check.cc (TraitItemReference::get_type_from_fn): Likewise.
	* typecheck/rust-substitution-mapper.h: Likewise.
	* typecheck/rust-typecheck-context.cc (TypeCheckContextItem::get_context_type): Likewise.
	* typecheck/rust-tyty-call.h: Likewise.
	* typecheck/rust-tyty.cc (TypeKindFormat::to_string): Likewise.
	(BaseType::monomorphized_clone): Likewise.
	(VariantDef::variant_type_string): Likewise.
	(ClosureType::handle_substitions): Likewise.
	(IntType::as_string): Likewise.
	(UintType::as_string): Likewise.
	(FloatType::as_string): Likewise.
	* typecheck/rust-unify.cc (UnifyRules::expect_projection): Likewise.
	* util/rust-token-converter.cc (convert): Likewise.
	(from_literal): Likewise.
	(from_group): Likewise.
	(from_tokentree): Likewise.

gcc/rust/ast/rust-ast-collector.cc

@@ -208,7 +208,7 @@ TokenCollector::visit (Attribute &attrib)
 	    break;
 	  }
 	default:
-	  gcc_unreachable ();
+	  rust_unreachable ();
 	}
     }
   push (Rust::Token::make (RIGHT_SQUARE, UNDEF_LOCATION));
@@ -668,7 +668,7 @@ TokenCollector::visit (GenericArg &arg)
       }
       break;
     case GenericArg::Kind::Error:
-      gcc_unreachable ();
+      rust_unreachable ();
     }
 }
 
@@ -822,11 +822,11 @@ TokenCollector::visit (Literal &lit, Location locus)
 	else if (value == "true")
 	  push (Rust::Token::make (TRUE_LITERAL, locus));
 	else
-	  gcc_unreachable (); // Not a boolean
+	  rust_unreachable (); // Not a boolean
 	break;
       }
     case Literal::LitType::ERROR:
-      gcc_unreachable ();
+      rust_unreachable ();
       break;
     }
 }
@@ -1188,7 +1188,7 @@ void
 TokenCollector::visit (StructExprStructBase &)
 {
   // FIXME: Implement this node
-  gcc_unreachable ();
+  rust_unreachable ();
 }
 
 void
@@ -2252,7 +2252,7 @@ get_delimiters (DelimType delim)
     case CURLY:
       return {LEFT_CURLY, RIGHT_CURLY};
     default:
-      gcc_unreachable ();
+      rust_unreachable ();
     }
 }
 

gcc/rust/ast/rust-ast-dump.h

@@ -71,7 +71,7 @@ class Dump
 	    previous = nullptr;
 	    break;
 	  default:
-	    gcc_unreachable ();
+	    rust_unreachable ();
 	  }
       }
   }

gcc/rust/ast/rust-ast-formatting.cc

@@ -51,7 +51,7 @@ get_string_in_delims (std::string str_input, DelimType delim_type)
     default:
       return "ERROR-MARK-STRING (delims)";
     }
-  gcc_unreachable ();
+  rust_unreachable ();
 }
 
 std::string
@@ -64,7 +64,7 @@ get_mode_dump_desc (AttrMode mode)
     case INNER:
       return "inner attributes";
     default:
-      gcc_unreachable ();
+      rust_unreachable ();
       return "";
     }
 }

gcc/rust/ast/rust-ast.cc

@@ -225,7 +225,7 @@ Visibility::as_string () const
     case PUB_IN_PATH:
       return std::string ("pub(in ") + in_path.as_string () + std::string (")");
     default:
-      gcc_unreachable ();
+      rust_unreachable ();
     }
 }
 
@@ -623,7 +623,7 @@ UseTreeGlob::as_string () const
       // some kind of error
       return "ERROR-PATH";
     }
-  gcc_unreachable ();
+  rust_unreachable ();
 }
 
 std::string

gcc/rust/ast/rust-ast.h

@@ -1887,7 +1887,7 @@ class SingleASTNode : public Visitable
 	return type == nullptr;
       }
 
-    gcc_unreachable ();
+    rust_unreachable ();
     return true;
   }
 
@@ -1913,7 +1913,7 @@ class SingleASTNode : public Visitable
 	return "Type: " + type->as_string ();
       }
 
-    gcc_unreachable ();
+    rust_unreachable ();
     return "";
   }
 };

gcc/rust/ast/rust-macro.h

@@ -473,14 +473,14 @@ class MacroRulesDefinition : public VisItem
 
   /**
    * Default function to use as an associated transcriber. This function should
-   * never be called, hence the gcc_unreachable().
+   * never be called, hence the rust_unreachable().
    * If this function is used, then the macro is not builtin and the compiler
    * should make use of the actual rules. If the macro is builtin, then another
    * associated transcriber should be used
    */
   static Fragment dummy_builtin (Location, MacroInvocData &)
   {
-    gcc_unreachable ();
+    rust_unreachable ();
     return Fragment::create_error ();
   }
 

gcc/rust/ast/rust-path.h

@@ -224,7 +224,7 @@ class GenericArg
       case Kind::Either:
 	break;
       case Kind::Error:
-	gcc_unreachable ();
+	rust_unreachable ();
       }
   }
 
@@ -254,7 +254,7 @@ class GenericArg
     switch (get_kind ())
       {
       case Kind::Error:
-	gcc_unreachable ();
+	rust_unreachable ();
       case Kind::Either:
 	return "Ambiguous: " + path.as_string ();
       case Kind::Const:

gcc/rust/backend/rust-compile-expr.cc

@@ -1117,7 +1117,7 @@ sort_tuple_patterns (HIR::MatchExpr &expr)
       else /* TuplePatternItemType::RANGED */
 	{
 	  // FIXME
-	  gcc_unreachable ();
+	  rust_unreachable ();
 	}
     }
 
@@ -1430,25 +1430,25 @@ CompileExpr::visit (HIR::MatchExpr &expr)
 	    else
 	      {
 		// FIXME: There are other cases, but it better not be a Tuple
-		gcc_unreachable ();
+		rust_unreachable ();
 	      }
 	  }
 	  break;
 
 	  case HIR::Expr::ExprType::Path: {
 	    // FIXME
-	    gcc_unreachable ();
+	    rust_unreachable ();
 	  }
 	  break;
 
 	default:
-	  gcc_unreachable ();
+	  rust_unreachable ();
 	}
     }
   else
     {
       // FIXME: match on other types of expressions not yet implemented.
-      gcc_unreachable ();
+      rust_unreachable ();
     }
 
   // setup the end label so the cases can exit properly
@@ -2856,7 +2856,7 @@ CompileExpr::generate_closure_fntype (HIR::ClosureExpr &expr,
   else
     {
       // FIXME error message?
-      gcc_unreachable ();
+      rust_unreachable ();
       return error_mark_node;
     }
 

gcc/rust/backend/rust-compile-intrinsic.cc

@@ -627,7 +627,7 @@ op_with_overflow_inner (Context *ctx, TyTy::FnType *fntype, tree_code op)
       break;
 
     default:
-      gcc_unreachable ();
+      rust_unreachable ();
       break;
     }
   rust_assert (overflow_builtin != error_mark_node);

gcc/rust/backend/rust-compile-pattern.cc

@@ -199,7 +199,7 @@ CompilePatternBindings::visit (HIR::TupleStructPattern &pattern)
     {
       case HIR::TupleStructItems::RANGE: {
 	// TODO
-	gcc_unreachable ();
+	rust_unreachable ();
       }
       break;
 
@@ -284,13 +284,13 @@ CompilePatternBindings::visit (HIR::StructPattern &pattern)
 	{
 	  case HIR::StructPatternField::ItemType::TUPLE_PAT: {
 	    // TODO
-	    gcc_unreachable ();
+	    rust_unreachable ();
 	  }
 	  break;
 
 	  case HIR::StructPatternField::ItemType::IDENT_PAT: {
 	    // TODO
-	    gcc_unreachable ();
+	    rust_unreachable ();
 	  }
 	  break;
 
@@ -467,7 +467,7 @@ CompilePatternLet::visit (HIR::TuplePattern &pattern)
 	return;
       }
       default: {
-	gcc_unreachable ();
+	rust_unreachable ();
       }
     }
 }

gcc/rust/backend/rust-constexpr.cc

@@ -1132,7 +1132,7 @@ base_field_constructor_elt (vec<constructor_elt, va_gc> *v, tree ref)
     if (ce->index == field)
       return ce;
 
-  gcc_unreachable ();
+  rust_unreachable ();
   return NULL;
 }
 
@@ -1618,7 +1618,7 @@ eval_array_reference (const constexpr_ctx *ctx, tree t, bool lval,
       /* We can't do anything with other tree codes, so use
 	 VERIFY_CONSTANT to complain and fail.  */
       VERIFY_CONSTANT (ary);
-      gcc_unreachable ();
+      rust_unreachable ();
     }
 
   bool found;
@@ -1855,7 +1855,7 @@ label_matches (const constexpr_ctx *ctx, tree *jump_target, tree stmt)
       break;
 
     default:
-      gcc_unreachable ();
+      rust_unreachable ();
     }
   return false;
 }
@@ -2695,7 +2695,7 @@ eval_store_expression (const constexpr_ctx *ctx, tree t, bool lval,
 	    if (TREE_CODE (probe) == ARRAY_REF)
 	      {
 		// TODO
-		gcc_unreachable ();
+		rust_unreachable ();
 		// elt = eval_and_check_array_index (ctx, probe, false,
 		// 				  non_constant_p, overflow_p);
 		if (*non_constant_p)
@@ -3372,7 +3372,7 @@ eval_call_expression (const constexpr_ctx *ctx, tree t, bool lval,
     {
       // return cxx_eval_internal_function (ctx, t, lval,
       //     			       non_constant_p, overflow_p);
-      gcc_unreachable ();
+      rust_unreachable ();
       return error_mark_node;
     }
 
@@ -3876,7 +3876,7 @@ build_data_member_initialization (tree t, vec<constructor_elt, va_gc> **vec)
 //	goto found;
 //
 //      default:
-//	gcc_unreachable ();
+//	rust_unreachable ();
 //      }
 // found:
 //
@@ -4143,7 +4143,7 @@ array_index_cmp (tree key, tree index)
 	  return 0;
       }
     default:
-      gcc_unreachable ();
+      rust_unreachable ();
     }
 }
 
@@ -4435,7 +4435,7 @@ get_array_or_vector_nelts (const constexpr_ctx *ctx, tree type,
   else if (VECTOR_TYPE_P (type))
     nelts = size_int (TYPE_VECTOR_SUBPARTS (type));
   else
-    gcc_unreachable ();
+    rust_unreachable ();
 
   /* For VLAs, the number of elements won't be an integer constant.  */
   nelts
@@ -4787,7 +4787,7 @@ eval_bit_field_ref (const constexpr_ctx *ctx, tree t, bool lval,
     }
   if (fld_seen)
     return fold_convert (TREE_TYPE (t), retval);
-  gcc_unreachable ();
+  rust_unreachable ();
   return error_mark_node;
 }
 
@@ -4876,7 +4876,7 @@ eval_loop_expr (const constexpr_ctx *ctx, tree t, bool *non_constant_p,
       count = -1;
       break;
     default:
-      gcc_unreachable ();
+      rust_unreachable ();
     }
   auto_vec<tree, 10> save_exprs;
   new_ctx.save_exprs = &save_exprs;
@@ -6433,7 +6433,7 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now,
 
     default:
       sorry ("unexpected AST of kind %s", get_tree_code_name (TREE_CODE (t)));
-      gcc_unreachable ();
+      rust_unreachable ();
       return false;
     }
 #undef RECUR

gcc/rust/backend/rust-mangle.cc

@@ -193,7 +193,7 @@ v0_simple_type_prefix (const TyTy::BaseType *ty)
       return "";
     }
 
-  gcc_unreachable ();
+  rust_unreachable ();
 }
 
 // Add an underscore-terminated base62 integer to the mangling string.
@@ -262,7 +262,7 @@ v0_type_prefix (const TyTy::BaseType *ty)
     return ty_prefix;
 
   // FIXME: We need to fetch more type prefixes
-  gcc_unreachable ();
+  rust_unreachable ();
 }
 
 static std::string
@@ -291,7 +291,7 @@ v0_mangle_item (const TyTy::BaseType *ty, const Resolver::CanonicalPath &path)
   v0_add_identifier (mangled, crate_name);
   v0_add_disambiguator (mangled, 62);
 
-  gcc_unreachable ();
+  rust_unreachable ();
 }
 
 std::string
@@ -305,7 +305,7 @@ Mangler::mangle_item (const TyTy::BaseType *ty,
     case Mangler::MangleVersion::V0:
       return v0_mangle_item (ty, path);
     default:
-      gcc_unreachable ();
+      rust_unreachable ();
     }
 }