diff --git a/core/bufio/read_writer.odin b/core/bufio/read_writer.odin
index 9026abcfd..ccd59a398 100644
--- a/core/bufio/read_writer.odin
+++ b/core/bufio/read_writer.odin
@@ -25,10 +25,6 @@ _read_writer_vtable := &io.Stream_VTable{
 		b := (^Read_Writer)(s.stream_data).r
 		return reader_read(b, p)
 	},
-	impl_read_byte = proc(s: io.Stream) -> (c: byte, err: io.Error) {
-		b := (^Read_Writer)(s.stream_data).r
-		return reader_read_byte(b)
-	},
 	impl_unread_byte = proc(s: io.Stream) -> io.Error {
 		b := (^Read_Writer)(s.stream_data).r
 		return reader_unread_byte(b)
diff --git a/core/io/conv.odin b/core/io/conv.odin
index baaf5a864..39a72d69d 100644
--- a/core/io/conv.odin
+++ b/core/io/conv.odin
@@ -122,73 +122,3 @@ to_write_seeker :: proc(s: Stream) -> (w: Write_Seeker, ok: bool = true) #option
 	}
 	return
 }
-
-
-to_byte_reader :: proc(s: Stream) -> (b: Byte_Reader, ok: bool = true) #optional_ok {
-	b.stream = s
-	if s.stream_vtable == nil || s.impl_read_byte == nil {
-		ok = false
-		if s.stream_vtable != nil && s.impl_read != nil {
-			ok = true
-		}
-	}
-	return
-}
-to_byte_scanner :: proc(s: Stream) -> (b: Byte_Scanner, ok: bool = true) #optional_ok {
-	b.stream = s
-	if s.stream_vtable != nil {
-		if s.impl_unread_byte == nil {
-			ok = false
-			return
-		}
-		if s.impl_read_byte != nil {
-			ok = true
-		} else if s.impl_read != nil {
-			ok = true
-		} else {
-			ok = false
-		}
-	}
-	return
-}
-to_byte_writer :: proc(s: Stream) -> (b: Byte_Writer, ok: bool = true) #optional_ok {
-	b.stream = s
-	if s.stream_vtable == nil || s.impl_write_byte == nil {
-		ok = false
-		if s.stream_vtable != nil && s.impl_write != nil {
-			ok = true
-		}
-	}
-	return
-}
-
-to_rune_reader :: proc(s: Stream) -> (r: Rune_Reader, ok: bool = true) #optional_ok {
-	r.stream = s
-	if s.stream_vtable == nil || s.impl_read_rune == nil {
-		ok = false
-		if s.stream_vtable != nil && s.impl_read != nil {
-			ok = true
-		}
-	}
-	return
-
-}
-to_rune_scanner :: proc(s: Stream) -> (r: Rune_Scanner, ok: bool = true) #optional_ok {
-	r.stream = s
-	if s.stream_vtable != nil {
-		if s.impl_unread_rune == nil {
-			ok = false
-			return
-		}
-		if s.impl_read_rune != nil {
-			ok = true
-		} else if s.impl_read != nil {
-			ok = true
-		} else {
-			ok = false
-		}
-	} else {
-		ok = false
-	}
-	return
-}
diff --git a/core/io/io.odin b/core/io/io.odin
index 3ad34d607..7faa500b1 100644
--- a/core/io/io.odin
+++ b/core/io/io.odin
@@ -123,13 +123,6 @@ Writer_At          :: struct {using stream: Stream}
 Reader_From        :: struct {using stream: Stream}
 Writer_To          :: struct {using stream: Stream}
 
-Byte_Reader        :: struct {using stream: Stream}
-Byte_Scanner       :: struct {using stream: Stream}
-Byte_Writer        :: struct {using stream: Stream}
-
-Rune_Reader        :: struct {using stream: Stream}
-Rune_Scanner       :: struct {using stream: Stream}
-
 
 destroy :: proc(s: Stream) -> Error {
 	close_err := close({s})
@@ -147,24 +140,48 @@ destroy :: proc(s: Stream) -> Error {
 // When read encounters an .EOF or error after successfully reading n > 0 bytes, it returns the number of
 // bytes read along with the error.
 read :: proc(s: Reader, p: []byte, n_read: ^int = nil) -> (n: int, err: Error) {
-	if s.stream_vtable != nil && s.impl_read != nil {
-		n, err = s->impl_read(p)
-		if n_read != nil {
-			n_read^ += n
+	if s.stream_vtable != nil {
+		if s.impl_read != nil {
+			n, err = s->impl_read(p)
+			if n_read != nil {
+				n_read^ += n
+			}
+			return
+		} else if s.impl_read_byte != nil {
+			bytes_read := 0
+			defer if n_read != nil {
+				n_read^ += bytes_read
+			}
+			for _, i in p {
+				p[i] = s->impl_read_byte() or_return
+				bytes_read += 1
+			}
+			return
 		}
-		return
 	}
 	return 0, .Empty
 }
 
 // write writes up to len(p) bytes into s. It returns the number of bytes written and any error if occurred.
 write :: proc(s: Writer, p: []byte, n_written: ^int = nil) -> (n: int, err: Error) {
-	if s.stream_vtable != nil && s.impl_write != nil {
-		n, err = s->impl_write(p)
-		if n_written != nil {
-			n_written^ += n
+	if s.stream_vtable != nil {
+		if s.impl_write != nil {
+			n, err = s->impl_write(p)
+			if n_written != nil {
+				n_written^ += n
+			}
+			return
+		} else if s.impl_write_byte != nil {
+			bytes_written := 0
+			defer if n_written != nil {
+				n_written^ += bytes_written
+			}
+			for c in p {
+				s->impl_write_byte(c) or_return
+				bytes_written += 1
+			}
+			return
 		}
-		return
 	}
 	return 0, .Empty
 }
@@ -319,7 +336,7 @@ read_from :: proc(w: Reader_From, r: Reader) -> (n: i64, err: Error) {
 
 
 // read_byte reads and returns the next byte from r.
-read_byte :: proc(r: Byte_Reader, n_read: ^int = nil) -> (b: byte, err: Error) {
+read_byte :: proc(r: Reader, n_read: ^int = nil) -> (b: byte, err: Error) {
 	defer if err == nil && n_read != nil {
 		n_read^ += 1
 	}
@@ -339,21 +356,12 @@ read_byte :: proc(r: Byte_Reader, n_read: ^int = nil) -> (b: byte, err: Error) {
 	return buf[0], err
 }
 
-write_byte :: proc{
-	write_byte_to_byte_writer,
-	write_byte_to_writer,
-}
-
-write_byte_to_byte_writer :: proc(w: Byte_Writer, c: byte, n_written: ^int = nil) -> Error {
-	return _write_byte(w, c, n_written)
-}
-
-write_byte_to_writer :: proc(w: Writer, c: byte, n_written: ^int = nil) -> Error {
+write_byte :: proc(w: Writer, c: byte, n_written: ^int = nil) -> Error {
 	return _write_byte(auto_cast w, c, n_written)
 }
 
 @(private)
-_write_byte :: proc(w: Byte_Writer, c: byte, n_written: ^int = nil) -> (err: Error) {
+_write_byte :: proc(w: Writer, c: byte, n_written: ^int = nil) -> (err: Error) {
 	defer if err == nil && n_written != nil {
 		n_written^ += 1
 	}
@@ -373,7 +381,7 @@ _write_byte :: proc(w: Byte_Writer, c: byte, n_written: ^int = nil) -> (err: Err
 }
 
 // read_rune reads a single UTF-8 encoded Unicode codepoint and returns the rune and its size in bytes.
-read_rune :: proc(br: Rune_Reader, n_read: ^int = nil) -> (ch: rune, size: int, err: Error) {
+read_rune :: proc(br: Reader, n_read: ^int = nil) -> (ch: rune, size: int, err: Error) {
 	defer if err == nil && n_read != nil {
 		n_read^ += size
 	}
@@ -417,13 +425,21 @@ read_rune :: proc(br: Rune_Reader, n_read: ^int = nil) -> (ch: rune, size: int,
 	return
 }
 
-unread_byte :: proc(s: Byte_Scanner) -> Error {
-	if s.stream_vtable != nil && s.impl_unread_byte != nil {
+unread_byte :: proc(s: Stream) -> Error {
+	if s.stream_vtable == nil {
+		return .Empty
+	}
+	if s.impl_unread_byte != nil {
 		return s->impl_unread_byte()
 	}
+	if s.impl_seek != nil {
+		_, err := s->impl_seek(-1, .Current)
+		return err
+	}
+
 	return .Empty
 }
-unread_rune :: proc(s: Rune_Scanner) -> Error {
+unread_rune :: proc(s: Writer) -> Error {
 	if s.stream_vtable != nil && s.impl_unread_rune != nil {
 		return s->impl_unread_rune()
 	}
@@ -442,7 +458,10 @@ write_rune :: proc(s: Writer, r: rune, n_written: ^int = nil) -> (size: int, err
 		n_written^ += size
 	}
 	
-	if s.stream_vtable != nil && s.impl_write_rune != nil {
+	if s.stream_vtable == nil {
+		return 0, .Empty
+	}
+	if s.impl_write_rune != nil {
 		return s->impl_write_rune(r)
 	}
 
diff --git a/core/odin/ast/ast.odin b/core/odin/ast/ast.odin
index c8f73a31b..99b2cde98 100644
--- a/core/odin/ast/ast.odin
+++ b/core/odin/ast/ast.odin
@@ -6,7 +6,7 @@ Proc_Tag :: enum {
 	Bounds_Check,
 	No_Bounds_Check,
 	Optional_Ok,
-	Optional_Second,
+	Optional_Allocator_Error,
 }
 Proc_Tags :: distinct bit_set[Proc_Tag; u32]
 
diff --git a/core/odin/parser/parser.odin b/core/odin/parser/parser.odin
index bd1422da3..b70c8528e 100644
--- a/core/odin/parser/parser.odin
+++ b/core/odin/parser/parser.odin
@@ -2062,7 +2062,7 @@ parse_proc_tags :: proc(p: ^Parser) -> (tags: ast.Proc_Tags) {
 		case "bounds_check":    tags += {.Bounds_Check}
 		case "no_bounds_check": tags += {.No_Bounds_Check}
 		case "optional_ok":     tags += {.Optional_Ok}
-		case "optional_second": tags += {.Optional_Second}
+		case "optional_allocator_error": tags += {.Optional_Allocator_Error}
 		case:
 		}
 	}
diff --git a/core/runtime/core_builtin.odin b/core/runtime/core_builtin.odin
index e3960088d..4c736b6f6 100644
--- a/core/runtime/core_builtin.odin
+++ b/core/runtime/core_builtin.odin
@@ -189,7 +189,7 @@ delete :: proc{
 // The new built-in procedure allocates memory. The first argument is a type, not a value, and the value
 // return is a pointer to a newly allocated value of that type using the specified allocator, default is context.allocator
 @builtin
-new :: proc($T: typeid, allocator := context.allocator, loc := #caller_location) -> (^T, Allocator_Error) #optional_second {
+new :: proc($T: typeid, allocator := context.allocator, loc := #caller_location) -> (^T, Allocator_Error) #optional_allocator_error {
 	return new_aligned(T, align_of(T), allocator, loc)
 }
 new_aligned :: proc($T: typeid, alignment: int, allocator := context.allocator, loc := #caller_location) -> (t: ^T, err: Allocator_Error) {
@@ -199,7 +199,7 @@ new_aligned :: proc($T: typeid, alignment: int, allocator := context.allocator,
 }
 
 @builtin
-new_clone :: proc(data: $T, allocator := context.allocator, loc := #caller_location) -> (t: ^T, err: Allocator_Error) #optional_second {
+new_clone :: proc(data: $T, allocator := context.allocator, loc := #caller_location) -> (t: ^T, err: Allocator_Error) #optional_allocator_error {
 	t_data := mem_alloc_bytes(size_of(T), align_of(T), allocator, loc) or_return
 	t = (^T)(raw_data(t_data))
 	if t != nil {
@@ -210,7 +210,7 @@ new_clone :: proc(data: $T, allocator := context.allocator, loc := #caller_locat
 
 DEFAULT_RESERVE_CAPACITY :: 16
 
-make_aligned :: proc($T: typeid/[]$E, #any_int len: int, alignment: int, allocator := context.allocator, loc := #caller_location) -> (T, Allocator_Error) #optional_second {
+make_aligned :: proc($T: typeid/[]$E, #any_int len: int, alignment: int, allocator := context.allocator, loc := #caller_location) -> (T, Allocator_Error) #optional_allocator_error {
 	make_slice_error_loc(loc, len)
 	data, err := mem_alloc_bytes(size_of(E)*len, alignment, allocator, loc)
 	if data == nil && size_of(E) != 0 {
@@ -221,19 +221,19 @@ make_aligned :: proc($T: typeid/[]$E, #any_int len: int, alignment: int, allocat
 }
 
 @(builtin)
-make_slice :: proc($T: typeid/[]$E, #any_int len: int, allocator := context.allocator, loc := #caller_location) -> (T, Allocator_Error) #optional_second {
+make_slice :: proc($T: typeid/[]$E, #any_int len: int, allocator := context.allocator, loc := #caller_location) -> (T, Allocator_Error) #optional_allocator_error {
 	return make_aligned(T, len, align_of(E), allocator, loc)
 }
 @(builtin)
-make_dynamic_array :: proc($T: typeid/[dynamic]$E, allocator := context.allocator, loc := #caller_location) -> (T, Allocator_Error) #optional_second {
+make_dynamic_array :: proc($T: typeid/[dynamic]$E, allocator := context.allocator, loc := #caller_location) -> (T, Allocator_Error) #optional_allocator_error {
 	return make_dynamic_array_len_cap(T, 0, DEFAULT_RESERVE_CAPACITY, allocator, loc)
 }
 @(builtin)
-make_dynamic_array_len :: proc($T: typeid/[dynamic]$E, #any_int len: int, allocator := context.allocator, loc := #caller_location) -> (T, Allocator_Error) #optional_second {
+make_dynamic_array_len :: proc($T: typeid/[dynamic]$E, #any_int len: int, allocator := context.allocator, loc := #caller_location) -> (T, Allocator_Error) #optional_allocator_error {
 	return make_dynamic_array_len_cap(T, len, len, allocator, loc)
 }
 @(builtin)
-make_dynamic_array_len_cap :: proc($T: typeid/[dynamic]$E, #any_int len: int, #any_int cap: int, allocator := context.allocator, loc := #caller_location) -> (array: T, err: Allocator_Error) #optional_second {
+make_dynamic_array_len_cap :: proc($T: typeid/[dynamic]$E, #any_int len: int, #any_int cap: int, allocator := context.allocator, loc := #caller_location) -> (array: T, err: Allocator_Error) #optional_allocator_error {
 	make_dynamic_array_error_loc(loc, len, cap)
 	data := mem_alloc_bytes(size_of(E)*cap, align_of(E), allocator, loc) or_return
 	s := Raw_Dynamic_Array{raw_data(data), len, cap, allocator}
@@ -253,7 +253,7 @@ make_map :: proc($T: typeid/map[$K]$E, #any_int cap: int = DEFAULT_RESERVE_CAPAC
 	return m
 }
 @(builtin)
-make_multi_pointer :: proc($T: typeid/[^]$E, #any_int len: int, allocator := context.allocator, loc := #caller_location) -> (mp: T, err: Allocator_Error) #optional_second {
+make_multi_pointer :: proc($T: typeid/[^]$E, #any_int len: int, allocator := context.allocator, loc := #caller_location) -> (mp: T, err: Allocator_Error) #optional_allocator_error {
 	make_slice_error_loc(loc, len)
 	data := mem_alloc_bytes(size_of(E)*len, align_of(E), allocator, loc) or_return
 	if data == nil && size_of(E) != 0 {
diff --git a/core/runtime/core_builtin_soa.odin b/core/runtime/core_builtin_soa.odin
index 077027a9a..a6b356642 100644
--- a/core/runtime/core_builtin_soa.odin
+++ b/core/runtime/core_builtin_soa.odin
@@ -79,7 +79,7 @@ raw_soa_footer :: proc{
 
 
 @builtin
-make_soa_aligned :: proc($T: typeid/#soa[]$E, length: int, alignment: int, allocator := context.allocator, loc := #caller_location) -> (array: T, err: Allocator_Error) #optional_second {
+make_soa_aligned :: proc($T: typeid/#soa[]$E, length: int, alignment: int, allocator := context.allocator, loc := #caller_location) -> (array: T, err: Allocator_Error) #optional_allocator_error {
 	if length <= 0 {
 		return
 	}
@@ -138,7 +138,7 @@ make_soa_aligned :: proc($T: typeid/#soa[]$E, length: int, alignment: int, alloc
 }
 
 @builtin
-make_soa_slice :: proc($T: typeid/#soa[]$E, length: int, allocator := context.allocator, loc := #caller_location) -> (array: T, err: Allocator_Error) #optional_second {
+make_soa_slice :: proc($T: typeid/#soa[]$E, length: int, allocator := context.allocator, loc := #caller_location) -> (array: T, err: Allocator_Error) #optional_allocator_error {
 	return make_soa_aligned(T, length, align_of(E), allocator, loc)
 }
 
diff --git a/core/strings/reader.odin b/core/strings/reader.odin
index 9b2e10b68..a38f1fbe4 100644
--- a/core/strings/reader.odin
+++ b/core/strings/reader.odin
@@ -42,20 +42,6 @@ to_reader_at :: proc(r: ^Reader, s: string) -> io.Reader_At {
 	return rr
 }
 
-// init a reader to the string `s` and return an io.Byte_Reader
-to_byte_reader :: proc(r: ^Reader, s: string) -> io.Byte_Reader {
-	reader_init(r, s)
-	rr, _ := io.to_byte_reader(reader_to_stream(r))
-	return rr
-}
-
-// init a reader to the string `s` and return an io.Rune_Reader
-to_rune_reader :: proc(r: ^Reader, s: string) -> io.Rune_Reader {
-	reader_init(r, s)
-	rr, _ := io.to_rune_reader(reader_to_stream(r))
-	return rr
-}
-
 // remaining length of the reader 
 reader_length :: proc(r: ^Reader) -> int {
 	if r.i >= i64(len(r.s)) {
diff --git a/core/strings/strings.odin b/core/strings/strings.odin
index fcfc133f3..a0f553a68 100644
--- a/core/strings/strings.odin
+++ b/core/strings/strings.odin
@@ -937,14 +937,14 @@ index_any :: proc(s, chars: string) -> int {
 }
 
 /*
-	returns the index of any first char of `chars` found in `s`, -1 if not found
+	returns the last matching index in `s` of any char in `chars` found in `s`, -1 if not found
 	iterates the string in reverse
 
-	strings.index_any("test", "s") -> 2
-	strings.index_any("test", "se") -> 2
-	strings.index_any("test", "et") -> 1
-	strings.index_any("test", "set") -> 3
-	strings.index_any("test", "x") -> -1
+	strings.last_index_any("test", "s") -> 2
+	strings.last_index_any("test", "se") -> 2
+	strings.last_index_any("test", "et") -> 3
+	strings.last_index_any("test", "set") -> 3
+	strings.last_index_any("test", "x") -> -1
 */
 last_index_any :: proc(s, chars: string) -> int {
 	if chars == "" {
diff --git a/src/build_settings.cpp b/src/build_settings.cpp
index b877b8cb7..fc5a9d19f 100644
--- a/src/build_settings.cpp
+++ b/src/build_settings.cpp
@@ -1355,6 +1355,12 @@ bool init_build_paths(String init_filename) {
 	// [BuildPathMainPackage] Turn given init path into a `Path`, which includes normalizing it into a full path.
 	bc->build_paths[BuildPath_Main_Package] = path_from_string(ha, init_filename);
 
+	{
+		String build_project_name  = last_path_element(bc->build_paths[BuildPath_Main_Package].basename);
+		GB_ASSERT(build_project_name.len > 0);
+		bc->ODIN_BUILD_PROJECT_NAME = build_project_name;
+	}
+
 	bool produces_output_file = false;
 	if (bc->command_kind == Command_doc && bc->cmd_doc_flags & CmdDocFlag_DocFormat) {
 		produces_output_file = true;
@@ -1538,12 +1544,6 @@ bool init_build_paths(String init_filename) {
 		enable_target_feature({}, bc->target_features_string);
 	}
 
-	{
-		String build_project_name  = last_path_element(bc->build_paths[BuildPath_Main_Package].basename);
-		GB_ASSERT(build_project_name.len > 0);
-		bc->ODIN_BUILD_PROJECT_NAME = build_project_name;
-	}
-
 	return true;
 }
 
diff --git a/src/check_type.cpp b/src/check_type.cpp
index 66417f97e..c024e0842 100644
--- a/src/check_type.cpp
+++ b/src/check_type.cpp
@@ -2006,22 +2006,21 @@ bool check_procedure_type(CheckerContext *ctx, Type *type, Ast *proc_type_node,
 			}
 		}
 	}
-	if (pt->tags & ProcTag_optional_second) {
+	if (pt->tags & ProcTag_optional_allocator_error) {
 		if (optional_ok) {
-			error(proc_type_node, "A procedure type cannot have both an #optional_ok tag and #optional_second");
+			error(proc_type_node, "A procedure type cannot have both an #optional_ok tag and #optional_allocator_error");
 		}
 		optional_ok = true;
 		if (result_count != 2) {
-			error(proc_type_node, "A procedure type with the #optional_second tag requires 2 return values, got %td", result_count);
+			error(proc_type_node, "A procedure type with the #optional_allocator_error tag requires 2 return values, got %td", result_count);
 		} else {
-			bool ok = false;
-			AstFile *file = proc_type_node->file();
-			if (file && file->pkg) {
-				ok = file->pkg->scope == ctx->info->runtime_package->scope;
-			}
+			init_mem_allocator(c->checker);
 
-			if (!ok) {
-				error(proc_type_node, "A procedure type with the #optional_second may only be allowed within 'package runtime'");
+			Type *type = results->Tuple.variables[1]->type;
+			if (!are_types_identical(type, t_allocator_error)) {
+				gbString t = type_to_string(type);
+				error(proc_type_node, "A procedure type with the #optional_allocator_error expects a `runtime.Allocator_Error`, got '%s'", t);
+				gb_string_free(t);
 			}
 		}
 	}
diff --git a/src/checker.cpp b/src/checker.cpp
index 16e480786..cdc0630bf 100644
--- a/src/checker.cpp
+++ b/src/checker.cpp
@@ -2809,17 +2809,9 @@ void init_mem_allocator(Checker *c) {
 	if (t_allocator != nullptr) {
 		return;
 	}
-	AstPackage *pkg = get_core_package(&c->info, str_lit("runtime"));
-
-	String name = str_lit("Allocator");
-	Entity *e = scope_lookup_current(pkg->scope, name);
-	if (e == nullptr) {
-		compiler_error("Could not find type declaration for '%.*s'\n", LIT(name));
-		// NOTE(bill): This will exit the program as it's cannot continue without it!
-	}
-
-	t_allocator = e->type;
+	t_allocator = find_core_type(c, str_lit("Allocator"));
 	t_allocator_ptr = alloc_type_pointer(t_allocator);
+	t_allocator_error = find_core_type(c, str_lit("Allocator_Error"));
 }
 
 void init_core_context(Checker *c) {
@@ -2827,7 +2819,6 @@ void init_core_context(Checker *c) {
 		return;
 	}
 	t_context = find_core_type(c, str_lit("Context"));
-	GB_ASSERT(t_context != nullptr);
 	t_context_ptr = alloc_type_pointer(t_context);
 }
 
diff --git a/src/llvm_backend_proc.cpp b/src/llvm_backend_proc.cpp
index 17501d657..82e577032 100644
--- a/src/llvm_backend_proc.cpp
+++ b/src/llvm_backend_proc.cpp
@@ -578,7 +578,7 @@ void lb_begin_procedure_body(lbProcedure *p) {
 					GB_ASSERT(!is_blank_ident(e->token));
 
 					lbAddr res = {};
-					if (return_ptr_value.value) {
+					if (return_ptr_value.value != nullptr) {
 						lbValue ptr = return_ptr_value;
 						if (results->variables.count != 1) {
 							ptr = lb_emit_struct_ep(p, ptr, cast(i32)i);
@@ -586,6 +586,7 @@ void lb_begin_procedure_body(lbProcedure *p) {
 
 						res = lb_addr(ptr);
 						lb_add_entity(p->module, e, ptr);
+						lb_add_debug_local_variable(p, ptr.value, e->type, e->token);
 					} else {
 						res = lb_add_local(p, e->type, e);
 					}
@@ -594,8 +595,10 @@ void lb_begin_procedure_body(lbProcedure *p) {
 						lbValue c = lb_handle_param_value(p, e->type, e->Variable.param_value, e->token.pos);
 						lb_addr_store(p, res, c);
 					}
+
 				}
 			}
+
 		}
 	}
 	if (p->type->Proc.calling_convention == ProcCC_Odin) {
diff --git a/src/parser.cpp b/src/parser.cpp
index 70a87d2a5..2109945ec 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -1857,7 +1857,7 @@ void parse_proc_tags(AstFile *f, u64 *tags) {
 
 		if (false) {}
 		ELSE_IF_ADD_TAG(optional_ok)
-		ELSE_IF_ADD_TAG(optional_second)
+		ELSE_IF_ADD_TAG(optional_allocator_error)
 		ELSE_IF_ADD_TAG(require_results)
 		ELSE_IF_ADD_TAG(bounds_check)
 		ELSE_IF_ADD_TAG(no_bounds_check)
diff --git a/src/parser.hpp b/src/parser.hpp
index 7433744e6..e384f1e7e 100644
--- a/src/parser.hpp
+++ b/src/parser.hpp
@@ -232,7 +232,7 @@ enum ProcTag {
 
 	ProcTag_require_results = 1<<4,
 	ProcTag_optional_ok     = 1<<5,
-	ProcTag_optional_second = 1<<6,
+	ProcTag_optional_allocator_error = 1<<6,
 };
 
 enum ProcCallingConvention : i32 {
diff --git a/src/types.cpp b/src/types.cpp
index b7cb4dd2c..e917d30fa 100644
--- a/src/types.cpp
+++ b/src/types.cpp
@@ -681,6 +681,7 @@ gb_global Type *t_allocator                      = nullptr;
 gb_global Type *t_allocator_ptr                  = nullptr;
 gb_global Type *t_context                        = nullptr;
 gb_global Type *t_context_ptr                    = nullptr;
+gb_global Type *t_allocator_error                = nullptr;
 
 gb_global Type *t_source_code_location           = nullptr;
 gb_global Type *t_source_code_location_ptr       = nullptr;