Add unimplemented and unreachable procedures; make os.exit a diverging procedure

core/os/os_linux.odin

@@ -139,7 +139,7 @@ foreign libc {
 	@(link_name="calloc")  _unix_calloc  :: proc(num, size: int) -> rawptr ---;
 	@(link_name="free")    _unix_free    :: proc(ptr: rawptr) ---;
 	@(link_name="realloc") _unix_realloc :: proc(ptr: rawptr, size: int) -> rawptr ---;
-	@(link_name="getenv")  _unix_getenv  :: proc(cstring) -> cstring ---;
+	@(link_name="getenv")  _unix_getenv  :: proc(cstring) -> cstring --- -> !;
 
 	@(link_name="exit")    _unix_exit    :: proc(status: int) ---;
 }
@@ -241,7 +241,7 @@ getenv :: proc(name: string) -> (string, bool) {
 	return string(cstr), true;
 }
 
-exit :: proc(code: int) {
+exit :: proc(code: int) -> ! {
 	_unix_exit(code);
 }
 

core/os/os_osx.odin

@@ -255,7 +255,7 @@ getenv :: proc(name: string) -> (string, bool) {
 	return string(cstr), true;
 }
 
-exit :: inline proc(code: int) {
+exit :: inline proc(code: int) -> ! {
 	_unix_exit(code);
 }
 

core/os/os_windows.odin

@@ -245,7 +245,7 @@ heap_free :: proc(ptr: rawptr) {
 }
 
 
-exit :: proc(code: int) {
+exit :: proc(code: int) -> ! {
 	win32.exit_process(u32(code));
 }
 

core/runtime/core.odin

@@ -590,6 +590,28 @@ panic :: proc "contextless" (message: string, loc := #caller_location) -> ! {
 	p("Panic", message, loc);
 }
 
+@(builtin)
+unimplemented :: proc "contextless" (message := "", loc := #caller_location) -> ! {
+	p := context.assertion_failure_proc;
+	if p == nil {
+		p = default_assertion_failure_proc;
+	}
+	p("not yet implemented", message, loc);
+}
+
+@(builtin)
+unreachable :: proc "contextless" (message := "", loc := #caller_location) -> ! {
+	p := context.assertion_failure_proc;
+	if p == nil {
+		p = default_assertion_failure_proc;
+	}
+	if message != "" {
+		p("internal error", message, loc);
+	} else {
+		p("internal error", "entered unreachable code", loc);
+	}
+}
+
 
 // Dynamic Array