Add `#warning(<string>)` builtin compile time procedure

core/odin/parser/parser.odin

@@ -1438,7 +1438,7 @@ parse_stmt :: proc(p: ^Parser) -> ^ast.Stmt {
 			case: error(p, stmt.pos, "#partial can only be applied to a switch statement")
 			}
 			return stmt
-		case "assert", "panic":
+		case "assert", "panic", "warning":
 			bd := ast.new(ast.Basic_Directive, tok.pos, end_pos(tag))
 			bd.tok  = tok
 			bd.name = name

src/check_builtin.cpp

@@ -1714,6 +1714,26 @@ gb_internal bool check_builtin_procedure_directive(CheckerContext *c, Operand *o
 
 		operand->type = t_untyped_bool;
 		operand->mode = Addressing_Constant;
+	} else if (name == "warning") {
+		ERROR_BLOCK();
+		if (ce->args.count != 1) {
+			error(call, "'#warning' expects 1 argument, got %td", ce->args.count);
+			return false;
+		}
+		if (!is_type_string(operand->type) && operand->mode != Addressing_Constant) {
+			gbString str = expr_to_string(ce->args[0]);
+			error(call, "'%s' is not a constant string", str);
+			gb_string_free(str);
+			return false;
+		}
+		warning(call, "%.*s", LIT(operand->value.value_string));
+		if (c->proc_name != "") {
+			gbString str = type_to_string(c->curr_proc_sig);
+			error_line("\tCalled within '%.*s' :: %s\n", LIT(c->proc_name), str);
+			gb_string_free(str);
+		}
+		operand->type = t_invalid;
+		operand->mode = Addressing_NoValue;
 	} else if (name == "panic") {
 		ERROR_BLOCK();
 		if (ce->args.count != 1) {

src/parser.cpp

@@ -5167,7 +5167,7 @@ gb_internal Ast *parse_stmt(AstFile *f) {
 				break;
 			}
 			return s;
-		} else if (tag == "assert" || tag == "panic") {
+		} else if (tag == "assert" || tag == "panic" || tag == "warning") {
 			Ast *t = ast_basic_directive(f, hash_token, name);
 			Ast *stmt = ast_expr_stmt(f, parse_call_expr(f, t));
 			expect_semicolon(f);