feat: support checked explicit sentinel slices

compiler/parser/parser.odin

@@ -1450,6 +1450,7 @@ parse_expression_bp :: proc(parser: ^Parser, minimum_binding_power, nesting: int
 			skip_newlines(parser)
 			start_expr := ast.INVALID_EXPR
 			end_expr := ast.INVALID_EXPR
+			sentinel_expr := ast.INVALID_EXPR
 			slicing := false
 			if _, ok := allow(parser, .Range); ok {
 				slicing = true
@@ -1463,12 +1464,19 @@ parse_expression_bp :: proc(parser: ^Parser, minimum_binding_power, nesting: int
 				}
 			}
 			skip_newlines(parser)
-			if slicing && current(parser).kind != .Right_Bracket {
+			if slicing && current(parser).kind != .Right_Bracket && current(parser).kind != .Semicolon {
 				parser.range_disabled += 1
 				end_expr = parse_expression_bp(parser, 0, nesting+1)
 				parser.range_disabled -= 1
 				skip_newlines(parser)
 			}
+			if slicing {
+				if _, ok := allow(parser, .Semicolon); ok {
+					skip_newlines(parser)
+					sentinel_expr = parse_expression_bp(parser, 0, nesting+1)
+					skip_newlines(parser)
+				}
+			}
 			end_token, ok := allow(parser, .Right_Bracket)
 			if !ok {
 				source.add(parser.diagnostics, current(parser).span, "expected ']' after index or slice")
@@ -1485,7 +1493,7 @@ parse_expression_bp :: proc(parser: ^Parser, minimum_binding_power, nesting: int
 					span=span_from(left_expr.span, end_token.span),
 					args=args,
 					left=left,
-					right=ast.INVALID_EXPR,
+					right=sentinel_expr,
 					diagnostic=source.INVALID_DIAGNOSTIC,
 				})
 			} else {