Support compile time slicing of untyped lists.

releasenotes.md

@@ -18,6 +18,7 @@
 - Support linking .o files in compilation command. #1417
 - Slicing constant strings at compile time works.
 - Allow the "self" parameter to be $/# for macro methods.
+- Support compile time slicing of untyped lists.
 
 ### Fixes
 - Issue where a lambda wasn't correctly registered as external. #1408

src/compiler/sema_expr.c

@@ -3314,6 +3314,12 @@ static inline bool sema_expr_analyse_slice(SemaContext *context, Expr *expr, Che
 				expr_rewrite_const_string(expr, data);
 				return true;
 			}
+			case CONST_UNTYPED_LIST:
+				assert(!type_is_arraylike(subscripted->type));
+				vec_erase_front(subscripted->const_expr.untyped_list, range->start_index);
+				vec_resize(subscripted->const_expr.untyped_list, range->len_index);
+				expr_replace(expr, subscripted);
+				return true;
 			default:
 				break;
 		}

src/utils/lib.h

@@ -277,6 +277,21 @@ static inline void vec_pop(void *vec)
 	header[-1].size--;
 }
 
+static inline void vec_erase_front(void  *vec, unsigned to_erase)
+{
+	if (!to_erase) return;
+	assert(vec);
+	unsigned size = vec_size(vec);
+	assert(size >= to_erase);
+	void **vecptr = (void**)vec;
+	for (int i = to_erase; i < size; i++)
+	{
+		vecptr[i - to_erase] = vecptr[i];
+	}
+	VHeader_ *header = vec;
+	header[-1].size -= to_erase;
+}
+
 static inline void vec_erase_at(void *vec, unsigned i)
 {
 	assert(vec);

test/unit/regression/ct_slice.c3

@@ -13,4 +13,17 @@ fn void! slice_string()
 	assert($d == "bc");
 	assert(d == "bc");
 	assert($a[..] == "abcd");
+}
+
+fn void slice_untyped()
+{
+	var $v = { 1, "hello", 3 };
+	int[1] v = $v[0:1];
+	assert(v == int[1] { 1 });
+	int[1] v2 = $v[2:1];
+	assert(v2 == int[1] { 3 });
+	String[1] v3 = $v[1:1];
+	assert(v3 == String[1] { "hello" });
+	int[] v4 = $v[0:1];
+	assert(v4 == int[] { 1 });
 }