usize indexing only

compiler_tests.odin

@@ -1867,6 +1867,92 @@ many_item_pointer_slices_require_end_bound :: proc(t: ^testing.T) {
 	testing.expect_value(t, end_bound_errors, 2)
 }
 
+@(test)
+indices_and_slice_bounds_require_usize :: proc(t: ^testing.T) {
+	text := `Index :: distinct u32
+main func() void {
+	values [2]i32 := [1, 2]
+	index := 1
+	start := 0
+	end := 1
+	small u32 := 0
+	id Index := Index(0)
+	_ = values[index]
+	_ = values[start..end]
+	_ = values[small]
+	_ = values[id]
+	_ = values[small..]
+	_ = values[..id]
+}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	ast_module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&ast_module)
+	hir_module := checker.check(&ast_module, &diagnostics, &symbols)
+	defer hir.destroy_module(&hir_module)
+
+	index_errors, bound_errors := 0, 0
+	for diagnostic in diagnostics.items {
+		index_errors += 1 if strings.contains(diagnostic.message, "index must have type usize") else 0
+		bound_errors += 1 if strings.contains(diagnostic.message, "slice bound must have type usize") else 0
+	}
+	testing.expect_value(t, len(diagnostics.items), 4)
+	testing.expect_value(t, index_errors, 2)
+	testing.expect_value(t, bound_errors, 2)
+}
+
+@(test)
+comptime_indices_infer_usize_and_reject_explicit_integer_types :: proc(t: ^testing.T) {
+	text := `good func($items [2]u8) u8 {
+	start := 0
+	end := 1
+	part :: items[start..end]
+	return part[start]
+}
+bad_index func($items [2]u8) u8 {
+	cursor u32 := 0
+	return items[cursor]
+}
+bad_bound func($items [2]u8) u8 {
+	start u32 := 0
+	return items[start..][0]
+}
+GOOD :: $good([7, 8])
+BAD_INDEX :: $bad_index([7, 8])
+BAD_BOUND :: $bad_bound([7, 8])
+main func() void {
+	_ = GOOD
+	_ = BAD_INDEX
+	_ = BAD_BOUND
+}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	ast_module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&ast_module)
+	hir_module := checker.check(&ast_module, &diagnostics, &symbols)
+	defer hir.destroy_module(&hir_module)
+
+	testing.expect_value(t, len(diagnostics.items), 2)
+	index_error, bound_error := false, false
+	for diagnostic in diagnostics.items {
+		index_error = index_error || strings.contains(diagnostic.message, "index must have type usize, got u32")
+		bound_error = bound_error || strings.contains(diagnostic.message, "slice bound must have type usize, got u32")
+	}
+	testing.expect(t, index_error && bound_error)
+}
+
 @(test)
 layout_builtins_compile_and_run :: proc(t: ^testing.T) {
 	directory := "/tmp/brolang-test-layout-builtins"
@@ -6107,7 +6193,7 @@ milestone_24_rejects_invalid_forms :: proc(t: ^testing.T) {
 	}
 	cases := [?]Case{
 		{"examples/programs/index_signed_error", "/tmp/brolang-test-index-signed-error"},
-		{"examples/programs/index_int_constraint_error", "/tmp/brolang-test-index-int-constraint-error"},
+		{"examples/programs/index_unsigned_error", "/tmp/brolang-test-index-unsigned-error"},
 		{"examples/programs/scalar_cast_error", "/tmp/brolang-test-scalar-cast-error"},
 		{"examples/programs/array_const_size_error", "/tmp/brolang-test-array-const-size-error"},
 	}