feat: contextually type empty mutable slice literals

compiler_tests.odin

@@ -1828,6 +1828,102 @@ immutable_pointer_and_slice_bindings_preserve_mutable_pointees :: proc(t: ^testi
 	testing.expect_value(t, len(diagnostics.items), 0)
 }
 
+@(test)
+fresh_empty_literals_initialize_mutable_slices_and_grow :: proc(t: ^testing.T) {
+	directory := "/tmp/brolang-test-contextual-empty-slices"
+	main_path := "/tmp/brolang-test-contextual-empty-slices/main.bro"
+	output := "/tmp/brolang-test-contextual-empty-slices-output"
+	text := `mem :: import "@std/mem"
+Item :: struct { value i32 }
+Views :: struct { integers []mut i32, records []mut Item }
+integers func(values []mut i32) usize { return values.len }
+records func(values []mut Item) usize { return values.len }
+generic func($T type, values []mut T, _ T) usize { return values.len }
+main func() i32 {
+	numbers []mut i32 := &[]
+	items []mut Item := &[]
+	views Views := {integers = &[], records = &[]}
+	if numbers.len != 0 or items.len != 0 { return 1 }
+	if integers(&[]) != 0 or records(&[]) != 0 { return 2 }
+	if views.integers.len != 0 or views.records.len != 0 { return 3 }
+	integer i32 := 7
+	item Item := {value = 9}
+	if generic(&[], integer) != 0 or generic(&[], item) != 0 { return 7 }
+	numbers = mem.realloc(mem.c_allocator, numbers, 2) catch |_| { return 4 }
+	defer mem.free(mem.c_allocator, numbers)
+	items = mem.realloc(mem.c_allocator, items, 1) catch |_| { return 5 }
+	defer mem.free(mem.c_allocator, items)
+	numbers[0] = 17
+	numbers[1] = 25
+	items[0] = {value = numbers[0] + numbers[1]}
+	if numbers.len != 2 or items.len != 1 or items[0].value != 42 { return 6 }
+	return 0
+}
+`
+	_ = os2.remove_all(directory)
+	defer _ = os2.remove_all(directory)
+	defer _ = os.remove(output)
+	testing.expect(t, os.make_directory(directory) == nil)
+	testing.expect(t, os.write_entire_file(main_path, transmute([]byte)text))
+	testing.expect_value(t, compiler_core.compile_package(
+		directory, output, nil, target.DEFAULT, cimport.Options{}, ".",
+	), 0)
+	state := run_executable(output)
+	testing.expect_value(t, state.exit_code, 0)
+}
+
+@(test)
+empty_literal_mutability_does_not_weaken_readonly_or_sentinel_rules :: proc(t: ^testing.T) {
+	cases := [?]string {
+		`main func() void {
+	values [0]i32 := []
+	view []mut i32 := &values
+	_ = view
+}
+`,
+		`main func() void {
+	view []mut i32 := &[1]
+	_ = view
+}
+`,
+		`main func() void {
+	readonly []i32 := &[]
+	view []mut i32 := readonly
+	_ = view
+}
+`,
+		`main func() void {
+	view [;0]i32 := &[]
+	_ = view
+}
+`,
+		`main func() void {
+	view [;0]mut i32 := &[]
+	_ = view
+}
+`,
+	}
+	for text in cases {
+		source_file := source.Source{path="invalid_empty_slice.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)
+		found_conversion := false
+		for diagnostic in diagnostics.items {
+			found_conversion = found_conversion ||
+				strings.contains(diagnostic.message, "cannot implicitly convert")
+		}
+		testing.expect(t, found_conversion, text)
+	}
+}
+
 @(test)
 many_item_pointer_slices_compile_and_run :: proc(t: ^testing.T) {
 	directory := "/tmp/brolang-test-pointer-slices"