1 //! `hir_expand` deals with macro expansion.
3 //! Specifically, it implements a concept of `MacroFile` -- a file whose syntax
4 //! tree originates not from the text of some `FileId`, but from some macro
11 pub mod builtin_attr_macro;
12 pub mod builtin_derive_macro;
13 pub mod builtin_fn_macro;
18 use base_db::ProcMacroKind;
21 pub use mbe::{ExpandError, ExpandResult, Origin};
23 use std::{hash::Hash, iter, sync::Arc};
25 use base_db::{impl_intern_key, salsa, CrateId, FileId, FileRange};
27 algo::{self, skip_trivia_token},
28 ast::{self, AstNode, HasAttrs},
29 Direction, SyntaxNode, SyntaxToken,
33 ast_id_map::FileAstId,
34 builtin_attr_macro::BuiltinAttrExpander,
35 builtin_derive_macro::BuiltinDeriveExpander,
36 builtin_fn_macro::{BuiltinFnLikeExpander, EagerExpander},
38 proc_macro::ProcMacroExpander,
41 /// Input to the analyzer is a set of files, where each file is identified by
42 /// `FileId` and contains source code. However, another source of source code in
43 /// Rust are macros: each macro can be thought of as producing a "temporary
44 /// file". To assign an id to such a file, we use the id of the macro call that
45 /// produced the file. So, a `HirFileId` is either a `FileId` (source code
46 /// written by user), or a `MacroCallId` (source code produced by macro).
48 /// What is a `MacroCallId`? Simplifying, it's a `HirFileId` of a file
49 /// containing the call plus the offset of the macro call in the file. Note that
50 /// this is a recursive definition! However, the size_of of `HirFileId` is
51 /// finite (because everything bottoms out at the real `FileId`) and small
52 /// (`MacroCallId` uses the location interning. You can check details here:
53 /// <https://en.wikipedia.org/wiki/String_interning>).
54 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
55 pub struct HirFileId(HirFileIdRepr);
57 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
62 impl From<FileId> for HirFileId {
63 fn from(id: FileId) -> Self {
64 HirFileId(HirFileIdRepr::FileId(id))
67 impl From<MacroFile> for HirFileId {
68 fn from(id: MacroFile) -> Self {
69 HirFileId(HirFileIdRepr::MacroFile(id))
73 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
74 pub struct MacroFile {
75 pub macro_call_id: MacroCallId,
78 /// `MacroCallId` identifies a particular macro invocation, like
79 /// `println!("Hello, {}", world)`.
80 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
81 pub struct MacroCallId(salsa::InternId);
82 impl_intern_key!(MacroCallId);
84 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
85 pub struct MacroCallLoc {
87 pub(crate) krate: CrateId,
88 eager: Option<EagerCallInfo>,
89 pub kind: MacroCallKind,
92 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
93 pub struct MacroDefId {
95 pub kind: MacroDefKind,
96 pub local_inner: bool,
99 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
100 pub enum MacroDefKind {
101 Declarative(AstId<ast::Macro>),
102 BuiltIn(BuiltinFnLikeExpander, AstId<ast::Macro>),
103 // FIXME: maybe just Builtin and rename BuiltinFnLikeExpander to BuiltinExpander
104 BuiltInAttr(BuiltinAttrExpander, AstId<ast::Macro>),
105 BuiltInDerive(BuiltinDeriveExpander, AstId<ast::Macro>),
106 BuiltInEager(EagerExpander, AstId<ast::Macro>),
107 ProcMacro(ProcMacroExpander, ProcMacroKind, AstId<ast::Fn>),
110 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
111 struct EagerCallInfo {
112 /// NOTE: This can be *either* the expansion result, *or* the argument to the eager macro!
113 arg_or_expansion: Arc<tt::Subtree>,
114 included_file: Option<FileId>,
117 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
118 pub enum MacroCallKind {
120 ast_id: AstId<ast::MacroCall>,
124 ast_id: AstId<ast::Item>,
125 derive_name: Box<str>,
126 /// Syntactical index of the invoking `#[derive]` attribute.
128 /// Outer attributes are counted first, then inner attributes. This does not support
129 /// out-of-line modules, which may have attributes spread across 2 files!
130 derive_attr_index: u32,
133 ast_id: AstId<ast::Item>,
135 attr_args: (tt::Subtree, mbe::TokenMap),
136 /// Syntactical index of the invoking `#[attribute]`.
138 /// Outer attributes are counted first, then inner attributes. This does not support
139 /// out-of-line modules, which may have attributes spread across 2 files!
140 invoc_attr_index: u32,
145 /// For macro-expansion files, returns the file original source file the
146 /// expansion originated from.
147 pub fn original_file(self, db: &dyn db::AstDatabase) -> FileId {
149 HirFileIdRepr::FileId(file_id) => file_id,
150 HirFileIdRepr::MacroFile(macro_file) => {
151 let loc: MacroCallLoc = db.lookup_intern_macro(macro_file.macro_call_id);
152 let file_id = match &loc.eager {
153 Some(EagerCallInfo { included_file: Some(file), .. }) => (*file).into(),
154 _ => loc.kind.file_id(),
156 file_id.original_file(db)
161 pub fn expansion_level(self, db: &dyn db::AstDatabase) -> u32 {
164 while let HirFileIdRepr::MacroFile(macro_file) = curr.0 {
165 let loc: MacroCallLoc = db.lookup_intern_macro(macro_file.macro_call_id);
168 curr = loc.kind.file_id();
173 /// If this is a macro call, returns the syntax node of the call.
174 pub fn call_node(self, db: &dyn db::AstDatabase) -> Option<InFile<SyntaxNode>> {
176 HirFileIdRepr::FileId(_) => None,
177 HirFileIdRepr::MacroFile(macro_file) => {
178 let loc: MacroCallLoc = db.lookup_intern_macro(macro_file.macro_call_id);
179 Some(loc.kind.to_node(db))
184 /// Return expansion information if it is a macro-expansion file
185 pub fn expansion_info(self, db: &dyn db::AstDatabase) -> Option<ExpansionInfo> {
187 HirFileIdRepr::FileId(_) => None,
188 HirFileIdRepr::MacroFile(macro_file) => {
189 let loc: MacroCallLoc = db.lookup_intern_macro(macro_file.macro_call_id);
191 let arg_tt = loc.kind.arg(db)?;
193 let def = loc.def.ast_id().left().and_then(|id| {
194 let def_tt = match id.to_node(db) {
195 ast::Macro::MacroRules(mac) => mac.token_tree()?,
196 ast::Macro::MacroDef(mac) => mac.body()?,
198 Some(InFile::new(id.file_id, def_tt))
200 let attr_input_or_mac_def = def.or_else(|| match loc.kind {
201 MacroCallKind::Attr { ast_id, invoc_attr_index, .. } => {
205 .nth(invoc_attr_index as usize)?
207 Some(InFile::new(ast_id.file_id, tt))
212 let macro_def = db.macro_def(loc.def).ok()?;
213 let (parse, exp_map) = db.parse_macro_expansion(macro_file).value?;
214 let macro_arg = db.macro_arg(macro_file.macro_call_id)?;
217 expanded: InFile::new(self, parse.syntax_node()),
218 arg: InFile::new(loc.kind.file_id(), arg_tt),
219 attr_input_or_mac_def,
220 macro_arg_shift: mbe::Shift::new(¯o_arg.0),
229 /// Indicate it is macro file generated for builtin derive
230 pub fn is_builtin_derive(&self, db: &dyn db::AstDatabase) -> Option<InFile<ast::Item>> {
232 HirFileIdRepr::FileId(_) => None,
233 HirFileIdRepr::MacroFile(macro_file) => {
234 let loc: MacroCallLoc = db.lookup_intern_macro(macro_file.macro_call_id);
235 let item = match loc.def.kind {
236 MacroDefKind::BuiltInDerive(..) => loc.kind.to_node(db),
239 Some(item.with_value(ast::Item::cast(item.value.clone())?))
244 pub fn is_custom_derive(&self, db: &dyn db::AstDatabase) -> bool {
246 HirFileIdRepr::FileId(_) => false,
247 HirFileIdRepr::MacroFile(macro_file) => {
248 let loc: MacroCallLoc = db.lookup_intern_macro(macro_file.macro_call_id);
250 MacroDefKind::ProcMacro(_, ProcMacroKind::CustomDerive, _) => true,
257 /// Return whether this file is an include macro
258 pub fn is_include_macro(&self, db: &dyn db::AstDatabase) -> bool {
260 HirFileIdRepr::MacroFile(macro_file) => {
261 let loc: MacroCallLoc = db.lookup_intern_macro(macro_file.macro_call_id);
262 matches!(loc.eager, Some(EagerCallInfo { included_file: Some(_), .. }))
268 /// Return whether this file is an include macro
269 pub fn is_attr_macro(&self, db: &dyn db::AstDatabase) -> bool {
271 HirFileIdRepr::MacroFile(macro_file) => {
272 let loc: MacroCallLoc = db.lookup_intern_macro(macro_file.macro_call_id);
273 matches!(loc.kind, MacroCallKind::Attr { .. })
279 pub fn is_macro(self) -> bool {
280 matches!(self.0, HirFileIdRepr::MacroFile(_))
285 pub fn as_lazy_macro(
287 db: &dyn db::AstDatabase,
291 db.intern_macro(MacroCallLoc { def: self, krate, eager: None, kind })
294 pub fn ast_id(&self) -> Either<AstId<ast::Macro>, AstId<ast::Fn>> {
295 let id = match &self.kind {
296 MacroDefKind::ProcMacro(.., id) => return Either::Right(*id),
297 MacroDefKind::Declarative(id)
298 | MacroDefKind::BuiltIn(_, id)
299 | MacroDefKind::BuiltInAttr(_, id)
300 | MacroDefKind::BuiltInDerive(_, id)
301 | MacroDefKind::BuiltInEager(_, id) => id,
306 pub fn is_proc_macro(&self) -> bool {
307 matches!(self.kind, MacroDefKind::ProcMacro(..))
310 pub fn is_attribute(&self) -> bool {
313 MacroDefKind::BuiltInAttr(..) | MacroDefKind::ProcMacro(_, ProcMacroKind::Attr, _)
318 // FIXME: attribute indices do not account for `cfg_attr`, which means that we'll strip the whole
319 // `cfg_attr` instead of just one of the attributes it expands to
322 /// Returns the file containing the macro invocation.
323 fn file_id(&self) -> HirFileId {
325 MacroCallKind::FnLike { ast_id, .. } => ast_id.file_id,
326 MacroCallKind::Derive { ast_id, .. } | MacroCallKind::Attr { ast_id, .. } => {
332 pub fn to_node(&self, db: &dyn db::AstDatabase) -> InFile<SyntaxNode> {
334 MacroCallKind::FnLike { ast_id, .. } => {
335 ast_id.with_value(ast_id.to_node(db).syntax().clone())
337 MacroCallKind::Derive { ast_id, .. } | MacroCallKind::Attr { ast_id, .. } => {
338 ast_id.with_value(ast_id.to_node(db).syntax().clone())
343 fn arg(&self, db: &dyn db::AstDatabase) -> Option<SyntaxNode> {
345 MacroCallKind::FnLike { ast_id, .. } => {
346 Some(ast_id.to_node(db).token_tree()?.syntax().clone())
348 MacroCallKind::Derive { ast_id, .. } | MacroCallKind::Attr { ast_id, .. } => {
349 Some(ast_id.to_node(db).syntax().clone())
354 fn expand_to(&self) -> ExpandTo {
356 MacroCallKind::FnLike { expand_to, .. } => *expand_to,
357 MacroCallKind::Derive { .. } => ExpandTo::Items,
358 MacroCallKind::Attr { .. } => ExpandTo::Items, // is this always correct?
364 pub fn as_file(self) -> HirFileId {
365 MacroFile { macro_call_id: self }.into()
369 /// ExpansionInfo mainly describes how to map text range between src and expanded macro
370 #[derive(Debug, Clone, PartialEq, Eq)]
371 pub struct ExpansionInfo {
372 expanded: InFile<SyntaxNode>,
373 arg: InFile<SyntaxNode>,
374 /// The `macro_rules!` arguments or attribute input.
375 attr_input_or_mac_def: Option<InFile<ast::TokenTree>>,
377 macro_def: Arc<TokenExpander>,
378 macro_arg: Arc<(tt::Subtree, mbe::TokenMap)>,
379 macro_arg_shift: mbe::Shift,
380 exp_map: Arc<mbe::TokenMap>,
384 pub fn expanded(&self) -> InFile<SyntaxNode> {
385 self.expanded.clone()
388 pub fn call_node(&self) -> Option<InFile<SyntaxNode>> {
389 Some(self.arg.with_value(self.arg.value.parent()?))
392 pub fn map_token_down(
394 db: &dyn db::AstDatabase,
395 item: Option<ast::Item>,
396 token: InFile<&SyntaxToken>,
397 ) -> Option<impl Iterator<Item = InFile<SyntaxToken>> + '_> {
398 assert_eq!(token.file_id, self.arg.file_id);
399 let token_id = if let Some(item) = item {
400 // check if we are mapping down in an attribute input
401 let call_id = match self.expanded.file_id.0 {
402 HirFileIdRepr::FileId(_) => return None,
403 HirFileIdRepr::MacroFile(macro_file) => macro_file.macro_call_id,
405 let loc = db.lookup_intern_macro(call_id);
407 let token_range = token.value.text_range();
409 MacroCallKind::Attr { attr_args, invoc_attr_index, .. } => {
410 let attr = item.attrs().nth(*invoc_attr_index as usize)?;
411 match attr.token_tree() {
413 if token_tree.syntax().text_range().contains_range(token_range) =>
415 let attr_input_start =
416 token_tree.left_delimiter_token()?.text_range().start();
417 let range = token.value.text_range().checked_sub(attr_input_start)?;
419 self.macro_arg_shift.shift(attr_args.1.token_by_range(range)?);
431 let token_id = match token_id {
432 Some(token_id) => token_id,
435 token.value.text_range().checked_sub(self.arg.value.text_range().start())?;
436 let token_id = self.macro_arg.1.token_by_range(range)?;
437 self.macro_def.map_id_down(token_id)
443 .ranges_by_token(token_id, token.value.kind())
444 .flat_map(move |range| self.expanded.value.covering_element(range).into_token());
446 Some(tokens.map(move |token| self.expanded.with_value(token)))
451 db: &dyn db::AstDatabase,
452 token: InFile<&SyntaxToken>,
453 ) -> Option<(InFile<SyntaxToken>, Origin)> {
454 let token_id = self.exp_map.token_by_range(token.value.text_range())?;
455 let (mut token_id, origin) = self.macro_def.map_id_up(token_id);
457 let call_id = match self.expanded.file_id.0 {
458 HirFileIdRepr::FileId(_) => return None,
459 HirFileIdRepr::MacroFile(macro_file) => macro_file.macro_call_id,
461 let loc = db.lookup_intern_macro(call_id);
463 let (token_map, tt) = match &loc.kind {
464 MacroCallKind::Attr { attr_args, .. } => match self.macro_arg_shift.unshift(token_id) {
466 token_id = unshifted;
467 (&attr_args.1, self.attr_input_or_mac_def.clone()?.syntax().cloned())
469 None => (&self.macro_arg.1, self.arg.clone()),
472 mbe::Origin::Call => (&self.macro_arg.1, self.arg.clone()),
473 mbe::Origin::Def => match (&*self.macro_def, &self.attr_input_or_mac_def) {
474 (TokenExpander::DeclarativeMacro { def_site_token_map, .. }, Some(tt)) => {
475 (def_site_token_map, tt.syntax().cloned())
477 _ => panic!("`Origin::Def` used with non-`macro_rules!` macro"),
482 let range = token_map.first_range_by_token(token_id, token.value.kind())?;
484 tt.value.covering_element(range + tt.value.text_range().start()).into_token()?;
485 Some((tt.with_value(token), origin))
489 /// `AstId` points to an AST node in any file.
491 /// It is stable across reparses, and can be used as salsa key/value.
492 // FIXME: isn't this just a `Source<FileAstId<N>>` ?
493 pub type AstId<N> = InFile<FileAstId<N>>;
495 impl<N: AstNode> AstId<N> {
496 pub fn to_node(&self, db: &dyn db::AstDatabase) -> N {
497 let root = db.parse_or_expand(self.file_id).unwrap();
498 db.ast_id_map(self.file_id).get(self.value).to_node(&root)
502 /// `InFile<T>` stores a value of `T` inside a particular file/syntax tree.
504 /// Typical usages are:
506 /// * `InFile<SyntaxNode>` -- syntax node in a file
507 /// * `InFile<ast::FnDef>` -- ast node in a file
508 /// * `InFile<TextSize>` -- offset in a file
509 #[derive(Debug, PartialEq, Eq, Clone, Copy, Hash)]
510 pub struct InFile<T> {
511 pub file_id: HirFileId,
516 pub fn new(file_id: HirFileId, value: T) -> InFile<T> {
517 InFile { file_id, value }
520 // Similarly, naming here is stupid...
521 pub fn with_value<U>(&self, value: U) -> InFile<U> {
522 InFile::new(self.file_id, value)
525 pub fn map<F: FnOnce(T) -> U, U>(self, f: F) -> InFile<U> {
526 InFile::new(self.file_id, f(self.value))
528 pub fn as_ref(&self) -> InFile<&T> {
529 self.with_value(&self.value)
531 pub fn file_syntax(&self, db: &dyn db::AstDatabase) -> SyntaxNode {
532 db.parse_or_expand(self.file_id).expect("source created from invalid file")
536 impl<T: Clone> InFile<&T> {
537 pub fn cloned(&self) -> InFile<T> {
538 self.with_value(self.value.clone())
542 impl<T> InFile<Option<T>> {
543 pub fn transpose(self) -> Option<InFile<T>> {
544 let value = self.value?;
545 Some(InFile::new(self.file_id, value))
549 impl InFile<SyntaxNode> {
550 pub fn ancestors_with_macros(
552 db: &dyn db::AstDatabase,
553 ) -> impl Iterator<Item = InFile<SyntaxNode>> + Clone + '_ {
554 iter::successors(Some(self), move |node| match node.value.parent() {
555 Some(parent) => Some(node.with_value(parent)),
557 let parent_node = node.file_id.call_node(db)?;
563 /// Skips the attributed item that caused the macro invocation we are climbing up
564 pub fn ancestors_with_macros_skip_attr_item(
566 db: &dyn db::AstDatabase,
567 ) -> impl Iterator<Item = InFile<SyntaxNode>> + '_ {
568 iter::successors(Some(self), move |node| match node.value.parent() {
569 Some(parent) => Some(node.with_value(parent)),
571 let parent_node = node.file_id.call_node(db)?;
572 if node.file_id.is_attr_macro(db) {
573 // macro call was an attributed item, skip it
574 // FIXME: does this fail if this is a direct expansion of another macro?
575 parent_node.map(|node| node.parent()).transpose()
584 impl<'a> InFile<&'a SyntaxNode> {
585 /// Falls back to the macro call range if the node cannot be mapped up fully.
586 pub fn original_file_range(self, db: &dyn db::AstDatabase) -> FileRange {
587 if let Some(res) = self.original_file_range_opt(db) {
591 // Fall back to whole macro call.
592 let mut node = self.cloned();
593 while let Some(call_node) = node.file_id.call_node(db) {
597 let orig_file = node.file_id.original_file(db);
598 assert_eq!(node.file_id, orig_file.into());
600 FileRange { file_id: orig_file, range: node.value.text_range() }
603 /// Attempts to map the syntax node back up its macro calls.
604 pub fn original_file_range_opt(self, db: &dyn db::AstDatabase) -> Option<FileRange> {
605 match ascend_node_border_tokens(db, self) {
606 Some(InFile { file_id, value: (first, last) }) => {
607 let original_file = file_id.original_file(db);
608 let range = first.text_range().cover(last.text_range());
609 if file_id != original_file.into() {
610 tracing::error!("Failed mapping up more for {:?}", range);
613 Some(FileRange { file_id: original_file, range })
615 _ if !self.file_id.is_macro() => Some(FileRange {
616 file_id: self.file_id.original_file(db),
617 range: self.value.text_range(),
624 fn ascend_node_border_tokens(
625 db: &dyn db::AstDatabase,
626 InFile { file_id, value: node }: InFile<&SyntaxNode>,
627 ) -> Option<InFile<(SyntaxToken, SyntaxToken)>> {
628 let expansion = file_id.expansion_info(db)?;
630 // the input node has only one token ?
631 let first = skip_trivia_token(node.first_token()?, Direction::Next)?;
632 let last = skip_trivia_token(node.last_token()?, Direction::Prev)?;
633 let is_single_token = first == last;
635 node.descendants().find_map(|it| {
636 let first = skip_trivia_token(it.first_token()?, Direction::Next)?;
637 let first = ascend_call_token(db, &expansion, InFile::new(file_id, first))?;
639 let last = skip_trivia_token(it.last_token()?, Direction::Prev)?;
640 let last = ascend_call_token(db, &expansion, InFile::new(file_id, last))?;
642 if (!is_single_token && first == last) || (first.file_id != last.file_id) {
646 Some(InFile::new(first.file_id, (first.value, last.value)))
650 fn ascend_call_token(
651 db: &dyn db::AstDatabase,
652 expansion: &ExpansionInfo,
653 token: InFile<SyntaxToken>,
654 ) -> Option<InFile<SyntaxToken>> {
655 let (mapped, origin) = expansion.map_token_up(db, token.as_ref())?;
656 if origin != Origin::Call {
659 if let Some(info) = mapped.file_id.expansion_info(db) {
660 return ascend_call_token(db, &info, mapped);
665 impl InFile<SyntaxToken> {
666 pub fn ancestors_with_macros(
668 db: &dyn db::AstDatabase,
669 ) -> impl Iterator<Item = InFile<SyntaxNode>> + '_ {
670 self.value.parent().into_iter().flat_map({
671 let file_id = self.file_id;
672 move |parent| InFile::new(file_id, parent).ancestors_with_macros(db)
677 impl<N: AstNode> InFile<N> {
678 pub fn descendants<T: AstNode>(self) -> impl Iterator<Item = InFile<T>> {
679 self.value.syntax().descendants().filter_map(T::cast).map(move |n| self.with_value(n))
682 pub fn original_ast_node(self, db: &dyn db::AstDatabase) -> Option<InFile<N>> {
683 match ascend_node_border_tokens(db, self.syntax()) {
684 Some(InFile { file_id, value: (first, last) }) => {
685 let original_file = file_id.original_file(db);
686 if file_id != original_file.into() {
687 let range = first.text_range().cover(last.text_range());
688 tracing::error!("Failed mapping up more for {:?}", range);
691 let anc = algo::least_common_ancestor(&first.parent()?, &last.parent()?)?;
692 Some(InFile::new(file_id, anc.ancestors().find_map(N::cast)?))
694 _ if !self.file_id.is_macro() => Some(self),
699 pub fn syntax(&self) -> InFile<&SyntaxNode> {
700 self.with_value(self.value.syntax())
704 /// In Rust, macros expand token trees to token trees. When we want to turn a
705 /// token tree into an AST node, we need to figure out what kind of AST node we
706 /// want: something like `foo` can be a type, an expression, or a pattern.
708 /// Naively, one would think that "what this expands to" is a property of a
709 /// particular macro: macro `m1` returns an item, while macro `m2` returns an
710 /// expression, etc. That's not the case -- macros are polymorphic in the
711 /// result, and can expand to any type of the AST node.
713 /// What defines the actual AST node is the syntactic context of the macro
714 /// invocation. As a contrived example, in `let T![*] = T![*];` the first `T`
715 /// expands to a pattern, while the second one expands to an expression.
717 /// `ExpandTo` captures this bit of information about a particular macro call
719 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
729 pub fn from_call_site(call: &ast::MacroCall) -> ExpandTo {
730 use syntax::SyntaxKind::*;
732 let syn = call.syntax();
734 let parent = match syn.parent() {
736 None => return ExpandTo::Statements,
739 match parent.kind() {
740 MACRO_ITEMS | SOURCE_FILE | ITEM_LIST => ExpandTo::Items,
741 MACRO_STMTS | EXPR_STMT | STMT_LIST => ExpandTo::Statements,
742 MACRO_PAT => ExpandTo::Pattern,
743 MACRO_TYPE => ExpandTo::Type,
745 ARG_LIST | TRY_EXPR | TUPLE_EXPR | PAREN_EXPR | ARRAY_EXPR | FOR_EXPR | PATH_EXPR
746 | CLOSURE_EXPR | CONDITION | BREAK_EXPR | RETURN_EXPR | MATCH_EXPR | MATCH_ARM
747 | MATCH_GUARD | RECORD_EXPR_FIELD | CALL_EXPR | INDEX_EXPR | METHOD_CALL_EXPR
748 | FIELD_EXPR | AWAIT_EXPR | CAST_EXPR | REF_EXPR | PREFIX_EXPR | RANGE_EXPR
749 | BIN_EXPR => ExpandTo::Expr,
751 // FIXME: Handle LHS Pattern
756 // Unknown , Just guess it is `Items`