//! Machinery for hygienic macros, inspired by the `MTWT[1]` paper.
//!
//! `[1]` Matthew Flatt, Ryan Culpepper, David Darais, and Robert Bruce Findler. 2012.
//! *Macros that work together: Compile-time bindings, partial expansion,
//! and definition contexts*. J. Funct. Program. 22, 2 (March 2012), 181-216.
//! DOI=10.1017/S0956796812000093 <https://doi.org/10.1017/S0956796812000093>
// Hygiene data is stored in a global variable and accessed via TLS, which
// means that accesses are somewhat expensive. (`HygieneData::with`
// encapsulates a single access.) Therefore, on hot code paths it is worth
// ensuring that multiple HygieneData accesses are combined into a single
// `HygieneData::with`.
//
// This explains why `HygieneData`, `SyntaxContext` and `ExpnId` have interfaces
// with a certain amount of redundancy in them. For example,
// `SyntaxContext::outer_expn_data` combines `SyntaxContext::outer` and
// `ExpnId::expn_data` so that two `HygieneData` accesses can be performed within
// a single `HygieneData::with` call.
//
// It also explains why many functions appear in `HygieneData` and again in
// `SyntaxContext` or `ExpnId`. For example, `HygieneData::outer` and
// `SyntaxContext::outer` do the same thing, but the former is for use within a
// `HygieneData::with` call while the latter is for use outside such a call.
// When modifying this file it is important to understand this distinction,
// because getting it wrong can lead to nested `HygieneData::with` calls that
// trigger runtime aborts. (Fortunately these are obvious and easy to fix.)
use crate::GLOBALS;
use crate::{Span, DUMMY_SP};
use crate::edition::Edition;
use crate::symbol::{kw, Symbol};
use rustc_serialize::{Encodable, Decodable, Encoder, Decoder};
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::sync::Lrc;
use std::fmt;
/// A `SyntaxContext` represents a chain of pairs `(ExpnId, Transparency)` named "marks".
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct SyntaxContext(u32);
#[derive(Debug)]
struct SyntaxContextData {
outer_expn: ExpnId,
outer_transparency: Transparency,
parent: SyntaxContext,
/// This context, but with all transparent and semi-transparent expansions filtered away.
opaque: SyntaxContext,
/// This context, but with all transparent expansions filtered away.
opaque_and_semitransparent: SyntaxContext,
/// Name of the crate to which `$crate` with this context would resolve.
dollar_crate_name: Symbol,
}
/// A unique ID associated with a macro invocation and expansion.
#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
pub struct ExpnId(u32);
/// A property of a macro expansion that determines how identifiers
/// produced by that expansion are resolved.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Hash, Debug, RustcEncodable, RustcDecodable)]
pub enum Transparency {
/// Identifier produced by a transparent expansion is always resolved at call-site.
/// Call-site spans in procedural macros, hygiene opt-out in `macro` should use this.
Transparent,
/// Identifier produced by a semi-transparent expansion may be resolved
/// either at call-site or at definition-site.
/// If it's a local variable, label or `$crate` then it's resolved at def-site.
/// Otherwise it's resolved at call-site.
/// `macro_rules` macros behave like this, built-in macros currently behave like this too,
/// but that's an implementation detail.
SemiTransparent,
/// Identifier produced by an opaque expansion is always resolved at definition-site.
/// Def-site spans in procedural macros, identifiers from `macro` by default use this.
Opaque,
}
impl ExpnId {
pub fn fresh(expn_data: Option<ExpnData>) -> Self {
HygieneData::with(|data| data.fresh_expn(expn_data))
}
/// The ID of the theoretical expansion that generates freshly parsed, unexpanded AST.
#[inline]
pub fn root() -> Self {
ExpnId(0)
}
#[inline]
pub fn as_u32(self) -> u32 {
self.0
}
#[inline]
pub fn from_u32(raw: u32) -> ExpnId {
ExpnId(raw)
}
#[inline]
pub fn expn_data(self) -> ExpnData {
HygieneData::with(|data| data.expn_data(self).clone())
}
#[inline]
pub fn set_expn_data(self, expn_data: ExpnData) {
HygieneData::with(|data| {
let old_expn_data = &mut data.expn_data[self.0 as usize];
assert!(old_expn_data.is_none(), "expansion data is reset for an expansion ID");
*old_expn_data = Some(expn_data);
})
}
pub fn is_descendant_of(self, ancestor: ExpnId) -> bool {
HygieneData::with(|data| data.is_descendant_of(self, ancestor))
}
/// `expn_id.outer_expn_is_descendant_of(ctxt)` is equivalent to but faster than
/// `expn_id.is_descendant_of(ctxt.outer_expn())`.
pub fn outer_expn_is_descendant_of(self, ctxt: SyntaxContext) -> bool {
HygieneData::with(|data| data.is_descendant_of(self, data.outer_expn(ctxt)))
}
}
#[derive(Debug)]
crate struct HygieneData {
/// Each expansion should have an associated expansion data, but sometimes there's a delay
/// between creation of an expansion ID and obtaining its data (e.g. macros are collected
/// first and then resolved later), so we use an `Option` here.
expn_data: Vec<Option<ExpnData>>,
syntax_context_data: Vec<SyntaxContextData>,
syntax_context_map: FxHashMap<(SyntaxContext, ExpnId, Transparency), SyntaxContext>,
}
impl HygieneData {
crate fn new(edition: Edition) -> Self {
HygieneData {
expn_data: vec![Some(ExpnData::default(ExpnKind::Root, DUMMY_SP, edition))],
syntax_context_data: vec![SyntaxContextData {
outer_expn: ExpnId::root(),
outer_transparency: Transparency::Opaque,
parent: SyntaxContext(0),
opaque: SyntaxContext(0),
opaque_and_semitransparent: SyntaxContext(0),
dollar_crate_name: kw::DollarCrate,
}],
syntax_context_map: FxHashMap::default(),
}
}
fn with<T, F: FnOnce(&mut HygieneData) -> T>(f: F) -> T {
GLOBALS.with(|globals| f(&mut *globals.hygiene_data.borrow_mut()))
}
fn fresh_expn(&mut self, expn_data: Option<ExpnData>) -> ExpnId {
self.expn_data.push(expn_data);
ExpnId(self.expn_data.len() as u32 - 1)
}
fn expn_data(&self, expn_id: ExpnId) -> &ExpnData {
self.expn_data[expn_id.0 as usize].as_ref()
.expect("no expansion data for an expansion ID")
}
fn is_descendant_of(&self, mut expn_id: ExpnId, ancestor: ExpnId) -> bool {
while expn_id != ancestor {
if expn_id == ExpnId::root() {
return false;
}
expn_id = self.expn_data(expn_id).parent;
}
true
}
fn modern(&self, ctxt: SyntaxContext) -> SyntaxContext {
self.syntax_context_data[ctxt.0 as usize].opaque
}
fn modern_and_legacy(&self, ctxt: SyntaxContext) -> SyntaxContext {
self.syntax_context_data[ctxt.0 as usize].opaque_and_semitransparent
}
fn outer_expn(&self, ctxt: SyntaxContext) -> ExpnId {
self.syntax_context_data[ctxt.0 as usize].outer_expn
}
fn outer_mark(&self, ctxt: SyntaxContext) -> (ExpnId, Transparency) {
let data = &self.syntax_context_data[ctxt.0 as usize];
(data.outer_expn, data.outer_transparency)
}
fn parent_ctxt(&self, ctxt: SyntaxContext) -> SyntaxContext {
self.syntax_context_data[ctxt.0 as usize].parent
}
fn remove_mark(&self, ctxt: &mut SyntaxContext) -> (ExpnId, Transparency) {
let outer_mark = self.outer_mark(*ctxt);
*ctxt = self.parent_ctxt(*ctxt);
outer_mark
}
fn marks(&self, mut ctxt: SyntaxContext) -> Vec<(ExpnId, Transparency)> {
let mut marks = Vec::new();
while ctxt != SyntaxContext::root() {
marks.push(self.outer_mark(ctxt));
ctxt = self.parent_ctxt(ctxt);
}
marks.reverse();
marks
}
fn walk_chain(&self, mut span: Span, to: SyntaxContext) -> Span {
while span.from_expansion() && span.ctxt() != to {
span = self.expn_data(self.outer_expn(span.ctxt())).call_site;
}
span
}
fn adjust(&self, ctxt: &mut SyntaxContext, expn_id: ExpnId) -> Option<ExpnId> {
let mut scope = None;
while !self.is_descendant_of(expn_id, self.outer_expn(*ctxt)) {
scope = Some(self.remove_mark(ctxt).0);
}
scope
}
fn apply_mark(
&mut self, ctxt: SyntaxContext, expn_id: ExpnId, transparency: Transparency
) -> SyntaxContext {
assert_ne!(expn_id, ExpnId::root());
if transparency == Transparency::Opaque {
return self.apply_mark_internal(ctxt, expn_id, transparency);
}
let call_site_ctxt = self.expn_data(expn_id).call_site.ctxt();
let mut call_site_ctxt = if transparency == Transparency::SemiTransparent {
self.modern(call_site_ctxt)
} else {
self.modern_and_legacy(call_site_ctxt)
};
if call_site_ctxt == SyntaxContext::root() {
return self.apply_mark_internal(ctxt, expn_id, transparency);
}
// Otherwise, `expn_id` is a macros 1.0 definition and the call site is in a
// macros 2.0 expansion, i.e., a macros 1.0 invocation is in a macros 2.0 definition.
//
// In this case, the tokens from the macros 1.0 definition inherit the hygiene
// at their invocation. That is, we pretend that the macros 1.0 definition
// was defined at its invocation (i.e., inside the macros 2.0 definition)
// so that the macros 2.0 definition remains hygienic.
//
// See the example at `test/ui/hygiene/legacy_interaction.rs`.
for (expn_id, transparency) in self.marks(ctxt) {
call_site_ctxt = self.apply_mark_internal(call_site_ctxt, expn_id, transparency);
}
self.apply_mark_internal(call_site_ctxt, expn_id, transparency)
}
fn apply_mark_internal(
&mut self, ctxt: SyntaxContext, expn_id: ExpnId, transparency: Transparency
) -> SyntaxContext {
let syntax_context_data = &mut self.syntax_context_data;
let mut opaque = syntax_context_data[ctxt.0 as usize].opaque;
let mut opaque_and_semitransparent =
syntax_context_data[ctxt.0 as usize].opaque_and_semitransparent;
if transparency >= Transparency::Opaque {
let parent = opaque;
opaque = *self.syntax_context_map.entry((parent, expn_id, transparency))
.or_insert_with(|| {
let new_opaque = SyntaxContext(syntax_context_data.len() as u32);
syntax_context_data.push(SyntaxContextData {
outer_expn: expn_id,
outer_transparency: transparency,
parent,
opaque: new_opaque,
opaque_and_semitransparent: new_opaque,
dollar_crate_name: kw::DollarCrate,
});
new_opaque
});
}
if transparency >= Transparency::SemiTransparent {
let parent = opaque_and_semitransparent;
opaque_and_semitransparent =
*self.syntax_context_map.entry((parent, expn_id, transparency))
.or_insert_with(|| {
let new_opaque_and_semitransparent =
SyntaxContext(syntax_context_data.len() as u32);
syntax_context_data.push(SyntaxContextData {
outer_expn: expn_id,
outer_transparency: transparency,
parent,
opaque,
opaque_and_semitransparent: new_opaque_and_semitransparent,
dollar_crate_name: kw::DollarCrate,
});
new_opaque_and_semitransparent
});
}
let parent = ctxt;
*self.syntax_context_map.entry((parent, expn_id, transparency)).or_insert_with(|| {
let new_opaque_and_semitransparent_and_transparent =
SyntaxContext(syntax_context_data.len() as u32);
syntax_context_data.push(SyntaxContextData {
outer_expn: expn_id,
outer_transparency: transparency,
parent,
opaque,
opaque_and_semitransparent,
dollar_crate_name: kw::DollarCrate,
});
new_opaque_and_semitransparent_and_transparent
})
}
}
pub fn clear_syntax_context_map() {
HygieneData::with(|data| data.syntax_context_map = FxHashMap::default());
}
pub fn walk_chain(span: Span, to: SyntaxContext) -> Span {
HygieneData::with(|data| data.walk_chain(span, to))
}
pub fn update_dollar_crate_names(mut get_name: impl FnMut(SyntaxContext) -> Symbol) {
// The new contexts that need updating are at the end of the list and have `$crate` as a name.
let (len, to_update) = HygieneData::with(|data| (
data.syntax_context_data.len(),
data.syntax_context_data.iter().rev()
.take_while(|scdata| scdata.dollar_crate_name == kw::DollarCrate).count()
));
// The callback must be called from outside of the `HygieneData` lock,
// since it will try to acquire it too.
let range_to_update = len - to_update .. len;
let names: Vec<_> =
range_to_update.clone().map(|idx| get_name(SyntaxContext::from_u32(idx as u32))).collect();
HygieneData::with(|data| range_to_update.zip(names.into_iter()).for_each(|(idx, name)| {
data.syntax_context_data[idx].dollar_crate_name = name;
}))
}
impl SyntaxContext {
#[inline]
pub const fn root() -> Self {
SyntaxContext(0)
}
#[inline]
crate fn as_u32(self) -> u32 {
self.0
}
#[inline]
crate fn from_u32(raw: u32) -> SyntaxContext {
SyntaxContext(raw)
}
/// Extend a syntax context with a given expansion and transparency.
crate fn apply_mark(self, expn_id: ExpnId, transparency: Transparency) -> SyntaxContext {
HygieneData::with(|data| data.apply_mark(self, expn_id, transparency))
}
/// Pulls a single mark off of the syntax context. This effectively moves the
/// context up one macro definition level. That is, if we have a nested macro
/// definition as follows:
///
/// ```rust
/// macro_rules! f {
/// macro_rules! g {
/// ...
/// }
/// }
/// ```
///
/// and we have a SyntaxContext that is referring to something declared by an invocation
/// of g (call it g1), calling remove_mark will result in the SyntaxContext for the
/// invocation of f that created g1.
/// Returns the mark that was removed.
pub fn remove_mark(&mut self) -> ExpnId {
HygieneData::with(|data| data.remove_mark(self).0)
}
pub fn marks(self) -> Vec<(ExpnId, Transparency)> {
HygieneData::with(|data| data.marks(self))
}
/// Adjust this context for resolution in a scope created by the given expansion.
/// For example, consider the following three resolutions of `f`:
///
/// ```rust
/// mod foo { pub fn f() {} } // `f`'s `SyntaxContext` is empty.
/// m!(f);
/// macro m($f:ident) {
/// mod bar {
/// pub fn f() {} // `f`'s `SyntaxContext` has a single `ExpnId` from `m`.
/// pub fn $f() {} // `$f`'s `SyntaxContext` is empty.
/// }
/// foo::f(); // `f`'s `SyntaxContext` has a single `ExpnId` from `m`
/// //^ Since `mod foo` is outside this expansion, `adjust` removes the mark from `f`,
/// //| and it resolves to `::foo::f`.
/// bar::f(); // `f`'s `SyntaxContext` has a single `ExpnId` from `m`
/// //^ Since `mod bar` not outside this expansion, `adjust` does not change `f`,
/// //| and it resolves to `::bar::f`.
/// bar::$f(); // `f`'s `SyntaxContext` is empty.
/// //^ Since `mod bar` is not outside this expansion, `adjust` does not change `$f`,
/// //| and it resolves to `::bar::$f`.
/// }
/// ```
/// This returns the expansion whose definition scope we use to privacy check the resolution,
/// or `None` if we privacy check as usual (i.e., not w.r.t. a macro definition scope).
pub fn adjust(&mut self, expn_id: ExpnId) -> Option<ExpnId> {
HygieneData::with(|data| data.adjust(self, expn_id))
}
/// Like `SyntaxContext::adjust`, but also modernizes `self`.
pub fn modernize_and_adjust(&mut self, expn_id: ExpnId) -> Option<ExpnId> {
HygieneData::with(|data| {
*self = data.modern(*self);
data.adjust(self, expn_id)
})
}
/// Adjust this context for resolution in a scope created by the given expansion
/// via a glob import with the given `SyntaxContext`.
/// For example:
///
/// ```rust
/// m!(f);
/// macro m($i:ident) {
/// mod foo {
/// pub fn f() {} // `f`'s `SyntaxContext` has a single `ExpnId` from `m`.
/// pub fn $i() {} // `$i`'s `SyntaxContext` is empty.
/// }
/// n(f);
/// macro n($j:ident) {
/// use foo::*;
/// f(); // `f`'s `SyntaxContext` has a mark from `m` and a mark from `n`
/// //^ `glob_adjust` removes the mark from `n`, so this resolves to `foo::f`.
/// $i(); // `$i`'s `SyntaxContext` has a mark from `n`
/// //^ `glob_adjust` removes the mark from `n`, so this resolves to `foo::$i`.
/// $j(); // `$j`'s `SyntaxContext` has a mark from `m`
/// //^ This cannot be glob-adjusted, so this is a resolution error.
/// }
/// }
/// ```
/// This returns `None` if the context cannot be glob-adjusted.
/// Otherwise, it returns the scope to use when privacy checking (see `adjust` for details).
pub fn glob_adjust(&mut self, expn_id: ExpnId, glob_span: Span) -> Option<Option<ExpnId>> {
HygieneData::with(|data| {
let mut scope = None;
let mut glob_ctxt = data.modern(glob_span.ctxt());
while !data.is_descendant_of(expn_id, data.outer_expn(glob_ctxt)) {
scope = Some(data.remove_mark(&mut glob_ctxt).0);
if data.remove_mark(self).0 != scope.unwrap() {
return None;
}
}
if data.adjust(self, expn_id).is_some() {
return None;
}
Some(scope)
})
}
/// Undo `glob_adjust` if possible:
///
/// ```rust
/// if let Some(privacy_checking_scope) = self.reverse_glob_adjust(expansion, glob_ctxt) {
/// assert!(self.glob_adjust(expansion, glob_ctxt) == Some(privacy_checking_scope));
/// }
/// ```
pub fn reverse_glob_adjust(&mut self, expn_id: ExpnId, glob_span: Span)
-> Option<Option<ExpnId>> {
HygieneData::with(|data| {
if data.adjust(self, expn_id).is_some() {
return None;
}
let mut glob_ctxt = data.modern(glob_span.ctxt());
let mut marks = Vec::new();
while !data.is_descendant_of(expn_id, data.outer_expn(glob_ctxt)) {
marks.push(data.remove_mark(&mut glob_ctxt));
}
let scope = marks.last().map(|mark| mark.0);
while let Some((expn_id, transparency)) = marks.pop() {
*self = data.apply_mark(*self, expn_id, transparency);
}
Some(scope)
})
}
pub fn hygienic_eq(self, other: SyntaxContext, expn_id: ExpnId) -> bool {
HygieneData::with(|data| {
let mut self_modern = data.modern(self);
data.adjust(&mut self_modern, expn_id);
self_modern == data.modern(other)
})
}
#[inline]
pub fn modern(self) -> SyntaxContext {
HygieneData::with(|data| data.modern(self))
}
#[inline]
pub fn modern_and_legacy(self) -> SyntaxContext {
HygieneData::with(|data| data.modern_and_legacy(self))
}
#[inline]
pub fn outer_expn(self) -> ExpnId {
HygieneData::with(|data| data.outer_expn(self))
}
/// `ctxt.outer_expn_data()` is equivalent to but faster than
/// `ctxt.outer_expn().expn_data()`.
#[inline]
pub fn outer_expn_data(self) -> ExpnData {
HygieneData::with(|data| data.expn_data(data.outer_expn(self)).clone())
}
#[inline]
pub fn outer_mark_with_data(self) -> (ExpnId, Transparency, ExpnData) {
HygieneData::with(|data| {
let (expn_id, transparency) = data.outer_mark(self);
(expn_id, transparency, data.expn_data(expn_id).clone())
})
}
pub fn dollar_crate_name(self) -> Symbol {
HygieneData::with(|data| data.syntax_context_data[self.0 as usize].dollar_crate_name)
}
}
impl fmt::Debug for SyntaxContext {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "#{}", self.0)
}
}
impl Span {
/// Creates a fresh expansion with given properties.
/// Expansions are normally created by macros, but in some cases expansions are created for
/// other compiler-generated code to set per-span properties like allowed unstable features.
/// The returned span belongs to the created expansion and has the new properties,
/// but its location is inherited from the current span.
pub fn fresh_expansion(self, expn_data: ExpnData) -> Span {
self.fresh_expansion_with_transparency(expn_data, Transparency::Transparent)
}
pub fn fresh_expansion_with_transparency(
self, expn_data: ExpnData, transparency: Transparency
) -> Span {
HygieneData::with(|data| {
let expn_id = data.fresh_expn(Some(expn_data));
self.with_ctxt(data.apply_mark(SyntaxContext::root(), expn_id, transparency))
})
}
}
/// A subset of properties from both macro definition and macro call available through global data.
/// Avoid using this if you have access to the original definition or call structures.
#[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
pub struct ExpnData {
// --- The part unique to each expansion.
/// The kind of this expansion - macro or compiler desugaring.
pub kind: ExpnKind,
/// The expansion that produced this expansion.
pub parent: ExpnId,
/// The location of the actual macro invocation or syntax sugar , e.g.
/// `let x = foo!();` or `if let Some(y) = x {}`
///
/// This may recursively refer to other macro invocations, e.g., if
/// `foo!()` invoked `bar!()` internally, and there was an
/// expression inside `bar!`; the call_site of the expression in
/// the expansion would point to the `bar!` invocation; that
/// call_site span would have its own ExpnData, with the call_site
/// pointing to the `foo!` invocation.
pub call_site: Span,
// --- The part specific to the macro/desugaring definition.
// --- It may be reasonable to share this part between expansions with the same definition,
// --- but such sharing is known to bring some minor inconveniences without also bringing
// --- noticeable perf improvements (PR #62898).
/// The span of the macro definition (possibly dummy).
/// This span serves only informational purpose and is not used for resolution.
pub def_site: Span,
/// List of #[unstable]/feature-gated features that the macro is allowed to use
/// internally without forcing the whole crate to opt-in
/// to them.
pub allow_internal_unstable: Option<Lrc<[Symbol]>>,
/// Whether the macro is allowed to use `unsafe` internally
/// even if the user crate has `#![forbid(unsafe_code)]`.
pub allow_internal_unsafe: bool,
/// Enables the macro helper hack (`ident!(...)` -> `$crate::ident!(...)`)
/// for a given macro.
pub local_inner_macros: bool,
/// Edition of the crate in which the macro is defined.
pub edition: Edition,
}
impl ExpnData {
/// Constructs expansion data with default properties.
pub fn default(kind: ExpnKind, call_site: Span, edition: Edition) -> ExpnData {
ExpnData {
kind,
parent: ExpnId::root(),
call_site,
def_site: DUMMY_SP,
allow_internal_unstable: None,
allow_internal_unsafe: false,
local_inner_macros: false,
edition,
}
}
pub fn allow_unstable(kind: ExpnKind, call_site: Span, edition: Edition,
allow_internal_unstable: Lrc<[Symbol]>) -> ExpnData {
ExpnData {
allow_internal_unstable: Some(allow_internal_unstable),
..ExpnData::default(kind, call_site, edition)
}
}
#[inline]
pub fn is_root(&self) -> bool {
if let ExpnKind::Root = self.kind { true } else { false }
}
}
/// Expansion kind.
#[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
pub enum ExpnKind {
/// No expansion, aka root expansion. Only `ExpnId::root()` has this kind.
Root,
/// Expansion produced by a macro.
Macro(MacroKind, Symbol),
/// Transform done by the compiler on the AST.
AstPass(AstPass),
/// Desugaring done by the compiler during HIR lowering.
Desugaring(DesugaringKind)
}
impl ExpnKind {
pub fn descr(&self) -> Symbol {
match *self {
ExpnKind::Root => kw::PathRoot,
ExpnKind::Macro(_, descr) => descr,
ExpnKind::AstPass(kind) => Symbol::intern(kind.descr()),
ExpnKind::Desugaring(kind) => Symbol::intern(kind.descr()),
}
}
}
/// The kind of macro invocation or definition.
#[derive(Clone, Copy, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
pub enum MacroKind {
/// A bang macro `foo!()`.
Bang,
/// An attribute macro `#[foo]`.
Attr,
/// A derive macro `#[derive(Foo)]`
Derive,
}
impl MacroKind {
pub fn descr(self) -> &'static str {
match self {
MacroKind::Bang => "macro",
MacroKind::Attr => "attribute macro",
MacroKind::Derive => "derive macro",
}
}
pub fn article(self) -> &'static str {
match self {
MacroKind::Attr => "an",
_ => "a",
}
}
}
/// The kind of AST transform.
#[derive(Clone, Copy, PartialEq, Debug, RustcEncodable, RustcDecodable)]
pub enum AstPass {
StdImports,
TestHarness,
ProcMacroHarness,
PluginMacroDefs,
}
impl AstPass {
fn descr(self) -> &'static str {
match self {
AstPass::StdImports => "standard library imports",
AstPass::TestHarness => "test harness",
AstPass::ProcMacroHarness => "proc macro harness",
AstPass::PluginMacroDefs => "plugin macro definitions",
}
}
}
/// The kind of compiler desugaring.
#[derive(Clone, Copy, PartialEq, Debug, RustcEncodable, RustcDecodable)]
pub enum DesugaringKind {
/// We desugar `if c { i } else { e }` to `match $ExprKind::Use(c) { true => i, _ => e }`.
/// However, we do not want to blame `c` for unreachability but rather say that `i`
/// is unreachable. This desugaring kind allows us to avoid blaming `c`.
/// This also applies to `while` loops.
CondTemporary,
QuestionMark,
TryBlock,
/// Desugaring of an `impl Trait` in return type position
/// to an `type Foo = impl Trait;` and replacing the
/// `impl Trait` with `Foo`.
OpaqueTy,
Async,
Await,
ForLoop,
}
impl DesugaringKind {
/// The description wording should combine well with "desugaring of {}".
fn descr(self) -> &'static str {
match self {
DesugaringKind::CondTemporary => "`if` or `while` condition",
DesugaringKind::Async => "`async` block or function",
DesugaringKind::Await => "`await` expression",
DesugaringKind::QuestionMark => "operator `?`",
DesugaringKind::TryBlock => "`try` block",
DesugaringKind::OpaqueTy => "`impl Trait`",
DesugaringKind::ForLoop => "`for` loop",
}
}
}
impl Encodable for ExpnId {
fn encode<E: Encoder>(&self, _: &mut E) -> Result<(), E::Error> {
Ok(()) // FIXME(jseyfried) intercrate hygiene
}
}
impl Decodable for ExpnId {
fn decode<D: Decoder>(_: &mut D) -> Result<Self, D::Error> {
Ok(ExpnId::root()) // FIXME(jseyfried) intercrate hygiene
}
}