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Auto merge of #56647 - petrochenkov:dcrate2, r=alexcrichton
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Rework treatment of `$crate` in procedural macros

Important clarification: `$crate` below means "processed `$crate`" or "output `$crate`". In the input of a decl macro `$crate` is just two separate tokens, but in the *output of a decl macro* `$crate` is a single keyword identifier (#55640 (comment)).

First of all, this PR removes the `eliminate_crate_var` hack.
`$crate::foo` is no longer replaced with `::foo` or `::crate_name::foo` in the input of derive proc macros, it's passed to the macro instead with its precise span and hygiene data, and can be treated as any other path segment keyword (like `crate` or `self`) after that. (Note: `eliminate_crate_var` was never used for non-derive proc macros.)

This creates an annoying problem - derive macros still may stringify their input before processing and expect `$crate` survive that stringification and refer to the same crate (the Rust 1.15-1.29 way of doing things).
Moreover, the input of proc macro attributes and derives (but not fn-like proc macros) also effectively survives stringification before being passed to the macro (also for legacy implementation reasons).

So we kind of resurrect the `eliminate_crate_var` hack in reduced form, but apply it only to AST pretty-printing.
If an AST fragment is pretty-printed, the resulting *text* will have `$crate` replaced with `crate` or `::crate_name`. This should be enough to keep all the legacy cases working.

Closes #55640
Closes #56622
r? @ghost
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bors committed Dec 20, 2018
2 parents 4755e2f + edab6c7 commit 9622f9d
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Showing 19 changed files with 487 additions and 189 deletions.
21 changes: 0 additions & 21 deletions src/libproc_macro/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -729,11 +729,6 @@ impl Punct {
/// which can be further configured with the `set_span` method below.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
pub fn new(ch: char, spacing: Spacing) -> Punct {
const LEGAL_CHARS: &[char] = &['=', '<', '>', '!', '~', '+', '-', '*', '/', '%', '^',
'&', '|', '@', '.', ',', ';', ':', '#', '$', '?', '\''];
if !LEGAL_CHARS.contains(&ch) {
panic!("unsupported character `{:?}`", ch)
}
Punct(bridge::client::Punct::new(ch, spacing))
}

Expand Down Expand Up @@ -800,16 +795,6 @@ impl fmt::Debug for Punct {
pub struct Ident(bridge::client::Ident);

impl Ident {
fn is_valid(string: &str) -> bool {
let mut chars = string.chars();
if let Some(start) = chars.next() {
(start == '_' || start.is_xid_start())
&& chars.all(|cont| cont == '_' || cont.is_xid_continue())
} else {
false
}
}

/// Creates a new `Ident` with the given `string` as well as the specified
/// `span`.
/// The `string` argument must be a valid identifier permitted by the
Expand All @@ -831,18 +816,12 @@ impl Ident {
/// tokens, requires a `Span` to be specified at construction.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
pub fn new(string: &str, span: Span) -> Ident {
if !Ident::is_valid(string) {
panic!("`{:?}` is not a valid identifier", string)
}
Ident(bridge::client::Ident::new(string, span.0, false))
}

/// Same as `Ident::new`, but creates a raw identifier (`r#ident`).
#[unstable(feature = "proc_macro_raw_ident", issue = "54723")]
pub fn new_raw(string: &str, span: Span) -> Ident {
if !Ident::is_valid(string) {
panic!("`{:?}` is not a valid identifier", string)
}
Ident(bridge::client::Ident::new(string, span.0, true))
}

Expand Down
9 changes: 3 additions & 6 deletions src/librustc/hir/print.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1622,8 +1622,7 @@ impl<'a> State<'a> {
if i > 0 {
self.s.word("::")?
}
if segment.ident.name != keywords::PathRoot.name() &&
segment.ident.name != keywords::DollarCrate.name() {
if segment.ident.name != keywords::PathRoot.name() {
self.print_ident(segment.ident)?;
segment.with_generic_args(|generic_args| {
self.print_generic_args(generic_args, segment.infer_types,
Expand All @@ -1636,8 +1635,7 @@ impl<'a> State<'a> {
}

pub fn print_path_segment(&mut self, segment: &hir::PathSegment) -> io::Result<()> {
if segment.ident.name != keywords::PathRoot.name() &&
segment.ident.name != keywords::DollarCrate.name() {
if segment.ident.name != keywords::PathRoot.name() {
self.print_ident(segment.ident)?;
segment.with_generic_args(|generic_args| {
self.print_generic_args(generic_args, segment.infer_types, false)
Expand All @@ -1664,8 +1662,7 @@ impl<'a> State<'a> {
if i > 0 {
self.s.word("::")?
}
if segment.ident.name != keywords::PathRoot.name() &&
segment.ident.name != keywords::DollarCrate.name() {
if segment.ident.name != keywords::PathRoot.name() {
self.print_ident(segment.ident)?;
segment.with_generic_args(|generic_args| {
self.print_generic_args(generic_args,
Expand Down
11 changes: 11 additions & 0 deletions src/librustc_resolve/build_reduced_graph.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1035,4 +1035,15 @@ impl<'a, 'b> Visitor<'a> for BuildReducedGraphVisitor<'a, 'b> {
}
visit::walk_attribute(self, attr);
}

fn visit_ident(&mut self, ident: Ident) {
if ident.name == keywords::DollarCrate.name() {
let name = match self.resolver.resolve_crate_root(ident).kind {
ModuleKind::Def(_, name) if name != keywords::Invalid.name() => name,
_ => keywords::Crate.name(),
};
ident.span.ctxt().set_dollar_crate_name(name);
}
visit::walk_ident(self, ident);
}
}
4 changes: 0 additions & 4 deletions src/librustc_resolve/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1173,10 +1173,6 @@ impl<'a> ModuleData<'a> {
}
}

fn is_local(&self) -> bool {
self.normal_ancestor_id.is_local()
}

fn nearest_item_scope(&'a self) -> Module<'a> {
if self.is_trait() { self.parent.unwrap() } else { self }
}
Expand Down
57 changes: 1 addition & 56 deletions src/librustc_resolve/macros.rs
Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@

use {AmbiguityError, AmbiguityKind, AmbiguityErrorMisc};
use {CrateLint, Resolver, ResolutionError, ScopeSet, Weak};
use {Module, ModuleKind, NameBinding, NameBindingKind, PathResult, Segment, ToNameBinding};
use {Module, NameBinding, NameBindingKind, PathResult, Segment, ToNameBinding};
use {is_known_tool, resolve_error};
use ModuleOrUniformRoot;
use Namespace::*;
Expand All @@ -30,8 +30,6 @@ use syntax::ext::expand::{AstFragment, Invocation, InvocationKind};
use syntax::ext::hygiene::{self, Mark};
use syntax::ext::tt::macro_rules;
use syntax::feature_gate::{feature_err, is_builtin_attr_name, GateIssue};
use syntax::fold::{self, Folder};
use syntax::ptr::P;
use syntax::symbol::{Symbol, keywords};
use syntax::util::lev_distance::find_best_match_for_name;
use syntax_pos::{Span, DUMMY_SP};
Expand Down Expand Up @@ -138,58 +136,6 @@ impl<'a> base::Resolver for Resolver<'a> {
mark
}

fn eliminate_crate_var(&mut self, item: P<ast::Item>) -> P<ast::Item> {
struct EliminateCrateVar<'b, 'a: 'b>(
&'b mut Resolver<'a>, Span
);

impl<'a, 'b> Folder for EliminateCrateVar<'a, 'b> {
fn fold_path(&mut self, path: ast::Path) -> ast::Path {
match self.fold_qpath(None, path) {
(None, path) => path,
_ => unreachable!(),
}
}

fn fold_qpath(&mut self, mut qself: Option<ast::QSelf>, mut path: ast::Path)
-> (Option<ast::QSelf>, ast::Path) {
qself = qself.map(|ast::QSelf { ty, path_span, position }| {
ast::QSelf {
ty: self.fold_ty(ty),
path_span: self.new_span(path_span),
position,
}
});

if path.segments[0].ident.name == keywords::DollarCrate.name() {
let module = self.0.resolve_crate_root(path.segments[0].ident);
path.segments[0].ident.name = keywords::PathRoot.name();
if !module.is_local() {
let span = path.segments[0].ident.span;
path.segments.insert(1, match module.kind {
ModuleKind::Def(_, name) => ast::PathSegment::from_ident(
ast::Ident::with_empty_ctxt(name).with_span_pos(span)
),
_ => unreachable!(),
});
if let Some(qself) = &mut qself {
qself.position += 1;
}
}
}
(qself, path)
}

fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
fold::noop_fold_mac(mac, self)
}
}

let ret = EliminateCrateVar(self, item.span).fold_item(item);
assert!(ret.len() == 1);
ret.into_iter().next().unwrap()
}

fn visit_ast_fragment_with_placeholders(&mut self, mark: Mark, fragment: &AstFragment,
derives: &[Mark]) {
let invocation = self.invocations[&mark];
Expand Down Expand Up @@ -259,7 +205,6 @@ impl<'a> base::Resolver for Resolver<'a> {
self.definitions.add_parent_module_of_macro_def(invoc.expansion_data.mark,
normal_module_def_id);
invoc.expansion_data.mark.set_default_transparency(ext.default_transparency());
invoc.expansion_data.mark.set_is_builtin(def_id.krate == CrateNum::BuiltinMacros);
}

Ok(Some(ext))
Expand Down
2 changes: 0 additions & 2 deletions src/libsyntax/ext/base.rs
Original file line number Diff line number Diff line change
Expand Up @@ -732,7 +732,6 @@ pub type NamedSyntaxExtension = (Name, SyntaxExtension);
pub trait Resolver {
fn next_node_id(&mut self) -> ast::NodeId;
fn get_module_scope(&mut self, id: ast::NodeId) -> Mark;
fn eliminate_crate_var(&mut self, item: P<ast::Item>) -> P<ast::Item>;

fn visit_ast_fragment_with_placeholders(&mut self, mark: Mark, fragment: &AstFragment,
derives: &[Mark]);
Expand Down Expand Up @@ -766,7 +765,6 @@ pub struct DummyResolver;
impl Resolver for DummyResolver {
fn next_node_id(&mut self) -> ast::NodeId { ast::DUMMY_NODE_ID }
fn get_module_scope(&mut self, _id: ast::NodeId) -> Mark { Mark::root() }
fn eliminate_crate_var(&mut self, item: P<ast::Item>) -> P<ast::Item> { item }

fn visit_ast_fragment_with_placeholders(&mut self, _invoc: Mark, _fragment: &AstFragment,
_derives: &[Mark]) {}
Expand Down
5 changes: 1 addition & 4 deletions src/libsyntax/ext/expand.rs
Original file line number Diff line number Diff line change
Expand Up @@ -203,10 +203,7 @@ fn macro_bang_format(path: &ast::Path) -> ExpnFormat {
if i != 0 {
path_str.push_str("::");
}

if segment.ident.name != keywords::PathRoot.name() &&
segment.ident.name != keywords::DollarCrate.name()
{
if segment.ident.name != keywords::PathRoot.name() {
path_str.push_str(&segment.ident.as_str())
}
}
Expand Down
4 changes: 3 additions & 1 deletion src/libsyntax/parse/token.rs
Original file line number Diff line number Diff line change
Expand Up @@ -633,7 +633,9 @@ impl Token {
(&Shebang(a), &Shebang(b)) => a == b,

(&Lifetime(a), &Lifetime(b)) => a.name == b.name,
(&Ident(a, b), &Ident(c, d)) => a.name == c.name && b == d,
(&Ident(a, b), &Ident(c, d)) => b == d && (a.name == c.name ||
a.name == keywords::DollarCrate.name() ||
c.name == keywords::DollarCrate.name()),

(&Literal(ref a, b), &Literal(ref c, d)) => {
b == d && a.probably_equal_for_proc_macro(c)
Expand Down
46 changes: 24 additions & 22 deletions src/libsyntax/print/pprust.rs
Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,6 @@ use util::parser::{self, AssocOp, Fixity};
use attr;
use source_map::{self, SourceMap, Spanned};
use syntax_pos::{self, BytePos};
use syntax_pos::hygiene::{Mark, SyntaxContext};
use parse::token::{self, BinOpToken, Token};
use parse::lexer::comments;
use parse::{self, ParseSess};
Expand Down Expand Up @@ -724,12 +723,12 @@ pub trait PrintState<'a> {
if i > 0 {
self.writer().word("::")?
}
if segment.ident.name != keywords::PathRoot.name() &&
segment.ident.name != keywords::DollarCrate.name()
{
self.writer().word(segment.ident.as_str().get())?;
} else if segment.ident.name == keywords::DollarCrate.name() {
self.print_dollar_crate(segment.ident.span.ctxt())?;
if segment.ident.name != keywords::PathRoot.name() {
if segment.ident.name == keywords::DollarCrate.name() {
self.print_dollar_crate(segment.ident)?;
} else {
self.writer().word(segment.ident.as_str().get())?;
}
}
}
Ok(())
Expand Down Expand Up @@ -843,17 +842,19 @@ pub trait PrintState<'a> {

fn nbsp(&mut self) -> io::Result<()> { self.writer().word(" ") }

fn print_dollar_crate(&mut self, mut ctxt: SyntaxContext) -> io::Result<()> {
if let Some(mark) = ctxt.adjust(Mark::root()) {
// Make a best effort to print something that complies
if mark.is_builtin() {
if let Some(name) = std_inject::injected_crate_name() {
self.writer().word("::")?;
self.writer().word(name)?;
}
}
// AST pretty-printer is used as a fallback for turning AST structures into token streams for
// proc macros. Additionally, proc macros may stringify their input and expect it survive the
// stringification (especially true for proc macro derives written between Rust 1.15 and 1.30).
// So we need to somehow pretty-print `$crate` in paths in a way preserving at least some of
// its hygiene data, most importantly name of the crate it refers to.
// As a result we print `$crate` as `crate` if it refers to the local crate
// and as `::other_crate_name` if it refers to some other crate.
fn print_dollar_crate(&mut self, ident: ast::Ident) -> io::Result<()> {
let name = ident.span.ctxt().dollar_crate_name();
if !ast::Ident::with_empty_ctxt(name).is_path_segment_keyword() {
self.writer().word("::")?;
}
Ok(())
self.writer().word(name.as_str().get())
}
}

Expand Down Expand Up @@ -2463,14 +2464,15 @@ impl<'a> State<'a> {
colons_before_params: bool)
-> io::Result<()>
{
if segment.ident.name != keywords::PathRoot.name() &&
segment.ident.name != keywords::DollarCrate.name() {
self.print_ident(segment.ident)?;
if segment.ident.name != keywords::PathRoot.name() {
if segment.ident.name == keywords::DollarCrate.name() {
self.print_dollar_crate(segment.ident)?;
} else {
self.print_ident(segment.ident)?;
}
if let Some(ref args) = segment.args {
self.print_generic_args(args, colons_before_params)?;
}
} else if segment.ident.name == keywords::DollarCrate.name() {
self.print_dollar_crate(segment.ident.span.ctxt())?;
}
Ok(())
}
Expand Down
4 changes: 3 additions & 1 deletion src/libsyntax/tokenstream.rs
Original file line number Diff line number Diff line change
Expand Up @@ -348,7 +348,9 @@ impl TokenStream {
| TokenTree::Token(_, Token::Semi)
// The pretty printer collapses whitespace arbitrarily and can
// introduce whitespace from `NoDelim`.
| TokenTree::Token(_, Token::Whitespace) => false,
| TokenTree::Token(_, Token::Whitespace)
// The pretty printer can turn `$crate` into `::crate_name`
| TokenTree::Token(_, Token::ModSep) => false,
_ => true
}
}
Expand Down
1 change: 0 additions & 1 deletion src/libsyntax_ext/deriving/custom.rs
Original file line number Diff line number Diff line change
Expand Up @@ -74,7 +74,6 @@ impl MultiItemModifier for ProcMacroDerive {
// Mark attributes as known, and used.
MarkAttrs(&self.attrs).visit_item(&item);

let item = ecx.resolver.eliminate_crate_var(item);
let token = Token::interpolated(token::NtItem(item));
let input = tokenstream::TokenTree::Token(DUMMY_SP, token).into();

Expand Down
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