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Auto merge of #46551 - jseyfried:improve_legacy_modern_macro_interact…
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…ion, r=nrc

macros: improve 1.0/2.0 interaction

This PR supports using unhygienic macros from hygienic macros without breaking the latter's hygiene.
```rust
// crate A:
#[macro_export]
macro_rules! m1 { () => {
    f(); // unhygienic: this macro needs `f` in its environment
    fn g() {} // (1) unhygienic: `g` is usable outside the macro definition
} }

// crate B:
#![feature(decl_macro)]
extern crate A;
use A::m1;

macro m2() {
    fn f() {} // (2)
    m1!(); // After this PR, `f()` in the expansion resolves to (2), not (3)
    g(); // After this PR, this resolves to `fn g() {}` from the above expansion.
         // Today, it is a resolution error.
}

fn test() {
    fn f() {} // (3)
    m2!(); // Today, `m2!()` can see (3) even though it should be hygienic.
    fn g() {} // Today, this conflicts with `fn g() {}` from the expansion, even though it should be hygienic.
}
```

Once this PR lands, you can make an existing unhygienic macro hygienic by wrapping it in a hygienic macro. There is an [example](b766fa8) of this in the tests.

r? @nrc
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bors committed Jan 12, 2018
2 parents 73ac5d6 + b766fa8 commit 0b90e4e
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Showing 11 changed files with 217 additions and 9 deletions.
2 changes: 1 addition & 1 deletion src/libproc_macro/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -95,7 +95,7 @@ impl FromStr for TokenStream {
// notify the expansion info that it is unhygienic
let mark = Mark::fresh(mark);
mark.set_expn_info(expn_info);
let span = call_site.with_ctxt(call_site.ctxt().apply_mark(mark));
let span = call_site.with_ctxt(SyntaxContext::empty().apply_mark(mark));
let stream = parse::parse_stream_from_source_str(name, src, sess, Some(span));
Ok(__internal::token_stream_wrap(stream))
})
Expand Down
2 changes: 1 addition & 1 deletion src/librustc_resolve/build_reduced_graph.rs
Original file line number Diff line number Diff line change
Expand Up @@ -156,7 +156,7 @@ impl<'a> Resolver<'a> {

// Disallow `use $crate;`
if source.name == keywords::DollarCrate.name() && path.segments.len() == 1 {
let crate_root = self.resolve_crate_root(source.ctxt);
let crate_root = self.resolve_crate_root(source.ctxt, true);
let crate_name = match crate_root.kind {
ModuleKind::Def(_, name) => name,
ModuleKind::Block(..) => unreachable!(),
Expand Down
19 changes: 14 additions & 5 deletions src/librustc_resolve/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,7 @@ use rustc::hir::{Freevar, FreevarMap, TraitCandidate, TraitMap, GlobMap};
use rustc::util::nodemap::{NodeMap, NodeSet, FxHashMap, FxHashSet, DefIdMap};

use syntax::codemap::{dummy_spanned, respan};
use syntax::ext::hygiene::{Mark, SyntaxContext};
use syntax::ext::hygiene::{Mark, MarkKind, SyntaxContext};
use syntax::ast::{self, Name, NodeId, Ident, SpannedIdent, FloatTy, IntTy, UintTy};
use syntax::ext::base::SyntaxExtension;
use syntax::ext::base::Determinacy::{self, Determined, Undetermined};
Expand Down Expand Up @@ -1789,8 +1789,17 @@ impl<'a> Resolver<'a> {
result
}

fn resolve_crate_root(&mut self, mut ctxt: SyntaxContext) -> Module<'a> {
let module = match ctxt.adjust(Mark::root()) {
fn resolve_crate_root(&mut self, mut ctxt: SyntaxContext, legacy: bool) -> Module<'a> {
let mark = if legacy {
// When resolving `$crate` from a `macro_rules!` invoked in a `macro`,
// we don't want to pretend that the `macro_rules!` definition is in the `macro`
// as described in `SyntaxContext::apply_mark`, so we ignore prepended modern marks.
ctxt.marks().into_iter().find(|&mark| mark.kind() != MarkKind::Modern)
} else {
ctxt = ctxt.modern();
ctxt.adjust(Mark::root())
};
let module = match mark {
Some(def) => self.macro_def_scope(def),
None => return self.graph_root,
};
Expand Down Expand Up @@ -2992,11 +3001,11 @@ impl<'a> Resolver<'a> {
(i == 1 && name == keywords::Crate.name() &&
path[0].node.name == keywords::CrateRoot.name()) {
// `::a::b` or `::crate::a::b`
module = Some(self.resolve_crate_root(ident.node.ctxt.modern()));
module = Some(self.resolve_crate_root(ident.node.ctxt, false));
continue
} else if i == 0 && name == keywords::DollarCrate.name() {
// `$crate::a::b`
module = Some(self.resolve_crate_root(ident.node.ctxt));
module = Some(self.resolve_crate_root(ident.node.ctxt, true));
continue
} else if i == 1 && !token::Ident(ident.node).is_path_segment_keyword() {
let prev_name = path[0].node.name;
Expand Down
2 changes: 1 addition & 1 deletion src/librustc_resolve/macros.rs
Original file line number Diff line number Diff line change
Expand Up @@ -140,7 +140,7 @@ impl<'a> base::Resolver for Resolver<'a> {
let ident = path.segments[0].identifier;
if ident.name == keywords::DollarCrate.name() {
path.segments[0].identifier.name = keywords::CrateRoot.name();
let module = self.0.resolve_crate_root(ident.ctxt);
let module = self.0.resolve_crate_root(ident.ctxt, true);
if !module.is_local() {
let span = path.segments[0].span;
path.segments.insert(1, match module.kind {
Expand Down
2 changes: 1 addition & 1 deletion src/librustc_resolve/resolve_imports.rs
Original file line number Diff line number Diff line change
Expand Up @@ -623,7 +623,7 @@ impl<'a, 'b:'a> ImportResolver<'a, 'b> {
"crate root imports need to be explicitly named: \
`use crate as name;`".to_string()));
} else {
Some(self.resolve_crate_root(source.ctxt.modern()))
Some(self.resolve_crate_root(source.ctxt.modern(), false))
}
} else if is_extern && !token::Ident(source).is_path_segment_keyword() {
let crate_id =
Expand Down
39 changes: 39 additions & 0 deletions src/libsyntax_pos/hygiene.rs
Original file line number Diff line number Diff line change
Expand Up @@ -188,6 +188,33 @@ impl SyntaxContext {

/// Extend a syntax context with a given mark
pub fn apply_mark(self, mark: Mark) -> SyntaxContext {
if mark.kind() == MarkKind::Modern {
return self.apply_mark_internal(mark);
}

let call_site_ctxt =
mark.expn_info().map_or(SyntaxContext::empty(), |info| info.call_site.ctxt()).modern();
if call_site_ctxt == SyntaxContext::empty() {
return self.apply_mark_internal(mark);
}

// Otherwise, `mark` 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/run-pass/hygiene/legacy_interaction.rs`.
let mut ctxt = call_site_ctxt;
for mark in self.marks() {
ctxt = ctxt.apply_mark_internal(mark);
}
ctxt.apply_mark_internal(mark)
}

fn apply_mark_internal(self, mark: Mark) -> SyntaxContext {
HygieneData::with(|data| {
let syntax_contexts = &mut data.syntax_contexts;
let mut modern = syntax_contexts[self.0 as usize].modern;
Expand Down Expand Up @@ -222,6 +249,18 @@ impl SyntaxContext {
})
}

pub fn marks(mut self) -> Vec<Mark> {
HygieneData::with(|data| {
let mut marks = Vec::new();
while self != SyntaxContext::empty() {
marks.push(data.syntax_contexts[self.0 as usize].outer_mark);
self = data.syntax_contexts[self.0 as usize].prev_ctxt;
}
marks.reverse();
marks
})
}

/// Adjust this context for resolution in a scope created by the given expansion.
/// For example, consider the following three resolutions of `f`:
///
Expand Down
19 changes: 19 additions & 0 deletions src/test/run-pass/hygiene/auxiliary/legacy_interaction.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,19 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// ignore-pretty pretty-printing is unhygienic

#[macro_export]
macro_rules! m {
() => {
fn f() {} // (2)
g(); // (1)
}
}
11 changes: 11 additions & 0 deletions src/test/run-pass/hygiene/auxiliary/my_crate.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

pub fn f() {}
37 changes: 37 additions & 0 deletions src/test/run-pass/hygiene/auxiliary/unhygienic_example.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,37 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

#![crate_type = "lib"]

extern crate my_crate;

pub fn g() {} // (a)

#[macro_export]
macro_rules! unhygienic_macro {
() => {
// (1) unhygienic: depends on `my_crate` in the crate root at the invocation site.
::my_crate::f();

// (2) unhygienic: defines `f` at the invocation site (in addition to the above point).
use my_crate::f;
f();

g(); // (3) unhygienic: `g` needs to be in scope at use site.

$crate::g(); // (4) hygienic: this always resolves to (a)
}
}

#[allow(unused)]
fn test_unhygienic() {
unhygienic_macro!();
f(); // `f` was defined at the use site
}
50 changes: 50 additions & 0 deletions src/test/run-pass/hygiene/legacy_interaction.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,50 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// ignore-pretty pretty-printing is unhygienic

// aux-build:legacy_interaction.rs

#![feature(decl_macro)]
#[allow(unused)]

extern crate legacy_interaction;
// ^ defines
// ```rust
// macro_rules! m {
// () => {
// fn f() // (1)
// g() // (2)
// }
// }
// ```rust

mod def_site {
// Unless this macro opts out of hygiene, it should resolve the same wherever it is invoked.
pub macro m2() {
::legacy_interaction::m!();
f(); // This should resolve to (1)
fn g() {} // We want (2) resolve to this, not to (4)
}
}

mod use_site {
fn test() {
fn f() -> bool { true } // (3)
fn g() -> bool { true } // (4)

::def_site::m2!();

let _: bool = f(); // This should resolve to (3)
let _: bool = g(); // This should resolve to (4)
}
}

fn main() {}
43 changes: 43 additions & 0 deletions src/test/run-pass/hygiene/wrap_unhygienic_example.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,43 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// ignore-pretty pretty-printing is unhygienic

// aux-build:my_crate.rs
// aux-build:unhygienic_example.rs

#![feature(decl_macro)]

extern crate unhygienic_example;
extern crate my_crate; // (b)

// Hygienic version of `unhygienic_macro`.
pub macro hygienic_macro() {
fn g() {} // (c)
::unhygienic_example::unhygienic_macro!();
// ^ Even though we invoke an unhygienic macro, `hygienic_macro` remains hygienic.
// In the above expansion:
// (1) `my_crate` always resolves to (b) regardless of invocation site.
// (2) The defined function `f` is only usable inside this macro definition.
// (3) `g` always resolves to (c) regardless of invocation site.
// (4) `$crate::g` remains hygienic and continues to resolve to (a).

f();
}

#[allow(unused)]
fn test_hygienic_macro() {
hygienic_macro!();

fn f() {} // (d) no conflict
f(); // resolves to (d)
}

fn main() {}

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