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Delay gensym creation for "underscore items" until name resolution
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Prohibit `static _`
Fis unused import warnings for `use foo as _`
Add more tests for `use foo as _`
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petrochenkov committed Dec 2, 2018
1 parent c658d73 commit 2d4b633
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Showing 16 changed files with 157 additions and 36 deletions.
10 changes: 7 additions & 3 deletions src/librustc_resolve/build_reduced_graph.rs
Original file line number Diff line number Diff line change
Expand Up @@ -157,7 +157,7 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
};
match use_tree.kind {
ast::UseTreeKind::Simple(rename, ..) => {
let mut ident = use_tree.ident();
let mut ident = use_tree.ident().gensym_if_underscore();
let mut module_path = prefix;
let mut source = module_path.pop().unwrap();
let mut type_ns_only = false;
Expand Down Expand Up @@ -334,7 +334,7 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
fn build_reduced_graph_for_item(&mut self, item: &Item, parent_scope: ParentScope<'a>) {
let parent = parent_scope.module;
let expansion = parent_scope.expansion;
let ident = item.ident;
let ident = item.ident.gensym_if_underscore();
let sp = item.span;
let vis = self.resolve_visibility(&item.vis);

Expand Down Expand Up @@ -628,7 +628,11 @@ impl<'a, 'cl> Resolver<'a, 'cl> {

/// Builds the reduced graph for a single item in an external crate.
fn build_reduced_graph_for_external_crate_def(&mut self, parent: Module<'a>, child: Export) {
let Export { ident, def, vis, span, .. } = child;
let Export { ident, def, vis, span } = child;
// FIXME: We shouldn't create the gensym here, it should come from metadata,
// but metadata cannot encode gensyms currently, so we create it here.
// This is only a guess, two equivalent idents may incorrectly get different gensyms here.
let ident = ident.gensym_if_underscore();
let def_id = def.def_id();
let expansion = Mark::root(); // FIXME(jseyfried) intercrate hygiene
match def {
Expand Down
14 changes: 9 additions & 5 deletions src/librustc_resolve/resolve_imports.rs
Original file line number Diff line number Diff line change
Expand Up @@ -888,9 +888,11 @@ impl<'a, 'b:'a, 'c: 'b> ImportResolver<'a, 'b, 'c> {
PathResult::Indeterminate | PathResult::NonModule(..) => unreachable!(),
};

let (ident, source_bindings, target_bindings, type_ns_only) = match directive.subclass {
SingleImport { source, ref source_bindings, ref target_bindings, type_ns_only, .. } =>
(source, source_bindings, target_bindings, type_ns_only),
let (ident, target, source_bindings, target_bindings, type_ns_only) =
match directive.subclass {
SingleImport { source, target, ref source_bindings,
ref target_bindings, type_ns_only } =>
(source, target, source_bindings, target_bindings, type_ns_only),
GlobImport { is_prelude, ref max_vis } => {
if directive.module_path.len() <= 1 {
// HACK(eddyb) `lint_if_path_starts_with_module` needs at least
Expand Down Expand Up @@ -944,8 +946,10 @@ impl<'a, 'b:'a, 'c: 'b> ImportResolver<'a, 'b, 'c> {
// Consistency checks, analogous to `finalize_current_module_macro_resolutions`.
let initial_def = source_bindings[ns].get().map(|initial_binding| {
all_ns_err = false;
this.record_use(ident, ns, initial_binding,
directive.module_path.is_empty());
if target.name == "_" &&
initial_binding.is_extern_crate() && !initial_binding.is_import() {
this.used_imports.insert((directive.id, TypeNS));
}
initial_binding.def_ignoring_ambiguity()
});
let def = binding.def_ignoring_ambiguity();
Expand Down
27 changes: 13 additions & 14 deletions src/libsyntax/parse/parser.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2017,6 +2017,17 @@ impl<'a> Parser<'a> {
}
}

fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
match self.token {
token::Ident(ident, false) if ident.name == keywords::Underscore.name() => {
let span = self.span;
self.bump();
Ok(Ident::new(ident.name, span))
}
_ => self.parse_ident(),
}
}

/// Parses qualified path.
/// Assumes that the leading `<` has been parsed already.
///
Expand Down Expand Up @@ -6435,13 +6446,7 @@ impl<'a> Parser<'a> {
}

fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
let id = match self.token {
token::Ident(ident, false) if ident.name == keywords::Underscore.name() => {
self.bump(); // `_`
ident.gensym()
},
_ => self.parse_ident()?,
};
let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
self.expect(&token::Eq)?;
Expand Down Expand Up @@ -7726,13 +7731,7 @@ impl<'a> Parser<'a> {

fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
if self.eat_keyword(keywords::As) {
match self.token {
token::Ident(ident, false) if ident.name == keywords::Underscore.name() => {
self.bump(); // `_`
Ok(Some(ident.gensym()))
}
_ => self.parse_ident().map(Some),
}
self.parse_ident_or_underscore().map(Some)
} else {
Ok(None)
}
Expand Down
6 changes: 5 additions & 1 deletion src/libsyntax_pos/symbol.rs
Original file line number Diff line number Diff line change
Expand Up @@ -80,6 +80,10 @@ impl Ident {
Ident::new(self.name.gensymed(), self.span)
}

pub fn gensym_if_underscore(self) -> Ident {
if self.name == keywords::Underscore.name() { self.gensym() } else { self }
}

pub fn as_str(self) -> LocalInternedString {
self.name.as_str()
}
Expand Down Expand Up @@ -465,7 +469,7 @@ impl Ident {
// We see this identifier in a normal identifier position, like variable name or a type.
// How was it written originally? Did it use the raw form? Let's try to guess.
pub fn is_raw_guess(self) -> bool {
self.name != keywords::Invalid.name() &&
self.name != keywords::Invalid.name() && self.name != keywords::Underscore.name() &&
self.is_reserved() && !self.is_path_segment_keyword()
}
}
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,5 @@
// except according to those terms.

const _: () = (); //~ ERROR is unstable
static _: () = (); //~ ERROR is unstable

fn main() {}
Original file line number Diff line number Diff line change
Expand Up @@ -6,14 +6,6 @@ LL | const _: () = (); //~ ERROR is unstable
|
= help: add #![feature(underscore_const_names)] to the crate attributes to enable

error[E0658]: naming constants with `_` is unstable (see issue #54912)
--> $DIR/underscore_const_names_feature_gate.rs:12:1
|
LL | static _: () = (); //~ ERROR is unstable
| ^^^^^^^^^^^^^^^^^^
|
= help: add #![feature(underscore_const_names)] to the crate attributes to enable

error: aborting due to 2 previous errors
error: aborting due to previous error

For more information about this error, try `rustc --explain E0658`.
3 changes: 3 additions & 0 deletions src/test/ui/parser/underscore_static.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
// compile-flags: -Z parse-only

static _: () = (); //~ ERROR expected identifier, found reserved identifier `_`
8 changes: 8 additions & 0 deletions src/test/ui/parser/underscore_static.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
error: expected identifier, found reserved identifier `_`
--> $DIR/underscore_static.rs:3:8
|
LL | static _: () = (); //~ ERROR expected identifier, found reserved identifier `_`
| ^ expected identifier, found reserved identifier

error: aborting due to previous error

14 changes: 14 additions & 0 deletions src/test/ui/rfc-2166-underscore-imports/auxiliary/duplicate.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
// force-host
// no-prefer-dynamic

#![crate_type = "proc-macro"]

extern crate proc_macro;

use proc_macro::*;

#[proc_macro_attribute]
pub fn duplicate(_: TokenStream, input: TokenStream) -> TokenStream {
let clone = input.clone();
input.into_iter().chain(clone.into_iter()).collect()
}
Original file line number Diff line number Diff line change
@@ -0,0 +1,22 @@
#![feature(underscore_imports)]

#[macro_export]
macro_rules! do_nothing {
() => ()
}

mod m1 {
pub trait InScope1 {
fn in_scope1(&self) {}
}
impl InScope1 for () {}
}
mod m2 {
pub trait InScope2 {
fn in_scope2(&self) {}
}
impl InScope2 for () {}
}

pub use m1::InScope1 as _;
pub use m2::InScope2 as _;
6 changes: 6 additions & 0 deletions src/test/ui/rfc-2166-underscore-imports/basic.rs
Original file line number Diff line number Diff line change
Expand Up @@ -9,10 +9,16 @@
// except according to those terms.

// compile-pass
// aux-build:underscore-imports.rs

#![feature(underscore_imports)]
#![warn(unused_imports, unused_extern_crates)]

#[macro_use]
extern crate underscore_imports as _;

do_nothing!(); // OK

struct S;

mod m {
Expand Down
6 changes: 3 additions & 3 deletions src/test/ui/rfc-2166-underscore-imports/basic.stderr
Original file line number Diff line number Diff line change
@@ -1,17 +1,17 @@
warning: unused import: `m::Tr1 as _`
--> $DIR/basic.rs:31:9
--> $DIR/basic.rs:37:9
|
LL | use m::Tr1 as _; //~ WARN unused import
| ^^^^^^^^^^^
|
note: lint level defined here
--> $DIR/basic.rs:14:9
--> $DIR/basic.rs:15:9
|
LL | #![warn(unused_imports, unused_extern_crates)]
| ^^^^^^^^^^^^^^

warning: unused import: `S as _`
--> $DIR/basic.rs:32:9
--> $DIR/basic.rs:38:9
|
LL | use S as _; //~ WARN unused import
| ^^^^^^
Expand Down
17 changes: 17 additions & 0 deletions src/test/ui/rfc-2166-underscore-imports/duplicate.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,17 @@
// compile-pass
// aux-build:duplicate.rs

#![feature(underscore_imports)]

extern crate duplicate;

#[duplicate::duplicate]
use main as _; // OK

macro_rules! duplicate {
($item: item) => { $item $item }
}

duplicate!(use std as _;); // OK

fn main() {}
11 changes: 11 additions & 0 deletions src/test/ui/rfc-2166-underscore-imports/intercrate.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
// compile-pass
// aux-build:underscore-imports.rs

extern crate underscore_imports;

use underscore_imports::*;

fn main() {
().in_scope1();
().in_scope2();
}
18 changes: 18 additions & 0 deletions src/test/ui/rfc-2166-underscore-imports/unused-2018.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
// edition:2018

#![feature(underscore_imports)]
#![deny(unused_imports)]

mod multi_segment {
use core::any; //~ ERROR unused import: `core::any`
}

mod single_segment {
use core; //~ ERROR unused import: `core`
}

mod single_segment_underscore {
use core as _; // OK
}

fn main() {}
20 changes: 20 additions & 0 deletions src/test/ui/rfc-2166-underscore-imports/unused-2018.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,20 @@
error: unused import: `core::any`
--> $DIR/unused-2018.rs:7:9
|
LL | use core::any; //~ ERROR unused import: `core::any`
| ^^^^^^^^^
|
note: lint level defined here
--> $DIR/unused-2018.rs:4:9
|
LL | #![deny(unused_imports)]
| ^^^^^^^^^^^^^^

error: unused import: `core`
--> $DIR/unused-2018.rs:11:9
|
LL | use core; //~ ERROR unused import: `core`
| ^^^^

error: aborting due to 2 previous errors

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