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Auto merge of #43878 - kennytm:fix-43869-put-impl-trait-out-of-the-lo…
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…op, r=alexcrichton

Exclude `impl Trait` functions from everybody_loops.

Fixes #43869.

cc #34511.
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bors committed Aug 17, 2017
2 parents e407206 + 034cd20 commit a7e0018
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Showing 2 changed files with 67 additions and 6 deletions.
41 changes: 35 additions & 6 deletions src/librustc_driver/pretty.rs
Original file line number Diff line number Diff line change
Expand Up @@ -620,6 +620,15 @@ impl UserIdentifiedItem {
}

// Note: Also used by librustdoc, see PR #43348. Consider moving this struct elsewhere.
//
// FIXME: Currently the `everybody_loops` transformation is not applied to:
// * `const fn`, due to issue #43636 that `loop` is not supported for const evaluation. We are
// waiting for miri to fix that.
// * `impl Trait`, due to issue #43869 that functions returning impl Trait cannot be diverging.
// Solving this may require `!` to implement every trait, which relies on the an even more
// ambitious form of the closed RFC #1637. See also [#34511].
//
// [#34511]: https://github.com/rust-lang/rust/issues/34511#issuecomment-322340401
pub struct ReplaceBodyWithLoop {
within_static_or_const: bool,
}
Expand All @@ -635,14 +644,34 @@ impl ReplaceBodyWithLoop {
self.within_static_or_const = old_const;
ret
}

fn should_ignore_fn(ret_ty: &ast::FnDecl) -> bool {
if let ast::FunctionRetTy::Ty(ref ty) = ret_ty.output {
fn involves_impl_trait(ty: &ast::Ty) -> bool {
match ty.node {
ast::TyKind::ImplTrait(_) => true,
ast::TyKind::Slice(ref subty) |
ast::TyKind::Array(ref subty, _) |
ast::TyKind::Ptr(ast::MutTy { ty: ref subty, .. }) |
ast::TyKind::Rptr(_, ast::MutTy { ty: ref subty, .. }) |
ast::TyKind::Paren(ref subty) => involves_impl_trait(subty),
ast::TyKind::Tup(ref tys) => tys.iter().any(|subty| involves_impl_trait(subty)),
_ => false,
}
}
involves_impl_trait(ty)
} else {
false
}
}
}

impl fold::Folder for ReplaceBodyWithLoop {
fn fold_item_kind(&mut self, i: ast::ItemKind) -> ast::ItemKind {
let is_const = match i {
ast::ItemKind::Static(..) | ast::ItemKind::Const(..) => true,
ast::ItemKind::Fn(_, _, ref constness, _, _, _) =>
constness.node == ast::Constness::Const,
ast::ItemKind::Fn(ref decl, _, ref constness, _, _, _) =>
constness.node == ast::Constness::Const || Self::should_ignore_fn(decl),
_ => false,
};
self.run(is_const, |s| fold::noop_fold_item_kind(i, s))
Expand All @@ -651,8 +680,8 @@ impl fold::Folder for ReplaceBodyWithLoop {
fn fold_trait_item(&mut self, i: ast::TraitItem) -> SmallVector<ast::TraitItem> {
let is_const = match i.node {
ast::TraitItemKind::Const(..) => true,
ast::TraitItemKind::Method(ast::MethodSig { ref constness, .. }, _) =>
constness.node == ast::Constness::Const,
ast::TraitItemKind::Method(ast::MethodSig { ref decl, ref constness, .. }, _) =>
constness.node == ast::Constness::Const || Self::should_ignore_fn(decl),
_ => false,
};
self.run(is_const, |s| fold::noop_fold_trait_item(i, s))
Expand All @@ -661,8 +690,8 @@ impl fold::Folder for ReplaceBodyWithLoop {
fn fold_impl_item(&mut self, i: ast::ImplItem) -> SmallVector<ast::ImplItem> {
let is_const = match i.node {
ast::ImplItemKind::Const(..) => true,
ast::ImplItemKind::Method(ast::MethodSig { ref constness, .. }, _) =>
constness.node == ast::Constness::Const,
ast::ImplItemKind::Method(ast::MethodSig { ref decl, ref constness, .. }, _) =>
constness.node == ast::Constness::Const || Self::should_ignore_fn(decl),
_ => false,
};
self.run(is_const, |s| fold::noop_fold_impl_item(i, s))
Expand Down
32 changes: 32 additions & 0 deletions src/test/rustdoc/issue-43869.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,32 @@
// 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.

#![feature(conservative_impl_trait)]

pub fn g() -> impl Iterator<Item=u8> {
Some(1u8).into_iter()
}

pub fn h() -> (impl Iterator<Item=u8>) {
Some(1u8).into_iter()
}

pub fn i() -> impl Iterator<Item=u8> + 'static {
Some(1u8).into_iter()
}

pub fn j() -> impl Iterator<Item=u8> + Clone {
Some(1u8).into_iter()
}

// @has issue_43869/fn.g.html
// @has issue_43869/fn.h.html
// @has issue_43869/fn.i.html
// @has issue_43869/fn.j.html

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