Auto merge of #50478 - pietroalbini:beta-backports, r=kennytm

[beta] Process backports

* #50419: rustdoc: Resolve nested `impl Trait`s
* #50474: Fix ICE in assertion macro

r? @Mark-Simulacrum

src/librustdoc/clean/mod.rs

@@ -1729,8 +1729,18 @@ pub struct Generics {
 
 impl Clean<Generics> for hir::Generics {
     fn clean(&self, cx: &DocContext) -> Generics {
+        let mut params = Vec::with_capacity(self.params.len());
+        for p in &self.params {
+            let p = p.clean(cx);
+            if let GenericParam::Type(ref tp) = p {
+                if tp.synthetic == Some(hir::SyntheticTyParamKind::ImplTrait) {
+                    cx.impl_trait_bounds.borrow_mut().insert(tp.did, tp.bounds.clone());
+                }
+            }
+            params.push(p);
+        }
         let mut g = Generics {
-            params: self.params.clean(cx),
+            params,
             where_predicates: self.where_clause.predicates.clean(cx)
         };
 
@@ -1843,9 +1853,11 @@ pub struct Method {
 
 impl<'a> Clean<Method> for (&'a hir::MethodSig, &'a hir::Generics, hir::BodyId) {
     fn clean(&self, cx: &DocContext) -> Method {
-        let generics = self.1.clean(cx);
+        let (generics, decl) = enter_impl_trait(cx, || {
+            (self.1.clean(cx), (&*self.0.decl, self.2).clean(cx))
+        });
         Method {
-            decl: enter_impl_trait(cx, &generics.params, || (&*self.0.decl, self.2).clean(cx)),
+            decl,
             generics,
             unsafety: self.0.unsafety,
             constness: self.0.constness,
@@ -1873,8 +1885,9 @@ pub struct Function {
 
 impl Clean<Item> for doctree::Function {
     fn clean(&self, cx: &DocContext) -> Item {
-        let generics = self.generics.clean(cx);
-        let decl = enter_impl_trait(cx, &generics.params, || (&self.decl, self.body).clean(cx));
+        let (generics, decl) = enter_impl_trait(cx, || {
+            (self.generics.clean(cx), (&self.decl, self.body).clean(cx))
+        });
         Item {
             name: Some(self.name.clean(cx)),
             attrs: self.attrs.clean(cx),
@@ -2113,12 +2126,12 @@ impl Clean<Item> for hir::TraitItem {
                 MethodItem((sig, &self.generics, body).clean(cx))
             }
             hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Required(ref names)) => {
-                let generics = self.generics.clean(cx);
+                let (generics, decl) = enter_impl_trait(cx, || {
+                    (self.generics.clean(cx), (&*sig.decl, &names[..]).clean(cx))
+                });
                 TyMethodItem(TyMethod {
                     unsafety: sig.unsafety.clone(),
-                    decl: enter_impl_trait(cx, &generics.params, || {
-                        (&*sig.decl, &names[..]).clean(cx)
-                    }),
+                    decl,
                     generics,
                     abi: sig.abi
                 })
@@ -3389,12 +3402,12 @@ pub struct BareFunctionDecl {
 
 impl Clean<BareFunctionDecl> for hir::BareFnTy {
     fn clean(&self, cx: &DocContext) -> BareFunctionDecl {
-        let generic_params = self.generic_params.clean(cx);
+        let (generic_params, decl) = enter_impl_trait(cx, || {
+            (self.generic_params.clean(cx), (&*self.decl, &self.arg_names[..]).clean(cx))
+        });
         BareFunctionDecl {
             unsafety: self.unsafety,
-            decl: enter_impl_trait(cx, &generic_params, || {
-                (&*self.decl, &self.arg_names[..]).clean(cx)
-            }),
+            decl,
             generic_params,
             abi: self.abi,
         }
@@ -3696,11 +3709,11 @@ impl Clean<Item> for hir::ForeignItem {
     fn clean(&self, cx: &DocContext) -> Item {
         let inner = match self.node {
             hir::ForeignItemFn(ref decl, ref names, ref generics) => {
-                let generics = generics.clean(cx);
+                let (generics, decl) = enter_impl_trait(cx, || {
+                    (generics.clean(cx), (&**decl, &names[..]).clean(cx))
+                });
                 ForeignFunctionItem(Function {
-                    decl: enter_impl_trait(cx, &generics.params, || {
-                        (&**decl, &names[..]).clean(cx)
-                    }),
+                    decl,
                     generics,
                     unsafety: hir::Unsafety::Unsafe,
                     abi: Abi::Rust,
@@ -4003,23 +4016,11 @@ pub fn def_id_to_path(cx: &DocContext, did: DefId, name: Option<String>) -> Vec<
     once(crate_name).chain(relative).collect()
 }
 
-pub fn enter_impl_trait<F, R>(cx: &DocContext, gps: &[GenericParam], f: F) -> R
+pub fn enter_impl_trait<F, R>(cx: &DocContext, f: F) -> R
 where
     F: FnOnce() -> R,
 {
-    let bounds = gps.iter()
-        .filter_map(|p| {
-            if let GenericParam::Type(ref tp) = *p {
-                if tp.synthetic == Some(hir::SyntheticTyParamKind::ImplTrait) {
-                    return Some((tp.did, tp.bounds.clone()));
-                }
-            }
-
-            None
-        })
-        .collect::<FxHashMap<DefId, Vec<TyParamBound>>>();
-
-    let old_bounds = mem::replace(&mut *cx.impl_trait_bounds.borrow_mut(), bounds);
+    let old_bounds = mem::replace(&mut *cx.impl_trait_bounds.borrow_mut(), Default::default());
     let r = f();
     assert!(cx.impl_trait_bounds.borrow().is_empty());
     *cx.impl_trait_bounds.borrow_mut() = old_bounds;

src/libsyntax/lib.rs

@@ -27,6 +27,7 @@
 #![cfg_attr(stage0, feature(i128_type))]
 #![feature(const_atomic_usize_new)]
 #![feature(rustc_attrs)]
+#![feature(str_escape)]
 
 // See librustc_cratesio_shim/Cargo.toml for a comment explaining this.
 #[allow(unused_extern_crates)]

src/libsyntax/print/pprust.rs

@@ -651,7 +651,7 @@ pub trait PrintState<'a> {
                     style: ast::StrStyle) -> io::Result<()> {
         let st = match style {
             ast::StrStyle::Cooked => {
-                (format!("\"{}\"", parse::escape_default(st)))
+                (format!("\"{}\"", st.escape_debug()))
             }
             ast::StrStyle::Raw(n) => {
                 (format!("r{delim}\"{string}\"{delim}",

src/libsyntax_ext/assert.rs

@@ -41,16 +41,13 @@ pub fn expand_assert<'cx>(
         tts: if let Some(ts) = custom_msg_args {
             ts.into()
         } else {
-            // `expr_to_string` escapes the string literals with `.escape_default()`
-            // which escapes all non-ASCII characters with `\u`.
-            let escaped_expr = escape_format_string(&unescape_printable_unicode(
-                &pprust::expr_to_string(&cond_expr),
-            ));
-
             TokenStream::from(TokenTree::Token(
                 DUMMY_SP,
                 token::Literal(
-                    token::Lit::Str_(Name::intern(&format!("assertion failed: {}", escaped_expr))),
+                    token::Lit::Str_(Name::intern(&format!(
+                        "assertion failed: {}",
+                        pprust::expr_to_string(&cond_expr).escape_debug()
+                    ))),
                     None,
                 ),
             )).into()
@@ -70,53 +67,3 @@ pub fn expand_assert<'cx>(
     );
     MacEager::expr(if_expr)
 }
-
-/// Escapes a string for use as a formatting string.
-fn escape_format_string(s: &str) -> String {
-    let mut res = String::with_capacity(s.len());
-    for c in s.chars() {
-        res.extend(c.escape_debug());
-        match c {
-            '{' | '}' => res.push(c),
-            _ => {}
-        }
-    }
-    res
-}
-
-#[test]
-fn test_escape_format_string() {
-    assert!(escape_format_string(r"foo{}\") == r"foo{{}}\\");
-}
-
-/// Unescapes the escaped unicodes (`\u{...}`) that are printable.
-fn unescape_printable_unicode(mut s: &str) -> String {
-    use std::{char, u32};
-
-    let mut res = String::with_capacity(s.len());
-
-    loop {
-        if let Some(start) = s.find(r"\u{") {
-            res.push_str(&s[0..start]);
-            s = &s[start..];
-            s.find('}')
-                .and_then(|end| {
-                    let v = u32::from_str_radix(&s[3..end], 16).ok()?;
-                    let c = char::from_u32(v)?;
-                    // Escape unprintable characters.
-                    res.extend(c.escape_debug());
-                    s = &s[end + 1..];
-                    Some(())
-                })
-                .expect("lexer should have rejected invalid escape sequences");
-        } else {
-            res.push_str(s);
-            return res;
-        }
-    }
-}
-
-#[test]
-fn test_unescape_printable_unicode() {
-    assert!(unescape_printable_unicode(r"\u{2603}\n\u{0}") == r"☃\n\u{0}");
-}

src/test/compile-fail/issue-50471.rs

@@ -0,0 +1,19 @@
+// Copyright 2018 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.
+
+// must-compile-successfully
+
+fn main() {
+    assert!({false});
+
+    assert!(r"\u{41}" == "A");
+
+    assert!(r"\u{".is_empty());
+}

src/test/rustdoc/universal-impl-trait.rs

@@ -11,6 +11,8 @@
 #![feature(universal_impl_trait)]
 #![crate_name = "foo"]
 
+use std::io::Read;
+
 // @has foo/fn.foo.html
 // @has - //pre 'foo('
 // @matches - '_x: impl <a class="trait" href="[^"]+/trait\.Clone\.html"'
@@ -39,6 +41,11 @@ impl<T> S<T> {
     // @matches - '_baz:.+struct\.S\.html.+impl .+trait\.Clone\.html'
     pub fn baz(_baz: S<impl Clone>) {
     }
+
+    // @has - 'qux</a>('
+    // @matches - 'trait\.Read\.html'
+    pub fn qux(_qux: impl IntoIterator<Item = S<impl Read>>) {
+    }
 }
 
 // @has - 'method</a>('