Auto merge of #60708 - Centril:rollup-j5smdo0, r=Centril

Rollup of 6 pull requests

Successful merges:

 - #60529 (RFC 2008: Uninhabitedness fixes for enum variants and tests)
 - #60620 (Fix a couple of FIXMEs in ext::tt::transcribe)
 - #60659 (Tweak `Symbol` and `InternedString`)
 - #60692 (Extend #60676 test for nested mut patterns.)
 - #60697 (add regression test for #60629)
 - #60701 (Update mailmap for mati865)

Failed merges:

r? @ghost

Author: bors

.mailmap

@@ -155,6 +155,8 @@ Mark Sinclair <mark.edward.x@gmail.com> =Mark Sinclair <=125axel125@gmail.com>
 Markus Westerlind <marwes91@gmail.com> Markus <marwes91@gmail.com>
 Martin Hafskjold Thoresen <martinhath@gmail.com>
 Matej Lach <matej.lach@gmail.com> Matej Ľach <matej.lach@gmail.com>
+Mateusz Mikuła <matti@marinelayer.io> <mati865@gmail.com>
+Mateusz Mikuła <matti@marinelayer.io> <mati865@users.noreply.github.com>
 Matt Brubeck <mbrubeck@limpet.net> <mbrubeck@cs.hmc.edu>
 Matthew Auld <matthew.auld@intel.com>
 Matthew McPherrin <matthew@mcpherrin.ca> <matt@mcpherrin.ca>

src/librustc/ty/inhabitedness/mod.rs

@@ -113,9 +113,14 @@ impl<'a, 'gcx, 'tcx> AdtDef {
         tcx: TyCtxt<'a, 'gcx, 'tcx>,
         substs: SubstsRef<'tcx>) -> DefIdForest
     {
-        DefIdForest::intersection(tcx, self.variants.iter().map(|v| {
-            v.uninhabited_from(tcx, substs, self.adt_kind())
-        }))
+        // Non-exhaustive ADTs from other crates are always considered inhabited.
+        if self.is_variant_list_non_exhaustive() && !self.did.is_local() {
+            DefIdForest::empty()
+        } else {
+            DefIdForest::intersection(tcx, self.variants.iter().map(|v| {
+                v.uninhabited_from(tcx, substs, self.adt_kind())
+            }))
+        }
     }
 }
 
@@ -134,9 +139,14 @@ impl<'a, 'gcx, 'tcx> VariantDef {
             AdtKind::Enum => true,
             AdtKind::Struct => false,
         };
-        DefIdForest::union(tcx, self.fields.iter().map(|f| {
-            f.uninhabited_from(tcx, substs, is_enum)
-        }))
+        // Non-exhaustive variants from other crates are always considered inhabited.
+        if self.is_field_list_non_exhaustive() && !self.def_id.is_local() {
+            DefIdForest::empty()
+        } else {
+            DefIdForest::union(tcx, self.fields.iter().map(|f| {
+                f.uninhabited_from(tcx, substs, is_enum)
+            }))
+        }
     }
 }
 

src/librustc_mir/hair/pattern/_match.rs

@@ -388,6 +388,18 @@ impl<'a, 'tcx> MatchCheckCtxt<'a, 'tcx> {
         }
     }
 
+    fn is_non_exhaustive_variant<'p>(&self, pattern: &'p Pattern<'tcx>) -> bool
+        where 'a: 'p
+    {
+        match *pattern.kind {
+            PatternKind::Variant { adt_def, variant_index, .. } => {
+                let ref variant = adt_def.variants[variant_index];
+                variant.is_field_list_non_exhaustive()
+            }
+            _ => false,
+        }
+    }
+
     fn is_non_exhaustive_enum(&self, ty: Ty<'tcx>) -> bool {
         match ty.sty {
             ty::Adt(adt_def, ..) => adt_def.is_variant_list_non_exhaustive(),
@@ -1097,10 +1109,17 @@ pub fn is_useful<'p, 'a: 'p, 'tcx: 'a>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
     debug!("is_useful_expand_first_col: pcx={:#?}, expanding {:#?}", pcx, v[0]);
 
     if let Some(constructors) = pat_constructors(cx, v[0], pcx) {
-        debug!("is_useful - expanding constructors: {:#?}", constructors);
-        split_grouped_constructors(cx.tcx, constructors, matrix, pcx.ty).into_iter().map(|c|
-            is_useful_specialized(cx, matrix, v, c, pcx.ty, witness)
-        ).find(|result| result.is_useful()).unwrap_or(NotUseful)
+        let is_declared_nonexhaustive = cx.is_non_exhaustive_variant(v[0]) && !cx.is_local(pcx.ty);
+        debug!("is_useful - expanding constructors: {:#?}, is_declared_nonexhaustive: {:?}",
+               constructors, is_declared_nonexhaustive);
+
+        if is_declared_nonexhaustive {
+            Useful
+        } else {
+            split_grouped_constructors(cx.tcx, constructors, matrix, pcx.ty).into_iter().map(|c|
+                is_useful_specialized(cx, matrix, v, c, pcx.ty, witness)
+            ).find(|result| result.is_useful()).unwrap_or(NotUseful)
+        }
     } else {
         debug!("is_useful - expanding wildcard");
 

src/librustc_mir/hair/pattern/check_match.rs

@@ -208,7 +208,11 @@ impl<'a, 'tcx> MatchVisitor<'a, 'tcx> {
                                     .map(|variant| variant.ident)
                                     .collect();
                             }
-                            def.variants.is_empty()
+
+                            let is_non_exhaustive_and_non_local =
+                                def.is_variant_list_non_exhaustive() && !def.did.is_local();
+
+                            !(is_non_exhaustive_and_non_local) && def.variants.is_empty()
                         },
                         _ => false
                     }

src/libsyntax/ext/tt/transcribe.rs

@@ -170,10 +170,9 @@ pub fn transcribe(
                     }
 
                     LockstepIterSize::Contradiction(ref msg) => {
-                        // FIXME: this should be impossible. I (mark-i-m) believe it would
-                        // represent a bug in the macro_parser.
-                        // FIXME #2887 blame macro invoker instead
-                        cx.span_fatal(seq.span(), &msg[..]);
+                        // This should never happen because the macro parser should generate
+                        // properly-sized matches for all meta-vars.
+                        cx.span_bug(seq.span(), &msg[..]);
                     }
 
                     LockstepIterSize::Constraint(len, _) => {
@@ -188,14 +187,13 @@ pub fn transcribe(
                         // Is the repetition empty?
                         if len == 0 {
                             if seq.op == quoted::KleeneOp::OneOrMore {
-                                // FIXME: this should be impossible because we check for this in
-                                // macro_parser.rs
-                                // FIXME #2887 blame invoker
-                                cx.span_fatal(sp.entire(), "this must repeat at least once");
+                                // This should be impossible because the macro parser would not
+                                // match the given macro arm.
+                                cx.span_bug(sp.entire(), "this must repeat at least once");
                             }
                         } else {
                             // 0 is the initial counter (we have done 0 repretitions so far). `len`
-                            //   is the total number of reptitions we should generate.
+                            // is the total number of reptitions we should generate.
                             repeats.push((0, len));
 
                             // The first time we encounter the sequence we push it to the stack. It

src/libsyntax_pos/symbol.rs

@@ -344,9 +344,22 @@ impl Decodable for Ident {
     }
 }
 
-/// A symbol is an interned or gensymed string. The use of `newtype_index!` means
-/// that `Option<Symbol>` only takes up 4 bytes, because `newtype_index!` reserves
-/// the last 256 values for tagging purposes.
+/// A symbol is an interned or gensymed string. A gensym is a symbol that is
+/// never equal to any other symbol. E.g.:
+/// ```
+/// assert_eq!(Symbol::intern("x"), Symbol::intern("x"))
+/// assert_ne!(Symbol::gensym("x"), Symbol::intern("x"))
+/// assert_ne!(Symbol::gensym("x"), Symbol::gensym("x"))
+/// ```
+/// Conceptually, a gensym can be thought of as a normal symbol with an
+/// invisible unique suffix. Gensyms are useful when creating new identifiers
+/// that must not match any existing identifiers, e.g. during macro expansion
+/// and syntax desugaring.
+///
+/// Internally, a Symbol is implemented as an index, and all operations
+/// (including hashing, equality, and ordering) operate on that index. The use
+/// of `newtype_index!` means that `Option<Symbol>` only takes up 4 bytes,
+/// because `newtype_index!` reserves the last 256 values for tagging purposes.
 ///
 /// Note that `Symbol` cannot directly be a `newtype_index!` because it implements
 /// `fmt::Debug`, `Encodable`, and `Decodable` in special ways.
@@ -367,10 +380,6 @@ impl Symbol {
         with_interner(|interner| interner.intern(string))
     }
 
-    pub fn interned(self) -> Self {
-        with_interner(|interner| interner.interned(self))
-    }
-
     /// Gensyms a new `usize`, using the current interner.
     pub fn gensym(string: &str) -> Self {
         with_interner(|interner| interner.gensym(string))
@@ -380,6 +389,7 @@ impl Symbol {
         with_interner(|interner| interner.gensymed(self))
     }
 
+    // WARNING: this function is deprecated and will be removed in the future.
     pub fn is_gensymed(self) -> bool {
         with_interner(|interner| interner.is_gensymed(self))
     }
@@ -488,11 +498,11 @@ impl Interner {
         name
     }
 
-    pub fn interned(&self, symbol: Symbol) -> Symbol {
+    fn interned(&self, symbol: Symbol) -> Symbol {
         if (symbol.0.as_usize()) < self.strings.len() {
             symbol
         } else {
-            self.interned(self.gensyms[(SymbolIndex::MAX_AS_U32 - symbol.0.as_u32()) as usize])
+            self.gensyms[(SymbolIndex::MAX_AS_U32 - symbol.0.as_u32()) as usize]
         }
     }
 
@@ -510,10 +520,15 @@ impl Interner {
         symbol.0.as_usize() >= self.strings.len()
     }
 
+    // Get the symbol as a string. `Symbol::as_str()` should be used in
+    // preference to this function.
     pub fn get(&self, symbol: Symbol) -> &str {
         match self.strings.get(symbol.0.as_usize()) {
             Some(string) => string,
-            None => self.get(self.gensyms[(SymbolIndex::MAX_AS_U32 - symbol.0.as_u32()) as usize]),
+            None => {
+                let symbol = self.gensyms[(SymbolIndex::MAX_AS_U32 - symbol.0.as_u32()) as usize];
+                self.strings[symbol.0.as_usize()]
+            }
         }
     }
 }
@@ -611,11 +626,17 @@ fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
     GLOBALS.with(|globals| f(&mut *globals.symbol_interner.lock()))
 }
 
-/// Represents a string stored in the interner. Because the interner outlives any thread
-/// which uses this type, we can safely treat `string` which points to interner data,
-/// as an immortal string, as long as this type never crosses between threads.
-// FIXME: ensure that the interner outlives any thread which uses `LocalInternedString`,
-// by creating a new thread right after constructing the interner.
+/// An alternative to `Symbol` and `InternedString`, useful when the chars
+/// within the symbol need to be accessed. It is best used for temporary
+/// values.
+///
+/// Because the interner outlives any thread which uses this type, we can
+/// safely treat `string` which points to interner data, as an immortal string,
+/// as long as this type never crosses between threads.
+//
+// FIXME: ensure that the interner outlives any thread which uses
+// `LocalInternedString`, by creating a new thread right after constructing the
+// interner.
 #[derive(Clone, Copy, Hash, PartialOrd, Eq, Ord)]
 pub struct LocalInternedString {
     string: &'static str,
@@ -708,7 +729,19 @@ impl Encodable for LocalInternedString {
     }
 }
 
-/// Represents a string stored in the string interner.
+/// An alternative to `Symbol` that is focused on string contents. It has two
+/// main differences to `Symbol`.
+///
+/// First, its implementations of `Hash`, `PartialOrd` and `Ord` work with the
+/// string chars rather than the symbol integer. This is useful when hash
+/// stability is required across compile sessions, or a guaranteed sort
+/// ordering is required.
+///
+/// Second, gensym-ness is irrelevant. E.g.:
+/// ```
+/// assert_ne!(Symbol::gensym("x"), Symbol::gensym("x"))
+/// assert_eq!(Symbol::gensym("x").as_interned_str(), Symbol::gensym("x").as_interned_str())
+/// ```
 #[derive(Clone, Copy, Eq)]
 pub struct InternedString {
     symbol: Symbol,
@@ -725,6 +758,15 @@ impl InternedString {
         unsafe { f(&*str) }
     }
 
+    fn with2<F: FnOnce(&str, &str) -> R, R>(self, other: &InternedString, f: F) -> R {
+        let (self_str, other_str) = with_interner(|interner| {
+            (interner.get(self.symbol) as *const str,
+             interner.get(other.symbol) as *const str)
+        });
+        // This is safe for the same reason that `with` is safe.
+        unsafe { f(&*self_str, &*other_str) }
+    }
+
     pub fn as_symbol(self) -> Symbol {
         self.symbol
     }
@@ -745,7 +787,7 @@ impl PartialOrd<InternedString> for InternedString {
         if self.symbol == other.symbol {
             return Some(Ordering::Equal);
         }
-        self.with(|self_str| other.with(|other_str| self_str.partial_cmp(other_str)))
+        self.with2(other, |self_str, other_str| self_str.partial_cmp(other_str))
     }
 }
 
@@ -754,7 +796,7 @@ impl Ord for InternedString {
         if self.symbol == other.symbol {
             return Ordering::Equal;
         }
-        self.with(|self_str| other.with(|other_str| self_str.cmp(&other_str)))
+        self.with2(other, |self_str, other_str| self_str.cmp(other_str))
     }
 }
 
@@ -794,12 +836,6 @@ impl<'a> PartialEq<InternedString> for &'a String {
     }
 }
 
-impl std::convert::From<InternedString> for String {
-    fn from(val: InternedString) -> String {
-        val.as_symbol().to_string()
-    }
-}
-
 impl fmt::Debug for InternedString {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         self.with(|str| fmt::Debug::fmt(&str, f))

src/test/incremental/issue-60629.rs

@@ -0,0 +1,10 @@
+// revisions:rpass1 rpass2
+
+struct A;
+
+#[cfg(rpass2)]
+impl From<A> for () {
+    fn from(_: A) {}
+}
+
+fn main() {}

src/test/ui/async-await/issue-60674.rs

@@ -11,4 +11,10 @@ extern crate issue_60674;
 #[issue_60674::attr]
 async fn f(mut x: u8) {}
 
+#[issue_60674::attr]
+async fn g((mut x, y, mut z): (u8, u8, u8)) {}
+
+#[issue_60674::attr]
+async fn g(mut x: u8, (a, mut b, c): (u8, u8, u8), y: u8) {}
+
 fn main() {}

src/test/ui/async-await/issue-60674.stdout

@@ -1 +1,3 @@
 async fn f(mut x: u8) { }
+async fn g((mut x, y, mut z): (u8, u8, u8)) { }
+async fn g(mut x: u8, (a, mut b, c): (u8, u8, u8), y: u8) { }

src/test/ui/pattern/const-pat-ice.stderr

@@ -1,4 +1,4 @@
-thread 'rustc' panicked at 'assertion failed: rows.iter().all(|r| r.len() == v.len())', src/librustc_mir/hair/pattern/_match.rs:1071:5
+thread 'rustc' panicked at 'assertion failed: rows.iter().all(|r| r.len() == v.len())', src/librustc_mir/hair/pattern/_match.rs:1083:5
 note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
 
 error: internal compiler error: unexpected panic