Auto merge of #60460 - Centril:rollup-gz5bc8i, r=Centril

Rollup of 7 pull requests

Successful merges:

 - #59634 (Added an explanation for the E0704 error.)
 - #60348 (move some functions from parser.rs to diagostics.rs)
 - #60385 (Emit metadata files earlier)
 - #60428 (Refactor `eval_body_using_ecx` so that it doesn't need to query for MIR)
 - #60437 (Ensure that drop order of `async fn` matches `fn` and that users cannot refer to generated arguments.)
 - #60439 (doc: Warn about possible zombie apocalypse)
 - #60452 (Remove Context and ContextKind)

Failed merges:

r? @ghost

3 files changed, 280 insertions, 177 deletions

diff --git a/src/libsyntax/parse/diagnostics.rs b/src/libsyntax/parse/diagnostics.rs
new file mode 100644
index 00000000000..32e1ee94f0d
--- /dev/null
+++ b/src/libsyntax/parse/diagnostics.rs
@@ -0,0 +1,226 @@
+use crate::ast;
+use crate::ast::{Expr, ExprKind, Item, ItemKind, Pat, PatKind, QSelf, Ty, TyKind};
+use crate::parse::parser::PathStyle;
+use crate::parse::token;
+use crate::parse::PResult;
+use crate::parse::Parser;
+use crate::print::pprust;
+use crate::ptr::P;
+use crate::ThinVec;
+use errors::Applicability;
+use syntax_pos::Span;
+
+pub trait RecoverQPath: Sized + 'static {
+    const PATH_STYLE: PathStyle = PathStyle::Expr;
+    fn to_ty(&self) -> Option<P<Ty>>;
+    fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self;
+}
+
+impl RecoverQPath for Ty {
+    const PATH_STYLE: PathStyle = PathStyle::Type;
+    fn to_ty(&self) -> Option<P<Ty>> {
+        Some(P(self.clone()))
+    }
+    fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
+        Self {
+            span: path.span,
+            node: TyKind::Path(qself, path),
+            id: ast::DUMMY_NODE_ID,
+        }
+    }
+}
+
+impl RecoverQPath for Pat {
+    fn to_ty(&self) -> Option<P<Ty>> {
+        self.to_ty()
+    }
+    fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
+        Self {
+            span: path.span,
+            node: PatKind::Path(qself, path),
+            id: ast::DUMMY_NODE_ID,
+        }
+    }
+}
+
+impl RecoverQPath for Expr {
+    fn to_ty(&self) -> Option<P<Ty>> {
+        self.to_ty()
+    }
+    fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
+        Self {
+            span: path.span,
+            node: ExprKind::Path(qself, path),
+            attrs: ThinVec::new(),
+            id: ast::DUMMY_NODE_ID,
+        }
+    }
+}
+
+impl<'a> Parser<'a> {
+    crate fn maybe_report_ambiguous_plus(
+        &mut self,
+        allow_plus: bool,
+        impl_dyn_multi: bool,
+        ty: &Ty,
+    ) {
+        if !allow_plus && impl_dyn_multi {
+            let sum_with_parens = format!("({})", pprust::ty_to_string(&ty));
+            self.struct_span_err(ty.span, "ambiguous `+` in a type")
+                .span_suggestion(
+                    ty.span,
+                    "use parentheses to disambiguate",
+                    sum_with_parens,
+                    Applicability::MachineApplicable,
+                )
+                .emit();
+        }
+    }
+
+    crate fn maybe_recover_from_bad_type_plus(
+        &mut self,
+        allow_plus: bool,
+        ty: &Ty,
+    ) -> PResult<'a, ()> {
+        // Do not add `+` to expected tokens.
+        if !allow_plus || !self.token.is_like_plus() {
+            return Ok(());
+        }
+
+        self.bump(); // `+`
+        let bounds = self.parse_generic_bounds(None)?;
+        let sum_span = ty.span.to(self.prev_span);
+
+        let mut err = struct_span_err!(
+            self.sess.span_diagnostic,
+            sum_span,
+            E0178,
+            "expected a path on the left-hand side of `+`, not `{}`",
+            pprust::ty_to_string(ty)
+        );
+
+        match ty.node {
+            TyKind::Rptr(ref lifetime, ref mut_ty) => {
+                let sum_with_parens = pprust::to_string(|s| {
+                    use crate::print::pprust::PrintState;
+
+                    s.s.word("&")?;
+                    s.print_opt_lifetime(lifetime)?;
+                    s.print_mutability(mut_ty.mutbl)?;
+                    s.popen()?;
+                    s.print_type(&mut_ty.ty)?;
+                    s.print_type_bounds(" +", &bounds)?;
+                    s.pclose()
+                });
+                err.span_suggestion(
+                    sum_span,
+                    "try adding parentheses",
+                    sum_with_parens,
+                    Applicability::MachineApplicable,
+                );
+            }
+            TyKind::Ptr(..) | TyKind::BareFn(..) => {
+                err.span_label(sum_span, "perhaps you forgot parentheses?");
+            }
+            _ => {
+                err.span_label(sum_span, "expected a path");
+            }
+        }
+        err.emit();
+        Ok(())
+    }
+
+    /// Try to recover from associated item paths like `[T]::AssocItem`/`(T, U)::AssocItem`.
+    /// Attempt to convert the base expression/pattern/type into a type, parse the `::AssocItem`
+    /// tail, and combine them into a `<Ty>::AssocItem` expression/pattern/type.
+    crate fn maybe_recover_from_bad_qpath<T: RecoverQPath>(
+        &mut self,
+        base: P<T>,
+        allow_recovery: bool,
+    ) -> PResult<'a, P<T>> {
+        // Do not add `::` to expected tokens.
+        if allow_recovery && self.token == token::ModSep {
+            if let Some(ty) = base.to_ty() {
+                return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
+            }
+        }
+        Ok(base)
+    }
+
+    /// Given an already parsed `Ty` parse the `::AssocItem` tail and
+    /// combine them into a `<Ty>::AssocItem` expression/pattern/type.
+    crate fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(
+        &mut self,
+        ty_span: Span,
+        ty: P<Ty>,
+    ) -> PResult<'a, P<T>> {
+        self.expect(&token::ModSep)?;
+
+        let mut path = ast::Path {
+            segments: Vec::new(),
+            span: syntax_pos::DUMMY_SP,
+        };
+        self.parse_path_segments(&mut path.segments, T::PATH_STYLE)?;
+        path.span = ty_span.to(self.prev_span);
+
+        let ty_str = self
+            .sess
+            .source_map()
+            .span_to_snippet(ty_span)
+            .unwrap_or_else(|_| pprust::ty_to_string(&ty));
+        self.diagnostic()
+            .struct_span_err(path.span, "missing angle brackets in associated item path")
+            .span_suggestion(
+                // this is a best-effort recovery
+                path.span,
+                "try",
+                format!("<{}>::{}", ty_str, path),
+                Applicability::MaybeIncorrect,
+            )
+            .emit();
+
+        let path_span = ty_span.shrink_to_hi(); // use an empty path since `position` == 0
+        Ok(P(T::recovered(
+            Some(QSelf {
+                ty,
+                path_span,
+                position: 0,
+            }),
+            path,
+        )))
+    }
+
+    crate fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
+        if self.eat(&token::Semi) {
+            let mut err = self.struct_span_err(self.prev_span, "expected item, found `;`");
+            err.span_suggestion_short(
+                self.prev_span,
+                "remove this semicolon",
+                String::new(),
+                Applicability::MachineApplicable,
+            );
+            if !items.is_empty() {
+                let previous_item = &items[items.len() - 1];
+                let previous_item_kind_name = match previous_item.node {
+                    // say "braced struct" because tuple-structs and
+                    // braceless-empty-struct declarations do take a semicolon
+                    ItemKind::Struct(..) => Some("braced struct"),
+                    ItemKind::Enum(..) => Some("enum"),
+                    ItemKind::Trait(..) => Some("trait"),
+                    ItemKind::Union(..) => Some("union"),
+                    _ => None,
+                };
+                if let Some(name) = previous_item_kind_name {
+                    err.help(&format!(
+                        "{} declarations are not followed by a semicolon",
+                        name
+                    ));
+                }
+            }
+            err.emit();
+            true
+        } else {
+            false
+        }
+    }
+}
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index 1abc7832ffa..85a74df2357 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -30,6 +30,7 @@ pub mod parser;
 pub mod lexer;
 pub mod token;
 pub mod attr;
+pub mod diagnostics;
 
 pub mod classify;
 
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 8efe84cdf01..f70acb3e7da 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -189,41 +189,6 @@ enum PrevTokenKind {
     Other,
 }
 
-trait RecoverQPath: Sized + 'static {
-    const PATH_STYLE: PathStyle = PathStyle::Expr;
-    fn to_ty(&self) -> Option<P<Ty>>;
-    fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self;
-}
-
-impl RecoverQPath for Ty {
-    const PATH_STYLE: PathStyle = PathStyle::Type;
-    fn to_ty(&self) -> Option<P<Ty>> {
-        Some(P(self.clone()))
-    }
-    fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
-        Self { span: path.span, node: TyKind::Path(qself, path), id: ast::DUMMY_NODE_ID }
-    }
-}
-
-impl RecoverQPath for Pat {
-    fn to_ty(&self) -> Option<P<Ty>> {
-        self.to_ty()
-    }
-    fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
-        Self { span: path.span, node: PatKind::Path(qself, path), id: ast::DUMMY_NODE_ID }
-    }
-}
-
-impl RecoverQPath for Expr {
-    fn to_ty(&self) -> Option<P<Ty>> {
-        self.to_ty()
-    }
-    fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
-        Self { span: path.span, node: ExprKind::Path(qself, path),
-               attrs: ThinVec::new(), id: ast::DUMMY_NODE_ID }
-    }
-}
-
 /* ident is handled by common.rs */
 
 #[derive(Clone)]
@@ -1479,7 +1444,7 @@ impl<'a> Parser<'a> {
     fn span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) {
         self.sess.span_diagnostic.span_err(sp, m)
     }
-    fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
+    crate fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
         self.sess.span_diagnostic.struct_span_err(sp, m)
     }
     fn struct_span_warn<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
@@ -1882,99 +1847,6 @@ impl<'a> Parser<'a> {
         Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
     }
 
-    fn maybe_report_ambiguous_plus(&mut self, allow_plus: bool, impl_dyn_multi: bool, ty: &Ty) {
-        if !allow_plus && impl_dyn_multi {
-            let sum_with_parens = format!("({})", pprust::ty_to_string(&ty));
-            self.struct_span_err(ty.span, "ambiguous `+` in a type")
-                .span_suggestion(
-                    ty.span,
-                    "use parentheses to disambiguate",
-                    sum_with_parens,
-                    Applicability::MachineApplicable
-                ).emit();
-        }
-    }
-
-    fn maybe_recover_from_bad_type_plus(&mut self, allow_plus: bool, ty: &Ty) -> PResult<'a, ()> {
-        // Do not add `+` to expected tokens.
-        if !allow_plus || !self.token.is_like_plus() {
-            return Ok(())
-        }
-
-        self.bump(); // `+`
-        let bounds = self.parse_generic_bounds(None)?;
-        let sum_span = ty.span.to(self.prev_span);
-
-        let mut err = struct_span_err!(self.sess.span_diagnostic, sum_span, E0178,
-            "expected a path on the left-hand side of `+`, not `{}`", pprust::ty_to_string(ty));
-
-        match ty.node {
-            TyKind::Rptr(ref lifetime, ref mut_ty) => {
-                let sum_with_parens = pprust::to_string(|s| {
-                    use crate::print::pprust::PrintState;
-
-                    s.s.word("&")?;
-                    s.print_opt_lifetime(lifetime)?;
-                    s.print_mutability(mut_ty.mutbl)?;
-                    s.popen()?;
-                    s.print_type(&mut_ty.ty)?;
-                    s.print_type_bounds(" +", &bounds)?;
-                    s.pclose()
-                });
-                err.span_suggestion(
-                    sum_span,
-                    "try adding parentheses",
-                    sum_with_parens,
-                    Applicability::MachineApplicable
-                );
-            }
-            TyKind::Ptr(..) | TyKind::BareFn(..) => {
-                err.span_label(sum_span, "perhaps you forgot parentheses?");
-            }
-            _ => {
-                err.span_label(sum_span, "expected a path");
-            },
-        }
-        err.emit();
-        Ok(())
-    }
-
-    /// Try to recover from associated item paths like `[T]::AssocItem`/`(T, U)::AssocItem`.
-    /// Attempt to convert the base expression/pattern/type into a type, parse the `::AssocItem`
-    /// tail, and combine them into a `<Ty>::AssocItem` expression/pattern/type.
-    fn maybe_recover_from_bad_qpath<T: RecoverQPath>(&mut self, base: P<T>, allow_recovery: bool)
-                                                     -> PResult<'a, P<T>> {
-        // Do not add `::` to expected tokens.
-        if allow_recovery && self.token == token::ModSep {
-            if let Some(ty) = base.to_ty() {
-                return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
-            }
-        }
-        Ok(base)
-    }
-
-    /// Given an already parsed `Ty` parse the `::AssocItem` tail and
-    /// combine them into a `<Ty>::AssocItem` expression/pattern/type.
-    fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(&mut self, ty_span: Span, ty: P<Ty>)
-                                                             -> PResult<'a, P<T>> {
-        self.expect(&token::ModSep)?;
-
-        let mut path = ast::Path { segments: Vec::new(), span: syntax_pos::DUMMY_SP };
-        self.parse_path_segments(&mut path.segments, T::PATH_STYLE)?;
-        path.span = ty_span.to(self.prev_span);
-
-        let ty_str = self.sess.source_map().span_to_snippet(ty_span)
-            .unwrap_or_else(|_| pprust::ty_to_string(&ty));
-        self.diagnostic()
-            .struct_span_err(path.span, "missing angle brackets in associated item path")
-            .span_suggestion( // this is a best-effort recovery
-                path.span, "try", format!("<{}>::{}", ty_str, path), Applicability::MaybeIncorrect
-            ).emit();
-
-        let path_span = ty_span.shrink_to_hi(); // use an empty path since `position` == 0
-        Ok(P(T::recovered(Some(QSelf { ty, path_span, position: 0 }), path)))
-    }
-
     fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
         let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
         let mutbl = self.parse_mutability();
@@ -2410,7 +2282,7 @@ impl<'a> Parser<'a> {
         self.parse_path(style)
     }
 
-    fn parse_path_segments(&mut self,
+    crate fn parse_path_segments(&mut self,
                            segments: &mut Vec<PathSegment>,
                            style: PathStyle)
                            -> PResult<'a, ()> {
@@ -5815,7 +5687,8 @@ impl<'a> Parser<'a> {
         return Ok(bounds);
     }
 
-    fn parse_generic_bounds(&mut self, colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
+    crate fn parse_generic_bounds(&mut self,
+                                  colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
         self.parse_generic_bounds_common(true, colon_span)
     }
 
@@ -7352,37 +7225,6 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
-        if self.eat(&token::Semi) {
-            let mut err = self.struct_span_err(self.prev_span, "expected item, found `;`");
-            err.span_suggestion_short(
-                self.prev_span,
-                "remove this semicolon",
-                String::new(),
-                Applicability::MachineApplicable,
-            );
-            if !items.is_empty() {
-                let previous_item = &items[items.len()-1];
-                let previous_item_kind_name = match previous_item.node {
-                    // say "braced struct" because tuple-structs and
-                    // braceless-empty-struct declarations do take a semicolon
-                    ItemKind::Struct(..) => Some("braced struct"),
-                    ItemKind::Enum(..) => Some("enum"),
-                    ItemKind::Trait(..) => Some("trait"),
-                    ItemKind::Union(..) => Some("union"),
-                    _ => None,
-                };
-                if let Some(name) = previous_item_kind_name {
-                    err.help(&format!("{} declarations are not followed by a semicolon", name));
-                }
-            }
-            err.emit();
-            true
-        } else {
-            false
-        }
-    }
-
     /// Given a termination token, parses all of the items in a module.
     fn parse_mod_items(&mut self, term: &token::Token, inner_lo: Span) -> PResult<'a, Mod> {
         let mut items = vec![];
@@ -8878,13 +8720,39 @@ impl<'a> Parser<'a> {
 
                 // Construct a name for our temporary argument.
                 let name = format!("__arg{}", index);
-                let ident = Ident::from_str(&name);
+                let ident = Ident::from_str(&name).gensym();
+
+                // Check if this is a ident pattern, if so, we can optimize and avoid adding a
+                // `let <pat> = __argN;` statement, instead just adding a `let <pat> = <pat>;`
+                // statement.
+                let (ident, is_simple_pattern) = match input.pat.node {
+                    PatKind::Ident(_, ident, _) => (ident, true),
+                    _ => (ident, false),
+                };
 
                 // Construct an argument representing `__argN: <ty>` to replace the argument of the
-                // async function.
-                let arg = Arg {
-                    ty: input.ty.clone(),
-                    id,
+                // async function if it isn't a simple pattern.
+                let arg = if is_simple_pattern {
+                    None
+                } else {
+                    Some(Arg {
+                        ty: input.ty.clone(),
+                        id,
+                        pat: P(Pat {
+                            id,
+                            node: PatKind::Ident(
+                                BindingMode::ByValue(Mutability::Immutable), ident, None,
+                            ),
+                            span,
+                        }),
+                        source: ArgSource::AsyncFn(input.pat.clone()),
+                    })
+                };
+
+                // Construct a `let __argN = __argN;` statement to insert at the top of the
+                // async closure. This makes sure that the argument is captured by the closure and
+                // that the drop order is correct.
+                let move_local = Local {
                     pat: P(Pat {
                         id,
                         node: PatKind::Ident(
@@ -8892,13 +8760,6 @@ impl<'a> Parser<'a> {
                         ),
                         span,
                     }),
-                    source: ArgSource::AsyncFn(input.pat.clone()),
-                };
-
-                // Construct a `let <pat> = __argN;` statement to insert at the top of the
-                // async closure.
-                let local = P(Local {
-                    pat: input.pat.clone(),
                     // We explicitly do not specify the type for this statement. When the user's
                     // argument type is `impl Trait` then this would require the
                     // `impl_trait_in_bindings` feature to also be present for that same type to
@@ -8918,10 +8779,25 @@ impl<'a> Parser<'a> {
                     span,
                     attrs: ThinVec::new(),
                     source: LocalSource::AsyncFn,
-                });
-                let stmt = Stmt { id, node: StmtKind::Local(local), span, };
+                };
+
+                // Construct a `let <pat> = __argN;` statement to insert at the top of the
+                // async closure if this isn't a simple pattern.
+                let pat_stmt = if is_simple_pattern {
+                    None
+                } else {
+                    Some(Stmt {
+                        id,
+                        node: StmtKind::Local(P(Local {
+                            pat: input.pat.clone(),
+                            ..move_local.clone()
+                        })),
+                        span,
+                    })
+                };
 
-                arguments.push(AsyncArgument { ident, arg, stmt });
+                let move_stmt = Stmt { id, node: StmtKind::Local(P(move_local)), span };
+                arguments.push(AsyncArgument { ident, arg, pat_stmt, move_stmt });
             }
         }
     }