Auto merge of #81596 - jonas-schievink:rollup-utk14gr, r=jonas-schievink

Rollup of 11 pull requests

Successful merges:

 - #80092 (2229: Fix issues with move closures and mutability)
 - #80404 (Remove const_in_array_repeat)
 - #81255 (Don't link with --export-dynamic on wasm32-wasi)
 - #81480 (Add suggestion for nested fields)
 - #81549 (Misc ip documentation fixes)
 - #81566 (Add a test for #71202)
 - #81568 (Fix an old FIXME in redundant paren lint)
 - #81571 (Fix typo in E0759)
 - #81572 (Edit multiple error code Markdown files)
 - #81589 (Fix small typo in string.rs)
 - #81590 (Stabilize int_bits_const)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_data_structures/src/lib.rs

@@ -13,7 +13,6 @@
 #![feature(unboxed_closures)]
 #![feature(generator_trait)]
 #![feature(fn_traits)]
-#![feature(int_bits_const)]
 #![feature(min_specialization)]
 #![feature(auto_traits)]
 #![feature(nll)]

compiler/rustc_error_codes/src/error_codes/E0013.md

@@ -8,7 +8,7 @@ static X: i32 = 42;
 const Y: i32 = X;
 ```
 
-In this example, `Y` cannot refer to `X` here. To fix this, the value can be
+In this example, `Y` cannot refer to `X`. To fix this, the value can be
 extracted as a const and then used:
 
 ```

compiler/rustc_error_codes/src/error_codes/E0038.md

@@ -287,5 +287,5 @@ the method `get_a()` would return an object of unknown type when called on the
 function. `Self` type parameters let us make object safe traits no longer safe,
 so they are forbidden when specifying supertraits.
 
-There's no easy fix for this, generally code will need to be refactored so that
+There's no easy fix for this. Generally, code will need to be refactored so that
 you no longer need to derive from `Super<Self>`.

compiler/rustc_error_codes/src/error_codes/E0107.md

@@ -1,4 +1,4 @@
-An incorrect number of generic arguments were provided.
+An incorrect number of generic arguments was provided.
 
 Erroneous code example:
 

compiler/rustc_error_codes/src/error_codes/E0116.md

@@ -10,7 +10,7 @@ You can only define an inherent implementation for a type in the same crate
 where the type was defined. For example, an `impl` block as above is not allowed
 since `Vec` is defined in the standard library.
 
-To fix this problem, you can do either of these things:
+To fix this problem, you can either:
 
  - define a trait that has the desired associated functions/types/constants and
    implement the trait for the type in question

compiler/rustc_error_codes/src/error_codes/E0277.md

@@ -59,9 +59,9 @@ fn main() {
 }
 ```
 
-Note that the error here is in the definition of the generic function: Although
+Note that the error here is in the definition of the generic function. Although
 we only call it with a parameter that does implement `Debug`, the compiler
-still rejects the function: It must work with all possible input types. In
+still rejects the function. It must work with all possible input types. In
 order to make this example compile, we need to restrict the generic type we're
 accepting:
 

compiler/rustc_error_codes/src/error_codes/E0309.md

@@ -25,7 +25,7 @@ where
 
 The type definition contains some field whose type requires an outlives
 annotation. Outlives annotations (e.g., `T: 'a`) are used to guarantee that all
-the data in T is valid for at least the lifetime `'a`. This scenario most
+the data in `T` is valid for at least the lifetime `'a`. This scenario most
 commonly arises when the type contains an associated type reference like
 `<T as SomeTrait<'a>>::Output`, as shown in the previous code.
 

compiler/rustc_error_codes/src/error_codes/E0597.md

@@ -1,4 +1,4 @@
-This error occurs because a value was dropped while it was still borrowed
+This error occurs because a value was dropped while it was still borrowed.
 
 Erroneous code example:
 
@@ -15,7 +15,7 @@ let mut x = Foo { x: None };
 println!("{:?}", x.x);
 ```
 
-In here, `y` is dropped at the end of the inner scope, but it is borrowed by
+Here, `y` is dropped at the end of the inner scope, but it is borrowed by
 `x` until the `println`. To fix the previous example, just remove the scope
 so that `y` isn't dropped until after the println
 

compiler/rustc_error_codes/src/error_codes/E0658.md

@@ -11,7 +11,7 @@ enum Foo {
 
 If you're using a stable or a beta version of rustc, you won't be able to use
 any unstable features. In order to do so, please switch to a nightly version of
-rustc (by using rustup).
+rustc (by using [rustup]).
 
 If you're using a nightly version of rustc, just add the corresponding feature
 to be able to use it:
@@ -24,3 +24,5 @@ enum Foo {
     Bar(u64),
 }
 ```
+
+[rustup]: https://rust-lang.github.io/rustup/concepts/channels.html

compiler/rustc_error_codes/src/error_codes/E0754.md

@@ -1,4 +1,4 @@
-An non-ascii identifier was used in an invalid context.
+A non-ASCII identifier was used in an invalid context.
 
 Erroneous code examples:
 
@@ -13,7 +13,7 @@ fn řųśť() {} // error!
 fn main() {}
 ```
 
-Non-ascii can be used as module names if it is inlined or if a `#[path]`
+Non-ASCII can be used as module names if it is inlined or if a `#[path]`
 attribute is specified. For example:
 
 ```

compiler/rustc_error_codes/src/error_codes/E0759.md

@@ -27,7 +27,7 @@ fn bar(x: &i32) -> Box<dyn Debug + 'static> { // ok!
 }
 ```
 
-Both [`dyn Trait`] and [`impl Trait`] in return types have a an implicit
+Both [`dyn Trait`] and [`impl Trait`] in return types have an implicit
 `'static` requirement, meaning that the value implementing them that is being
 returned has to be either a `'static` borrow or an owned value.
 

compiler/rustc_feature/src/active.rs

@@ -485,9 +485,6 @@ declare_features! (
     /// Allows `async || body` closures.
     (active, async_closure, "1.37.0", Some(62290), None),
 
-    /// Allows `[x; N]` where `x` is a constant (RFC 2203).
-    (active, const_in_array_repeat_expressions, "1.37.0", Some(49147), None),
-
     /// Allows `impl Trait` to be used inside type aliases (RFC 2515).
     (active, type_alias_impl_trait, "1.38.0", Some(63063), None),
 

compiler/rustc_feature/src/removed.rs

@@ -97,6 +97,9 @@ declare_features! (
     (removed, extern_in_paths, "1.33.0", Some(55600), None,
      Some("subsumed by `::foo::bar` paths")),
     (removed, quote, "1.33.0", Some(29601), None, None),
+    /// Allows `[x; N]` where `x` is a constant (RFC 2203).
+    (removed, const_in_array_repeat_expressions,  "1.37.0", Some(49147), None,
+     Some("removed due to causing promotable bugs")),
     /// Allows using `#[unsafe_destructor_blind_to_params]` (RFC 1238).
     (removed, dropck_parametricity, "1.38.0", Some(28498), None, None),
     (removed, await_macro, "1.38.0", Some(50547), None,

compiler/rustc_lint/src/unused.rs

@@ -977,8 +977,6 @@ impl UnusedDelimLint for UnusedBraces {
                 }
             }
             ast::ExprKind::Let(_, ref expr) => {
-                // FIXME(#60336): Properly handle `let true = (false && true)`
-                // actually needing the parenthesis.
                 self.check_unused_delims_expr(
                     cx,
                     expr,

compiler/rustc_middle/src/traits/mod.rs

@@ -228,8 +228,7 @@ pub enum ObligationCauseCode<'tcx> {
     /// Inline asm operand type must be `Sized`.
     InlineAsmSized,
     /// `[T, ..n]` implies that `T` must be `Copy`.
-    /// If `true`, suggest `const_in_array_repeat_expressions` feature flag.
-    RepeatVec(bool),
+    RepeatVec,
 
     /// Types of fields (other than the last, except for packed structs) in a struct must be sized.
     FieldSized {

compiler/rustc_middle/src/ty/mod.rs

@@ -661,11 +661,28 @@ pub type RootVariableMinCaptureList<'tcx> = FxIndexMap<hir::HirId, MinCaptureLis
 /// Part of `MinCaptureInformationMap`; List of `CapturePlace`s.
 pub type MinCaptureList<'tcx> = Vec<CapturedPlace<'tcx>>;
 
-/// A `Place` and the corresponding `CaptureInfo`.
+/// A composite describing a `Place` that is captured by a closure.
 #[derive(PartialEq, Clone, Debug, TyEncodable, TyDecodable, TypeFoldable, HashStable)]
 pub struct CapturedPlace<'tcx> {
+    /// The `Place` that is captured.
     pub place: HirPlace<'tcx>,
+
+    /// `CaptureKind` and expression(s) that resulted in such capture of `place`.
     pub info: CaptureInfo<'tcx>,
+
+    /// Represents if `place` can be mutated or not.
+    pub mutability: hir::Mutability,
+}
+
+impl CapturedPlace<'tcx> {
+    /// Returns the hir-id of the root variable for the captured place.
+    /// e.g., if `a.b.c` was captured, would return the hir-id for `a`.
+    pub fn get_root_variable(&self) -> hir::HirId {
+        match self.place.base {
+            HirPlaceBase::Upvar(upvar_id) => upvar_id.var_path.hir_id,
+            base => bug!("Expected upvar, found={:?}", base),
+        }
+    }
 }
 
 pub fn place_to_string_for_capture(tcx: TyCtxt<'tcx>, place: &HirPlace<'tcx>) -> String {

compiler/rustc_mir/src/borrow_check/diagnostics/mod.rs

@@ -215,6 +215,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             PlaceRef { local, projection: [proj_base @ .., elem] } => {
                 match elem {
                     ProjectionElem::Deref => {
+                        // FIXME(project-rfc_2229#36): print capture precisely here.
                         let upvar_field_projection = self.is_upvar_field_projection(place);
                         if let Some(field) = upvar_field_projection {
                             let var_index = field.index();
@@ -259,6 +260,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     ProjectionElem::Field(field, _ty) => {
                         autoderef = true;
 
+                        // FIXME(project-rfc_2229#36): print capture precisely here.
                         let upvar_field_projection = self.is_upvar_field_projection(place);
                         if let Some(field) = upvar_field_projection {
                             let var_index = field.index();

compiler/rustc_mir/src/borrow_check/diagnostics/move_errors.rs

@@ -345,7 +345,9 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 };
 
                 let upvar = &self.upvars[upvar_field.unwrap().index()];
-                let upvar_hir_id = upvar.var_hir_id;
+                // FIXME(project-rfc-2229#8): Improve borrow-check diagnostics in case of precise
+                //                            capture.
+                let upvar_hir_id = upvar.place.get_root_variable();
                 let upvar_name = upvar.name;
                 let upvar_span = self.infcx.tcx.hir().span(upvar_hir_id);
 

compiler/rustc_mir/src/borrow_check/diagnostics/mutability_errors.rs

@@ -64,12 +64,29 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     Place::ty_from(local, proj_base, self.body, self.infcx.tcx).ty
                 ));
 
-                item_msg = format!("`{}`", access_place_desc.unwrap());
-                if self.is_upvar_field_projection(access_place.as_ref()).is_some() {
-                    reason = ", as it is not declared as mutable".to_string();
+                let imm_borrow_derefed = self.upvars[upvar_index.index()]
+                    .place
+                    .place
+                    .deref_tys()
+                    .any(|ty| matches!(ty.kind(), ty::Ref(.., hir::Mutability::Not)));
+
+                // If the place is immutable then:
+                //
+                // - Either we deref a immutable ref to get to our final place.
+                //    - We don't capture derefs of raw ptrs
+                // - Or the final place is immut because the root variable of the capture
+                //   isn't marked mut and we should suggest that to the user.
+                if imm_borrow_derefed {
+                    // If we deref an immutable ref then the suggestion here doesn't help.
+                    return;
                 } else {
-                    let name = self.upvars[upvar_index.index()].name;
-                    reason = format!(", as `{}` is not declared as mutable", name);
+                    item_msg = format!("`{}`", access_place_desc.unwrap());
+                    if self.is_upvar_field_projection(access_place.as_ref()).is_some() {
+                        reason = ", as it is not declared as mutable".to_string();
+                    } else {
+                        let name = self.upvars[upvar_index.index()].name;
+                        reason = format!(", as `{}` is not declared as mutable", name);
+                    }
                 }
             }
 
@@ -259,9 +276,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     Place::ty_from(local, proj_base, self.body, self.infcx.tcx).ty
                 ));
 
+                let captured_place = &self.upvars[upvar_index.index()].place;
+
                 err.span_label(span, format!("cannot {ACT}", ACT = act));
 
-                let upvar_hir_id = self.upvars[upvar_index.index()].var_hir_id;
+                let upvar_hir_id = captured_place.get_root_variable();
+
                 if let Some(Node::Binding(pat)) = self.infcx.tcx.hir().find(upvar_hir_id) {
                     if let hir::PatKind::Binding(
                         hir::BindingAnnotation::Unannotated,

compiler/rustc_mir/src/borrow_check/diagnostics/var_name.rs

@@ -12,7 +12,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         tcx: TyCtxt<'tcx>,
         body: &Body<'tcx>,
         local_names: &IndexVec<Local, Option<Symbol>>,
-        upvars: &[Upvar],
+        upvars: &[Upvar<'tcx>],
         fr: RegionVid,
     ) -> Option<(Option<Symbol>, Span)> {
         debug!("get_var_name_and_span_for_region(fr={:?})", fr);
@@ -21,6 +21,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         debug!("get_var_name_and_span_for_region: attempting upvar");
         self.get_upvar_index_for_region(tcx, fr)
             .map(|index| {
+                // FIXME(project-rfc-2229#8): Use place span for diagnostics
                 let (name, span) = self.get_upvar_name_and_span_for_region(tcx, upvars, index);
                 (Some(name), span)
             })
@@ -59,10 +60,10 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     crate fn get_upvar_name_and_span_for_region(
         &self,
         tcx: TyCtxt<'tcx>,
-        upvars: &[Upvar],
+        upvars: &[Upvar<'tcx>],
         upvar_index: usize,
     ) -> (Symbol, Span) {
-        let upvar_hir_id = upvars[upvar_index].var_hir_id;
+        let upvar_hir_id = upvars[upvar_index].place.get_root_variable();
         debug!("get_upvar_name_and_span_for_region: upvar_hir_id={:?}", upvar_hir_id);
 
         let upvar_name = tcx.hir().name(upvar_hir_id);