Remove suggestions of making pin const mutable

Author: frank-king

compiler/rustc_middle/src/mir/mod.rs

@@ -20,6 +20,7 @@ use rustc_hir::def::{CtorKind, Namespace};
 use rustc_hir::def_id::{CRATE_DEF_ID, DefId};
 use rustc_hir::{
     self as hir, BindingMode, ByRef, CoroutineDesugaring, CoroutineKind, HirId, ImplicitSelfKind,
+    Pinnedness,
 };
 use rustc_index::bit_set::DenseBitSet;
 use rustc_index::{Idx, IndexSlice, IndexVec};
@@ -1122,7 +1123,8 @@ impl<'tcx> LocalDecl<'tcx> {
             self.local_info(),
             LocalInfo::User(
                 BindingForm::Var(VarBindingForm {
-                    binding_mode: BindingMode(ByRef::No, _, _),
+                    // FIXME(pin_ergonomics): `pin const` can also be made mutable, but needs special handling.
+                    binding_mode: BindingMode(ByRef::No, Pinnedness::Not, _),
                     opt_ty_info: _,
                     opt_match_place: _,
                     pat_span: _,

tests/ui/async-await/pin-ergonomics/pinned-local-no-const.stderr

@@ -6,8 +6,9 @@ LL |     let pin x = Foo;
    |
 help: there is a keyword `in` with a similar name
    |
-LL |     let in x = Foo;
-   |         ~~
+LL -     let pin x = Foo;
+LL +     let in x = Foo;
+   |
 
 error: aborting due to 1 previous error
 

tests/ui/async-await/pin-ergonomics/pinned-local.stderr

@@ -6,11 +6,6 @@ LL |     let pin const y = Foo;
 LL |     x = Foo; // FIXME: this should be an error
 LL |     y = Foo;
    |     ^^^^^^^ cannot assign twice to immutable variable
-   |
-help: consider making this binding mutable
-   |
-LL |     let mut pin const y = Foo;
-   |         +++
 
 error[E0384]: cannot assign twice to immutable variable `y`
   --> $DIR/pinned-local.rs:16:5
@@ -20,15 +15,6 @@ LL |     let (pin mut x, pin const y) = (Foo, Foo);
 LL |     x = Foo; // FIXME: this should be an error
 LL |     y = Foo;
    |     ^^^^^^^ cannot assign twice to immutable variable
-   |
-help: consider making this binding mutable
-   |
-LL |     let (pin mut x, mut pin const y) = (Foo, Foo);
-   |                     +++
-help: to modify the original value, take a borrow instead
-   |
-LL |     let (pin mut x, ref mut pin const y) = (Foo, Foo);
-   |                     +++++++
 
 error: aborting due to 2 previous errors
 

tests/ui/feature-gates/feature-gate-pin_ergonomics.stderr

@@ -94,11 +94,6 @@ LL |     let pin const y = Foo;
 LL |     x = Foo; // FIXME: this should be an error
 LL |     y = Foo;
    |     ^^^^^^^ cannot assign twice to immutable variable
-   |
-help: consider making this binding mutable
-   |
-LL |     let mut pin const y = Foo;
-   |         +++
 
 error: aborting due to 8 previous errors