Rollup merge of #141811 - mejrs:bye_locals, r=compiler-errors

Unimplement unsized_locals

Implements https://github.com/rust-lang/compiler-team/issues/630

Tracking issue here: https://github.com/rust-lang/rust/issues/111942

Note that this just removes the feature, not the implementation, and does not touch `unsized_fn_params`. This is because it is required to support `Box<dyn FnOnce()>: FnOnce()`.

There may be more that should be removed (possibly in follow up prs)
- the `forget_unsized` function and `forget` intrinsic.
- the `unsized_locals` test directory; I've just fixed up the tests for now
- various codegen support for unsized values and allocas

cc ``@JakobDegen`` ``@oli-obk`` ``@Noratrieb`` ``@programmerjake`` ``@bjorn3``

``@rustbot`` label F-unsized_locals

Fixes rust-lang/rust#79409

2 files changed, 3 insertions, 12 deletions

diff --git a/compiler/rustc_mir_transform/src/coroutine.rs b/compiler/rustc_mir_transform/src/coroutine.rs
index d5d0d56f528..06c6b46a9c2 100644
--- a/compiler/rustc_mir_transform/src/coroutine.rs
+++ b/compiler/rustc_mir_transform/src/coroutine.rs
@@ -1417,9 +1417,9 @@ fn check_field_tys_sized<'tcx>(
     coroutine_layout: &CoroutineLayout<'tcx>,
     def_id: LocalDefId,
 ) {
-    // No need to check if unsized_locals/unsized_fn_params is disabled,
+    // No need to check if unsized_fn_params is disabled,
     // since we will error during typeck.
-    if !tcx.features().unsized_locals() && !tcx.features().unsized_fn_params() {
+    if !tcx.features().unsized_fn_params() {
         return;
     }
 
diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs
index 92c30d239b5..bda71ceaa55 100644
--- a/compiler/rustc_mir_transform/src/gvn.rs
+++ b/compiler/rustc_mir_transform/src/gvn.rs
@@ -240,8 +240,6 @@ struct VnState<'body, 'tcx> {
     next_opaque: usize,
     /// Cache the deref values.
     derefs: Vec<VnIndex>,
-    /// Cache the value of the `unsized_locals` features, to avoid fetching it repeatedly in a loop.
-    feature_unsized_locals: bool,
     ssa: &'body SsaLocals,
     dominators: Dominators<BasicBlock>,
     reused_locals: DenseBitSet<Local>,
@@ -273,7 +271,6 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
             evaluated: IndexVec::with_capacity(num_values),
             next_opaque: 1,
             derefs: Vec::new(),
-            feature_unsized_locals: tcx.features().unsized_locals(),
             ssa,
             dominators,
             reused_locals: DenseBitSet::new_empty(local_decls.len()),
@@ -329,13 +326,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
     fn assign(&mut self, local: Local, value: VnIndex) {
         debug_assert!(self.ssa.is_ssa(local));
         self.locals[local] = Some(value);
-
-        // Only register the value if its type is `Sized`, as we will emit copies of it.
-        let is_sized = !self.feature_unsized_locals
-            || self.local_decls[local].ty.is_sized(self.tcx, self.typing_env());
-        if is_sized {
-            self.rev_locals[value].push(local);
-        }
+        self.rev_locals[value].push(local);
     }
 
     fn insert_constant(&mut self, value: Const<'tcx>) -> VnIndex {