Remove UnsafetyState.

`FnCtxt::ps` is the only occurrence. It gets updated during HIR
typechecking, but is never looked at.

Author: nnethercote

compiler/rustc_hir_typeck/src/check.rs

@@ -1,7 +1,7 @@
 use crate::coercion::CoerceMany;
 use crate::gather_locals::GatherLocalsVisitor;
 use crate::FnCtxt;
-use crate::{GeneratorTypes, UnsafetyState};
+use crate::GeneratorTypes;
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::intravisit::Visitor;
@@ -30,7 +30,6 @@ pub(super) fn check_fn<'a, 'tcx>(
     can_be_generator: Option<hir::Movability>,
 ) -> Option<GeneratorTypes<'tcx>> {
     let fn_id = fcx.tcx.hir().local_def_id_to_hir_id(fn_def_id);
-    fcx.ps.set(UnsafetyState::function(fn_sig.unsafety, fn_id));
 
     let tcx = fcx.tcx;
     let hir = tcx.hir();

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -1393,8 +1393,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         blk: &'tcx hir::Block<'tcx>,
         expected: Expectation<'tcx>,
     ) -> Ty<'tcx> {
-        let prev = self.ps.replace(self.ps.get().recurse(blk));
-
         // In some cases, blocks have just one exit, but other blocks
         // can be targeted by multiple breaks. This can happen both
         // with labeled blocks as well as when we desugar
@@ -1558,7 +1556,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         self.write_ty(blk.hir_id, ty);
 
-        self.ps.set(prev);
         ty
     }
 

compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs

@@ -8,7 +8,7 @@ use rustc_errors::ErrorGuaranteed;
 pub use suggestions::*;
 
 use crate::coercion::DynamicCoerceMany;
-use crate::{Diverges, EnclosingBreakables, Inherited, UnsafetyState};
+use crate::{Diverges, EnclosingBreakables, Inherited};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir_analysis::astconv::AstConv;
@@ -74,8 +74,6 @@ pub struct FnCtxt<'a, 'tcx> {
 
     pub(super) resume_yield_tys: Option<(Ty<'tcx>, Ty<'tcx>)>,
 
-    pub(super) ps: Cell<UnsafetyState>,
-
     /// Whether the last checked node generates a divergence (e.g.,
     /// `return` will set this to `Always`). In general, when entering
     /// an expression or other node in the tree, the initial value
@@ -129,7 +127,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             ret_coercion: None,
             ret_coercion_span: Cell::new(None),
             resume_yield_tys: None,
-            ps: Cell::new(UnsafetyState::function(hir::Unsafety::Normal, hir::CRATE_HIR_ID)),
             diverges: Cell::new(Diverges::Maybe),
             enclosing_breakables: RefCell::new(EnclosingBreakables {
                 stack: Vec::new(),

compiler/rustc_hir_typeck/src/lib.rs

@@ -89,38 +89,6 @@ pub struct LocalTy<'tcx> {
     revealed_ty: Ty<'tcx>,
 }
 
-#[derive(Copy, Clone)]
-pub struct UnsafetyState {
-    pub def: hir::HirId,
-    pub unsafety: hir::Unsafety,
-    from_fn: bool,
-}
-
-impl UnsafetyState {
-    pub fn function(unsafety: hir::Unsafety, def: hir::HirId) -> UnsafetyState {
-        UnsafetyState { def, unsafety, from_fn: true }
-    }
-
-    pub fn recurse(self, blk: &hir::Block<'_>) -> UnsafetyState {
-        use hir::BlockCheckMode;
-        match self.unsafety {
-            // If this unsafe, then if the outer function was already marked as
-            // unsafe we shouldn't attribute the unsafe'ness to the block. This
-            // way the block can be warned about instead of ignoring this
-            // extraneous block (functions are never warned about).
-            hir::Unsafety::Unsafe if self.from_fn => self,
-
-            unsafety => {
-                let (unsafety, def) = match blk.rules {
-                    BlockCheckMode::UnsafeBlock(..) => (hir::Unsafety::Unsafe, blk.hir_id),
-                    BlockCheckMode::DefaultBlock => (unsafety, self.def),
-                };
-                UnsafetyState { def, unsafety, from_fn: false }
-            }
-        }
-    }
-}
-
 /// If this `DefId` is a "primary tables entry", returns
 /// `Some((body_id, body_ty, fn_sig))`. Otherwise, returns `None`.
 ///