Auto merge of #113376 - Nilstrieb:pointer-coercions-are-not-casts-because-that-sounds-way-to-general-aaaa, r=oli-obk

Rename `adjustment::PointerCast` and variants using it to `PointerCoercion`

It makes it sounds like the `ExprKind` and `Rvalue` are supposed to represent all pointer related casts, when in reality their just used to share a little enum variants. Make it clear there these are only coercions and that people who see this and think "why are so many pointer related casts not in these variants" aren't insane.

This enum was added in #59987. I'm not sure whether the variant sharing is actually worth it, but this at least makes it less confusing.

r? oli-obk

compiler/rustc_const_eval/src/interpret/cast.rs

@@ -4,7 +4,7 @@ use rustc_apfloat::ieee::{Double, Single};
 use rustc_apfloat::{Float, FloatConvert};
 use rustc_middle::mir::interpret::{InterpResult, PointerArithmetic, Scalar};
 use rustc_middle::mir::CastKind;
-use rustc_middle::ty::adjustment::PointerCast;
+use rustc_middle::ty::adjustment::PointerCoercion;
 use rustc_middle::ty::layout::{IntegerExt, LayoutOf, TyAndLayout};
 use rustc_middle::ty::{self, FloatTy, Ty, TypeAndMut};
 use rustc_target::abi::Integer;
@@ -24,51 +24,52 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         cast_ty: Ty<'tcx>,
         dest: &PlaceTy<'tcx, M::Provenance>,
     ) -> InterpResult<'tcx> {
-        use rustc_middle::mir::CastKind::*;
         // FIXME: In which cases should we trigger UB when the source is uninit?
         match cast_kind {
-            Pointer(PointerCast::Unsize) => {
+            CastKind::PointerCoercion(PointerCoercion::Unsize) => {
                 let cast_ty = self.layout_of(cast_ty)?;
                 self.unsize_into(src, cast_ty, dest)?;
             }
 
-            PointerExposeAddress => {
+            CastKind::PointerExposeAddress => {
                 let src = self.read_immediate(src)?;
                 let res = self.pointer_expose_address_cast(&src, cast_ty)?;
                 self.write_immediate(res, dest)?;
             }
 
-            PointerFromExposedAddress => {
+            CastKind::PointerFromExposedAddress => {
                 let src = self.read_immediate(src)?;
                 let res = self.pointer_from_exposed_address_cast(&src, cast_ty)?;
                 self.write_immediate(res, dest)?;
             }
 
-            IntToInt | IntToFloat => {
+            CastKind::IntToInt | CastKind::IntToFloat => {
                 let src = self.read_immediate(src)?;
                 let res = self.int_to_int_or_float(&src, cast_ty)?;
                 self.write_immediate(res, dest)?;
             }
 
-            FloatToFloat | FloatToInt => {
+            CastKind::FloatToFloat | CastKind::FloatToInt => {
                 let src = self.read_immediate(src)?;
                 let res = self.float_to_float_or_int(&src, cast_ty)?;
                 self.write_immediate(res, dest)?;
             }
 
-            FnPtrToPtr | PtrToPtr => {
+            CastKind::FnPtrToPtr | CastKind::PtrToPtr => {
                 let src = self.read_immediate(&src)?;
                 let res = self.ptr_to_ptr(&src, cast_ty)?;
                 self.write_immediate(res, dest)?;
             }
 
-            Pointer(PointerCast::MutToConstPointer | PointerCast::ArrayToPointer) => {
+            CastKind::PointerCoercion(
+                PointerCoercion::MutToConstPointer | PointerCoercion::ArrayToPointer,
+            ) => {
                 // These are NOPs, but can be wide pointers.
                 let v = self.read_immediate(src)?;
                 self.write_immediate(*v, dest)?;
             }
 
-            Pointer(PointerCast::ReifyFnPointer) => {
+            CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer) => {
                 // All reifications must be monomorphic, bail out otherwise.
                 ensure_monomorphic_enough(*self.tcx, src.layout.ty)?;
 
@@ -90,7 +91,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 }
             }
 
-            Pointer(PointerCast::UnsafeFnPointer) => {
+            CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer) => {
                 let src = self.read_immediate(src)?;
                 match cast_ty.kind() {
                     ty::FnPtr(_) => {
@@ -101,7 +102,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 }
             }
 
-            Pointer(PointerCast::ClosureFnPointer(_)) => {
+            CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_)) => {
                 // All reifications must be monomorphic, bail out otherwise.
                 ensure_monomorphic_enough(*self.tcx, src.layout.ty)?;
 
@@ -122,7 +123,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 }
             }
 
-            DynStar => {
+            CastKind::DynStar => {
                 if let ty::Dynamic(data, _, ty::DynStar) = cast_ty.kind() {
                     // Initial cast from sized to dyn trait
                     let vtable = self.get_vtable_ptr(src.layout.ty, data.principal())?;
@@ -136,7 +137,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 }
             }
 
-            Transmute => {
+            CastKind::Transmute => {
                 assert!(src.layout.is_sized());
                 assert!(dest.layout.is_sized());
                 if src.layout.size != dest.layout.size {

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -9,7 +9,7 @@ use rustc_infer::traits::{ImplSource, Obligation, ObligationCause};
 use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts};
-use rustc_middle::ty::{self, adjustment::PointerCast, Instance, InstanceDef, Ty, TyCtxt};
+use rustc_middle::ty::{self, adjustment::PointerCoercion, Instance, InstanceDef, Ty, TyCtxt};
 use rustc_middle::ty::{TraitRef, TypeVisitableExt};
 use rustc_mir_dataflow::{self, Analysis};
 use rustc_span::{sym, Span, Symbol};
@@ -521,12 +521,12 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
             }
 
             Rvalue::Cast(
-                CastKind::Pointer(
-                    PointerCast::MutToConstPointer
-                    | PointerCast::ArrayToPointer
-                    | PointerCast::UnsafeFnPointer
-                    | PointerCast::ClosureFnPointer(_)
-                    | PointerCast::ReifyFnPointer,
+                CastKind::PointerCoercion(
+                    PointerCoercion::MutToConstPointer
+                    | PointerCoercion::ArrayToPointer
+                    | PointerCoercion::UnsafeFnPointer
+                    | PointerCoercion::ClosureFnPointer(_)
+                    | PointerCoercion::ReifyFnPointer,
                 ),
                 _,
                 _,
@@ -534,7 +534,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                 // These are all okay; they only change the type, not the data.
             }
 
-            Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), _, _) => {
+            Rvalue::Cast(CastKind::PointerCoercion(PointerCoercion::Unsize), _, _) => {
                 // Unsizing is implemented for CTFE.
             }
 

compiler/rustc_const_eval/src/transform/validate.rs

@@ -650,7 +650,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                     // FIXME: Add Checks for these
                     CastKind::PointerFromExposedAddress
                     | CastKind::PointerExposeAddress
-                    | CastKind::Pointer(_) => {}
+                    | CastKind::PointerCoercion(_) => {}
                     CastKind::IntToInt | CastKind::IntToFloat => {
                         let input_valid = op_ty.is_integral() || op_ty.is_char() || op_ty.is_bool();
                         let target_valid = target_type.is_numeric() || target_type.is_char();