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

1 files changed, 13 insertions, 9 deletions

diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
index ab9eb421c5a..956f03d2578 100644
--- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -11,7 +11,7 @@ use rustc_middle::mir;
 use rustc_middle::mir::Operand;
 use rustc_middle::ty::cast::{CastTy, IntTy};
 use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf, TyAndLayout};
-use rustc_middle::ty::{self, adjustment::PointerCast, Instance, Ty, TyCtxt};
+use rustc_middle::ty::{self, adjustment::PointerCoercion, Instance, Ty, TyCtxt};
 use rustc_session::config::OptLevel;
 use rustc_span::source_map::{Span, DUMMY_SP};
 use rustc_target::abi::{self, FIRST_VARIANT};
@@ -32,7 +32,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 cg_operand.val.store(bx, dest);
             }
 
-            mir::Rvalue::Cast(mir::CastKind::Pointer(PointerCast::Unsize), ref source, _) => {
+            mir::Rvalue::Cast(
+                mir::CastKind::PointerCoercion(PointerCoercion::Unsize),
+                ref source,
+                _,
+            ) => {
                 // The destination necessarily contains a fat pointer, so if
                 // it's a scalar pair, it's a fat pointer or newtype thereof.
                 if bx.cx().is_backend_scalar_pair(dest.layout) {
@@ -411,7 +415,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         let lladdr = bx.ptrtoint(llptr, llcast_ty);
                         OperandValue::Immediate(lladdr)
                     }
-                    mir::CastKind::Pointer(PointerCast::ReifyFnPointer) => {
+                    mir::CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer) => {
                         match *operand.layout.ty.kind() {
                             ty::FnDef(def_id, substs) => {
                                 let instance = ty::Instance::resolve_for_fn_ptr(
@@ -427,7 +431,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             _ => bug!("{} cannot be reified to a fn ptr", operand.layout.ty),
                         }
                     }
-                    mir::CastKind::Pointer(PointerCast::ClosureFnPointer(_)) => {
+                    mir::CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_)) => {
                         match *operand.layout.ty.kind() {
                             ty::Closure(def_id, substs) => {
                                 let instance = Instance::resolve_closure(
@@ -443,11 +447,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             _ => bug!("{} cannot be cast to a fn ptr", operand.layout.ty),
                         }
                     }
-                    mir::CastKind::Pointer(PointerCast::UnsafeFnPointer) => {
+                    mir::CastKind::PointerCoercion(PointerCoercion::UnsafeFnPointer) => {
                         // This is a no-op at the LLVM level.
                         operand.val
                     }
-                    mir::CastKind::Pointer(PointerCast::Unsize) => {
+                    mir::CastKind::PointerCoercion(PointerCoercion::Unsize) => {
                         assert!(bx.cx().is_backend_scalar_pair(cast));
                         let (lldata, llextra) = match operand.val {
                             OperandValue::Pair(lldata, llextra) => {
@@ -470,7 +474,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             base::unsize_ptr(bx, lldata, operand.layout.ty, cast.ty, llextra);
                         OperandValue::Pair(lldata, llextra)
                     }
-                    mir::CastKind::Pointer(PointerCast::MutToConstPointer)
+                    mir::CastKind::PointerCoercion(PointerCoercion::MutToConstPointer)
                     | mir::CastKind::PtrToPtr
                         if bx.cx().is_backend_scalar_pair(operand.layout) =>
                     {
@@ -504,8 +508,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             base::cast_to_dyn_star(bx, lldata, operand.layout, cast.ty, llextra);
                         OperandValue::Pair(lldata, llextra)
                     }
-                    mir::CastKind::Pointer(
-                        PointerCast::MutToConstPointer | PointerCast::ArrayToPointer,
+                    mir::CastKind::PointerCoercion(
+                        PointerCoercion::MutToConstPointer | PointerCoercion::ArrayToPointer,
                     )
                     | mir::CastKind::IntToInt
                     | mir::CastKind::FloatToInt