Rename adjustment::PointerCast and variants using it to PointerCoercion

It makes it sound like the `ExprKind` and `Rvalue` are supposed to represent all pointer related
casts, when in reality their just used to share a some enum variants. Make it clear there these
are only coercion to make it clear why only some pointer related "casts" are in the enum.

compiler/rustc_middle/src/mir/mod.rs

@@ -2014,7 +2014,7 @@ impl<'tcx> Rvalue<'tcx> {
                 | CastKind::IntToFloat
                 | CastKind::FnPtrToPtr
                 | CastKind::PtrToPtr
-                | CastKind::Pointer(_)
+                | CastKind::PointerCoercion(_)
                 | CastKind::PointerFromExposedAddress
                 | CastKind::DynStar
                 | CastKind::Transmute,

compiler/rustc_middle/src/mir/syntax.rs

@@ -7,7 +7,7 @@ use super::{BasicBlock, Constant, Local, SwitchTargets, UserTypeProjection};
 
 use crate::mir::coverage::{CodeRegion, CoverageKind};
 use crate::traits::Reveal;
-use crate::ty::adjustment::PointerCast;
+use crate::ty::adjustment::PointerCoercion;
 use crate::ty::subst::SubstsRef;
 use crate::ty::{self, List, Ty};
 use crate::ty::{Region, UserTypeAnnotationIndex};
@@ -1230,9 +1230,9 @@ pub enum CastKind {
     /// An address-to-pointer cast that picks up an exposed provenance.
     /// See the docs on `from_exposed_addr` for more details.
     PointerFromExposedAddress,
-    /// All sorts of pointer-to-pointer casts. Note that reference-to-raw-ptr casts are
+    /// Pointer related casts that are done by coercions. Note that reference-to-raw-ptr casts are
     /// translated into `&raw mut/const *r`, i.e., they are not actually casts.
-    Pointer(PointerCast),
+    PointerCoercion(PointerCoercion),
     /// Cast into a dyn* object.
     DynStar,
     IntToInt,

compiler/rustc_middle/src/thir.rs

@@ -18,7 +18,7 @@ use rustc_index::IndexVec;
 use rustc_middle::middle::region;
 use rustc_middle::mir::interpret::AllocId;
 use rustc_middle::mir::{self, BinOp, BorrowKind, FakeReadCause, Mutability, UnOp};
-use rustc_middle::ty::adjustment::PointerCast;
+use rustc_middle::ty::adjustment::PointerCoercion;
 use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::{self, AdtDef, FnSig, List, Ty, UpvarSubsts};
 use rustc_middle::ty::{CanonicalUserType, CanonicalUserTypeAnnotation};
@@ -329,9 +329,10 @@ pub enum ExprKind<'tcx> {
     NeverToAny {
         source: ExprId,
     },
-    /// A pointer cast. More information can be found in [`PointerCast`].
-    Pointer {
-        cast: PointerCast,
+    /// A pointer coercion. More information can be found in [`PointerCoercion`].
+    /// Pointer casts that cannot be done by coercions are represented by [`ExprKind::Cast`].
+    PointerCoercion {
+        cast: PointerCoercion,
         source: ExprId,
     },
     /// A `loop` expression.

compiler/rustc_middle/src/thir/visit.rs

@@ -65,7 +65,7 @@ pub fn walk_expr<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, expr: &Exp
         Cast { source } => visitor.visit_expr(&visitor.thir()[source]),
         Use { source } => visitor.visit_expr(&visitor.thir()[source]),
         NeverToAny { source } => visitor.visit_expr(&visitor.thir()[source]),
-        Pointer { source, cast: _ } => visitor.visit_expr(&visitor.thir()[source]),
+        PointerCoercion { source, cast: _ } => visitor.visit_expr(&visitor.thir()[source]),
         Let { expr, .. } => {
             visitor.visit_expr(&visitor.thir()[expr]);
         }

compiler/rustc_middle/src/ty/adjustment.rs

@@ -6,7 +6,7 @@ use rustc_span::Span;
 use rustc_target::abi::FieldIdx;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
-pub enum PointerCast {
+pub enum PointerCoercion {
     /// Go from a fn-item type to a fn-pointer type.
     ReifyFnPointer,
 
@@ -99,7 +99,7 @@ pub enum Adjust<'tcx> {
     /// Take the address and produce either a `&` or `*` pointer.
     Borrow(AutoBorrow<'tcx>),
 
-    Pointer(PointerCast),
+    Pointer(PointerCoercion),
 
     /// Cast into a dyn* object.
     DynStar,

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -332,7 +332,7 @@ TrivialTypeTraversalAndLiftImpls! {
     crate::ty::IntVarValue,
     crate::ty::ParamConst,
     crate::ty::ParamTy,
-    crate::ty::adjustment::PointerCast,
+    crate::ty::adjustment::PointerCoercion,
     crate::ty::RegionVid,
     crate::ty::UniverseIndex,
     crate::ty::Variance,