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.

Author: Noratrieb

clippy_lints/src/derivable_impls.rs

@@ -9,7 +9,7 @@ use rustc_hir::{
     Body, Expr, ExprKind, GenericArg, Impl, ImplItemKind, Item, ItemKind, Node, PathSegment, QPath, TyKind,
 };
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::adjustment::{Adjust, PointerCast};
+use rustc_middle::ty::adjustment::{Adjust, PointerCoercion};
 use rustc_middle::ty::{self, Adt, AdtDef, SubstsRef, Ty, TypeckResults};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::sym;
@@ -116,7 +116,7 @@ fn check_struct<'tcx>(
     let is_default_without_adjusts = |expr| {
         is_default_equivalent(cx, expr)
             && typeck_results.expr_adjustments(expr).iter().all(|adj| {
-                !matches!(adj.kind, Adjust::Pointer(PointerCast::Unsize)
+                !matches!(adj.kind, Adjust::Pointer(PointerCoercion::Unsize)
                     if contains_trait_object(adj.target))
             })
     };

clippy_lints/src/pass_by_ref_or_value.rs

@@ -14,7 +14,7 @@ use rustc_hir as hir;
 use rustc_hir::intravisit::FnKind;
 use rustc_hir::{BindingAnnotation, Body, FnDecl, Impl, ItemKind, MutTy, Mutability, Node, PatKind};
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::adjustment::{Adjust, PointerCast};
+use rustc_middle::ty::adjustment::{Adjust, PointerCoercion};
 use rustc_middle::ty::layout::LayoutOf;
 use rustc_middle::ty::{self, RegionKind};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
@@ -195,7 +195,7 @@ impl<'tcx> PassByRefOrValue {
                                     .adjustments()
                                     .items()
                                     .flat_map(|(_, a)| a)
-                                    .any(|a| matches!(a.kind, Adjust::Pointer(PointerCast::UnsafeFnPointer)))
+                                    .any(|a| matches!(a.kind, Adjust::Pointer(PointerCoercion::UnsafeFnPointer)))
                             {
                                 continue;
                             }

clippy_utils/src/qualify_min_const_fn.rs

@@ -16,7 +16,7 @@ use rustc_middle::mir::{
 };
 use rustc_middle::traits::{ImplSource, ObligationCause};
 use rustc_middle::ty::subst::GenericArgKind;
-use rustc_middle::ty::{self, adjustment::PointerCast, Ty, TyCtxt};
+use rustc_middle::ty::{self, adjustment::PointerCoercion, Ty, TyCtxt};
 use rustc_middle::ty::{BoundConstness, TraitRef};
 use rustc_semver::RustcVersion;
 use rustc_span::symbol::sym;
@@ -119,18 +119,18 @@ fn check_rvalue<'tcx>(
             | CastKind::FloatToFloat
             | CastKind::FnPtrToPtr
             | CastKind::PtrToPtr
-            | CastKind::Pointer(PointerCast::MutToConstPointer | PointerCast::ArrayToPointer),
+            | CastKind::PointerCoercion(PointerCoercion::MutToConstPointer | PointerCoercion::ArrayToPointer),
             operand,
             _,
         ) => check_operand(tcx, operand, span, body),
         Rvalue::Cast(
-            CastKind::Pointer(
-                PointerCast::UnsafeFnPointer | PointerCast::ClosureFnPointer(_) | PointerCast::ReifyFnPointer,
+            CastKind::PointerCoercion(
+                PointerCoercion::UnsafeFnPointer | PointerCoercion::ClosureFnPointer(_) | PointerCoercion::ReifyFnPointer,
             ),
             _,
             _,
         ) => Err((span, "function pointer casts are not allowed in const fn".into())),
-        Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), op, cast_ty) => {
+        Rvalue::Cast(CastKind::PointerCoercion(PointerCoercion::Unsize), op, cast_ty) => {
             let pointee_ty = if let Some(deref_ty) = cast_ty.builtin_deref(true) {
                 deref_ty.ty
             } else {