Rollup merge of #131202 - Urgau:wide-ptrs-compiler, r=jieyouxu

Use wide pointers consistenly across the compiler

This PR replace every use of "fat pointer" for the more recent "wide pointer" terminology.

Since some time T-lang as preferred the "wide pointer" terminology, as can be seen on [the last RFCs](https://github.com/search?q=repo%3Arust-lang%2Frfcs+%22wide+pointer%22&type=code), on some [lints](https://doc.rust-lang.org/rustc/lints/listing/warn-by-default.html#ambiguous-wide-pointer-comparisons), but also in [the reference](https://doc.rust-lang.org/stable/reference/expressions/operator-expr.html?highlight=wide%20pointer#pointer-to-pointer-cast).

Currently we have a [mix of both](https://github.com/search?q=repo%3Arust-lang%2Frust+%22wide+pointer%22&type=code) (including in error messages), which isn't great, but with this PR no more.

r? `@jieyouxu` (feel free to re-roll)

compiler/rustc_codegen_cranelift/example/std_example.rs

@@ -168,7 +168,7 @@ fn main() {
 
     foo(I64X2([0, 0]));
 
-    transmute_fat_pointer();
+    transmute_wide_pointer();
 
     rust_call_abi();
 
@@ -192,7 +192,7 @@ type TwoPtrs = i64;
 #[cfg(target_pointer_width = "64")]
 type TwoPtrs = i128;
 
-fn transmute_fat_pointer() -> TwoPtrs {
+fn transmute_wide_pointer() -> TwoPtrs {
     unsafe { transmute::<_, TwoPtrs>("true !") }
 }
 

compiler/rustc_codegen_cranelift/src/base.rs

@@ -713,17 +713,17 @@ fn codegen_stmt<'tcx>(
                     let from_ty = operand.layout().ty;
                     let to_ty = fx.monomorphize(to_ty);
 
-                    fn is_fat_ptr<'tcx>(fx: &FunctionCx<'_, '_, 'tcx>, ty: Ty<'tcx>) -> bool {
+                    fn is_wide_ptr<'tcx>(fx: &FunctionCx<'_, '_, 'tcx>, ty: Ty<'tcx>) -> bool {
                         ty.builtin_deref(true)
                             .is_some_and(|pointee_ty| has_ptr_meta(fx.tcx, pointee_ty))
                     }
 
-                    if is_fat_ptr(fx, from_ty) {
+                    if is_wide_ptr(fx, from_ty) {
-                        if is_fat_ptr(fx, to_ty) {
+                        if is_wide_ptr(fx, to_ty) {
-                            // fat-ptr -> fat-ptr
+                            // wide-ptr -> wide-ptr
                             lval.write_cvalue(fx, operand.cast_pointer_to(dest_layout));
                         } else {
-                            // fat-ptr -> thin-ptr
+                            // wide-ptr -> thin-ptr
                             let (ptr, _extra) = operand.load_scalar_pair(fx);
                             lval.write_cvalue(fx, CValue::by_val(ptr, dest_layout))
                         }

compiler/rustc_codegen_cranelift/src/common.rs

@@ -101,7 +101,7 @@ fn clif_pair_type_from_ty<'tcx>(
     })
 }
 
-/// Is a pointer to this type a fat ptr?
+/// Is a pointer to this type a wide ptr?
 pub(crate) fn has_ptr_meta<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> bool {
     if ty.is_sized(tcx, ParamEnv::reveal_all()) {
         return false;

compiler/rustc_codegen_cranelift/src/debuginfo/types.rs

@@ -139,7 +139,7 @@ impl DebugContext {
 
             pointer_type_id
         } else {
-            // FIXME implement debuginfo for fat pointers
+            // FIXME implement debuginfo for wide pointers
             self.placeholder_for_type(tcx, type_dbg, ptr_type)
         }
     }

compiler/rustc_codegen_gcc/src/intrinsic/simd.rs

@@ -478,7 +478,7 @@ pub fn generic_simd_intrinsic<'a, 'gcc, 'tcx>(
                 let metadata = p_ty.ptr_metadata_ty(bx.tcx, |ty| {
                     bx.tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), ty)
                 });
-                require!(metadata.is_unit(), InvalidMonomorphization::CastFatPointer {
+                require!(metadata.is_unit(), InvalidMonomorphization::CastWidePointer {
                     span,
                     name,
                     ty: in_elem
@@ -493,7 +493,7 @@ pub fn generic_simd_intrinsic<'a, 'gcc, 'tcx>(
                 let metadata = p_ty.ptr_metadata_ty(bx.tcx, |ty| {
                     bx.tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), ty)
                 });
-                require!(metadata.is_unit(), InvalidMonomorphization::CastFatPointer {
+                require!(metadata.is_unit(), InvalidMonomorphization::CastWidePointer {
                     span,
                     name,
                     ty: out_elem

compiler/rustc_codegen_gcc/src/type_of.rs

@@ -207,7 +207,7 @@ impl<'tcx> LayoutGccExt<'tcx> for TyAndLayout<'tcx> {
         // layout.
         if let Abi::Scalar(ref scalar) = self.abi {
             // Use a different cache for scalars because pointers to DSTs
-            // can be either fat or thin (data pointers of fat pointers).
+            // can be either wide or thin (data pointers of wide pointers).
             if let Some(&ty) = cx.scalar_types.borrow().get(&self.ty) {
                 return ty;
             }

compiler/rustc_codegen_llvm/src/abi.rs

@@ -7,7 +7,7 @@ use rustc_codegen_ssa::mir::place::{PlaceRef, PlaceValue};
 use rustc_codegen_ssa::traits::*;
 use rustc_middle::ty::Ty;
 use rustc_middle::ty::layout::LayoutOf;
-pub(crate) use rustc_middle::ty::layout::{FAT_PTR_ADDR, FAT_PTR_EXTRA};
+pub(crate) use rustc_middle::ty::layout::{WIDE_PTR_ADDR, WIDE_PTR_EXTRA};
 use rustc_middle::{bug, ty};
 use rustc_session::config;
 pub(crate) use rustc_target::abi::call::*;

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -34,7 +34,7 @@ use super::utils::{
 };
 use crate::common::CodegenCx;
 use crate::debuginfo::metadata::type_map::build_type_with_children;
-use crate::debuginfo::utils::{FatPtrKind, fat_pointer_kind};
+use crate::debuginfo::utils::{WidePtrKind, wide_pointer_kind};
 use crate::llvm::debuginfo::{
     DIDescriptor, DIFile, DIFlags, DILexicalBlock, DIScope, DIType, DebugEmissionKind,
     DebugNameTableKind,
@@ -161,7 +161,7 @@ fn build_pointer_or_reference_di_node<'ll, 'tcx>(
     unique_type_id: UniqueTypeId<'tcx>,
 ) -> DINodeCreationResult<'ll> {
     // The debuginfo generated by this function is only valid if `ptr_type` is really just
-    // a (fat) pointer. Make sure it is not called for e.g. `Box<T, NonZSTAllocator>`.
+    // a (wide) pointer. Make sure it is not called for e.g. `Box<T, NonZSTAllocator>`.
     assert_eq!(
         cx.size_and_align_of(ptr_type),
         cx.size_and_align_of(Ty::new_mut_ptr(cx.tcx, pointee_type))
@@ -174,7 +174,7 @@ fn build_pointer_or_reference_di_node<'ll, 'tcx>(
     let data_layout = &cx.tcx.data_layout;
     let ptr_type_debuginfo_name = compute_debuginfo_type_name(cx.tcx, ptr_type, true);
 
-    match fat_pointer_kind(cx, pointee_type) {
+    match wide_pointer_kind(cx, pointee_type) {
         None => {
             // This is a thin pointer. Create a regular pointer type and give it the correct name.
             assert_eq!(
@@ -197,7 +197,7 @@ fn build_pointer_or_reference_di_node<'ll, 'tcx>(
 
             DINodeCreationResult { di_node, already_stored_in_typemap: false }
         }
-        Some(fat_pointer_kind) => {
+        Some(wide_pointer_kind) => {
             type_map::build_type_with_children(
                 cx,
                 type_map::stub(
@@ -210,7 +210,7 @@ fn build_pointer_or_reference_di_node<'ll, 'tcx>(
                     DIFlags::FlagZero,
                 ),
                 |cx, owner| {
-                    // FIXME: If this fat pointer is a `Box` then we don't want to use its
+                    // FIXME: If this wide pointer is a `Box` then we don't want to use its
                     //        type layout and instead use the layout of the raw pointer inside
                     //        of it.
                     //        The proper way to handle this is to not treat Box as a pointer
@@ -227,16 +227,16 @@ fn build_pointer_or_reference_di_node<'ll, 'tcx>(
                     };
 
                     let layout = cx.layout_of(layout_type);
-                    let addr_field = layout.field(cx, abi::FAT_PTR_ADDR);
+                    let addr_field = layout.field(cx, abi::WIDE_PTR_ADDR);
-                    let extra_field = layout.field(cx, abi::FAT_PTR_EXTRA);
+                    let extra_field = layout.field(cx, abi::WIDE_PTR_EXTRA);
 
-                    let (addr_field_name, extra_field_name) = match fat_pointer_kind {
+                    let (addr_field_name, extra_field_name) = match wide_pointer_kind {
-                        FatPtrKind::Dyn => ("pointer", "vtable"),
+                        WidePtrKind::Dyn => ("pointer", "vtable"),
-                        FatPtrKind::Slice => ("data_ptr", "length"),
+                        WidePtrKind::Slice => ("data_ptr", "length"),
                     };
 
-                    assert_eq!(abi::FAT_PTR_ADDR, 0);
+                    assert_eq!(abi::WIDE_PTR_ADDR, 0);
-                    assert_eq!(abi::FAT_PTR_EXTRA, 1);
+                    assert_eq!(abi::WIDE_PTR_EXTRA, 1);
 
                     // The data pointer type is a regular, thin pointer, regardless of whether this
                     // is a slice or a trait object.
@@ -258,7 +258,7 @@ fn build_pointer_or_reference_di_node<'ll, 'tcx>(
                             owner,
                             addr_field_name,
                             (addr_field.size, addr_field.align.abi),
-                            layout.fields.offset(abi::FAT_PTR_ADDR),
+                            layout.fields.offset(abi::WIDE_PTR_ADDR),
                             DIFlags::FlagZero,
                             data_ptr_type_di_node,
                         ),
@@ -267,7 +267,7 @@ fn build_pointer_or_reference_di_node<'ll, 'tcx>(
                             owner,
                             extra_field_name,
                             (extra_field.size, extra_field.align.abi),
-                            layout.fields.offset(abi::FAT_PTR_EXTRA),
+                            layout.fields.offset(abi::WIDE_PTR_EXTRA),
                             DIFlags::FlagZero,
                             type_di_node(cx, extra_field.ty),
                         ),
@@ -391,7 +391,7 @@ fn build_dyn_type_di_node<'ll, 'tcx>(
 ///
 /// NOTE: We currently emit just emit the debuginfo for the element type here
 /// (i.e. `T` for slices and `u8` for `str`), so that we end up with
-/// `*const T` for the `data_ptr` field of the corresponding fat-pointer
+/// `*const T` for the `data_ptr` field of the corresponding wide-pointer
 /// debuginfo of `&[T]`.
 ///
 /// It would be preferable and more accurate if we emitted a DIArray of T

compiler/rustc_codegen_llvm/src/debuginfo/utils.rs

@@ -49,23 +49,23 @@ pub(crate) fn get_namespace_for_item<'ll>(cx: &CodegenCx<'ll, '_>, def_id: DefId
 }
 
 #[derive(Debug, PartialEq, Eq)]
-pub(crate) enum FatPtrKind {
+pub(crate) enum WidePtrKind {
     Slice,
     Dyn,
 }
 
 /// Determines if `pointee_ty` is slice-like or trait-object-like, i.e.
-/// if the second field of the fat pointer is a length or a vtable-pointer.
+/// if the second field of the wide pointer is a length or a vtable-pointer.
-/// If `pointee_ty` does not require a fat pointer (because it is Sized) then
+/// If `pointee_ty` does not require a wide pointer (because it is Sized) then
 /// the function returns `None`.
-pub(crate) fn fat_pointer_kind<'ll, 'tcx>(
+pub(crate) fn wide_pointer_kind<'ll, 'tcx>(
     cx: &CodegenCx<'ll, 'tcx>,
     pointee_ty: Ty<'tcx>,
-) -> Option<FatPtrKind> {
+) -> Option<WidePtrKind> {
     let pointee_tail_ty = cx.tcx.struct_tail_for_codegen(pointee_ty, cx.param_env());
     let layout = cx.layout_of(pointee_tail_ty);
     trace!(
-        "fat_pointer_kind: {:?} has layout {:?} (is_unsized? {})",
+        "wide_pointer_kind: {:?} has layout {:?} (is_unsized? {})",
         pointee_tail_ty,
         layout,
         layout.is_unsized()
@@ -76,8 +76,8 @@ pub(crate) fn fat_pointer_kind<'ll, 'tcx>(
     }
 
     match *pointee_tail_ty.kind() {
-        ty::Str | ty::Slice(_) => Some(FatPtrKind::Slice),
+        ty::Str | ty::Slice(_) => Some(WidePtrKind::Slice),
-        ty::Dynamic(..) => Some(FatPtrKind::Dyn),
+        ty::Dynamic(..) => Some(WidePtrKind::Dyn),
         ty::Foreign(_) => {
             // Assert that pointers to foreign types really are thin:
             assert_eq!(
@@ -90,7 +90,7 @@ pub(crate) fn fat_pointer_kind<'ll, 'tcx>(
             // For all other pointee types we should already have returned None
             // at the beginning of the function.
             panic!(
-                "fat_pointer_kind() - Encountered unexpected `pointee_tail_ty`: {pointee_tail_ty:?}"
+                "wide_pointer_kind() - Encountered unexpected `pointee_tail_ty`: {pointee_tail_ty:?}"
             )
         }
     }

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -2185,7 +2185,7 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
                 let metadata = p_ty.ptr_metadata_ty(bx.tcx, |ty| {
                     bx.tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), ty)
                 });
-                require!(metadata.is_unit(), InvalidMonomorphization::CastFatPointer {
+                require!(metadata.is_unit(), InvalidMonomorphization::CastWidePointer {
                     span,
                     name,
                     ty: in_elem
@@ -2200,7 +2200,7 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
                 let metadata = p_ty.ptr_metadata_ty(bx.tcx, |ty| {
                     bx.tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), ty)
                 });
-                require!(metadata.is_unit(), InvalidMonomorphization::CastFatPointer {
+                require!(metadata.is_unit(), InvalidMonomorphization::CastWidePointer {
                     span,
                     name,
                     ty: out_elem

compiler/rustc_codegen_llvm/src/type_of.rs

@@ -199,7 +199,7 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
         // layout.
         if let Abi::Scalar(scalar) = self.abi {
             // Use a different cache for scalars because pointers to DSTs
-            // can be either fat or thin (data pointers of fat pointers).
+            // can be either wide or thin (data pointers of wide pointers).
             if let Some(&llty) = cx.scalar_lltypes.borrow().get(&self.ty) {
                 return llty;
             }

compiler/rustc_codegen_ssa/messages.ftl

@@ -82,7 +82,7 @@ codegen_ssa_invalid_monomorphization_basic_integer_type = invalid monomorphizati
 
 codegen_ssa_invalid_monomorphization_cannot_return = invalid monomorphization of `{$name}` intrinsic: cannot return `{$ret_ty}`, expected `u{$expected_int_bits}` or `[u8; {$expected_bytes}]`
 
-codegen_ssa_invalid_monomorphization_cast_fat_pointer = invalid monomorphization of `{$name}` intrinsic: cannot cast fat pointer `{$ty}`
+codegen_ssa_invalid_monomorphization_cast_wide_pointer = invalid monomorphization of `{$name}` intrinsic: cannot cast wide pointer `{$ty}`
 
 codegen_ssa_invalid_monomorphization_expected_element_type = invalid monomorphization of `{$name}` intrinsic: expected element type `{$expected_element}` of second argument `{$second_arg}` to be a pointer to the element type `{$in_elem}` of the first argument `{$in_ty}`, found `{$expected_element}` != `{$mutability} {$in_elem}`
 

compiler/rustc_codegen_ssa/src/errors.rs

@@ -916,8 +916,8 @@ pub enum InvalidMonomorphization<'tcx> {
         ret_ty: Ty<'tcx>,
     },
 
-    #[diag(codegen_ssa_invalid_monomorphization_cast_fat_pointer, code = E0511)]
+    #[diag(codegen_ssa_invalid_monomorphization_cast_wide_pointer, code = E0511)]
-    CastFatPointer {
+    CastWidePointer {
         #[primary_span]
         span: Span,
         name: Symbol,

compiler/rustc_codegen_ssa/src/mir/mod.rs

@@ -133,9 +133,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 enum LocalRef<'tcx, V> {
     Place(PlaceRef<'tcx, V>),
     /// `UnsizedPlace(p)`: `p` itself is a thin pointer (indirect place).
-    /// `*p` is the fat pointer that references the actual unsized place.
+    /// `*p` is the wide pointer that references the actual unsized place.
     /// Every time it is initialized, we have to reallocate the place
-    /// and update the fat pointer. That's the reason why it is indirect.
+    /// and update the wide pointer. That's the reason why it is indirect.
     UnsizedPlace(PlaceRef<'tcx, V>),
     /// The backend [`OperandValue`] has already been generated.
     Operand(OperandRef<'tcx, V>),
@@ -429,7 +429,7 @@ fn arg_local_refs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
                 // Unsized indirect qrguments
                 PassMode::Indirect { attrs: _, meta_attrs: Some(_), on_stack: _ } => {
                     // As the storage for the indirect argument lives during
-                    // the whole function call, we just copy the fat pointer.
+                    // the whole function call, we just copy the wide pointer.
                     let llarg = bx.get_param(llarg_idx);
                     llarg_idx += 1;
                     let llextra = bx.get_param(llarg_idx);

compiler/rustc_codegen_ssa/src/mir/operand.rs

@@ -41,7 +41,7 @@ pub enum OperandValue<V> {
     /// The backend value in this variant must be the *immediate* backend type,
     /// as returned by [`LayoutTypeCodegenMethods::immediate_backend_type`].
     Immediate(V),
-    /// A pair of immediate LLVM values. Used by fat pointers too.
+    /// A pair of immediate LLVM values. Used by wide pointers too.
     ///
     /// An `OperandValue` *must* be this variant for any type for which
     /// [`LayoutTypeCodegenMethods::is_backend_scalar_pair`] returns `true`.

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -38,10 +38,10 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 ref source,
                 _,
             ) => {
-                // The destination necessarily contains a fat pointer, so if
+                // The destination necessarily contains a wide pointer, so if
-                // it's a scalar pair, it's a fat pointer or newtype thereof.
+                // it's a scalar pair, it's a wide pointer or newtype thereof.
                 if bx.cx().is_backend_scalar_pair(dest.layout) {
-                    // Into-coerce of a thin pointer to a fat pointer -- just
+                    // Into-coerce of a thin pointer to a wide pointer -- just
                     // use the operand path.
                     let temp = self.codegen_rvalue_operand(bx, rvalue);
                     temp.val.store(bx, dest);
@@ -519,7 +519,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             if bx.cx().is_backend_scalar_pair(cast) {
                                 OperandValue::Pair(data_ptr, meta)
                             } else {
-                                // Cast of fat-ptr to thin-ptr is an extraction of data-ptr.
+                                // Cast of wide-ptr to thin-ptr is an extraction of data-ptr.
                                 OperandValue::Immediate(data_ptr)
                             }
                         } else {
@@ -622,7 +622,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     (
                         OperandValue::Pair(lhs_addr, lhs_extra),
                         OperandValue::Pair(rhs_addr, rhs_extra),
-                    ) => self.codegen_fat_ptr_binop(
+                    ) => self.codegen_wide_ptr_binop(
                         bx,
                         op,
                         lhs_addr,
@@ -984,7 +984,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         }
     }
 
-    fn codegen_fat_ptr_binop(
+    fn codegen_wide_ptr_binop(
         &mut self,
         bx: &mut Bx,
         op: mir::BinOp,
@@ -1021,7 +1021,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 bx.or(lhs, rhs)
             }
             _ => {
-                bug!("unexpected fat ptr binop");
+                bug!("unexpected wide ptr binop");
             }
         }
     }

compiler/rustc_const_eval/src/interpret/cast.rs

@@ -204,12 +204,12 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
     ) -> InterpResult<'tcx, ImmTy<'tcx, M::Provenance>> {
         assert!(src.layout.ty.is_any_ptr());
         assert!(cast_to.ty.is_unsafe_ptr());
-        // Handle casting any ptr to raw ptr (might be a fat ptr).
+        // Handle casting any ptr to raw ptr (might be a wide ptr).
         if cast_to.size == src.layout.size {
-            // Thin or fat pointer that just has the ptr kind of target type changed.
+            // Thin or wide pointer that just has the ptr kind of target type changed.
             return interp_ok(ImmTy::from_immediate(**src, cast_to));
         } else {
-            // Casting the metadata away from a fat ptr.
+            // Casting the metadata away from a wide ptr.
             assert_eq!(src.layout.size, 2 * self.pointer_size());
             assert_eq!(cast_to.size, self.pointer_size());
             assert!(src.layout.ty.is_unsafe_ptr());

compiler/rustc_error_codes/src/error_codes/E0607.md

@@ -1,4 +1,4 @@
-A cast between a thin and a fat pointer was attempted.
+A cast between a thin and a wide pointer was attempted.
 
 Erroneous code example:
 
@@ -7,18 +7,18 @@ let v = core::ptr::null::<u8>();
 v as *const [u8];
 ```
 
-First: what are thin and fat pointers?
+First: what are thin and wide pointers?
 
 Thin pointers are "simple" pointers: they are purely a reference to a memory
 address.
 
-Fat pointers are pointers referencing Dynamically Sized Types (also called
+Wide pointers are pointers referencing Dynamically Sized Types (also called
 DSTs). DSTs don't have a statically known size, therefore they can only exist
 behind some kind of pointer that contains additional information. For example,
 slices and trait objects are DSTs. In the case of slices, the additional
-information the fat pointer holds is their size.
+information the wide pointer holds is their size.
 
-To fix this error, don't try to cast directly between thin and fat pointers.
+To fix this error, don't try to cast directly between thin and wide pointers.
 
 For more information about type casts, take a look at the section of the
 [The Rust Reference][1] on type cast expressions.

compiler/rustc_hir_analysis/src/check/check.rs

@@ -1105,7 +1105,7 @@ fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {
         // Check that we use types valid for use in the lanes of a SIMD "vector register"
         // These are scalar types which directly match a "machine" type
         // Yes: Integers, floats, "thin" pointers
-        // No: char, "fat" pointers, compound types
+        // No: char, "wide" pointers, compound types
         match element_ty.kind() {
             ty::Param(_) => (), // pass struct<T>([T; 4]) through, let monomorphization catch errors
             ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::RawPtr(_, _) => (), // struct([u8; 4]) is ok

compiler/rustc_hir_analysis/src/coherence/builtin.rs

@@ -424,7 +424,7 @@ pub(crate) fn coerce_unsized_info<'tcx>(
             // Here `U = [i32; 3]` and `V = [i32]`. At runtime,
             // when this coercion occurs, we would be changing the
             // field `ptr` from a thin pointer of type `*mut [i32;
-            // 3]` to a fat pointer of type `*mut [i32]` (with
+            // 3]` to a wide pointer of type `*mut [i32]` (with
             // extra data `3`). **The purpose of this check is to
             // make sure that we know how to do this conversion.**
             //

compiler/rustc_hir_typeck/messages.ftl

@@ -23,17 +23,17 @@ hir_typeck_cannot_cast_to_bool = cannot cast `{$expr_ty}` as `bool`
 
 hir_typeck_cast_enum_drop = cannot cast enum `{$expr_ty}` into integer `{$cast_ty}` because it implements `Drop`
 
-hir_typeck_cast_thin_pointer_to_fat_pointer = cannot cast thin pointer `{$expr_ty}` to fat pointer `{$cast_ty}`
+hir_typeck_cast_thin_pointer_to_wide_pointer = cannot cast thin pointer `{$expr_ty}` to wide pointer `{$cast_ty}`
     .teach_help = Thin pointers are "simple" pointers: they are purely a reference to a
         memory address.
 
-        Fat pointers are pointers referencing "Dynamically Sized Types" (also
+        Wide pointers are pointers referencing "Dynamically Sized Types" (also
         called DST). DST don't have a statically known size, therefore they can
         only exist behind some kind of pointers that contain additional
         information. Slices and trait objects are DSTs. In the case of slices,
-        the additional information the fat pointer holds is their size.
+        the additional information the wide pointer holds is their size.
 
-        To fix this error, don't try to cast directly between thin and fat
+        To fix this error, don't try to cast directly between thin and wide
         pointers.
 
         For more information about casts, take a look at The Book:

compiler/rustc_hir_typeck/src/cast.rs

@@ -66,7 +66,7 @@ pub(crate) struct CastCheck<'tcx> {
 }
 
 /// The kind of pointer and associated metadata (thin, length or vtable) - we
-/// only allow casts between fat pointers if their metadata have the same
+/// only allow casts between wide pointers if their metadata have the same
 /// kind.
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TypeVisitable, TypeFoldable)]
 enum PointerKind<'tcx> {
@@ -162,7 +162,7 @@ enum CastError<'tcx> {
         src_kind: PointerKind<'tcx>,
         dst_kind: PointerKind<'tcx>,
     },
-    /// Cast of thin to fat raw ptr (e.g., `*const () as *const [u8]`).
+    /// Cast of thin to wide raw ptr (e.g., `*const () as *const [u8]`).
     SizedUnsizedCast,
     IllegalCast,
     NeedDeref,
@@ -172,12 +172,12 @@ enum CastError<'tcx> {
     NonScalar,
     UnknownExprPtrKind,
     UnknownCastPtrKind,
-    /// Cast of int to (possibly) fat raw pointer.
+    /// Cast of int to (possibly) wide raw pointer.
     ///
     /// Argument is the specific name of the metadata in plain words, such as "a vtable"
     /// or "a length". If this argument is None, then the metadata is unknown, for example,
     /// when we're typechecking a type parameter with a ?Sized bound.
-    IntToFatCast(Option<&'static str>),
+    IntToWideCast(Option<&'static str>),
     ForeignNonExhaustiveAdt,
 }
 
@@ -545,14 +545,14 @@ impl<'a, 'tcx> CastCheck<'tcx> {
                 err.emit();
             }
             CastError::SizedUnsizedCast => {
-                fcx.dcx().emit_err(errors::CastThinPointerToFatPointer {
+                fcx.dcx().emit_err(errors::CastThinPointerToWidePointer {
                     span: self.span,
                     expr_ty: self.expr_ty,
                     cast_ty: fcx.ty_to_string(self.cast_ty),
                     teach: fcx.tcx.sess.teach(E0607),
                 });
             }
-            CastError::IntToFatCast(known_metadata) => {
+            CastError::IntToWideCast(known_metadata) => {
                 let expr_if_nightly = fcx.tcx.sess.is_nightly_build().then_some(self.expr_span);
                 let cast_ty = fcx.resolve_vars_if_possible(self.cast_ty);
                 let expr_ty = fcx.ty_to_string(self.expr_ty);
@@ -861,7 +861,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
             return Ok(CastKind::PtrPtrCast);
         }
 
-        // We can't cast to fat pointer if source pointer kind is unknown
+        // We can't cast to wide pointer if source pointer kind is unknown
         let Some(src_kind) = src_kind else {
             return Err(CastError::UnknownCastPtrKind);
         };
@@ -1054,10 +1054,10 @@ impl<'a, 'tcx> CastCheck<'tcx> {
         match fcx.pointer_kind(m_cast.ty, self.span)? {
             None => Err(CastError::UnknownCastPtrKind),
             Some(PointerKind::Thin) => Ok(CastKind::AddrPtrCast),
-            Some(PointerKind::VTable(_)) => Err(CastError::IntToFatCast(Some("a vtable"))),
+            Some(PointerKind::VTable(_)) => Err(CastError::IntToWideCast(Some("a vtable"))),
-            Some(PointerKind::Length) => Err(CastError::IntToFatCast(Some("a length"))),
+            Some(PointerKind::Length) => Err(CastError::IntToWideCast(Some("a length"))),
             Some(PointerKind::OfAlias(_) | PointerKind::OfParam(_)) => {
-                Err(CastError::IntToFatCast(None))
+                Err(CastError::IntToWideCast(None))
             }
         }
     }

compiler/rustc_hir_typeck/src/errors.rs

@@ -699,8 +699,8 @@ pub(crate) struct ReplaceWithName {
 }
 
 #[derive(Diagnostic)]
-#[diag(hir_typeck_cast_thin_pointer_to_fat_pointer, code = E0607)]
+#[diag(hir_typeck_cast_thin_pointer_to_wide_pointer, code = E0607)]
-pub(crate) struct CastThinPointerToFatPointer<'tcx> {
+pub(crate) struct CastThinPointerToWidePointer<'tcx> {
     #[primary_span]
     pub span: Span,
     pub expr_ty: Ty<'tcx>,

compiler/rustc_hir_typeck/src/expectation.rs

@@ -55,7 +55,7 @@ impl<'a, 'tcx> Expectation<'tcx> {
     /// be checked higher up, as is the case with `&expr` and `box expr`), but
     /// is useful in determining the concrete type.
     ///
-    /// The primary use case is where the expected type is a fat pointer,
+    /// The primary use case is where the expected type is a wide pointer,
     /// like `&[isize]`. For example, consider the following statement:
     ///
     ///    let x: &[isize] = &[1, 2, 3];

compiler/rustc_hir_typeck/src/expr.rs

@@ -413,7 +413,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 ty::Ref(_, ty, _) | ty::RawPtr(ty, _) => {
                     if oprnd.is_syntactic_place_expr() {
                         // Places may legitimately have unsized types.
-                        // For example, dereferences of a fat pointer and
+                        // For example, dereferences of a wide pointer and
                         // the last field of a struct can be unsized.
                         ExpectHasType(*ty)
                     } else {

compiler/rustc_middle/src/ty/adjustment.rs

@@ -25,10 +25,10 @@ pub enum PointerCoercion {
     ArrayToPointer,
 
     /// Unsize a pointer/reference value, e.g., `&[T; n]` to
-    /// `&[T]`. Note that the source could be a thin or fat pointer.
+    /// `&[T]`. Note that the source could be a thin or wide pointer.
-    /// This will do things like convert thin pointers to fat
+    /// This will do things like convert thin pointers to wide
     /// pointers, or convert structs containing thin pointers to
-    /// structs containing fat pointers, or convert between fat
+    /// structs containing wide pointers, or convert between wide
     /// pointers. We don't store the details of how the transform is
     /// done (in fact, we don't know that, because it might depend on
     /// the precise type parameters). We just store the target

compiler/rustc_middle/src/ty/layout.rs

@@ -164,17 +164,17 @@ impl Primitive {
     }
 }
 
-/// The first half of a fat pointer.
+/// The first half of a wide pointer.
 ///
 /// - For a trait object, this is the address of the box.
 /// - For a slice, this is the base address.
-pub const FAT_PTR_ADDR: usize = 0;
+pub const WIDE_PTR_ADDR: usize = 0;
 
-/// The second half of a fat pointer.
+/// The second half of a wide pointer.
 ///
 /// - For a trait object, this is the address of the vtable.
 /// - For a slice, this is the length.
-pub const FAT_PTR_EXTRA: usize = 1;
+pub const WIDE_PTR_EXTRA: usize = 1;
 
 /// The maximum supported number of lanes in a SIMD vector.
 ///
@@ -312,7 +312,7 @@ pub enum SizeSkeleton<'tcx> {
     /// that another SizeSkeleton is of equal size.
     Generic(ty::Const<'tcx>),
 
-    /// A potentially-fat pointer.
+    /// A potentially-wide pointer.
     Pointer {
         /// If true, this pointer is never null.
         non_zero: bool,
@@ -785,11 +785,11 @@ where
                     bug!("TyAndLayout::field({:?}): not applicable", this)
                 }
 
-                // Potentially-fat pointers.
+                // Potentially-wide pointers.
                 ty::Ref(_, pointee, _) | ty::RawPtr(pointee, _) => {
                     assert!(i < this.fields.count());
 
-                    // Reuse the fat `*T` type as its own thin pointer data field.
+                    // Reuse the wide `*T` type as its own thin pointer data field.
                     // This provides information about, e.g., DST struct pointees
                     // (which may have no non-DST form), and will work as long
                     // as the `Abi` or `FieldsShape` is checked by users.

compiler/rustc_middle/src/ty/sty.rs

@@ -1589,7 +1589,7 @@ impl<'tcx> Ty<'tcx> {
             .map_bound(|fn_sig| fn_sig.output().no_bound_vars().unwrap())
     }
 
-    /// Returns the type of metadata for (potentially fat) pointers to this type,
+    /// Returns the type of metadata for (potentially wide) pointers to this type,
     /// or the struct tail if the metadata type cannot be determined.
     pub fn ptr_metadata_ty_or_tail(
         self,
@@ -1648,7 +1648,7 @@ impl<'tcx> Ty<'tcx> {
         }
     }
 
-    /// Returns the type of metadata for (potentially fat) pointers to this type.
+    /// Returns the type of metadata for (potentially wide) pointers to this type.
     /// Causes an ICE if the metadata type cannot be determined.
     pub fn ptr_metadata_ty(
         self,

compiler/rustc_mir_transform/src/gvn.rs

@@ -1137,7 +1137,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
             (UnOp::PtrMetadata, Value::Aggregate(AggregateTy::RawPtr { .. }, _, fields)) => {
                 return Some(fields[1]);
             }
-            // We have an unsizing cast, which assigns the length to fat pointer metadata.
+            // We have an unsizing cast, which assigns the length to wide pointer metadata.
             (
                 UnOp::PtrMetadata,
                 Value::Cast {
@@ -1421,7 +1421,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
 
         let mut inner = self.simplify_place_value(place, location)?;
 
-        // The length information is stored in the fat pointer.
+        // The length information is stored in the wide pointer.
         // Reborrowing copies length information from one pointer to the other.
         while let Value::Address { place: borrowed, .. } = self.get(inner)
             && let [PlaceElem::Deref] = borrowed.projection[..]
@@ -1430,7 +1430,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
             inner = borrowed;
         }
 
-        // We have an unsizing cast, which assigns the length to fat pointer metadata.
+        // We have an unsizing cast, which assigns the length to wide pointer metadata.
         if let Value::Cast { kind, from, to, .. } = self.get(inner)
             && let CastKind::PointerCoercion(ty::adjustment::PointerCoercion::Unsize, _) = kind
             && let Some(from) = from.builtin_deref(true)

compiler/rustc_monomorphize/src/collector.rs

@@ -119,7 +119,7 @@
 //!
 //! #### Unsizing Casts
 //! A subtle way of introducing use edges is by casting to a trait object.
-//! Since the resulting fat-pointer contains a reference to a vtable, we need to
+//! Since the resulting wide-pointer contains a reference to a vtable, we need to
 //! instantiate all dyn-compatible methods of the trait, as we need to store
 //! pointers to these functions even if they never get called anywhere. This can
 //! be seen as a special case of taking a function reference.
@@ -661,7 +661,7 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirUsedCollector<'a, 'tcx> {
         let span = self.body.source_info(location).span;
 
         match *rvalue {
-            // When doing an cast from a regular pointer to a fat pointer, we
+            // When doing an cast from a regular pointer to a wide pointer, we
             // have to instantiate all methods of the trait being cast to, so we
             // can build the appropriate vtable.
             mir::Rvalue::Cast(
@@ -985,7 +985,7 @@ fn should_codegen_locally<'tcx>(tcx: TyCtxtAt<'tcx>, instance: Instance<'tcx>) -
 /// ```
 ///
 /// Then the output of this function would be (SomeStruct, SomeTrait) since for
-/// constructing the `target` fat-pointer we need the vtable for that pair.
+/// constructing the `target` wide-pointer we need the vtable for that pair.
 ///
 /// Things can get more complicated though because there's also the case where
 /// the unsized type occurs as a field:
@@ -999,7 +999,7 @@ fn should_codegen_locally<'tcx>(tcx: TyCtxtAt<'tcx>, instance: Instance<'tcx>) -
 /// ```
 ///
 /// In this case, if `T` is sized, `&ComplexStruct<T>` is a thin pointer. If `T`
-/// is unsized, `&SomeStruct` is a fat pointer, and the vtable it points to is
+/// is unsized, `&SomeStruct` is a wide pointer, and the vtable it points to is
 /// for the pair of `T` (which is a trait) and the concrete type that `T` was
 /// originally coerced from:
 ///

compiler/rustc_target/src/abi/call/mod.rs

@@ -637,7 +637,7 @@ impl<'a, Ty> ArgAbi<'a, Ty> {
         }
     }
 
-    /// Pass this argument indirectly, by passing a (thin or fat) pointer to the argument instead.
+    /// Pass this argument indirectly, by passing a (thin or wide) pointer to the argument instead.
     /// This is valid for both sized and unsized arguments.
     pub fn make_indirect(&mut self) {
         match self.mode {

compiler/rustc_target/src/abi/mod.rs

@@ -135,7 +135,7 @@ impl<'a> Layout<'a> {
 /// Note that the layout is NOT guaranteed to always be identical
 /// to that obtained from `layout_of(ty)`, as we need to produce
 /// layouts for which Rust types do not exist, such as enum variants
-/// or synthetic fields of enums (i.e., discriminants) and fat pointers.
+/// or synthetic fields of enums (i.e., discriminants) and wide pointers.
 #[derive(Copy, Clone, PartialEq, Eq, Hash, HashStable_Generic)]
 pub struct TyAndLayout<'a, Ty> {
     pub ty: Ty,

compiler/rustc_ty_utils/src/abi.rs

@@ -357,7 +357,7 @@ fn fn_abi_of_instance<'tcx>(
     )
 }
 
-// Handle safe Rust thin and fat pointers.
+// Handle safe Rust thin and wide pointers.
 fn adjust_for_rust_scalar<'tcx>(
     cx: LayoutCx<'tcx>,
     attrs: &mut ArgAttributes,
@@ -810,7 +810,7 @@ fn make_thin_self_ptr<'tcx>(
     layout: TyAndLayout<'tcx>,
 ) -> TyAndLayout<'tcx> {
     let tcx = cx.tcx();
-    let fat_pointer_ty = if layout.is_unsized() {
+    let wide_pointer_ty = if layout.is_unsized() {
         // unsized `self` is passed as a pointer to `self`
         // FIXME (mikeyhew) change this to use &own if it is ever added to the language
         Ty::new_mut_ptr(tcx, layout.ty)
@@ -825,15 +825,15 @@ fn make_thin_self_ptr<'tcx>(
         // elsewhere in the compiler as a method on a `dyn Trait`.
         // To get the type `*mut RcBox<Self>`, we just keep unwrapping newtypes until we
         // get a built-in pointer type
-        let mut fat_pointer_layout = layout;
+        let mut wide_pointer_layout = layout;
-        while !fat_pointer_layout.ty.is_unsafe_ptr() && !fat_pointer_layout.ty.is_ref() {
+        while !wide_pointer_layout.ty.is_unsafe_ptr() && !wide_pointer_layout.ty.is_ref() {
-            fat_pointer_layout = fat_pointer_layout
+            wide_pointer_layout = wide_pointer_layout
                 .non_1zst_field(cx)
                 .expect("not exactly one non-1-ZST field in a `DispatchFromDyn` type")
                 .1
         }
 
-        fat_pointer_layout.ty
+        wide_pointer_layout.ty
     };
 
     // we now have a type like `*mut RcBox<dyn Trait>`
@@ -842,7 +842,7 @@ fn make_thin_self_ptr<'tcx>(
     let unit_ptr_ty = Ty::new_mut_ptr(tcx, tcx.types.unit);
 
     TyAndLayout {
-        ty: fat_pointer_ty,
+        ty: wide_pointer_ty,
 
         // NOTE(eddyb) using an empty `ParamEnv`, and `unwrap`-ing the `Result`
         // should always work because the type is always `*mut ()`.

compiler/stable_mir/src/mir/body.rs

@@ -946,10 +946,10 @@ pub enum PointerCoercion {
     ArrayToPointer,
 
     /// Unsize a pointer/reference value, e.g., `&[T; n]` to
-    /// `&[T]`. Note that the source could be a thin or fat pointer.
+    /// `&[T]`. Note that the source could be a thin or wide pointer.
-    /// This will do things like convert thin pointers to fat
+    /// This will do things like convert thin pointers to wide
     /// pointers, or convert structs containing thin pointers to
-    /// structs containing fat pointers, or convert between fat
+    /// structs containing wide pointers, or convert between wide
     /// pointers.
     Unsize,
 }

tests/ui/cast/fat-ptr-cast.stderr

@@ -44,7 +44,7 @@ LL |     p as usize;
    |
    = help: cast through a thin pointer first
 
-error[E0607]: cannot cast thin pointer `*const i32` to fat pointer `*const [i32]`
+error[E0607]: cannot cast thin pointer `*const i32` to wide pointer `*const [i32]`
   --> $DIR/fat-ptr-cast.rs:19:5
    |
 LL |     q as *const [i32];

tests/ui/consts/slice_elem_ty_mismatch_in_unsizing_cast.stderr

@@ -1,4 +1,4 @@
-error[E0607]: cannot cast thin pointer `*const [i64; 0]` to fat pointer `*const [u8]`
+error[E0607]: cannot cast thin pointer `*const [i64; 0]` to wide pointer `*const [u8]`
   --> $DIR/slice_elem_ty_mismatch_in_unsizing_cast.rs:1:31
    |
 LL | const FOO: &str = unsafe { &*(1_usize as *const [i64; 0] as *const [u8] as *const str) };

tests/ui/error-codes/E0607.stderr

@@ -1,4 +1,4 @@
-error[E0607]: cannot cast thin pointer `*const u8` to fat pointer `*const [u8]`
+error[E0607]: cannot cast thin pointer `*const u8` to wide pointer `*const [u8]`
   --> $DIR/E0607.rs:3:5
    |
 LL |     v as *const [u8];

tests/ui/error-festival.stderr

@@ -81,7 +81,7 @@ help: dereference the expression
 LL |     let y: u32 = *x as u32;
    |                  +
 
-error[E0607]: cannot cast thin pointer `*const u8` to fat pointer `*const [u8]`
+error[E0607]: cannot cast thin pointer `*const u8` to wide pointer `*const [u8]`
   --> $DIR/error-festival.rs:41:5
    |
 LL |     v as *const [u8];

tests/ui/issues/issue-31511.rs

@@ -1,6 +1,6 @@
 fn cast_thin_to_fat(x: *const ()) {
     x as *const [u8];
-    //~^ ERROR: cannot cast thin pointer `*const ()` to fat pointer `*const [u8]`
+    //~^ ERROR: cannot cast thin pointer `*const ()` to wide pointer `*const [u8]`
 }
 
 fn main() {}

tests/ui/issues/issue-31511.stderr

@@ -1,4 +1,4 @@
-error[E0607]: cannot cast thin pointer `*const ()` to fat pointer `*const [u8]`
+error[E0607]: cannot cast thin pointer `*const ()` to wide pointer `*const [u8]`
   --> $DIR/issue-31511.rs:2:5
    |
 LL |     x as *const [u8];

tests/ui/mismatched_types/cast-rfc0401.stderr

@@ -158,7 +158,7 @@ LL |     let _ = 42usize as *const [u8];
    |             |
    |             consider casting this expression to `*const ()`, then using `core::ptr::from_raw_parts`
 
-error[E0607]: cannot cast thin pointer `*const u8` to fat pointer `*const [u8]`
+error[E0607]: cannot cast thin pointer `*const u8` to wide pointer `*const [u8]`
   --> $DIR/cast-rfc0401.rs:52:13
    |
 LL |     let _ = v as *const [u8];