Simplify pointer handling.

The existing derive code allows for various possibilities that aren't
needed in practice, which complicates the code. There are only a few
auto-derived traits and new ones are unlikely, so this commit simplifies
things.

- `PtrTy` has been eliminated. The `Raw` variant was never used, and the
  lifetime for the `Borrowed` variant was always `None`. That left just
  the mutability field, which has been inlined as necessary.
- `MethodDef::explicit_self` was a confusing `Option<Option<PtrTy>>`.
  Indicating either `&self` or nothing. It's now a `bool`.
- `borrowed_self` is renamed as `self_ref`.
- `Ty::Ptr` is renamed to `Ty::Ref`.

Author: nnethercote

compiler/rustc_builtin_macros/src/deriving/clone.rs

@@ -79,7 +79,7 @@ pub fn expand_deriving_clone(
         methods: vec![MethodDef {
             name: sym::clone,
             generics: Bounds::empty(),
-            explicit_self: borrowed_explicit_self(),
+            explicit_self: true,
             args: Vec::new(),
             ret_ty: Self_,
             attributes: attrs,

compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs

@@ -31,7 +31,7 @@ pub fn expand_deriving_eq(
         methods: vec![MethodDef {
             name: sym::assert_receiver_is_total_eq,
             generics: Bounds::empty(),
-            explicit_self: borrowed_explicit_self(),
+            explicit_self: true,
             args: vec![],
             ret_ty: nil_ty(),
             attributes: attrs,

compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs

@@ -27,8 +27,8 @@ pub fn expand_deriving_ord(
         methods: vec![MethodDef {
             name: sym::cmp,
             generics: Bounds::empty(),
-            explicit_self: borrowed_explicit_self(),
-            args: vec![(borrowed_self(), sym::other)],
+            explicit_self: true,
+            args: vec![(self_ref(), sym::other)],
             ret_ty: Literal(path_std!(cmp::Ordering)),
             attributes: attrs,
             unify_fieldless_variants: true,

compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs

@@ -69,8 +69,8 @@ pub fn expand_deriving_partial_eq(
             MethodDef {
                 name: $name,
                 generics: Bounds::empty(),
-                explicit_self: borrowed_explicit_self(),
-                args: vec![(borrowed_self(), sym::other)],
+                explicit_self: true,
+                args: vec![(self_ref(), sym::other)],
                 ret_ty: Literal(path_local!(bool)),
                 attributes: attrs,
                 unify_fieldless_variants: true,

compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs

@@ -29,8 +29,8 @@ pub fn expand_deriving_partial_ord(
     let partial_cmp_def = MethodDef {
         name: sym::partial_cmp,
         generics: Bounds::empty(),
-        explicit_self: borrowed_explicit_self(),
-        args: vec![(borrowed_self(), sym::other)],
+        explicit_self: true,
+        args: vec![(self_ref(), sym::other)],
         ret_ty,
         attributes: attrs,
         unify_fieldless_variants: true,

compiler/rustc_builtin_macros/src/deriving/debug.rs

@@ -16,8 +16,7 @@ pub fn expand_deriving_debug(
     push: &mut dyn FnMut(Annotatable),
 ) {
     // &mut ::std::fmt::Formatter
-    let fmtr =
-        Ptr(Box::new(Literal(path_std!(fmt::Formatter))), Borrowed(None, ast::Mutability::Mut));
+    let fmtr = Ref(Box::new(Literal(path_std!(fmt::Formatter))), ast::Mutability::Mut);
 
     let trait_def = TraitDef {
         span,
@@ -29,7 +28,7 @@ pub fn expand_deriving_debug(
         methods: vec![MethodDef {
             name: sym::fmt,
             generics: Bounds::empty(),
-            explicit_self: borrowed_explicit_self(),
+            explicit_self: true,
             args: vec![(fmtr, sym::f)],
             ret_ty: Literal(path_std!(fmt::Result)),
             attributes: Vec::new(),

compiler/rustc_builtin_macros/src/deriving/decodable.rs

@@ -35,11 +35,8 @@ pub fn expand_deriving_rustc_decodable(
                     vec![Path::new_(vec![krate, sym::Decoder], None, vec![], PathKind::Global)],
                 )],
             },
-            explicit_self: None,
-            args: vec![(
-                Ptr(Box::new(Literal(Path::new_local(typaram))), Borrowed(None, Mutability::Mut)),
-                sym::d,
-            )],
+            explicit_self: false,
+            args: vec![(Ref(Box::new(Literal(Path::new_local(typaram))), Mutability::Mut), sym::d)],
             ret_ty: Literal(Path::new_(
                 pathvec_std!(result::Result),
                 None,

compiler/rustc_builtin_macros/src/deriving/default.rs

@@ -34,7 +34,7 @@ pub fn expand_deriving_default(
         methods: vec![MethodDef {
             name: kw::Default,
             generics: Bounds::empty(),
-            explicit_self: None,
+            explicit_self: false,
             args: Vec::new(),
             ret_ty: Self_,
             attributes: attrs,

compiler/rustc_builtin_macros/src/deriving/encodable.rs

@@ -120,11 +120,8 @@ pub fn expand_deriving_rustc_encodable(
                     vec![Path::new_(vec![krate, sym::Encoder], None, vec![], PathKind::Global)],
                 )],
             },
-            explicit_self: borrowed_explicit_self(),
-            args: vec![(
-                Ptr(Box::new(Literal(Path::new_local(typaram))), Borrowed(None, Mutability::Mut)),
-                sym::s,
-            )],
+            explicit_self: true,
+            args: vec![(Ref(Box::new(Literal(Path::new_local(typaram))), Mutability::Mut), sym::s)],
             ret_ty: Literal(Path::new_(
                 pathvec_std!(result::Result),
                 None,

compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -188,7 +188,7 @@ use rustc_expand::base::{Annotatable, ExtCtxt};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::Span;
 
-use ty::{Bounds, Path, Ptr, PtrTy, Self_, Ty};
+use ty::{Bounds, Path, Ref, Self_, Ty};
 
 use crate::deriving;
 
@@ -224,10 +224,8 @@ pub struct MethodDef<'a> {
     /// List of generics, e.g., `R: rand::Rng`
     pub generics: Bounds,
 
-    /// Whether there is a self argument (outer Option) i.e., whether
-    /// this is a static function, and whether it is a pointer (inner
-    /// Option)
-    pub explicit_self: Option<Option<PtrTy>>,
+    /// Is there is a `&self` argument? If not, it is a static function.
+    pub explicit_self: bool,
 
     /// Arguments other than the self argument
     pub args: Vec<(Ty, Symbol)>,
@@ -844,7 +842,7 @@ impl<'a> MethodDef<'a> {
     }
 
     fn is_static(&self) -> bool {
-        self.explicit_self.is_none()
+        !self.explicit_self
     }
 
     fn split_self_nonself_args(
@@ -857,17 +855,15 @@ impl<'a> MethodDef<'a> {
         let mut self_args = Vec::new();
         let mut nonself_args = Vec::new();
         let mut arg_tys = Vec::new();
-        let mut nonstatic = false;
         let span = trait_.span;
 
-        let ast_explicit_self = self.explicit_self.as_ref().map(|self_ptr| {
-            let (self_expr, explicit_self) = ty::get_explicit_self(cx, span, self_ptr);
-
+        let ast_explicit_self = if self.explicit_self {
+            let (self_expr, explicit_self) = ty::get_explicit_self(cx, span);
             self_args.push(self_expr);
-            nonstatic = true;
-
-            explicit_self
-        });
+            Some(explicit_self)
+        } else {
+            None
+        };
 
         for (ty, name) in self.args.iter() {
             let ast_ty = ty.to_ty(cx, span, type_ident, generics);
@@ -879,10 +875,10 @@ impl<'a> MethodDef<'a> {
             match *ty {
                 // for static methods, just treat any Self
                 // arguments as a normal arg
-                Self_ if nonstatic => {
+                Self_ if !self.is_static() => {
                     self_args.push(arg_expr);
                 }
-                Ptr(ref ty, _) if matches!(**ty, Self_) && nonstatic => {
+                Ref(ref ty, _) if matches!(**ty, Self_) && !self.is_static() => {
                     self_args.push(cx.expr_deref(span, arg_expr))
                 }
                 _ => {

compiler/rustc_builtin_macros/src/deriving/generic/ty.rs

@@ -1,7 +1,6 @@
 //! A mini version of ast::Ty, which is easier to use, and features an explicit `Self` type to use
 //! when specifying impls to be derived.
 
-pub use PtrTy::*;
 pub use Ty::*;
 
 use rustc_ast::ptr::P;
@@ -11,16 +10,6 @@ use rustc_span::source_map::{respan, DUMMY_SP};
 use rustc_span::symbol::{kw, Ident, Symbol};
 use rustc_span::Span;
 
-/// The types of pointers
-#[derive(Clone)]
-pub enum PtrTy {
-    /// &'lifetime mut
-    Borrowed(Option<Ident>, ast::Mutability),
-    /// *mut
-    #[allow(dead_code)]
-    Raw(ast::Mutability),
-}
-
 /// A path, e.g., `::std::option::Option::<i32>` (global). Has support
 /// for type parameters and a lifetime.
 #[derive(Clone)]
@@ -92,28 +81,17 @@ impl Path {
 #[derive(Clone)]
 pub enum Ty {
     Self_,
-    /// &/Box/ Ty
-    Ptr(Box<Ty>, PtrTy),
+    /// A reference.
+    Ref(Box<Ty>, ast::Mutability),
     /// `mod::mod::Type<[lifetime], [Params...]>`, including a plain type
     /// parameter, and things like `i32`
     Literal(Path),
     /// includes unit
     Tuple(Vec<Ty>),
 }
 
-pub fn borrowed_ptrty() -> PtrTy {
-    Borrowed(None, ast::Mutability::Not)
-}
-pub fn borrowed(ty: Box<Ty>) -> Ty {
-    Ptr(ty, borrowed_ptrty())
-}
-
-pub fn borrowed_explicit_self() -> Option<Option<PtrTy>> {
-    Some(Some(borrowed_ptrty()))
-}
-
-pub fn borrowed_self() -> Ty {
-    borrowed(Box::new(Self_))
+pub fn self_ref() -> Ty {
+    Ref(Box::new(Self_), ast::Mutability::Not)
 }
 
 pub fn nil_ty() -> Ty {
@@ -136,20 +114,14 @@ impl Ty {
         self_ty: Ident,
         self_generics: &Generics,
     ) -> P<ast::Ty> {
-        match *self {
-            Ptr(ref ty, ref ptr) => {
+        match self {
+            Ref(ty, mutbl) => {
                 let raw_ty = ty.to_ty(cx, span, self_ty, self_generics);
-                match *ptr {
-                    Borrowed(ref lt, mutbl) => {
-                        let lt = mk_lifetime(cx, span, lt);
-                        cx.ty_rptr(span, raw_ty, lt, mutbl)
-                    }
-                    Raw(mutbl) => cx.ty_ptr(span, raw_ty, mutbl),
-                }
+                cx.ty_rptr(span, raw_ty, None, *mutbl)
             }
-            Literal(ref p) => p.to_ty(cx, span, self_ty, self_generics),
+            Literal(p) => p.to_ty(cx, span, self_ty, self_generics),
             Self_ => cx.ty_path(self.to_path(cx, span, self_ty, self_generics)),
-            Tuple(ref fields) => {
+            Tuple(fields) => {
                 let ty = ast::TyKind::Tup(
                     fields.iter().map(|f| f.to_ty(cx, span, self_ty, self_generics)).collect(),
                 );
@@ -186,7 +158,7 @@ impl Ty {
                 cx.path_all(span, false, vec![self_ty], params)
             }
             Literal(ref p) => p.to_path(cx, span, self_ty, generics),
-            Ptr(..) => cx.span_bug(span, "pointer in a path in generic `derive`"),
+            Ref(..) => cx.span_bug(span, "ref in a path in generic `derive`"),
             Tuple(..) => cx.span_bug(span, "tuple in a path in generic `derive`"),
         }
     }
@@ -245,28 +217,10 @@ impl Bounds {
     }
 }
 
-pub fn get_explicit_self(
-    cx: &ExtCtxt<'_>,
-    span: Span,
-    self_ptr: &Option<PtrTy>,
-) -> (P<Expr>, ast::ExplicitSelf) {
+pub fn get_explicit_self(cx: &ExtCtxt<'_>, span: Span) -> (P<Expr>, ast::ExplicitSelf) {
     // this constructs a fresh `self` path
     let self_path = cx.expr_self(span);
-    match *self_ptr {
-        None => (self_path, respan(span, SelfKind::Value(ast::Mutability::Not))),
-        Some(ref ptr) => {
-            let self_ty = respan(
-                span,
-                match *ptr {
-                    Borrowed(ref lt, mutbl) => {
-                        let lt = lt.map(|s| cx.lifetime(span, s));
-                        SelfKind::Region(lt, mutbl)
-                    }
-                    Raw(_) => cx.span_bug(span, "attempted to use *self in deriving definition"),
-                },
-            );
-            let self_expr = cx.expr_deref(span, self_path);
-            (self_expr, self_ty)
-        }
-    }
+    let self_ty = respan(span, SelfKind::Region(None, ast::Mutability::Not));
+    let self_expr = cx.expr_deref(span, self_path);
+    (self_expr, self_ty)
 }

compiler/rustc_builtin_macros/src/deriving/hash.rs

@@ -30,8 +30,8 @@ pub fn expand_deriving_hash(
         methods: vec![MethodDef {
             name: sym::hash,
             generics: Bounds { bounds: vec![(typaram, vec![path_std!(hash::Hasher)])] },
-            explicit_self: borrowed_explicit_self(),
-            args: vec![(Ptr(Box::new(Literal(arg)), Borrowed(None, Mutability::Mut)), sym::state)],
+            explicit_self: true,
+            args: vec![(Ref(Box::new(Literal(arg)), Mutability::Mut), sym::state)],
             ret_ty: nil_ty(),
             attributes: vec![],
             unify_fieldless_variants: true,