Rollup merge of #33644 - petrochenkov:selfast, r=nrc

 The AST part of #33505.
#33505 isn't landed yet, so this PR is based on top of it.

r? @nrc

plugin-[breaking-change] cc #31645 @Manishearth

Author: Manishearth

src/librustc/hir/lowering.rs

@@ -273,7 +273,7 @@ impl<'a> LoweringContext<'a> {
         P(hir::Ty {
             id: t.id,
             node: match t.node {
-                Infer => hir::TyInfer,
+                Infer | ImplicitSelf => hir::TyInfer,
                 Vec(ref ty) => hir::TyVec(self.lower_ty(ty)),
                 Ptr(ref mt) => hir::TyPtr(self.lower_mt(mt)),
                 Rptr(ref region, ref mt) => {
@@ -791,23 +791,24 @@ impl<'a> LoweringContext<'a> {
     }
 
     fn lower_method_sig(&mut self, sig: &MethodSig) -> hir::MethodSig {
-        // Check for `self: _` and `self: &_`
-        if let SelfKind::Explicit(ref ty, _) = sig.explicit_self.node {
-            match sig.decl.inputs.get(0).and_then(Arg::to_self).map(|eself| eself.node) {
-                Some(SelfKind::Value(..)) | Some(SelfKind::Region(..)) => {
-                    self.id_assigner.diagnostic().span_err(ty.span,
-                        "the type placeholder `_` is not allowed within types on item signatures");
-                }
-                _ => {}
-            }
-        }
-        hir::MethodSig {
+        let hir_sig = hir::MethodSig {
             generics: self.lower_generics(&sig.generics),
             abi: sig.abi,
             unsafety: self.lower_unsafety(sig.unsafety),
             constness: self.lower_constness(sig.constness),
             decl: self.lower_fn_decl(&sig.decl),
+        };
+        // Check for `self: _` and `self: &_`
+        if let Some(SelfKind::Explicit(..)) = sig.decl.get_self().map(|eself| eself.node) {
+            match hir_sig.decl.get_self().map(|eself| eself.node) {
+                Some(hir::SelfKind::Value(..)) | Some(hir::SelfKind::Region(..)) => {
+                    self.id_assigner.diagnostic().span_err(sig.decl.inputs[0].ty.span,
+                        "the type placeholder `_` is not allowed within types on item signatures");
+                }
+                _ => {}
+            }
         }
+        hir_sig
     }
 
     fn lower_unsafety(&mut self, u: Unsafety) -> hir::Unsafety {

src/librustc/hir/mod.rs

@@ -1177,6 +1177,9 @@ pub struct FnDecl {
 }
 
 impl FnDecl {
+    pub fn get_self(&self) -> Option<ExplicitSelf> {
+        self.inputs.get(0).and_then(Arg::to_self)
+    }
     pub fn has_self(&self) -> bool {
         self.inputs.get(0).map(Arg::is_self).unwrap_or(false)
     }

src/librustc/lint/context.rs

@@ -1043,11 +1043,6 @@ impl<'a, 'v> ast_visit::Visitor<'v> for EarlyContext<'a> {
         run_lints!(self, check_lifetime_def, early_passes, lt);
     }
 
-    fn visit_explicit_self(&mut self, es: &ast::ExplicitSelf) {
-        run_lints!(self, check_explicit_self, early_passes, es);
-        ast_visit::walk_explicit_self(self, es);
-    }
-
     fn visit_path(&mut self, p: &ast::Path, id: ast::NodeId) {
         run_lints!(self, check_path, early_passes, p, id);
         ast_visit::walk_path(self, p);

src/librustc/lint/mod.rs

@@ -167,7 +167,6 @@ pub trait LateLintPass: LintPass {
     fn check_variant_post(&mut self, _: &LateContext, _: &hir::Variant, _: &hir::Generics) { }
     fn check_lifetime(&mut self, _: &LateContext, _: &hir::Lifetime) { }
     fn check_lifetime_def(&mut self, _: &LateContext, _: &hir::LifetimeDef) { }
-    fn check_explicit_self(&mut self, _: &LateContext, _: &hir::ExplicitSelf) { }
     fn check_path(&mut self, _: &LateContext, _: &hir::Path, _: ast::NodeId) { }
     fn check_path_list_item(&mut self, _: &LateContext, _: &hir::PathListItem) { }
     fn check_attribute(&mut self, _: &LateContext, _: &ast::Attribute) { }
@@ -218,7 +217,6 @@ pub trait EarlyLintPass: LintPass {
     fn check_variant_post(&mut self, _: &EarlyContext, _: &ast::Variant, _: &ast::Generics) { }
     fn check_lifetime(&mut self, _: &EarlyContext, _: &ast::Lifetime) { }
     fn check_lifetime_def(&mut self, _: &EarlyContext, _: &ast::LifetimeDef) { }
-    fn check_explicit_self(&mut self, _: &EarlyContext, _: &ast::ExplicitSelf) { }
     fn check_path(&mut self, _: &EarlyContext, _: &ast::Path, _: ast::NodeId) { }
     fn check_path_list_item(&mut self, _: &EarlyContext, _: &ast::PathListItem) { }
     fn check_attribute(&mut self, _: &EarlyContext, _: &ast::Attribute) { }

src/librustc_resolve/build_reduced_graph.rs

@@ -35,7 +35,7 @@ use syntax::codemap::{Span, DUMMY_SP};
 use syntax::ast::{Block, Crate, DeclKind};
 use syntax::ast::{ForeignItem, ForeignItemKind, Item, ItemKind};
 use syntax::ast::{Mutability, PathListItemKind};
-use syntax::ast::{SelfKind, Stmt, StmtKind, TraitItemKind};
+use syntax::ast::{Stmt, StmtKind, TraitItemKind};
 use syntax::ast::{Variant, ViewPath, ViewPathGlob, ViewPathList, ViewPathSimple};
 use syntax::visit::{self, Visitor};
 
@@ -335,7 +335,7 @@ impl<'b> Resolver<'b> {
                     let (def, ns) = match item.node {
                         TraitItemKind::Const(..) => (Def::AssociatedConst(item_def_id), ValueNS),
                         TraitItemKind::Method(ref sig, _) => {
-                            is_static_method = sig.explicit_self.node == SelfKind::Static;
+                            is_static_method = !sig.decl.has_self();
                             (Def::Method(item_def_id), ValueNS)
                         }
                         TraitItemKind::Type(..) => (Def::AssociatedTy(def_id, item_def_id), TypeNS),

src/librustc_resolve/lib.rs

@@ -67,7 +67,7 @@ use syntax::ast::{Arm, BindingMode, Block, Crate, Expr, ExprKind};
 use syntax::ast::{FnDecl, ForeignItem, ForeignItemKind, Generics};
 use syntax::ast::{Item, ItemKind, ImplItem, ImplItemKind};
 use syntax::ast::{Local, Pat, PatKind, Path};
-use syntax::ast::{PathSegment, PathParameters, SelfKind, TraitItemKind, TraitRef, Ty, TyKind};
+use syntax::ast::{PathSegment, PathParameters, TraitItemKind, TraitRef, Ty, TyKind};
 
 use std::collections::{HashMap, HashSet};
 use std::cell::{Cell, RefCell};
@@ -607,7 +607,7 @@ impl<'a, 'v> Visitor<'v> for Resolver<'a> {
             }
             FnKind::Method(_, sig, _) => {
                 self.visit_generics(&sig.generics);
-                MethodRibKind(sig.explicit_self.node == SelfKind::Static)
+                MethodRibKind(!sig.decl.has_self())
             }
             FnKind::Closure => ClosureRibKind(node_id),
         };
@@ -1676,9 +1676,7 @@ impl<'a> Resolver<'a> {
                                     let type_parameters =
                                         HasTypeParameters(&sig.generics,
                                                           FnSpace,
-                                                          MethodRibKind(
-                                                             sig.explicit_self.node ==
-                                                             SelfKind::Static));
+                                                          MethodRibKind(!sig.decl.has_self()));
                                     this.with_type_parameter_rib(type_parameters, |this| {
                                         visit::walk_trait_item(this, trait_item)
                                     });
@@ -2007,9 +2005,7 @@ impl<'a> Resolver<'a> {
                                     let type_parameters =
                                         HasTypeParameters(&sig.generics,
                                                           FnSpace,
-                                                          MethodRibKind(
-                                                            sig.explicit_self.node ==
-                                                            SelfKind::Static));
+                                                          MethodRibKind(!sig.decl.has_self()));
                                     this.with_type_parameter_rib(type_parameters, |this| {
                                         visit::walk_impl_item(this, impl_item);
                                     });

src/librustc_typeck/astconv.rs

@@ -1833,8 +1833,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
         // lifetime elision, we can determine it in two ways. First (determined
         // here), if self is by-reference, then the implied output region is the
         // region of the self parameter.
-        let explicit_self = decl.inputs.get(0).and_then(hir::Arg::to_self);
-        let (self_ty, explicit_self_category) = match (opt_untransformed_self_ty, explicit_self) {
+        let (self_ty, explicit_self_category) = match (opt_untransformed_self_ty, decl.get_self()) {
             (Some(untransformed_self_ty), Some(explicit_self)) => {
                 let self_type = self.determine_self_type(&rb, untransformed_self_ty,
                                                          &explicit_self);

src/libsyntax/ast.rs

@@ -1389,7 +1389,6 @@ pub struct MethodSig {
     pub abi: Abi,
     pub decl: P<FnDecl>,
     pub generics: Generics,
-    pub explicit_self: ExplicitSelf,
 }
 
 /// Represents an item declaration within a trait declaration,
@@ -1640,6 +1639,8 @@ pub enum TyKind {
     /// TyKind::Infer means the type should be inferred instead of it having been
     /// specified. This can appear anywhere in a type.
     Infer,
+    /// Inferred type of a `self` or `&self` argument in a method.
+    ImplicitSelf,
     // A macro in the type position.
     Mac(Mac),
 }
@@ -1679,81 +1680,65 @@ pub struct Arg {
     pub id: NodeId,
 }
 
-/// Represents the kind of 'self' associated with a method.
-/// String representation of `Ident` here is always "self", but hygiene contexts may differ.
+/// Alternative representation for `Arg`s describing `self` parameter of methods.
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub enum SelfKind {
-    /// No self
-    Static,
     /// `self`, `mut self`
-    Value(Ident),
+    Value(Mutability),
     /// `&'lt self`, `&'lt mut self`
-    Region(Option<Lifetime>, Mutability, Ident),
+    Region(Option<Lifetime>, Mutability),
     /// `self: TYPE`, `mut self: TYPE`
-    Explicit(P<Ty>, Ident),
+    Explicit(P<Ty>, Mutability),
 }
 
 pub type ExplicitSelf = Spanned<SelfKind>;
 
 impl Arg {
-    #[unstable(feature = "rustc_private", issue = "27812")]
-    #[rustc_deprecated(since = "1.10.0", reason = "use `from_self` instead")]
-    pub fn new_self(span: Span, mutability: Mutability, self_ident: Ident) -> Arg {
-        let path = Spanned{span:span,node:self_ident};
-        Arg {
-            // HACK(eddyb) fake type for the self argument.
-            ty: P(Ty {
-                id: DUMMY_NODE_ID,
-                node: TyKind::Infer,
-                span: DUMMY_SP,
-            }),
-            pat: P(Pat {
-                id: DUMMY_NODE_ID,
-                node: PatKind::Ident(BindingMode::ByValue(mutability), path, None),
-                span: span
-            }),
-            id: DUMMY_NODE_ID
-        }
-    }
-
     pub fn to_self(&self) -> Option<ExplicitSelf> {
-        if let PatKind::Ident(_, ident, _) = self.pat.node {
+        if let PatKind::Ident(BindingMode::ByValue(mutbl), ident, _) = self.pat.node {
             if ident.node.name == keywords::SelfValue.name() {
                 return match self.ty.node {
-                    TyKind::Infer => Some(respan(self.pat.span, SelfKind::Value(ident.node))),
-                    TyKind::Rptr(lt, MutTy{ref ty, mutbl}) if ty.node == TyKind::Infer => {
-                        Some(respan(self.pat.span, SelfKind::Region(lt, mutbl, ident.node)))
+                    TyKind::ImplicitSelf => Some(respan(self.pat.span, SelfKind::Value(mutbl))),
+                    TyKind::Rptr(lt, MutTy{ref ty, mutbl}) if ty.node == TyKind::ImplicitSelf => {
+                        Some(respan(self.pat.span, SelfKind::Region(lt, mutbl)))
                     }
                     _ => Some(respan(mk_sp(self.pat.span.lo, self.ty.span.hi),
-                                     SelfKind::Explicit(self.ty.clone(), ident.node))),
+                                     SelfKind::Explicit(self.ty.clone(), mutbl))),
                 }
             }
         }
         None
     }
 
-    pub fn from_self(eself: ExplicitSelf, ident_sp: Span, mutbl: Mutability) -> Arg {
-        let pat = |ident, span| P(Pat {
-            id: DUMMY_NODE_ID,
-            node: PatKind::Ident(BindingMode::ByValue(mutbl), respan(ident_sp, ident), None),
-            span: span,
-        });
+    pub fn is_self(&self) -> bool {
+        if let PatKind::Ident(_, ident, _) = self.pat.node {
+            ident.node.name == keywords::SelfValue.name()
+        } else {
+            false
+        }
+    }
+
+    pub fn from_self(eself: ExplicitSelf, eself_ident: SpannedIdent) -> Arg {
         let infer_ty = P(Ty {
             id: DUMMY_NODE_ID,
-            node: TyKind::Infer,
+            node: TyKind::ImplicitSelf,
             span: DUMMY_SP,
         });
-        let arg = |ident, ty, span| Arg {
-            pat: pat(ident, span),
+        let arg = |mutbl, ty, span| Arg {
+            pat: P(Pat {
+                id: DUMMY_NODE_ID,
+                node: PatKind::Ident(BindingMode::ByValue(mutbl), eself_ident, None),
+                span: span,
+            }),
             ty: ty,
             id: DUMMY_NODE_ID,
         };
         match eself.node {
-            SelfKind::Static => panic!("bug: `Arg::from_self` is called \
-                                        with `SelfKind::Static` argument"),
-            SelfKind::Explicit(ty, ident) => arg(ident, ty, mk_sp(eself.span.lo, ident_sp.hi)),
-            SelfKind::Value(ident) => arg(ident, infer_ty, eself.span),
-            SelfKind::Region(lt, mutbl, ident) => arg(ident, P(Ty {
+            SelfKind::Explicit(ty, mutbl) => {
+                arg(mutbl, ty, mk_sp(eself.span.lo, eself_ident.span.hi))
+            }
+            SelfKind::Value(mutbl) => arg(mutbl, infer_ty, eself.span),
+            SelfKind::Region(lt, mutbl) => arg(Mutability::Immutable, P(Ty {
                 id: DUMMY_NODE_ID,
                 node: TyKind::Rptr(lt, MutTy { ty: infer_ty, mutbl: mutbl }),
                 span: DUMMY_SP,
@@ -1770,6 +1755,15 @@ pub struct FnDecl {
     pub variadic: bool
 }
 
+impl FnDecl {
+    pub fn get_self(&self) -> Option<ExplicitSelf> {
+        self.inputs.get(0).and_then(Arg::to_self)
+    }
+    pub fn has_self(&self) -> bool {
+        self.inputs.get(0).map(Arg::is_self).unwrap_or(false)
+    }
+}
+
 #[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub enum Unsafety {
     Unsafe,

src/libsyntax/ext/expand.rs

@@ -950,7 +950,6 @@ fn expand_and_rename_method(sig: ast::MethodSig, body: P<ast::Block>,
     (ast::MethodSig {
         generics: fld.fold_generics(sig.generics),
         abi: sig.abi,
-        explicit_self: fld.fold_explicit_self(sig.explicit_self),
         unsafety: sig.unsafety,
         constness: sig.constness,
         decl: rewritten_fn_decl

src/libsyntax/fold.rs

@@ -179,14 +179,6 @@ pub trait Folder : Sized {
         // fold::noop_fold_mac(_mac, self)
     }
 
-    fn fold_explicit_self(&mut self, es: ExplicitSelf) -> ExplicitSelf {
-        noop_fold_explicit_self(es, self)
-    }
-
-    fn fold_explicit_self_kind(&mut self, es: SelfKind) -> SelfKind {
-        noop_fold_explicit_self_kind(es, self)
-    }
-
     fn fold_lifetime(&mut self, l: Lifetime) -> Lifetime {
         noop_fold_lifetime(l, self)
     }
@@ -383,7 +375,7 @@ pub fn noop_fold_ty<T: Folder>(t: P<Ty>, fld: &mut T) -> P<Ty> {
     t.map(|Ty {id, node, span}| Ty {
         id: fld.new_id(id),
         node: match node {
-            TyKind::Infer => node,
+            TyKind::Infer | TyKind::ImplicitSelf => node,
             TyKind::Vec(ty) => TyKind::Vec(fld.fold_ty(ty)),
             TyKind::Ptr(mt) => TyKind::Ptr(fld.fold_mt(mt)),
             TyKind::Rptr(region, mt) => {
@@ -523,28 +515,6 @@ pub fn noop_fold_attribute<T: Folder>(at: Attribute, fld: &mut T) -> Option<Attr
     })
 }
 
-pub fn noop_fold_explicit_self_kind<T: Folder>(es: SelfKind, fld: &mut T)
-                                                     -> SelfKind {
-    match es {
-        SelfKind::Static | SelfKind::Value(_) => es,
-        SelfKind::Region(lifetime, m, ident) => {
-            SelfKind::Region(fld.fold_opt_lifetime(lifetime), m, ident)
-        }
-        SelfKind::Explicit(typ, ident) => {
-            SelfKind::Explicit(fld.fold_ty(typ), ident)
-        }
-    }
-}
-
-pub fn noop_fold_explicit_self<T: Folder>(Spanned {span, node}: ExplicitSelf, fld: &mut T)
-                                          -> ExplicitSelf {
-    Spanned {
-        node: fld.fold_explicit_self_kind(node),
-        span: fld.new_span(span)
-    }
-}
-
-
 pub fn noop_fold_mac<T: Folder>(Spanned {node, span}: Mac, fld: &mut T) -> Mac {
     Spanned {
         node: Mac_ {
@@ -1096,7 +1066,6 @@ pub fn noop_fold_method_sig<T: Folder>(sig: MethodSig, folder: &mut T) -> Method
     MethodSig {
         generics: folder.fold_generics(sig.generics),
         abi: sig.abi,
-        explicit_self: folder.fold_explicit_self(sig.explicit_self),
         unsafety: sig.unsafety,
         constness: sig.constness,
         decl: folder.fold_fn_decl(sig.decl)