Auto merge of #46550 - jseyfried:cleanup_builtin_hygiene, r=nrc

macros: hygienize use of `core`/`std` in builtin macros

Today, if a builtin macro wants to access an item from `core` or `std` (depending `#![no_std]`), it generates `::core::path::to::item` or `::std::path::to::item` respectively (c.f. `fn std_path()` in `libsyntax/ext/base.rs`).

This PR refactors the builtin macros to instead always emit `$crate::path::to::item` here. That is, the def site of builtin macros is taken to be in `extern crate core;` or `extern crate std;`. Since builtin macros are macros 1.0 (i.e. mostly unhygienic), changing the def site can only effect the resolution of `$crate`.

r? @nrc

14 files changed, 77 insertions, 86 deletions

diff --git a/src/libsyntax_ext/deriving/bounds.rs b/src/libsyntax_ext/deriving/bounds.rs
index 0bc802283fb..7f03001d9c6 100644
--- a/src/libsyntax_ext/deriving/bounds.rs
+++ b/src/libsyntax_ext/deriving/bounds.rs
@@ -8,9 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use deriving::path_std;
 use deriving::generic::*;
 use deriving::generic::ty::*;
-
 use syntax::ast::MetaItem;
 use syntax::ext::base::{Annotatable, ExtCtxt};
 use syntax_pos::Span;
@@ -28,15 +28,10 @@ pub fn expand_deriving_copy(cx: &mut ExtCtxt,
                             mitem: &MetaItem,
                             item: &Annotatable,
                             push: &mut FnMut(Annotatable)) {
-    let mut v = cx.crate_root.map(|s| vec![s]).unwrap_or(Vec::new());
-    v.push("marker");
-    v.push("Copy");
-    let path = Path::new(v);
-
     let trait_def = TraitDef {
         span,
         attributes: Vec::new(),
-        path,
+        path: path_std!(cx, marker::Copy),
         additional_bounds: Vec::new(),
         generics: LifetimeBounds::empty(),
         is_unsafe: false,
diff --git a/src/libsyntax_ext/deriving/clone.rs b/src/libsyntax_ext/deriving/clone.rs
index 5d93c2a5f72..35def632fc1 100644
--- a/src/libsyntax_ext/deriving/clone.rs
+++ b/src/libsyntax_ext/deriving/clone.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use deriving::path_std;
 use deriving::generic::*;
 use deriving::generic::ty::*;
 
@@ -55,7 +56,7 @@ pub fn expand_deriving_clone(cx: &mut ExtCtxt,
                     }));
                 }
                 ItemKind::Union(..) => {
-                    bounds = vec![Literal(path_std!(cx, core::marker::Copy))];
+                    bounds = vec![Literal(path_std!(cx, marker::Copy))];
                     is_shallow = true;
                     substructure = combine_substructure(Box::new(|c, s, sub| {
                         cs_clone_shallow("Clone", c, s, sub, true)
@@ -79,7 +80,7 @@ pub fn expand_deriving_clone(cx: &mut ExtCtxt,
     let trait_def = TraitDef {
         span,
         attributes: Vec::new(),
-        path: path_std!(cx, core::clone::Clone),
+        path: path_std!(cx, clone::Clone),
         additional_bounds: bounds,
         generics: LifetimeBounds::empty(),
         is_unsafe: false,
diff --git a/src/libsyntax_ext/deriving/cmp/eq.rs b/src/libsyntax_ext/deriving/cmp/eq.rs
index a282ff5bd04..237c8654edf 100644
--- a/src/libsyntax_ext/deriving/cmp/eq.rs
+++ b/src/libsyntax_ext/deriving/cmp/eq.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use deriving::path_std;
 use deriving::generic::*;
 use deriving::generic::ty::*;
 
@@ -30,7 +31,7 @@ pub fn expand_deriving_eq(cx: &mut ExtCtxt,
     let trait_def = TraitDef {
         span,
         attributes: Vec::new(),
-        path: path_std!(cx, core::cmp::Eq),
+        path: path_std!(cx, cmp::Eq),
         additional_bounds: Vec::new(),
         generics: LifetimeBounds::empty(),
         is_unsafe: false,
diff --git a/src/libsyntax_ext/deriving/cmp/ord.rs b/src/libsyntax_ext/deriving/cmp/ord.rs
index 9b057aacece..1a392ac3765 100644
--- a/src/libsyntax_ext/deriving/cmp/ord.rs
+++ b/src/libsyntax_ext/deriving/cmp/ord.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use deriving::path_std;
 use deriving::generic::*;
 use deriving::generic::ty::*;
 
@@ -28,7 +29,7 @@ pub fn expand_deriving_ord(cx: &mut ExtCtxt,
     let trait_def = TraitDef {
         span,
         attributes: Vec::new(),
-        path: path_std!(cx, core::cmp::Ord),
+        path: path_std!(cx, cmp::Ord),
         additional_bounds: Vec::new(),
         generics: LifetimeBounds::empty(),
         is_unsafe: false,
@@ -38,7 +39,7 @@ pub fn expand_deriving_ord(cx: &mut ExtCtxt,
                           generics: LifetimeBounds::empty(),
                           explicit_self: borrowed_explicit_self(),
                           args: vec![borrowed_self()],
-                          ret_ty: Literal(path_std!(cx, core::cmp::Ordering)),
+                          ret_ty: Literal(path_std!(cx, cmp::Ordering)),
                           attributes: attrs,
                           is_unsafe: false,
                           unify_fieldless_variants: true,
diff --git a/src/libsyntax_ext/deriving/cmp/partial_eq.rs b/src/libsyntax_ext/deriving/cmp/partial_eq.rs
index e635c6bebcd..75db7cc1e4c 100644
--- a/src/libsyntax_ext/deriving/cmp/partial_eq.rs
+++ b/src/libsyntax_ext/deriving/cmp/partial_eq.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use deriving::{path_local, path_std};
 use deriving::generic::*;
 use deriving::generic::ty::*;
 
@@ -93,7 +94,7 @@ pub fn expand_deriving_partial_eq(cx: &mut ExtCtxt,
     let trait_def = TraitDef {
         span,
         attributes: Vec::new(),
-        path: path_std!(cx, core::cmp::PartialEq),
+        path: path_std!(cx, cmp::PartialEq),
         additional_bounds: Vec::new(),
         generics: LifetimeBounds::empty(),
         is_unsafe: false,
diff --git a/src/libsyntax_ext/deriving/cmp/partial_ord.rs b/src/libsyntax_ext/deriving/cmp/partial_ord.rs
index e7e1c108760..92183c58eb2 100644
--- a/src/libsyntax_ext/deriving/cmp/partial_ord.rs
+++ b/src/libsyntax_ext/deriving/cmp/partial_ord.rs
@@ -10,6 +10,7 @@
 
 pub use self::OrderingOp::*;
 
+use deriving::{path_local, pathvec_std, path_std};
 use deriving::generic::*;
 use deriving::generic::ty::*;
 
@@ -45,11 +46,11 @@ pub fn expand_deriving_partial_ord(cx: &mut ExtCtxt,
         } }
     }
 
-    let ordering_ty = Literal(path_std!(cx, core::cmp::Ordering));
-    let ret_ty = Literal(Path::new_(pathvec_std!(cx, core::option::Option),
+    let ordering_ty = Literal(path_std!(cx, cmp::Ordering));
+    let ret_ty = Literal(Path::new_(pathvec_std!(cx, option::Option),
                                     None,
                                     vec![Box::new(ordering_ty)],
-                                    true));
+                                    PathKind::Std));
 
     let inline = cx.meta_word(span, Symbol::intern("inline"));
     let attrs = vec![cx.attribute(span, inline)];
@@ -84,7 +85,7 @@ pub fn expand_deriving_partial_ord(cx: &mut ExtCtxt,
     let trait_def = TraitDef {
         span,
         attributes: vec![],
-        path: path_std!(cx, core::cmp::PartialOrd),
+        path: path_std!(cx, cmp::PartialOrd),
         additional_bounds: vec![],
         generics: LifetimeBounds::empty(),
         is_unsafe: false,
diff --git a/src/libsyntax_ext/deriving/debug.rs b/src/libsyntax_ext/deriving/debug.rs
index ab6dd04520c..82fc09fca69 100644
--- a/src/libsyntax_ext/deriving/debug.rs
+++ b/src/libsyntax_ext/deriving/debug.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use deriving::path_std;
 use deriving::generic::*;
 use deriving::generic::ty::*;
 
@@ -24,13 +25,13 @@ pub fn expand_deriving_debug(cx: &mut ExtCtxt,
                              item: &Annotatable,
                              push: &mut FnMut(Annotatable)) {
     // &mut ::std::fmt::Formatter
-    let fmtr = Ptr(Box::new(Literal(path_std!(cx, core::fmt::Formatter))),
+    let fmtr = Ptr(Box::new(Literal(path_std!(cx, fmt::Formatter))),
                    Borrowed(None, ast::Mutability::Mutable));
 
     let trait_def = TraitDef {
         span,
         attributes: Vec::new(),
-        path: path_std!(cx, core::fmt::Debug),
+        path: path_std!(cx, fmt::Debug),
         additional_bounds: Vec::new(),
         generics: LifetimeBounds::empty(),
         is_unsafe: false,
@@ -40,7 +41,7 @@ pub fn expand_deriving_debug(cx: &mut ExtCtxt,
                           generics: LifetimeBounds::empty(),
                           explicit_self: borrowed_explicit_self(),
                           args: vec![fmtr],
-                          ret_ty: Literal(path_std!(cx, core::fmt::Result)),
+                          ret_ty: Literal(path_std!(cx, fmt::Result)),
                           attributes: Vec::new(),
                           is_unsafe: false,
                           unify_fieldless_variants: false,
diff --git a/src/libsyntax_ext/deriving/decodable.rs b/src/libsyntax_ext/deriving/decodable.rs
index 517221af1d4..46dada256b8 100644
--- a/src/libsyntax_ext/deriving/decodable.rs
+++ b/src/libsyntax_ext/deriving/decodable.rs
@@ -10,7 +10,7 @@
 
 //! The compiler code necessary for `#[derive(Decodable)]`. See encodable.rs for more.
 
-use deriving;
+use deriving::{self, pathvec_std};
 use deriving::generic::*;
 use deriving::generic::ty::*;
 use deriving::warn_if_deprecated;
@@ -46,20 +46,12 @@ fn expand_deriving_decodable_imp(cx: &mut ExtCtxt,
                                  item: &Annotatable,
                                  push: &mut FnMut(Annotatable),
                                  krate: &'static str) {
-    if cx.crate_root != Some("std") {
-        // FIXME(#21880): lift this requirement.
-        cx.span_err(span,
-                    "this trait cannot be derived with #![no_std] \
-                           or #![no_core]");
-        return;
-    }
-
     let typaram = &*deriving::hygienic_type_parameter(item, "__D");
 
     let trait_def = TraitDef {
         span,
         attributes: Vec::new(),
-        path: Path::new_(vec![krate, "Decodable"], None, vec![], true),
+        path: Path::new_(vec![krate, "Decodable"], None, vec![], PathKind::Global),
         additional_bounds: Vec::new(),
         generics: LifetimeBounds::empty(),
         is_unsafe: false,
@@ -72,18 +64,18 @@ fn expand_deriving_decodable_imp(cx: &mut ExtCtxt,
                                             vec![Path::new_(vec![krate, "Decoder"],
                                                             None,
                                                             vec![],
-                                                            true)])],
+                                                            PathKind::Global)])],
                           },
                           explicit_self: None,
                           args: vec![Ptr(Box::new(Literal(Path::new_local(typaram))),
                                          Borrowed(None, Mutability::Mutable))],
                           ret_ty:
-                              Literal(Path::new_(pathvec_std!(cx, core::result::Result),
+                              Literal(Path::new_(pathvec_std!(cx, result::Result),
                                                  None,
                                                  vec![Box::new(Self_), Box::new(Literal(Path::new_(
-                        vec![typaram, "Error"], None, vec![], false
+                        vec![typaram, "Error"], None, vec![], PathKind::Local
                     )))],
-                                                 true)),
+                                                 PathKind::Std)),
                           attributes: Vec::new(),
                           is_unsafe: false,
                           unify_fieldless_variants: false,
diff --git a/src/libsyntax_ext/deriving/default.rs b/src/libsyntax_ext/deriving/default.rs
index 0c8e3c39395..99e7bb4baef 100644
--- a/src/libsyntax_ext/deriving/default.rs
+++ b/src/libsyntax_ext/deriving/default.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use deriving::path_std;
 use deriving::generic::*;
 use deriving::generic::ty::*;
 
@@ -28,7 +29,7 @@ pub fn expand_deriving_default(cx: &mut ExtCtxt,
     let trait_def = TraitDef {
         span,
         attributes: Vec::new(),
-        path: path_std!(cx, core::default::Default),
+        path: path_std!(cx, default::Default),
         additional_bounds: Vec::new(),
         generics: LifetimeBounds::empty(),
         is_unsafe: false,
diff --git a/src/libsyntax_ext/deriving/encodable.rs b/src/libsyntax_ext/deriving/encodable.rs
index c2c862f043f..0e6e96438d8 100644
--- a/src/libsyntax_ext/deriving/encodable.rs
+++ b/src/libsyntax_ext/deriving/encodable.rs
@@ -92,7 +92,7 @@
 //! }
 //! ```
 
-use deriving;
+use deriving::{self, pathvec_std};
 use deriving::generic::*;
 use deriving::generic::ty::*;
 use deriving::warn_if_deprecated;
@@ -127,20 +127,12 @@ fn expand_deriving_encodable_imp(cx: &mut ExtCtxt,
                                  item: &Annotatable,
                                  push: &mut FnMut(Annotatable),
                                  krate: &'static str) {
-    if cx.crate_root != Some("std") {
-        // FIXME(#21880): lift this requirement.
-        cx.span_err(span,
-                    "this trait cannot be derived with #![no_std] \
-                           or #![no_core]");
-        return;
-    }
-
     let typaram = &*deriving::hygienic_type_parameter(item, "__S");
 
     let trait_def = TraitDef {
         span,
         attributes: Vec::new(),
-        path: Path::new_(vec![krate, "Encodable"], None, vec![], true),
+        path: Path::new_(vec![krate, "Encodable"], None, vec![], PathKind::Global),
         additional_bounds: Vec::new(),
         generics: LifetimeBounds::empty(),
         is_unsafe: false,
@@ -150,19 +142,21 @@ fn expand_deriving_encodable_imp(cx: &mut ExtCtxt,
                 name: "encode",
                 generics: LifetimeBounds {
                     lifetimes: Vec::new(),
-                    bounds: vec![(typaram,
-                                  vec![Path::new_(vec![krate, "Encoder"], None, vec![], true)])]
+                    bounds: vec![
+                        (typaram,
+                         vec![Path::new_(vec![krate, "Encoder"], None, vec![], PathKind::Global)])
+                    ],
                 },
                 explicit_self: borrowed_explicit_self(),
                 args: vec![Ptr(Box::new(Literal(Path::new_local(typaram))),
                            Borrowed(None, Mutability::Mutable))],
                 ret_ty: Literal(Path::new_(
-                    pathvec_std!(cx, core::result::Result),
+                    pathvec_std!(cx, result::Result),
                     None,
                     vec![Box::new(Tuple(Vec::new())), Box::new(Literal(Path::new_(
-                        vec![typaram, "Error"], None, vec![], false
+                        vec![typaram, "Error"], None, vec![], PathKind::Local
                     )))],
-                    true
+                    PathKind::Std
                 )),
                 attributes: Vec::new(),
                 is_unsafe: false,
diff --git a/src/libsyntax_ext/deriving/generic/ty.rs b/src/libsyntax_ext/deriving/generic/ty.rs
index 47b5f40832a..e4faf652389 100644
--- a/src/libsyntax_ext/deriving/generic/ty.rs
+++ b/src/libsyntax_ext/deriving/generic/ty.rs
@@ -21,6 +21,8 @@ use syntax::ext::build::AstBuilder;
 use syntax::codemap::respan;
 use syntax::ptr::P;
 use syntax_pos::Span;
+use syntax_pos::hygiene::SyntaxContext;
+use syntax_pos::symbol::keywords;
 
 /// The types of pointers
 #[derive(Clone, Eq, PartialEq)]
@@ -36,29 +38,36 @@ pub enum PtrTy<'a> {
 /// for type parameters and a lifetime.
 #[derive(Clone, Eq, PartialEq)]
 pub struct Path<'a> {
-    pub path: Vec<&'a str>,
-    pub lifetime: Option<&'a str>,
-    pub params: Vec<Box<Ty<'a>>>,
-    pub global: bool,
+    path: Vec<&'a str>,
+    lifetime: Option<&'a str>,
+    params: Vec<Box<Ty<'a>>>,
+    kind: PathKind,
+}
+
+#[derive(Clone, Eq, PartialEq)]
+pub enum PathKind {
+    Local,
+    Global,
+    Std,
 }
 
 impl<'a> Path<'a> {
     pub fn new<'r>(path: Vec<&'r str>) -> Path<'r> {
-        Path::new_(path, None, Vec::new(), true)
+        Path::new_(path, None, Vec::new(), PathKind::Std)
     }
     pub fn new_local<'r>(path: &'r str) -> Path<'r> {
-        Path::new_(vec![path], None, Vec::new(), false)
+        Path::new_(vec![path], None, Vec::new(), PathKind::Local)
     }
     pub fn new_<'r>(path: Vec<&'r str>,
                     lifetime: Option<&'r str>,
                     params: Vec<Box<Ty<'r>>>,
-                    global: bool)
+                    kind: PathKind)
                     -> Path<'r> {
         Path {
             path,
             lifetime,
             params,
-            global,
+            kind,
         }
     }
 
@@ -76,11 +85,20 @@ impl<'a> Path<'a> {
                    self_ty: Ident,
                    self_generics: &Generics)
                    -> ast::Path {
-        let idents = self.path.iter().map(|s| cx.ident_of(*s)).collect();
+        let mut idents = self.path.iter().map(|s| cx.ident_of(*s)).collect();
         let lt = mk_lifetimes(cx, span, &self.lifetime);
         let tys = self.params.iter().map(|t| t.to_ty(cx, span, self_ty, self_generics)).collect();
 
-        cx.path_all(span, self.global, idents, lt, tys, Vec::new())
+        match self.kind {
+            PathKind::Global => cx.path_all(span, true, idents, lt, tys, Vec::new()),
+            PathKind::Local => cx.path_all(span, false, idents, lt, tys, Vec::new()),
+            PathKind::Std => {
+                let def_site = SyntaxContext::empty().apply_mark(cx.current_expansion.mark);
+                idents.insert(0, Ident { ctxt: def_site, ..keywords::DollarCrate.ident() });
+                cx.path_all(span, false, idents, lt, tys, Vec::new())
+            }
+        }
+
     }
 }
 
diff --git a/src/libsyntax_ext/deriving/hash.rs b/src/libsyntax_ext/deriving/hash.rs
index 6c78eea186d..b192ab2527e 100644
--- a/src/libsyntax_ext/deriving/hash.rs
+++ b/src/libsyntax_ext/deriving/hash.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use deriving;
+use deriving::{self, pathvec_std, path_std};
 use deriving::generic::*;
 use deriving::generic::ty::*;
 
@@ -24,7 +24,7 @@ pub fn expand_deriving_hash(cx: &mut ExtCtxt,
                             item: &Annotatable,
                             push: &mut FnMut(Annotatable)) {
 
-    let path = Path::new_(pathvec_std!(cx, core::hash::Hash), None, vec![], true);
+    let path = Path::new_(pathvec_std!(cx, hash::Hash), None, vec![], PathKind::Std);
 
     let typaram = &*deriving::hygienic_type_parameter(item, "__H");
 
@@ -41,7 +41,7 @@ pub fn expand_deriving_hash(cx: &mut ExtCtxt,
                           name: "hash",
                           generics: LifetimeBounds {
                               lifetimes: Vec::new(),
-                              bounds: vec![(typaram, vec![path_std!(cx, core::hash::Hasher)])],
+                              bounds: vec![(typaram, vec![path_std!(cx, hash::Hasher)])],
                           },
                           explicit_self: borrowed_explicit_self(),
                           args: vec![Ptr(Box::new(Literal(arg)),
diff --git a/src/libsyntax_ext/deriving/mod.rs b/src/libsyntax_ext/deriving/mod.rs
index ccf3d550234..a6696b53369 100644
--- a/src/libsyntax_ext/deriving/mod.rs
+++ b/src/libsyntax_ext/deriving/mod.rs
@@ -19,32 +19,16 @@ use syntax::ptr::P;
 use syntax::symbol::Symbol;
 use syntax_pos::Span;
 
-macro_rules! pathvec {
-    ($($x:ident)::+) => (
-        vec![ $( stringify!($x) ),+ ]
-    )
+macro path_local($x:ident) {
+    generic::ty::Path::new_local(stringify!($x))
 }
 
-macro_rules! path_local {
-    ($x:ident) => (
-        ::deriving::generic::ty::Path::new_local(stringify!($x))
-    )
-}
-
-macro_rules! pathvec_std {
-    ($cx:expr, $first:ident :: $($rest:ident)::+) => ({
-        let mut v = pathvec![$($rest)::+];
-        if let Some(s) = $cx.crate_root {
-            v.insert(0, s);
-        }
-        v
-    })
-}
+macro pathvec_std($cx:expr, $($rest:ident)::+) {{
+    vec![ $( stringify!($rest) ),+ ]
+}}
 
-macro_rules! path_std {
-    ($($x:tt)*) => (
-        ::deriving::generic::ty::Path::new( pathvec_std!( $($x)* ) )
-    )
+macro path_std($($x:tt)*) {
+    generic::ty::Path::new( pathvec_std!( $($x)* ) )
 }
 
 pub mod bounds;
diff --git a/src/libsyntax_ext/lib.rs b/src/libsyntax_ext/lib.rs
index 42bbb4ae0cb..82d6ee5afa0 100644
--- a/src/libsyntax_ext/lib.rs
+++ b/src/libsyntax_ext/lib.rs
@@ -16,6 +16,7 @@
 #![deny(warnings)]
 
 #![feature(proc_macro_internals)]
+#![feature(decl_macro)]
 
 extern crate fmt_macros;
 #[macro_use]