attr: remove dep on ExtCtxt

src/libsyntax/attr/builtin.rs

@@ -2,7 +2,6 @@
 
 use crate::ast::{self, Attribute, MetaItem, NestedMetaItem};
 use crate::early_buffered_lints::BufferedEarlyLintId;
-use crate::ext::base::ExtCtxt;
 use crate::feature_gate::{Features, GatedCfg};
 use crate::print::pprust;
 use crate::sess::ParseSess;
@@ -32,6 +31,10 @@ pub struct AttributeTemplate {
 }
 
 impl AttributeTemplate {
+    pub fn only_word() -> Self {
+        Self { word: true, list: None, name_value_str: None }
+    }
+
     /// Checks that the given meta-item is compatible with this template.
     fn compatible(&self, meta_item_kind: &ast::MetaItemKind) -> bool {
         match meta_item_kind {
@@ -937,14 +940,7 @@ pub fn find_transparency(
     (transparency.map_or(fallback, |t| t.0), error)
 }
 
-pub fn check_builtin_macro_attribute(ecx: &ExtCtxt<'_>, meta_item: &MetaItem, name: Symbol) {
-    // All the built-in macro attributes are "words" at the moment.
-    let template = AttributeTemplate { word: true, list: None, name_value_str: None };
-    let attr = ecx.attribute(meta_item.clone());
-    check_builtin_attribute(ecx.parse_sess, &attr, name, template);
-}
-
-crate fn check_builtin_attribute(
+pub fn check_builtin_attribute(
     sess: &ParseSess, attr: &ast::Attribute, name: Symbol, template: AttributeTemplate
 ) {
     // Some special attributes like `cfg` must be checked

src/libsyntax_ext/global_allocator.rs

@@ -1,6 +1,7 @@
+use crate::util::check_builtin_macro_attribute;
+
 use syntax::ast::{ItemKind, Mutability, Stmt, Ty, TyKind, Unsafety};
 use syntax::ast::{self, Param, Attribute, Expr, FnHeader, Generics, Ident};
-use syntax::attr::check_builtin_macro_attribute;
 use syntax::ext::allocator::{AllocatorKind, AllocatorMethod, AllocatorTy, ALLOCATOR_METHODS};
 use syntax::ext::base::{Annotatable, ExtCtxt};
 use syntax::ptr::P;

src/libsyntax_ext/lib.rs

@@ -37,6 +37,7 @@ mod log_syntax;
 mod source_util;
 mod test;
 mod trace_macros;
+mod util;
 
 pub mod cmdline_attrs;
 pub mod plugin_macro_defs;

src/libsyntax_ext/test.rs

@@ -1,8 +1,10 @@
 /// The expansion from a test function to the appropriate test struct for libtest
 /// Ideally, this code would be in libtest but for efficiency and error messages it lives here.
 
+use crate::util::check_builtin_macro_attribute;
+
 use syntax::ast;
-use syntax::attr::{self, check_builtin_macro_attribute};
+use syntax::attr;
 use syntax::ext::base::*;
 use syntax::print::pprust;
 use syntax::source_map::respan;

src/libsyntax_ext/util.rs

@@ -0,0 +1,11 @@
+use syntax_pos::Symbol;
+use syntax::ast::MetaItem;
+use syntax::attr::{check_builtin_attribute, AttributeTemplate};
+use syntax::ext::base::ExtCtxt;
+
+pub fn check_builtin_macro_attribute(ecx: &ExtCtxt<'_>, meta_item: &MetaItem, name: Symbol) {
+    // All the built-in macro attributes are "words" at the moment.
+    let template = AttributeTemplate::only_word();
+    let attr = ecx.attribute(meta_item.clone());
+    check_builtin_attribute(ecx.parse_sess, &attr, name, template);
+}