Break dependencies between `syntax_ext` and some other crates

Move `source_uitil` macros into `syntax_ext`
Cleanup dependencies of `rustc_driver`

1 files changed, 7 insertions, 0 deletions

diff --git a/src/libsyntax/ext/proc_macro.rs b/src/libsyntax/ext/proc_macro.rs
new file mode 100644
index 00000000000..3aac79e241a
--- /dev/null
+++ b/src/libsyntax/ext/proc_macro.rs
@@ -0,0 +1,7 @@
+use crate::ast::Attribute;
+use crate::symbol::sym;
+
+pub fn is_proc_macro_attr(attr: &Attribute) -> bool {
+    [sym::proc_macro, sym::proc_macro_attribute, sym::proc_macro_derive]
+        .iter().any(|kind| attr.check_name(*kind))
+}