Add an ExpnKind for AST passes

src/librustc/ich/impls_syntax.rs

@@ -411,9 +411,17 @@ impl_stable_hash_for!(struct ::syntax_pos::hygiene::ExpnData {
 impl_stable_hash_for!(enum ::syntax_pos::hygiene::ExpnKind {
     Root,
     Macro(kind, descr),
+    AstPass(kind),
     Desugaring(kind)
 });
 
+impl_stable_hash_for!(enum ::syntax_pos::hygiene::AstPass {
+    StdImports,
+    TestHarness,
+    ProcMacroHarness,
+    PluginMacroDefs,
+});
+
 impl_stable_hash_for!(enum ::syntax_pos::hygiene::DesugaringKind {
     CondTemporary,
     Async,

src/librustc/lint/mod.rs

@@ -888,7 +888,7 @@ pub fn in_external_macro(sess: &Session, span: Span) -> bool {
     let expn_data = span.ctxt().outer_expn_data();
     match expn_data.kind {
         ExpnKind::Root | ExpnKind::Desugaring(DesugaringKind::ForLoop) => false,
-        ExpnKind::Desugaring(_) => true, // well, it's "external"
+        ExpnKind::AstPass(_) | ExpnKind::Desugaring(_) => true, // well, it's "external"
         ExpnKind::Macro(MacroKind::Bang, _) => {
             if expn_data.def_site.is_dummy() {
                 // dummy span for the def_site means it's an external macro

src/libsyntax_pos/hygiene.rs

@@ -639,8 +639,9 @@ pub enum ExpnKind {
     /// No expansion, aka root expansion. Only `ExpnId::root()` has this kind.
     Root,
     /// Expansion produced by a macro.
-    /// FIXME: Some code injected by the compiler before HIR lowering also gets this kind.
     Macro(MacroKind, Symbol),
+    /// Transform done by the compiler on the AST.
+    AstPass(AstPass),
     /// Desugaring done by the compiler during HIR lowering.
     Desugaring(DesugaringKind)
 }
@@ -650,6 +651,7 @@ impl ExpnKind {
         match *self {
             ExpnKind::Root => kw::PathRoot,
             ExpnKind::Macro(_, descr) => descr,
+            ExpnKind::AstPass(kind) => Symbol::intern(kind.descr()),
             ExpnKind::Desugaring(kind) => Symbol::intern(kind.descr()),
         }
     }
@@ -683,6 +685,26 @@ impl MacroKind {
     }
 }
 
+/// The kind of AST transform.
+#[derive(Clone, Copy, PartialEq, Debug, RustcEncodable, RustcDecodable)]
+pub enum AstPass {
+    StdImports,
+    TestHarness,
+    ProcMacroHarness,
+    PluginMacroDefs,
+}
+
+impl AstPass {
+    fn descr(self) -> &'static str {
+        match self {
+            AstPass::StdImports => "standard library imports",
+            AstPass::TestHarness => "test harness",
+            AstPass::ProcMacroHarness => "proc macro harness",
+            AstPass::PluginMacroDefs => "plugin macro definitions",
+        }
+    }
+}
+
 /// The kind of compiler desugaring.
 #[derive(Clone, Copy, PartialEq, Debug, RustcEncodable, RustcDecodable)]
 pub enum DesugaringKind {

src/libsyntax_pos/lib.rs

@@ -442,6 +442,7 @@ impl Span {
                 let (pre, post) = match expn_data.kind {
                     ExpnKind::Root => break,
                     ExpnKind::Desugaring(..) => ("desugaring of ", ""),
+                    ExpnKind::AstPass(..) => ("", ""),
                     ExpnKind::Macro(macro_kind, _) => match macro_kind {
                         MacroKind::Bang => ("", "!"),
                         MacroKind::Attr => ("#[", "]"),