---

yaml
---
r: 224147
b: refs/heads/beta
c: 07afe91
h: refs/heads/master
i:
  224145: 9884993
  224143: 48134a4
v: v3

Author: pnkfelix

[refs]

@@ -23,7 +23,7 @@ refs/tags/0.9: 36870b185fc5f5486636d4515f0e22677493f225
 refs/tags/0.10: ac33f2b15782272ae348dbd7b14b8257b2148b5a
 refs/tags/0.11.0: e1247cb1d0d681be034adb4b558b5a0c0d5720f9
 refs/tags/0.12.0: f0c419429ef30723ceaf6b42f9b5a2aeb5d2e2d1
-refs/heads/beta: cb5f0b4971481fd8985c78c7a24e422f45ea6560
+refs/heads/beta: 07afe91fda3df8e3b7bbb14006a64d136627f33c
 refs/tags/1.0.0-alpha: e42bd6d93a1d3433c486200587f8f9e12590a4d7
 refs/heads/tmp: 938f5d7af401e2d8238522fed4a612943b6e77fd
 refs/tags/1.0.0-alpha.2: 4c705f6bc559886632d3871b04f58aab093bfa2f

branches/beta/src/libsyntax/ext/expand.rs

@@ -50,12 +50,23 @@ pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
             callee: NameAndSpan {
                 name: expansion_desc.to_string(),
                 format: CompilerExpansion,
+
+                // This does *not* mean code generated after
+                // `push_compiler_expansion` is automatically exempt
+                // from stability lints; must also tag such code with
+                // an appropriate span from `fld.cx.backtrace()`.
                 allow_internal_unstable: true,
+
                 span: None,
             },
         });
     }
 
+    // Sets the expn_id so that we can use unstable methods.
+    fn allow_unstable(fld: &mut MacroExpander, span: Span) -> Span {
+        Span { expn_id: fld.cx.backtrace(), ..span }
+    }
+
     let expr_span = e.span;
     return e.and_then(|ast::Expr {id, node, span}| match node {
 
@@ -101,6 +112,8 @@ pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
                 &fld.cx.parse_sess.span_diagnostic,
                 expr_span);
 
+            push_compiler_expansion(fld, expr_span, "placement-in expansion");
+
             let value_span = value_expr.span;
             let placer_span = placer.span;
 
@@ -121,9 +134,14 @@ pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
             let inplace_finalize = ["ops", "InPlace", "finalize"];
 
             let make_call = |fld: &mut MacroExpander, p, args| {
-                let path = mk_core_path(fld, placer_span, p);
+                // We feed in the `expr_span` because codemap's span_allows_unstable
+                // allows the call_site span to inherit the `allow_internal_unstable`
+                // setting.
+                let span_unstable = allow_unstable(fld, expr_span);
+                let path = mk_core_path(fld, span_unstable, p);
                 let path = fld.cx.expr_path(path);
-                fld.cx.expr_call(span, path, args)
+                let expr_span_unstable = allow_unstable(fld, span);
+                fld.cx.expr_call(expr_span_unstable, path, args)
             };
 
             let stmt_let = |fld: &mut MacroExpander, bind, expr| {
@@ -166,7 +184,9 @@ pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
             };
 
             let block = fld.cx.block_all(span, vec![s1, s2, s3], expr);
-            fld.cx.expr_block(block)
+            let result = fld.cx.expr_block(block);
+            fld.cx.bt_pop();
+            result
         }
 
         // Issue #22181: