Auto merge of #42105 - Mark-Simulacrum:rollup, r=Mark-Simulacrum

Rollup of 17 pull requests

- Successful merges: #41870, #41910, #41958, #41971, #42006, #42024, #42037, #42056, #42067, #42070, #42079, #42080, #42082, #42089, #42092, #42096, #42100
- Failed merges:

2 files changed, 5 insertions, 5 deletions

diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index 00483b1ea5f..1930f61121b 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -700,7 +700,7 @@ impl<'a> ExtCtxt<'a> {
     /// Returns span for the macro which originally caused the current expansion to happen.
     ///
     /// Stops backtracing at include! boundary.
-    pub fn expansion_cause(&self) -> Span {
+    pub fn expansion_cause(&self) -> Option<Span> {
         let mut ctxt = self.backtrace();
         let mut last_macro = None;
         loop {
@@ -716,7 +716,7 @@ impl<'a> ExtCtxt<'a> {
                 break
             }
         }
-        last_macro.expect("missing expansion backtrace")
+        last_macro
     }
 
     pub fn struct_span_warn(&self,
diff --git a/src/libsyntax/ext/source_util.rs b/src/libsyntax/ext/source_util.rs
index 4183583d66f..3cdd3a4b2c3 100644
--- a/src/libsyntax/ext/source_util.rs
+++ b/src/libsyntax/ext/source_util.rs
@@ -35,7 +35,7 @@ pub fn expand_line(cx: &mut ExtCtxt, sp: Span, tts: &[tokenstream::TokenTree])
                    -> Box<base::MacResult+'static> {
     base::check_zero_tts(cx, sp, tts, "line!");
 
-    let topmost = cx.expansion_cause();
+    let topmost = cx.expansion_cause().unwrap_or(sp);
     let loc = cx.codemap().lookup_char_pos(topmost.lo);
 
     base::MacEager::expr(cx.expr_u32(topmost, loc.line as u32))
@@ -46,7 +46,7 @@ pub fn expand_column(cx: &mut ExtCtxt, sp: Span, tts: &[tokenstream::TokenTree])
                   -> Box<base::MacResult+'static> {
     base::check_zero_tts(cx, sp, tts, "column!");
 
-    let topmost = cx.expansion_cause();
+    let topmost = cx.expansion_cause().unwrap_or(sp);
     let loc = cx.codemap().lookup_char_pos(topmost.lo);
 
     base::MacEager::expr(cx.expr_u32(topmost, loc.col.to_usize() as u32))
@@ -59,7 +59,7 @@ pub fn expand_file(cx: &mut ExtCtxt, sp: Span, tts: &[tokenstream::TokenTree])
                    -> Box<base::MacResult+'static> {
     base::check_zero_tts(cx, sp, tts, "file!");
 
-    let topmost = cx.expansion_cause();
+    let topmost = cx.expansion_cause().unwrap_or(sp);
     let loc = cx.codemap().lookup_char_pos(topmost.lo);
     base::MacEager::expr(cx.expr_str(topmost, Symbol::intern(&loc.file.name)))
 }