Auto merge of #64469 - matthewjasper:increase-hygiene-use, r=petrochenkov

Cleanup handling of hygiene for built-in macros

This makes most identifiers generated by built-in macros use def-site hygiene, not only the ones that previously used gensyms.

* `ExtCtxt::ident_of` now takes a `Span` and is preferred to `Ident::{from_str, from_str_and_span}`
* Remove `Span::with_legacy_ctxt`
    * `assert` now uses call-site hygiene because it needs to resolve `panic` unhygienically.
    * `concat_idents` now uses call-site hygiene because it wouldn't be very useful with def-site hygiene.
    * everything else is moved to def-site hygiene

r? @petrochenkov

1 files changed, 3 insertions, 1 deletions

diff --git a/src/libsyntax_ext/assert.rs b/src/libsyntax_ext/assert.rs
index 001996e1db7..cbfe14fa439 100644
--- a/src/libsyntax_ext/assert.rs
+++ b/src/libsyntax_ext/assert.rs
@@ -23,7 +23,9 @@ pub fn expand_assert<'cx>(
         }
     };
 
-    let sp = cx.with_legacy_ctxt(sp);
+    // `core::panic` and `std::panic` are different macros, so we use call-site
+    // context to pick up whichever is currently in scope.
+    let sp = cx.with_call_site_ctxt(sp);
     let panic_call = Mac {
         path: Path::from_ident(Ident::new(sym::panic, sp)),
         tts: custom_message.unwrap_or_else(|| {