Add `ErrorGuaranteed` to `ast::LitKind::Err`, `token::LitKind::Err`.

This mostly works well, and eliminates a couple of delayed bugs.

One annoying thing is that we should really also add an
`ErrorGuaranteed` to `proc_macro::bridge::LitKind::Err`. But that's
difficult because `proc_macro` doesn't have access to `ErrorGuaranteed`,
so we have to fake it.

2 files changed, 7 insertions, 3 deletions

diff --git a/library/proc_macro/src/bridge/mod.rs b/library/proc_macro/src/bridge/mod.rs
index 55e24b6491c..9b337f23867 100644
--- a/library/proc_macro/src/bridge/mod.rs
+++ b/library/proc_macro/src/bridge/mod.rs
@@ -337,7 +337,11 @@ pub enum LitKind {
     ByteStrRaw(u8),
     CStr,
     CStrRaw(u8),
-    Err,
+    // This should have an `ErrorGuaranteed`, except that type isn't available
+    // in this crate. (Imagine it is there.) Hence the `WithGuar` suffix. Must
+    // only be constructed in `LitKind::from_internal`, where an
+    // `ErrorGuaranteed` is available.
+    ErrWithGuar,
 }
 
 rpc_encode_decode!(
@@ -352,7 +356,7 @@ rpc_encode_decode!(
         ByteStrRaw(n),
         CStr,
         CStrRaw(n),
-        Err,
+        ErrWithGuar,
     }
 );
 
diff --git a/library/proc_macro/src/lib.rs b/library/proc_macro/src/lib.rs
index 90b76cbc26e..7c492941713 100644
--- a/library/proc_macro/src/lib.rs
+++ b/library/proc_macro/src/lib.rs
@@ -1451,7 +1451,7 @@ impl Literal {
                 f(&["cr", hashes, "\"", symbol, "\"", hashes, suffix])
             }
 
-            bridge::LitKind::Integer | bridge::LitKind::Float | bridge::LitKind::Err => {
+            bridge::LitKind::Integer | bridge::LitKind::Float | bridge::LitKind::ErrWithGuar => {
                 f(&[symbol, suffix])
             }
         })