Don't expand macros in the same expansion tree after overflow

crates/hir-expand/src/lib.rs

@@ -55,6 +55,7 @@ pub type ExpandResult<T> = ValueResult<T, ExpandError>;
 pub enum ExpandError {
     UnresolvedProcMacro(CrateId),
     Mbe(mbe::ExpandError),
+    RecursionOverflowPosioned,
     Other(Box<str>),
 }
 
@@ -69,6 +70,9 @@ impl fmt::Display for ExpandError {
         match self {
             ExpandError::UnresolvedProcMacro(_) => f.write_str("unresolved proc-macro"),
             ExpandError::Mbe(it) => it.fmt(f),
+            ExpandError::RecursionOverflowPosioned => {
+                f.write_str("overflow expanding the original macro")
+            }
             ExpandError::Other(it) => f.write_str(it),
         }
     }