better name for AdjustForForeignAbiError error variant in InterpError

Author: RalfJung

Diff for: compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -347,7 +347,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> FnAbiOfHelpers<'tcx> for InterpCx
     ) -> InterpErrorInfo<'tcx> {
         match err {
             FnAbiError::Layout(err) => err_inval!(Layout(err)).into(),
-            FnAbiError::AdjustForForeignAbi(err) => err_inval!(FnAbi(err)).into(),
+            FnAbiError::AdjustForForeignAbi(err) => {
+                err_inval!(FnAbiAdjustForForeignAbi(err)).into()
+            }
         }
     }
 }

Diff for: compiler/rustc_middle/src/mir/interpret/error.rs

@@ -141,9 +141,10 @@ pub enum InvalidProgramInfo<'tcx> {
     AlreadyReported(ErrorReported),
     /// An error occurred during layout computation.
     Layout(layout::LayoutError<'tcx>),
-    /// An error occurred during FnAbi computation.
-    /// (Not using `FnAbiError` as that contains a nested `LayoutError`.)
-    FnAbi(call::AdjustForForeignAbiError),
+    /// An error occurred during FnAbi computation: the passed --target lacks FFI support
+    /// (which unfortunately typeck does not reject).
+    /// Not using `FnAbiError` as that contains a nested `LayoutError`.
+    FnAbiAdjustForForeignAbi(call::AdjustForForeignAbiError),
     /// An invalid transmute happened.
     TransmuteSizeDiff(Ty<'tcx>, Ty<'tcx>),
     /// SizeOf of unsized type was requested.
@@ -160,7 +161,7 @@ impl fmt::Display for InvalidProgramInfo<'_> {
                 write!(f, "encountered constants with type errors, stopping evaluation")
             }
             Layout(ref err) => write!(f, "{}", err),
-            FnAbi(ref err) => write!(f, "{}", err),
+            FnAbiAdjustForForeignAbi(ref err) => write!(f, "{}", err),
             TransmuteSizeDiff(from_ty, to_ty) => write!(
                 f,
                 "transmuting `{}` to `{}` is not possible, because these types do not have the same size",