Warn when using panic-strategy abort for proc-macro crates

compiler/rustc_interface/src/errors.rs

@@ -87,3 +87,7 @@ pub struct FailedWritingFile<'a> {
     pub path: &'a Path,
     pub error: io::Error,
 }
+
+#[derive(Diagnostic)]
+#[diag(interface_proc_macro_crate_panic_abort)]
+pub struct ProcMacroCratePanicAbort;

compiler/rustc_interface/src/passes.rs

@@ -1,7 +1,8 @@
 use crate::errors::{
     CantEmitMIR, EmojiIdentifier, ErrorWritingDependencies, FerrisIdentifier,
     GeneratedFileConflictsWithDirectory, InputFileWouldBeOverWritten, MixedBinCrate,
-    MixedProcMacroCrate, OutDirError, ProcMacroDocWithoutArg, TempsDirError,
+    MixedProcMacroCrate, OutDirError, ProcMacroCratePanicAbort, ProcMacroDocWithoutArg,
+    TempsDirError,
 };
 use crate::interface::{Compiler, Result};
 use crate::proc_macro_decls;
@@ -36,6 +37,7 @@ use rustc_session::search_paths::PathKind;
 use rustc_session::{Limit, Session};
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::FileName;
+use rustc_target::spec::PanicStrategy;
 use rustc_trait_selection::traits;
 
 use std::any::Any;
@@ -380,6 +382,10 @@ pub fn configure_and_expand(
         }
     }
 
+    if is_proc_macro_crate && sess.panic_strategy() == PanicStrategy::Abort {
+        sess.emit_warning(ProcMacroCratePanicAbort);
+    }
+
     // For backwards compatibility, we don't try to run proc macro injection
     // if rustdoc is run on a proc macro crate without '--crate-type proc-macro' being
     // specified. This should only affect users who manually invoke 'rustdoc', as