From ce8880d1d8b10cfaebc44449a37b6ad9fc628cb9 Mon Sep 17 00:00:00 2001
From: Mazdak Farrokhzad <twingoow@gmail.com>
Date: Tue, 17 Mar 2020 10:56:00 +0100
Subject: [PATCH] defatalize AttrProcMacro::expand

---
 src/librustc_expand/base.rs       |  6 +++---
 src/librustc_expand/expand.rs     |  7 +++++--
 src/librustc_expand/proc_macro.rs | 21 ++++++++-------------
 3 files changed, 16 insertions(+), 18 deletions(-)

diff --git a/src/librustc_expand/base.rs b/src/librustc_expand/base.rs
index 20e1895270a7..4947730a4aa7 100644
--- a/src/librustc_expand/base.rs
+++ b/src/librustc_expand/base.rs
@@ -326,7 +326,7 @@ pub trait AttrProcMacro {
         span: Span,
         annotation: TokenStream,
         annotated: TokenStream,
-    ) -> TokenStream;
+    ) -> Result<TokenStream, ErrorReported>;
 }
 
 impl<F> AttrProcMacro for F
@@ -339,9 +339,9 @@ where
         _span: Span,
         annotation: TokenStream,
         annotated: TokenStream,
-    ) -> TokenStream {
+    ) -> Result<TokenStream, ErrorReported> {
         // FIXME setup implicit context in TLS before calling self.
-        (*self)(annotation, annotated)
+        Ok((*self)(annotation, annotated))
     }
 }
 
diff --git a/src/librustc_expand/expand.rs b/src/librustc_expand/expand.rs
index 57314824d5a8..cbb695a815ac 100644
--- a/src/librustc_expand/expand.rs
+++ b/src/librustc_expand/expand.rs
@@ -712,8 +712,11 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                     if let MacArgs::Eq(..) = attr_item.args {
                         self.cx.span_err(span, "key-value macro attributes are not supported");
                     }
-                    let tok_result =
-                        expander.expand(self.cx, span, attr_item.args.inner_tokens(), tokens);
+                    let inner_tokens = attr_item.args.inner_tokens();
+                    let tok_result = match expander.expand(self.cx, span, inner_tokens, tokens) {
+                        Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
+                        Ok(ts) => ts,
+                    };
                     self.parse_ast_fragment(tok_result, fragment_kind, &attr_item.path, span)
                 }
                 SyntaxExtensionKind::LegacyAttr(expander) => {
diff --git a/src/librustc_expand/proc_macro.rs b/src/librustc_expand/proc_macro.rs
index 404f29f1fcf0..40b5e63756be 100644
--- a/src/librustc_expand/proc_macro.rs
+++ b/src/librustc_expand/proc_macro.rs
@@ -45,21 +45,16 @@ impl base::AttrProcMacro for AttrProcMacro {
         span: Span,
         annotation: TokenStream,
         annotated: TokenStream,
-    ) -> TokenStream {
+    ) -> Result<TokenStream, ErrorReported> {
         let server = proc_macro_server::Rustc::new(ecx);
-        match self.client.run(&EXEC_STRATEGY, server, annotation, annotated) {
-            Ok(stream) => stream,
-            Err(e) => {
-                let msg = "custom attribute panicked";
-                let mut err = ecx.struct_span_fatal(span, msg);
-                if let Some(s) = e.as_str() {
-                    err.help(&format!("message: {}", s));
-                }
-
-                err.emit();
-                FatalError.raise();
+        self.client.run(&EXEC_STRATEGY, server, annotation, annotated).map_err(|e| {
+            let mut err = ecx.struct_span_err(span, "custom attribute panicked");
+            if let Some(s) = e.as_str() {
+                err.help(&format!("message: {}", s));
             }
-        }
+            err.emit();
+            ErrorReported
+        })
     }
 }