Auto merge of #47031 - topecongiro:issue-41719, r=jseyfried

Report an error when resolving non-ident macro path failed

Closes #41719.

Please feel free to bikeshed on the error message.

src/librustc_resolve/macros.rs

@@ -429,7 +429,15 @@ fn resolve_macro_to_def_inner(&mut self, scope: Mark, path: &ast::Path,
             let def = match self.resolve_path(&path, Some(MacroNS), false, span) {
                 PathResult::NonModule(path_res) => match path_res.base_def() {
                     Def::Err => Err(Determinacy::Determined),
-                    def @ _ => Ok(def),
+                    def @ _ => {
+                        if path_res.unresolved_segments() > 0 {
+                            self.found_unresolved_macro = true;
+                            self.session.span_err(span, "fail to resolve non-ident macro path");
+                            Err(Determinacy::Determined)
+                        } else {
+                            Ok(def)
+                        }
+                    }
                 },
                 PathResult::Module(..) => unreachable!(),
                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),

src/test/compile-fail/extern-macro.rs

@@ -0,0 +1,18 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// #41719
+
+#![feature(use_extern_macros)]
+
+fn main() {
+    enum Foo {}
+    let _ = Foo::bar!(); //~ ERROR fail to resolve non-ident macro path
+}