1 files changed, 89 insertions, 0 deletions
diff --git a/tests/ui/proc-macro/auxiliary/macro-only-syntax.rs b/tests/ui/proc-macro/auxiliary/macro-only-syntax.rs
new file mode 100644
index 00000000000..c72306c3d50
--- /dev/null
+++ b/tests/ui/proc-macro/auxiliary/macro-only-syntax.rs
@@ -0,0 +1,89 @@
+// force-host
+// no-prefer-dynamic
+
+// These are tests for syntax that is accepted by the Rust parser but
+// unconditionally rejected semantically after macro expansion. Attribute macros
+// are permitted to accept such syntax as long as they replace it with something
+// that makes sense to Rust.
+//
+// We also inspect some of the spans to verify the syntax is not triggering the
+// lossy string reparse hack (https://github.com/rust-lang/rust/issues/43081).
+
+#![crate_type = "proc-macro"]
+#![feature(proc_macro_span)]
+
+extern crate proc_macro;
+use proc_macro::{token_stream, Delimiter, TokenStream, TokenTree};
+use std::path::Component;
+
+// unsafe mod m {
+//     pub unsafe mod inner;
+// }
+#[proc_macro_attribute]
+pub fn expect_unsafe_mod(_attrs: TokenStream, input: TokenStream) -> TokenStream {
+    let tokens = &mut input.into_iter();
+    expect(tokens, "unsafe");
+    expect(tokens, "mod");
+    expect(tokens, "m");
+    let tokens = &mut expect_brace(tokens);
+    expect(tokens, "pub");
+    expect(tokens, "unsafe");
+    expect(tokens, "mod");
+    let ident = expect(tokens, "inner");
+    expect(tokens, ";");
+    check_useful_span(ident, "unsafe-mod.rs");
+    TokenStream::new()
+}
+
+// unsafe extern {
+//     type T;
+// }
+#[proc_macro_attribute]
+pub fn expect_unsafe_foreign_mod(_attrs: TokenStream, input: TokenStream) -> TokenStream {
+    let tokens = &mut input.into_iter();
+    expect(tokens, "unsafe");
+    expect(tokens, "extern");
+    let tokens = &mut expect_brace(tokens);
+    expect(tokens, "type");
+    let ident = expect(tokens, "T");
+    expect(tokens, ";");
+    check_useful_span(ident, "unsafe-foreign-mod.rs");
+    TokenStream::new()
+}
+
+// unsafe extern "C++" {}
+#[proc_macro_attribute]
+pub fn expect_unsafe_extern_cpp_mod(_attrs: TokenStream, input: TokenStream) -> TokenStream {
+    let tokens = &mut input.into_iter();
+    expect(tokens, "unsafe");
+    expect(tokens, "extern");
+    let abi = expect(tokens, "\"C++\"");
+    expect_brace(tokens);
+    check_useful_span(abi, "unsafe-foreign-mod.rs");
+    TokenStream::new()
+}
+
+fn expect(tokens: &mut token_stream::IntoIter, expected: &str) -> TokenTree {
+    match tokens.next() {
+        Some(token) if token.to_string() == expected => token,
+        wrong => panic!("unexpected token: {:?}, expected `{}`", wrong, expected),
+    }
+}
+
+fn expect_brace(tokens: &mut token_stream::IntoIter) -> token_stream::IntoIter {
+    match tokens.next() {
+        Some(TokenTree::Group(group)) if group.delimiter() == Delimiter::Brace => {
+            group.stream().into_iter()
+        }
+        wrong => panic!("unexpected token: {:?}, expected `{{`", wrong),
+    }
+}
+
+fn check_useful_span(token: TokenTree, expected_filename: &str) {
+    let span = token.span();
+    assert!(span.start().column < span.end().column);
+
+    let source_path = span.source_file().path();
+    let filename = source_path.components().last().unwrap();
+    assert_eq!(filename, Component::Normal(expected_filename.as_ref()));
+}