diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs index 250ba0442ba..009075540fa 100644 --- a/src/libsyntax/ext/tt/macro_rules.rs +++ b/src/libsyntax/ext/tt/macro_rules.rs @@ -29,6 +29,11 @@ use std::rc::Rc; struct ParserAnyMacro<'a> { parser: RefCell>, + + /// Span of the expansion site of the macro this parser is for + site_span: Span, + /// The ident of the macro we're parsing + macro_ident: ast::Ident } impl<'a> ParserAnyMacro<'a> { @@ -50,6 +55,12 @@ impl<'a> ParserAnyMacro<'a> { token_str); let span = parser.span; parser.span_err(span, &msg[..]); + + let name = token::get_ident(self.macro_ident); + let msg = format!("caused by the macro expansion here; the usage \ + of `{}` is likely invalid in this context", + name); + parser.span_note(self.site_span, &msg[..]); } } } @@ -169,6 +180,12 @@ fn generic_extension<'cx>(cx: &'cx ExtCtxt, // Weird, but useful for X-macros. return box ParserAnyMacro { parser: RefCell::new(p), + + // Pass along the original expansion site and the name of the macro + // so we can print a useful error message if the parse of the expanded + // macro leaves unparsed tokens. + site_span: sp, + macro_ident: name } } Failure(sp, ref msg) => if sp.lo >= best_fail_spot.lo { diff --git a/src/test/compile-fail/macro-incomplete-parse.rs b/src/test/compile-fail/macro-incomplete-parse.rs index 53b29ccb0c0..b3ce84c7e6f 100644 --- a/src/test/compile-fail/macro-incomplete-parse.rs +++ b/src/test/compile-fail/macro-incomplete-parse.rs @@ -24,12 +24,12 @@ macro_rules! ignored_pat { () => ( 1, 2 ) //~ ERROR macro expansion ignores token `,` } -ignored_item!(); +ignored_item!(); //~ NOTE caused by the macro expansion here fn main() { - ignored_expr!(); + ignored_expr!(); //~ NOTE caused by the macro expansion here match 1 { - ignored_pat!() => (), + ignored_pat!() => (), //~ NOTE caused by the macro expansion here _ => (), } }