show macro backtrace with env var

Author: durka

src/librustc_errors/emitter.rs

@@ -23,6 +23,7 @@ use std::rc::Rc;
 use term;
 use std::collections::HashMap;
 use std::cmp::min;
+use std::env;
 
 /// Emitter trait for emitting errors.
 pub trait Emitter {
@@ -786,18 +787,20 @@ impl EmitterWriter {
  fn fix_multispans_in_std_macros(&mut self,
  span: &mut MultiSpan,
  children: &mut Vec<SubDiagnostic>) {
- let mut spans_updated = self.fix_multispan_in_std_macros(span);
- for child in children.iter_mut() {
- spans_updated |= self.fix_multispan_in_std_macros(&mut child.span);
- }
- if spans_updated {
- children.push(SubDiagnostic {
- level: Level::Note,
- message: vec![("this error originates in a macro outside of the current crate"
- .to_string(), Style::NoStyle)],
- span: MultiSpan::new(),
- render_span: None,
- });
+ if env::var_os("RUST_MACRO_BACKTRACE").is_none() {
+ let mut spans_updated = self.fix_multispan_in_std_macros(span);
+ for child in children.iter_mut() {
+ spans_updated |= self.fix_multispan_in_std_macros(&mut child.span);
+ }
+ if spans_updated {
+ children.push(SubDiagnostic {
+ level: Level::Note,
+ message: vec![("this error originates in a macro outside of the current crate (run with RUST_MACRO_BACKTRACE=1 for more info)"
+ .to_string(), Style::NoStyle)],
+ span: MultiSpan::new(),
+ render_span: None,
+ });
+ }
  }
  }
 
@@ -1079,6 +1082,12 @@ impl EmitterWriter {
  }
  }
 
+ if env::var_os("RUST_MACRO_BACKTRACE").is_some() {
+ if let Some(ref primary_span) = msp.primary_span().as_ref() {
+ self.render_macro_backtrace_old_school(primary_span, &mut buffer)?;
+ }
+ }
+
  // final step: take our styled buffer, render it, then output it
  emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
 
@@ -1226,6 +1235,30 @@ impl EmitterWriter {
  }
  }
  }
+
+ fn render_macro_backtrace_old_school(&self,
+ sp: &Span,
+ buffer: &mut StyledBuffer) -> io::Result<()> {
+ if let Some(ref cm) = self.cm {
+ for trace in sp.macro_backtrace().iter().rev() {
+ let line_offset = buffer.num_lines();
+ 
+ let mut diag_string =
+ format!("in this expansion of {}", trace.macro_decl_name);
+ if let Some(def_site_span) = trace.def_site_span {
+ diag_string.push_str(
+ &format!(" (defined in {})",
+ cm.span_to_filename(def_site_span)));
+ }
+ let snippet = cm.span_to_string(trace.call_site);
+ buffer.append(line_offset, &format!("{} ", snippet), Style::NoStyle);
+ buffer.append(line_offset, "note", Style::Level(Level::Note));
+ buffer.append(line_offset, ": ", Style::NoStyle);
+ buffer.append(line_offset, &diag_string, Style::OldSchoolNoteText);
+ }
+ }
+ Ok(())
+ }
 }
 
 fn draw_col_separator(buffer: &mut StyledBuffer, line: usize, col: usize) {
@@ -1415,7 +1448,7 @@ impl Destination {
  }
  }
  Style::Quotation => {}
- Style::HeaderMsg => {
+ Style::OldSchoolNoteText | Style::HeaderMsg => {
  self.start_attr(term::Attr::Bold)?;
  if cfg!(windows) {
  self.start_attr(term::Attr::ForegroundColor(term::color::BRIGHT_WHITE))?;

src/librustc_errors/snippet.rs

@@ -213,6 +213,7 @@ pub enum Style {
  UnderlineSecondary,
  LabelPrimary,
  LabelSecondary,
+ OldSchoolNoteText,
  NoStyle,
  Level(Level),
  Highlight,