use -Z flag instead of env var

src/librustc/session/config.rs

@@ -1036,6 +1036,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
           "run all passes except translation; no output"),
     treat_err_as_bug: bool = (false, parse_bool, [TRACKED],
           "treat all errors that occur as bugs"),
+    macro_backtrace: bool = (false, parse_bool, [UNTRACKED],
+          "show macro backtraces even for foreign macros"),
     continue_parse_after_error: bool = (false, parse_bool, [TRACKED],
           "attempt to recover from parse errors (experimental)"),
     incremental: Option<String> = (None, parse_opt_string, [UNTRACKED],

src/librustc/session/mod.rs

@@ -731,6 +731,8 @@ pub fn build_session_with_codemap(sopts: config::Options,
 
     let treat_err_as_bug = sopts.debugging_opts.treat_err_as_bug;
 
+    let macro_backtrace = sopts.debugging_opts.macro_backtrace;
+
     let emitter: Box<Emitter> = match (sopts.error_format, emitter_dest) {
         (config::ErrorOutputType::HumanReadable(color_config), None) => {
             Box::new(EmitterWriter::stderr(color_config, Some(codemap.clone()), false))
@@ -755,6 +757,7 @@ pub fn build_session_with_codemap(sopts: config::Options,
     let diagnostic_handler =
         errors::Handler::with_emitter(can_print_warnings,
                                       treat_err_as_bug,
+                                      macro_backtrace,
                                       emitter);
 
     build_session_(sopts,
@@ -925,7 +928,7 @@ pub fn early_error(output: config::ErrorOutputType, msg: &str) -> ! {
             Box::new(EmitterWriter::stderr(color_config, None, true))
         }
     };
-    let handler = errors::Handler::with_emitter(true, false, emitter);
+    let handler = errors::Handler::with_emitter(true, false, false, emitter);
     handler.emit(&MultiSpan::new(), msg, errors::Level::Fatal);
     panic!(errors::FatalError);
 }
@@ -940,7 +943,7 @@ pub fn early_warn(output: config::ErrorOutputType, msg: &str) {
             Box::new(EmitterWriter::stderr(color_config, None, true))
         }
     };
-    let handler = errors::Handler::with_emitter(true, false, emitter);
+    let handler = errors::Handler::with_emitter(true, false, false, emitter);
     handler.emit(&MultiSpan::new(), msg, errors::Level::Warning);
 }
 

src/librustc_driver/lib.rs

@@ -141,7 +141,7 @@ pub fn run<F>(run_compiler: F) -> isize
                         errors::emitter::EmitterWriter::stderr(errors::ColorConfig::Auto,
                                                                None,
                                                                true);
-                    let handler = errors::Handler::with_emitter(true, false, Box::new(emitter));
+                    let handler = errors::Handler::with_emitter(true, false, false, Box::new(emitter));
                     handler.emit(&MultiSpan::new(),
                                  "aborting due to previous error(s)",
                                  errors::Level::Fatal);
@@ -1221,7 +1221,7 @@ pub fn monitor<F: FnOnce() + Send + 'static>(f: F) {
                 Box::new(errors::emitter::EmitterWriter::stderr(errors::ColorConfig::Auto,
                                                                 None,
                                                                 false));
-            let handler = errors::Handler::with_emitter(true, false, emitter);
+            let handler = errors::Handler::with_emitter(true, false, false, emitter);
 
             // a .span_bug or .bug call has already printed what
             // it wants to print.

src/librustc_driver/test.rs

@@ -104,7 +104,7 @@ fn test_env<F>(source_string: &str,
     let mut options = config::basic_options();
     options.debugging_opts.verbose = true;
     options.unstable_features = UnstableFeatures::Allow;
-    let diagnostic_handler = errors::Handler::with_emitter(true, false, emitter);
+    let diagnostic_handler = errors::Handler::with_emitter(true, false, false, emitter);
 
     let cstore = Rc::new(CStore::new(::DefaultTransCrate::metadata_loader()));
     let sess = session::build_session_(options,

src/librustc_errors/diagnostic_builder.rs

@@ -23,7 +23,7 @@ use syntax_pos::{MultiSpan, Span};
 #[must_use]
 #[derive(Clone)]
 pub struct DiagnosticBuilder<'a> {
-    handler: &'a Handler,
+    pub handler: &'a Handler,
     diagnostic: Diagnostic,
 }
 

src/librustc_errors/emitter.rs

@@ -23,7 +23,6 @@ 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 {
@@ -65,8 +64,11 @@ impl Emitter for EmitterWriter {
             }
         }
 
-        self.fix_multispans_in_std_macros(&mut primary_span, &mut children);
+        if !db.handler.macro_backtrace {
+            self.fix_multispans_in_std_macros(&mut primary_span, &mut children);
+        }
         self.emit_messages_default(&db.level,
+                                   db.handler.macro_backtrace,
                                    &db.styled_message(),
                                    &db.code,
                                    &primary_span,
@@ -787,23 +789,21 @@ impl EmitterWriter {
     fn fix_multispans_in_std_macros(&mut self,
                                     span: &mut MultiSpan,
                                     children: &mut Vec<SubDiagnostic>) {
-        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)"].join(" "),
-                         Style::NoStyle),
-                    ],
-                    span: MultiSpan::new(),
-                    render_span: 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 -Z macro-backtrace for more info)"].join(" "),
+                     Style::NoStyle),
+                ],
+                span: MultiSpan::new(),
+                render_span: None,
+            });
         }
     }
 
@@ -888,6 +888,7 @@ impl EmitterWriter {
                             msg: &Vec<(String, Style)>,
                             code: &Option<DiagnosticId>,
                             level: &Level,
+                            macro_backtrace: bool,
                             max_line_num_len: usize,
                             is_secondary: bool)
                             -> io::Result<()> {
@@ -1085,7 +1086,7 @@ impl EmitterWriter {
             }
         }
 
-        if env::var_os("RUST_MACRO_BACKTRACE").is_some() {
+        if macro_backtrace {
             if let Some(ref primary_span) = msp.primary_span().as_ref() {
                 self.render_macro_backtrace_old_school(primary_span, &mut buffer)?;
             }
@@ -1182,6 +1183,7 @@ impl EmitterWriter {
     }
     fn emit_messages_default(&mut self,
                              level: &Level,
+                             macro_backtrace: bool,
                              message: &Vec<(String, Style)>,
                              code: &Option<DiagnosticId>,
                              span: &MultiSpan,
@@ -1190,7 +1192,13 @@ impl EmitterWriter {
         let max_line_num = self.get_max_line_num(span, children);
         let max_line_num_len = max_line_num.to_string().len();
 
-        match self.emit_message_default(span, message, code, level, max_line_num_len, false) {
+        match self.emit_message_default(span,
+                                        message,
+                                        code,
+                                        level,
+                                        macro_backtrace,
+                                        max_line_num_len,
+                                        false) {
             Ok(()) => {
                 if !children.is_empty() {
                     let mut buffer = StyledBuffer::new();
@@ -1210,6 +1218,7 @@ impl EmitterWriter {
                                                         &child.styled_message(),
                                                         &None,
                                                         &child.level,
+                                                        macro_backtrace,
                                                         max_line_num_len,
                                                         true) {
                             Err(e) => panic!("failed to emit error: {}", e),

src/librustc_errors/lib.rs

@@ -237,6 +237,7 @@ pub struct Handler {
     emitter: RefCell<Box<Emitter>>,
     pub can_emit_warnings: bool,
     treat_err_as_bug: bool,
+    pub macro_backtrace: bool,
     continue_after_error: Cell<bool>,
     delayed_span_bug: RefCell<Option<Diagnostic>>,
     tracked_diagnostics: RefCell<Option<Vec<Diagnostic>>>,
@@ -251,21 +252,24 @@ impl Handler {
     pub fn with_tty_emitter(color_config: ColorConfig,
                             can_emit_warnings: bool,
                             treat_err_as_bug: bool,
+                            macro_backtrace: bool,
                             cm: Option<Rc<CodeMapper>>)
                             -> Handler {
         let emitter = Box::new(EmitterWriter::stderr(color_config, cm, false));
-        Handler::with_emitter(can_emit_warnings, treat_err_as_bug, emitter)
+        Handler::with_emitter(can_emit_warnings, treat_err_as_bug, macro_backtrace, emitter)
     }
 
     pub fn with_emitter(can_emit_warnings: bool,
                         treat_err_as_bug: bool,
+                        macro_backtrace: bool,
                         e: Box<Emitter>)
                         -> Handler {
         Handler {
             err_count: Cell::new(0),
             emitter: RefCell::new(e),
             can_emit_warnings,
             treat_err_as_bug,
+            macro_backtrace,
             continue_after_error: Cell::new(true),
             delayed_span_bug: RefCell::new(None),
             tracked_diagnostics: RefCell::new(None),

src/librustc_trans/back/write.rs

@@ -353,7 +353,7 @@ pub struct CodegenContext {
 
 impl CodegenContext {
     pub fn create_diag_handler(&self) -> Handler {
-        Handler::with_emitter(true, false, Box::new(self.diag_emitter.clone()))
+        Handler::with_emitter(true, false, false, Box::new(self.diag_emitter.clone()))
     }
 
     pub fn config(&self, kind: ModuleKind) -> &ModuleConfig {

src/librustdoc/core.rs

@@ -141,6 +141,7 @@ pub fn run_core(search_paths: SearchPaths,
     let diagnostic_handler = errors::Handler::with_tty_emitter(ColorConfig::Auto,
                                                                true,
                                                                false,
+                                                               false,
                                                                Some(codemap.clone()));
 
     let cstore = Rc::new(CStore::new(box rustc_trans::LlvmMetadataLoader));

src/librustdoc/test.rs

@@ -81,7 +81,7 @@ pub fn run(input: &str,
 
     let codemap = Rc::new(CodeMap::new(sessopts.file_path_mapping()));
     let handler =
-        errors::Handler::with_tty_emitter(ColorConfig::Auto, true, false, Some(codemap.clone()));
+        errors::Handler::with_tty_emitter(ColorConfig::Auto, true, false, false, Some(codemap.clone()));
 
     let cstore = Rc::new(CStore::new(box rustc_trans::LlvmMetadataLoader));
     let mut sess = session::build_session_(
@@ -244,7 +244,7 @@ fn run_test(test: &str, cratename: &str, filename: &str, cfgs: Vec<String>, libs
     let _bomb = Bomb(data.clone(), old.unwrap_or(box io::stdout()));
 
     // Compile the code
-    let diagnostic_handler = errors::Handler::with_emitter(true, false, box emitter);
+    let diagnostic_handler = errors::Handler::with_emitter(true, false, false, box emitter);
 
     let cstore = Rc::new(CStore::new(box rustc_trans::LlvmMetadataLoader));
     let mut sess = session::build_session_(

src/libsyntax/parse/lexer/mod.rs

@@ -1726,7 +1726,7 @@ mod tests {
                                                           Some(cm.clone()),
                                                           false);
         ParseSess {
-            span_diagnostic: errors::Handler::with_emitter(true, false, Box::new(emitter)),
+            span_diagnostic: errors::Handler::with_emitter(true, false, false, Box::new(emitter)),
             unstable_features: UnstableFeatures::from_environment(),
             config: CrateConfig::new(),
             included_mod_stack: RefCell::new(Vec::new()),

src/libsyntax/parse/mod.rs

@@ -58,6 +58,7 @@ impl ParseSess {
         let handler = Handler::with_tty_emitter(ColorConfig::Auto,
                                                 true,
                                                 false,
+                                                false,
                                                 Some(cm.clone()));
         ParseSess::with_span_handler(handler, cm)
     }

src/libsyntax/test_snippet.rs

@@ -62,7 +62,7 @@ fn test_harness(file_text: &str, span_labels: Vec<SpanLabel>, expected_output: &
     let emitter = EmitterWriter::new(Box::new(Shared { data: output.clone() }),
                                      Some(code_map.clone()),
                                      false);
-    let handler = Handler::with_emitter(true, false, Box::new(emitter));
+    let handler = Handler::with_emitter(true, false, false, Box::new(emitter));
     handler.span_err(msp, "foo");
 
     assert!(expected_output.chars().next() == Some('\n'),

src/test/ui/codemap_tests/bad-format-args.stderr

@@ -4,23 +4,23 @@ error: requires at least a format string argument
 12 |     format!();
    |     ^^^^^^^^^^
    |
-   = note: this error originates in a macro outside of the current crate (run with RUST_MACRO_BACKTRACE=1 for more info)
+   = note: this error originates in a macro outside of the current crate (run with -Z macro-backtrace for more info)
 
 error: expected token: `,`
   --> $DIR/bad-format-args.rs:13:5
    |
 13 |     format!("" 1);
    |     ^^^^^^^^^^^^^^
    |
-   = note: this error originates in a macro outside of the current crate (run with RUST_MACRO_BACKTRACE=1 for more info)
+   = note: this error originates in a macro outside of the current crate (run with -Z macro-backtrace for more info)
 
 error: expected token: `,`
   --> $DIR/bad-format-args.rs:14:5
    |
 14 |     format!("", 1 1);
    |     ^^^^^^^^^^^^^^^^^
    |
-   = note: this error originates in a macro outside of the current crate (run with RUST_MACRO_BACKTRACE=1 for more info)
+   = note: this error originates in a macro outside of the current crate (run with -Z macro-backtrace for more info)
 
 error: aborting due to 3 previous errors
 

src/test/ui/codemap_tests/issue-28308.stderr

@@ -4,7 +4,7 @@ error[E0600]: cannot apply unary operator `!` to type `&'static str`
 12 |     assert!("foo");
    |     ^^^^^^^^^^^^^^^
    |
-   = note: this error originates in a macro outside of the current crate (run with RUST_MACRO_BACKTRACE=1 for more info)
+   = note: this error originates in a macro outside of the current crate (run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 

src/test/ui/cross-crate-macro-backtrace/main.stderr

@@ -4,7 +4,7 @@ error: 1 positional argument in format string, but no arguments were given
 16 |     myprintln!("{}"); //~ ERROR in this macro
    |     ^^^^^^^^^^^^^^^^^
    |
-   = note: this error originates in a macro outside of the current crate (run with RUST_MACRO_BACKTRACE=1 for more info)
+   = note: this error originates in a macro outside of the current crate (run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 

src/test/ui/fmt/format-string-error.stderr

@@ -5,7 +5,7 @@ error: invalid format string: expected `'}'` but string was terminated
    |     ^^^^^^^^^^^^^^
    |
    = note: if you intended to print `{`, you can escape it using `{{`
-   = note: this error originates in a macro outside of the current crate (run with RUST_MACRO_BACKTRACE=1 for more info)
+   = note: this error originates in a macro outside of the current crate (run with -Z macro-backtrace for more info)
 
 error: invalid format string: unmatched `}` found
   --> $DIR/format-string-error.rs:14:5
@@ -14,7 +14,7 @@ error: invalid format string: unmatched `}` found
    |     ^^^^^^^^^^^^^^
    |
    = note: if you intended to print `}`, you can escape it using `}}`
-   = note: this error originates in a macro outside of the current crate (run with RUST_MACRO_BACKTRACE=1 for more info)
+   = note: this error originates in a macro outside of the current crate (run with -Z macro-backtrace for more info)
 
 error: aborting due to 2 previous errors
 

src/test/ui/lifetimes/borrowck-let-suggestion.stderr

@@ -9,7 +9,7 @@ error[E0597]: borrowed value does not live long enough
    | - temporary value needs to live until here
    |
    = note: consider using a `let` binding to increase its lifetime
-   = note: this error originates in a macro outside of the current crate (run with RUST_MACRO_BACKTRACE=1 for more info)
+   = note: this error originates in a macro outside of the current crate (run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 

src/test/ui/macro_backtrace/main.rs

@@ -10,7 +10,7 @@
 
 // Test that the macro backtrace facility works
 // aux-build:ping.rs
-// rustc-env:RUST_MACRO_BACKTRACE
+// compile-flags: -Z macro-backtrace
 
 #[macro_use] extern crate ping;
 

src/test/ui/macros/format-foreign.stderr

@@ -11,7 +11,7 @@ error: multiple unused formatting arguments
    = help: `%.*3$s` should be written as `{:.2$}`
    = help: `%s` should be written as `{}`
    = note: printf formatting not supported; see the documentation for `std::fmt`
-   = note: this error originates in a macro outside of the current crate (run with RUST_MACRO_BACKTRACE=1 for more info)
+   = note: this error originates in a macro outside of the current crate (run with -Z macro-backtrace for more info)
 
 error: argument never used
   --> $DIR/format-foreign.rs:13:29

src/test/ui/macros/format-unused-lables.stderr

@@ -8,7 +8,7 @@ error: multiple unused formatting arguments
    |                      |    unused
    |                      unused
    |
-   = note: this error originates in a macro outside of the current crate (run with RUST_MACRO_BACKTRACE=1 for more info)
+   = note: this error originates in a macro outside of the current crate (run with -Z macro-backtrace for more info)
 
 error: multiple unused formatting arguments
   --> $DIR/format-unused-lables.rs:14:5
@@ -23,7 +23,7 @@ error: multiple unused formatting arguments
 18 | |     );
    | |______^
    |
-   = note: this error originates in a macro outside of the current crate (run with RUST_MACRO_BACKTRACE=1 for more info)
+   = note: this error originates in a macro outside of the current crate (run with -Z macro-backtrace for more info)
 
 error: named argument never used
   --> $DIR/format-unused-lables.rs:20:35
@@ -47,7 +47,7 @@ error: multiple unused formatting arguments
    |
    = help: `$STUFF` should be written as `{STUFF}`
    = note: shell formatting not supported; see the documentation for `std::fmt`
-   = note: this error originates in a macro outside of the current crate (run with RUST_MACRO_BACKTRACE=1 for more info)
+   = note: this error originates in a macro outside of the current crate (run with -Z macro-backtrace for more info)
 
 error: aborting due to 4 previous errors