Auto merge of #66453 - Centril:rollup-w1ohzxs, r=Centril

Rollup of 5 pull requests

Successful merges:

 - #66350 (protect creation of destructors by a mutex)
 - #66407 (Add more tests for fixed ICEs)
 - #66415 (Add --force-run-in-process unstable option to libtest)
 - #66427 (Move the JSON error emitter to librustc_errors)
 - #66441 (libpanic_unwind for Miri: make sure we have the SEH lang items when needed)

Failed merges:

r? @ghost

5 files changed, 665 insertions, 75 deletions

diff --git a/src/librustc_errors/annotate_snippet_emitter_writer.rs b/src/librustc_errors/annotate_snippet_emitter_writer.rs
index 491bc2aa6a2..4c5d0178b2c 100644
--- a/src/librustc_errors/annotate_snippet_emitter_writer.rs
+++ b/src/librustc_errors/annotate_snippet_emitter_writer.rs
@@ -6,9 +6,10 @@
 //! [annotate_snippets]: https://docs.rs/crate/annotate-snippets/
 
 use syntax_pos::{SourceFile, MultiSpan, Loc};
+use syntax_pos::source_map::SourceMap;
 use crate::{
     Level, CodeSuggestion, Diagnostic, Emitter,
-    SourceMapperDyn, SubDiagnostic, DiagnosticId
+    SubDiagnostic, DiagnosticId
 };
 use crate::emitter::FileWithAnnotatedLines;
 use rustc_data_structures::sync::Lrc;
@@ -20,7 +21,7 @@ use annotate_snippets::formatter::DisplayListFormatter;
 
 /// Generates diagnostics using annotate-snippet
 pub struct AnnotateSnippetEmitterWriter {
-    source_map: Option<Lrc<SourceMapperDyn>>,
+    source_map: Option<Lrc<SourceMap>>,
     /// If true, hides the longer explanation text
     short_message: bool,
     /// If true, will normalize line numbers with `LL` to prevent noise in UI test diffs.
@@ -49,7 +50,7 @@ impl Emitter for AnnotateSnippetEmitterWriter {
                                    &suggestions);
     }
 
-    fn source_map(&self) -> Option<&Lrc<SourceMapperDyn>> {
+    fn source_map(&self) -> Option<&Lrc<SourceMap>> {
         self.source_map.as_ref()
     }
 
@@ -61,7 +62,7 @@ impl Emitter for AnnotateSnippetEmitterWriter {
 /// Collects all the data needed to generate the data structures needed for the
 /// `annotate-snippets` library.
 struct DiagnosticConverter<'a> {
-    source_map: Option<Lrc<SourceMapperDyn>>,
+    source_map: Option<Lrc<SourceMap>>,
     level: Level,
     message: String,
     code: Option<DiagnosticId>,
@@ -168,7 +169,7 @@ impl<'a>  DiagnosticConverter<'a> {
 
 impl AnnotateSnippetEmitterWriter {
     pub fn new(
-        source_map: Option<Lrc<SourceMapperDyn>>,
+        source_map: Option<Lrc<SourceMap>>,
         short_message: bool,
         external_macro_backtrace: bool,
     ) -> Self {
diff --git a/src/librustc_errors/emitter.rs b/src/librustc_errors/emitter.rs
index 291920f17f6..ea779982ba9 100644
--- a/src/librustc_errors/emitter.rs
+++ b/src/librustc_errors/emitter.rs
@@ -10,10 +10,11 @@
 use Destination::*;
 
 use syntax_pos::{SourceFile, Span, MultiSpan};
+use syntax_pos::source_map::SourceMap;
 
 use crate::{
     Level, CodeSuggestion, Diagnostic, SubDiagnostic, pluralize,
-    SuggestionStyle, SourceMapper, SourceMapperDyn, DiagnosticId,
+    SuggestionStyle, DiagnosticId,
 };
 use crate::Level::Error;
 use crate::snippet::{Annotation, AnnotationType, Line, MultilineAnnotation, StyledString, Style};
@@ -49,7 +50,7 @@ impl HumanReadableErrorType {
     pub fn new_emitter(
         self,
         dst: Box<dyn Write + Send>,
-        source_map: Option<Lrc<SourceMapperDyn>>,
+        source_map: Option<Lrc<SourceMap>>,
         teach: bool,
         terminal_width: Option<usize>,
         external_macro_backtrace: bool,
@@ -192,7 +193,7 @@ pub trait Emitter {
         true
     }
 
-    fn source_map(&self) -> Option<&Lrc<SourceMapperDyn>>;
+    fn source_map(&self) -> Option<&Lrc<SourceMap>>;
 
     /// Formats the substitutions of the primary_span
     ///
@@ -271,7 +272,7 @@ pub trait Emitter {
     // point directly at <*macros>. Since these are often difficult to read, this
     // will change the span to point at the use site.
     fn fix_multispans_in_std_macros(&self,
-                                    source_map: &Option<Lrc<SourceMapperDyn>>,
+                                    source_map: &Option<Lrc<SourceMap>>,
                                     span: &mut MultiSpan,
                                     children: &mut Vec<SubDiagnostic>,
                                     level: &Level,
@@ -311,7 +312,7 @@ pub trait Emitter {
     // <*macros>. Since these locations are often difficult to read, we move these Spans from
     // <*macros> to their corresponding use site.
     fn fix_multispan_in_std_macros(&self,
-                                   source_map: &Option<Lrc<SourceMapperDyn>>,
+                                   source_map: &Option<Lrc<SourceMap>>,
                                    span: &mut MultiSpan,
                                    always_backtrace: bool) -> bool {
         let sm = match source_map {
@@ -397,7 +398,7 @@ pub trait Emitter {
 }
 
 impl Emitter for EmitterWriter {
-    fn source_map(&self) -> Option<&Lrc<SourceMapperDyn>> {
+    fn source_map(&self) -> Option<&Lrc<SourceMap>> {
         self.sm.as_ref()
     }
 
@@ -428,7 +429,7 @@ impl Emitter for EmitterWriter {
 pub struct SilentEmitter;
 
 impl Emitter for SilentEmitter {
-    fn source_map(&self) -> Option<&Lrc<SourceMapperDyn>> { None }
+    fn source_map(&self) -> Option<&Lrc<SourceMap>> { None }
     fn emit_diagnostic(&mut self, _: &Diagnostic) {}
 }
 
@@ -476,7 +477,7 @@ impl ColorConfig {
 /// Handles the writing of `HumanReadableErrorType::Default` and `HumanReadableErrorType::Short`
 pub struct EmitterWriter {
     dst: Destination,
-    sm: Option<Lrc<SourceMapperDyn>>,
+    sm: Option<Lrc<SourceMap>>,
     short_message: bool,
     teach: bool,
     ui_testing: bool,
@@ -495,7 +496,7 @@ pub struct FileWithAnnotatedLines {
 impl EmitterWriter {
     pub fn stderr(
         color_config: ColorConfig,
-        source_map: Option<Lrc<SourceMapperDyn>>,
+        source_map: Option<Lrc<SourceMap>>,
         short_message: bool,
         teach: bool,
         terminal_width: Option<usize>,
@@ -515,7 +516,7 @@ impl EmitterWriter {
 
     pub fn new(
         dst: Box<dyn Write + Send>,
-        source_map: Option<Lrc<SourceMapperDyn>>,
+        source_map: Option<Lrc<SourceMap>>,
         short_message: bool,
         teach: bool,
         colored: bool,
@@ -1685,7 +1686,7 @@ impl FileWithAnnotatedLines {
     /// This helps us quickly iterate over the whole message (including secondary file spans)
     pub fn collect_annotations(
         msp: &MultiSpan,
-        source_map: &Option<Lrc<SourceMapperDyn>>
+        source_map: &Option<Lrc<SourceMap>>
     ) -> Vec<FileWithAnnotatedLines> {
         fn add_annotation_to_file(file_vec: &mut Vec<FileWithAnnotatedLines>,
                                   file: Lrc<SourceFile>,
@@ -2067,7 +2068,7 @@ impl<'a> Drop for WritableDst<'a> {
 }
 
 /// Whether the original and suggested code are visually similar enough to warrant extra wording.
-pub fn is_case_difference(sm: &dyn SourceMapper, suggested: &str, sp: Span) -> bool {
+pub fn is_case_difference(sm: &SourceMap, suggested: &str, sp: Span) -> bool {
     // FIXME: this should probably be extended to also account for `FO0` → `FOO` and unicode.
     let found = sm.span_to_snippet(sp).unwrap();
     let ascii_confusables = &['c', 'f', 'i', 'k', 'o', 's', 'u', 'v', 'w', 'x', 'y', 'z'];
diff --git a/src/librustc_errors/json.rs b/src/librustc_errors/json.rs
new file mode 100644
index 00000000000..ebbd49bd84a
--- /dev/null
+++ b/src/librustc_errors/json.rs
@@ -0,0 +1,434 @@
+//! A JSON emitter for errors.
+//!
+//! This works by converting errors to a simplified structural format (see the
+//! structs at the start of the file) and then serializing them. These should
+//! contain as much information about the error as possible.
+//!
+//! The format of the JSON output should be considered *unstable*. For now the
+//! structs at the end of this file (Diagnostic*) specify the error format.
+
+// FIXME: spec the JSON output properly.
+
+use syntax_pos::source_map::{SourceMap, FilePathMapping};
+
+use crate::registry::Registry;
+use crate::{SubDiagnostic, CodeSuggestion};
+use crate::{DiagnosticId, Applicability};
+use crate::emitter::{Emitter, HumanReadableErrorType};
+
+use syntax_pos::{MacroBacktrace, Span, SpanLabel, MultiSpan};
+use rustc_data_structures::sync::Lrc;
+use std::io::{self, Write};
+use std::path::Path;
+use std::vec;
+use std::sync::{Arc, Mutex};
+
+use rustc_serialize::json::{as_json, as_pretty_json};
+
+#[cfg(test)]
+mod tests;
+
+pub struct JsonEmitter {
+    dst: Box<dyn Write + Send>,
+    registry: Option<Registry>,
+    sm: Lrc<SourceMap>,
+    pretty: bool,
+    ui_testing: bool,
+    json_rendered: HumanReadableErrorType,
+    external_macro_backtrace: bool,
+}
+
+impl JsonEmitter {
+    pub fn stderr(
+        registry: Option<Registry>,
+        source_map: Lrc<SourceMap>,
+        pretty: bool,
+        json_rendered: HumanReadableErrorType,
+        external_macro_backtrace: bool,
+    ) -> JsonEmitter {
+        JsonEmitter {
+            dst: Box::new(io::stderr()),
+            registry,
+            sm: source_map,
+            pretty,
+            ui_testing: false,
+            json_rendered,
+            external_macro_backtrace,
+        }
+    }
+
+    pub fn basic(
+        pretty: bool,
+        json_rendered: HumanReadableErrorType,
+        external_macro_backtrace: bool,
+    ) -> JsonEmitter {
+        let file_path_mapping = FilePathMapping::empty();
+        JsonEmitter::stderr(None, Lrc::new(SourceMap::new(file_path_mapping)),
+                            pretty, json_rendered, external_macro_backtrace)
+    }
+
+    pub fn new(
+        dst: Box<dyn Write + Send>,
+        registry: Option<Registry>,
+        source_map: Lrc<SourceMap>,
+        pretty: bool,
+        json_rendered: HumanReadableErrorType,
+        external_macro_backtrace: bool,
+    ) -> JsonEmitter {
+        JsonEmitter {
+            dst,
+            registry,
+            sm: source_map,
+            pretty,
+            ui_testing: false,
+            json_rendered,
+            external_macro_backtrace,
+        }
+    }
+
+    pub fn ui_testing(self, ui_testing: bool) -> Self {
+        Self { ui_testing, ..self }
+    }
+}
+
+impl Emitter for JsonEmitter {
+    fn emit_diagnostic(&mut self, diag: &crate::Diagnostic) {
+        let data = Diagnostic::from_errors_diagnostic(diag, self);
+        let result = if self.pretty {
+            writeln!(&mut self.dst, "{}", as_pretty_json(&data))
+        } else {
+            writeln!(&mut self.dst, "{}", as_json(&data))
+        };
+        if let Err(e) = result {
+            panic!("failed to print diagnostics: {:?}", e);
+        }
+    }
+
+    fn emit_artifact_notification(&mut self, path: &Path, artifact_type: &str) {
+        let data = ArtifactNotification { artifact: path, emit: artifact_type };
+        let result = if self.pretty {
+            writeln!(&mut self.dst, "{}", as_pretty_json(&data))
+        } else {
+            writeln!(&mut self.dst, "{}", as_json(&data))
+        };
+        if let Err(e) = result {
+            panic!("failed to print notification: {:?}", e);
+        }
+    }
+
+    fn source_map(&self) -> Option<&Lrc<SourceMap>> {
+        Some(&self.sm)
+    }
+
+    fn should_show_explain(&self) -> bool {
+        match self.json_rendered {
+            HumanReadableErrorType::Short(_) => false,
+            _ => true,
+        }
+    }
+}
+
+// The following data types are provided just for serialisation.
+
+#[derive(RustcEncodable)]
+struct Diagnostic {
+    /// The primary error message.
+    message: String,
+    code: Option<DiagnosticCode>,
+    /// "error: internal compiler error", "error", "warning", "note", "help".
+    level: &'static str,
+    spans: Vec<DiagnosticSpan>,
+    /// Associated diagnostic messages.
+    children: Vec<Diagnostic>,
+    /// The message as rustc would render it.
+    rendered: Option<String>,
+}
+
+#[derive(RustcEncodable)]
+struct DiagnosticSpan {
+    file_name: String,
+    byte_start: u32,
+    byte_end: u32,
+    /// 1-based.
+    line_start: usize,
+    line_end: usize,
+    /// 1-based, character offset.
+    column_start: usize,
+    column_end: usize,
+    /// Is this a "primary" span -- meaning the point, or one of the points,
+    /// where the error occurred?
+    is_primary: bool,
+    /// Source text from the start of line_start to the end of line_end.
+    text: Vec<DiagnosticSpanLine>,
+    /// Label that should be placed at this location (if any)
+    label: Option<String>,
+    /// If we are suggesting a replacement, this will contain text
+    /// that should be sliced in atop this span.
+    suggested_replacement: Option<String>,
+    /// If the suggestion is approximate
+    suggestion_applicability: Option<Applicability>,
+    /// Macro invocations that created the code at this span, if any.
+    expansion: Option<Box<DiagnosticSpanMacroExpansion>>,
+}
+
+#[derive(RustcEncodable)]
+struct DiagnosticSpanLine {
+    text: String,
+
+    /// 1-based, character offset in self.text.
+    highlight_start: usize,
+
+    highlight_end: usize,
+}
+
+#[derive(RustcEncodable)]
+struct DiagnosticSpanMacroExpansion {
+    /// span where macro was applied to generate this code; note that
+    /// this may itself derive from a macro (if
+    /// `span.expansion.is_some()`)
+    span: DiagnosticSpan,
+
+    /// name of macro that was applied (e.g., "foo!" or "#[derive(Eq)]")
+    macro_decl_name: String,
+
+    /// span where macro was defined (if known)
+    def_site_span: DiagnosticSpan,
+}
+
+#[derive(RustcEncodable)]
+struct DiagnosticCode {
+    /// The code itself.
+    code: String,
+    /// An explanation for the code.
+    explanation: Option<&'static str>,
+}
+
+#[derive(RustcEncodable)]
+struct ArtifactNotification<'a> {
+    /// The path of the artifact.
+    artifact: &'a Path,
+    /// What kind of artifact we're emitting.
+    emit: &'a str,
+}
+
+impl Diagnostic {
+    fn from_errors_diagnostic(diag: &crate::Diagnostic,
+                               je: &JsonEmitter)
+                               -> Diagnostic {
+        let sugg = diag.suggestions.iter().map(|sugg| {
+            Diagnostic {
+                message: sugg.msg.clone(),
+                code: None,
+                level: "help",
+                spans: DiagnosticSpan::from_suggestion(sugg, je),
+                children: vec![],
+                rendered: None,
+            }
+        });
+
+        // generate regular command line output and store it in the json
+
+        // A threadsafe buffer for writing.
+        #[derive(Default, Clone)]
+        struct BufWriter(Arc<Mutex<Vec<u8>>>);
+
+        impl Write for BufWriter {
+            fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+                self.0.lock().unwrap().write(buf)
+            }
+            fn flush(&mut self) -> io::Result<()> {
+                self.0.lock().unwrap().flush()
+            }
+        }
+        let buf = BufWriter::default();
+        let output = buf.clone();
+        je.json_rendered.new_emitter(
+            Box::new(buf), Some(je.sm.clone()), false, None, je.external_macro_backtrace
+        ).ui_testing(je.ui_testing).emit_diagnostic(diag);
+        let output = Arc::try_unwrap(output.0).unwrap().into_inner().unwrap();
+        let output = String::from_utf8(output).unwrap();
+
+        Diagnostic {
+            message: diag.message(),
+            code: DiagnosticCode::map_opt_string(diag.code.clone(), je),
+            level: diag.level.to_str(),
+            spans: DiagnosticSpan::from_multispan(&diag.span, je),
+            children: diag.children.iter().map(|c| {
+                Diagnostic::from_sub_diagnostic(c, je)
+            }).chain(sugg).collect(),
+            rendered: Some(output),
+        }
+    }
+
+    fn from_sub_diagnostic(diag: &SubDiagnostic, je: &JsonEmitter) -> Diagnostic {
+        Diagnostic {
+            message: diag.message(),
+            code: None,
+            level: diag.level.to_str(),
+            spans: diag.render_span.as_ref()
+                     .map(|sp| DiagnosticSpan::from_multispan(sp, je))
+                     .unwrap_or_else(|| DiagnosticSpan::from_multispan(&diag.span, je)),
+            children: vec![],
+            rendered: None,
+        }
+    }
+}
+
+impl DiagnosticSpan {
+    fn from_span_label(span: SpanLabel,
+                       suggestion: Option<(&String, Applicability)>,
+                       je: &JsonEmitter)
+                       -> DiagnosticSpan {
+        Self::from_span_etc(span.span,
+                            span.is_primary,
+                            span.label,
+                            suggestion,
+                            je)
+    }
+
+    fn from_span_etc(span: Span,
+                     is_primary: bool,
+                     label: Option<String>,
+                     suggestion: Option<(&String, Applicability)>,
+                     je: &JsonEmitter)
+                     -> DiagnosticSpan {
+        // obtain the full backtrace from the `macro_backtrace`
+        // helper; in some ways, it'd be better to expand the
+        // backtrace ourselves, but the `macro_backtrace` helper makes
+        // some decision, such as dropping some frames, and I don't
+        // want to duplicate that logic here.
+        let backtrace = span.macro_backtrace().into_iter();
+        DiagnosticSpan::from_span_full(span,
+                                       is_primary,
+                                       label,
+                                       suggestion,
+                                       backtrace,
+                                       je)
+    }
+
+    fn from_span_full(span: Span,
+                      is_primary: bool,
+                      label: Option<String>,
+                      suggestion: Option<(&String, Applicability)>,
+                      mut backtrace: vec::IntoIter<MacroBacktrace>,
+                      je: &JsonEmitter)
+                      -> DiagnosticSpan {
+        let start = je.sm.lookup_char_pos(span.lo());
+        let end = je.sm.lookup_char_pos(span.hi());
+        let backtrace_step = backtrace.next().map(|bt| {
+            let call_site =
+                Self::from_span_full(bt.call_site,
+                                     false,
+                                     None,
+                                     None,
+                                     backtrace,
+                                     je);
+            let def_site_span =
+                Self::from_span_full(bt.def_site_span,
+                                     false,
+                                     None,
+                                     None,
+                                     vec![].into_iter(),
+                                     je);
+            Box::new(DiagnosticSpanMacroExpansion {
+                span: call_site,
+                macro_decl_name: bt.macro_decl_name,
+                def_site_span,
+            })
+        });
+
+        DiagnosticSpan {
+            file_name: start.file.name.to_string(),
+            byte_start: start.file.original_relative_byte_pos(span.lo()).0,
+            byte_end: start.file.original_relative_byte_pos(span.hi()).0,
+            line_start: start.line,
+            line_end: end.line,
+            column_start: start.col.0 + 1,
+            column_end: end.col.0 + 1,
+            is_primary,
+            text: DiagnosticSpanLine::from_span(span, je),
+            suggested_replacement: suggestion.map(|x| x.0.clone()),
+            suggestion_applicability: suggestion.map(|x| x.1),
+            expansion: backtrace_step,
+            label,
+        }
+    }
+
+    fn from_multispan(msp: &MultiSpan, je: &JsonEmitter) -> Vec<DiagnosticSpan> {
+        msp.span_labels()
+           .into_iter()
+           .map(|span_str| Self::from_span_label(span_str, None, je))
+           .collect()
+    }
+
+    fn from_suggestion(suggestion: &CodeSuggestion, je: &JsonEmitter)
+                       -> Vec<DiagnosticSpan> {
+        suggestion.substitutions
+                      .iter()
+                      .flat_map(|substitution| {
+                          substitution.parts.iter().map(move |suggestion_inner| {
+                              let span_label = SpanLabel {
+                                  span: suggestion_inner.span,
+                                  is_primary: true,
+                                  label: None,
+                              };
+                              DiagnosticSpan::from_span_label(span_label,
+                                                              Some((&suggestion_inner.snippet,
+                                                                   suggestion.applicability)),
+                                                              je)
+                          })
+                      })
+                      .collect()
+    }
+}
+
+impl DiagnosticSpanLine {
+    fn line_from_source_file(fm: &syntax_pos::SourceFile,
+                         index: usize,
+                         h_start: usize,
+                         h_end: usize)
+                         -> DiagnosticSpanLine {
+        DiagnosticSpanLine {
+            text: fm.get_line(index).map_or(String::new(), |l| l.into_owned()),
+            highlight_start: h_start,
+            highlight_end: h_end,
+        }
+    }
+
+    /// Creates a list of DiagnosticSpanLines from span - each line with any part
+    /// of `span` gets a DiagnosticSpanLine, with the highlight indicating the
+    /// `span` within the line.
+    fn from_span(span: Span, je: &JsonEmitter) -> Vec<DiagnosticSpanLine> {
+        je.sm.span_to_lines(span)
+            .map(|lines| {
+                let fm = &*lines.file;
+                lines.lines
+                    .iter()
+                    .map(|line| DiagnosticSpanLine::line_from_source_file(
+                        fm,
+                        line.line_index,
+                        line.start_col.0 + 1,
+                        line.end_col.0 + 1,
+                    )).collect()
+            }).unwrap_or_else(|_| vec![])
+    }
+}
+
+impl DiagnosticCode {
+    fn map_opt_string(s: Option<DiagnosticId>, je: &JsonEmitter) -> Option<DiagnosticCode> {
+        s.map(|s| {
+            let s = match s {
+                DiagnosticId::Error(s) => s,
+                DiagnosticId::Lint(s) => s,
+            };
+            let explanation = je.registry
+                                .as_ref()
+                                .and_then(|registry| registry.find_description(&s));
+
+            DiagnosticCode {
+                code: s,
+                explanation,
+            }
+        })
+    }
+}
diff --git a/src/librustc_errors/json/tests.rs b/src/librustc_errors/json/tests.rs
new file mode 100644
index 00000000000..4ab5cd21b0b
--- /dev/null
+++ b/src/librustc_errors/json/tests.rs
@@ -0,0 +1,205 @@
+use super::*;
+
+use crate::json::JsonEmitter;
+use syntax_pos::source_map::{FilePathMapping, SourceMap};
+
+use crate::emitter::{ColorConfig, HumanReadableErrorType};
+use crate::Handler;
+use rustc_serialize::json::decode;
+use syntax_pos::{BytePos, Span};
+
+use std::str;
+
+#[derive(RustcDecodable, Debug, PartialEq, Eq)]
+struct TestData {
+    spans: Vec<SpanTestData>,
+}
+
+#[derive(RustcDecodable, Debug, PartialEq, Eq)]
+struct SpanTestData {
+    pub byte_start: u32,
+    pub byte_end: u32,
+    pub line_start: u32,
+    pub column_start: u32,
+    pub line_end: u32,
+    pub column_end: u32,
+}
+
+struct Shared<T> {
+    data: Arc<Mutex<T>>,
+}
+
+impl<T: Write> Write for Shared<T> {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.data.lock().unwrap().write(buf)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        self.data.lock().unwrap().flush()
+    }
+}
+
+fn with_default_globals(f: impl FnOnce()) {
+    let globals = syntax_pos::Globals::new(syntax_pos::edition::DEFAULT_EDITION);
+    syntax_pos::GLOBALS.set(&globals, || {
+        syntax_pos::GLOBALS.set(&globals, f)
+    })
+}
+
+/// Test the span yields correct positions in JSON.
+fn test_positions(code: &str, span: (u32, u32), expected_output: SpanTestData) {
+    let expected_output = TestData { spans: vec![expected_output] };
+
+    with_default_globals(|| {
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        sm.new_source_file(Path::new("test.rs").to_owned().into(), code.to_owned());
+
+        let output = Arc::new(Mutex::new(Vec::new()));
+        let je = JsonEmitter::new(
+            Box::new(Shared { data: output.clone() }),
+            None,
+            sm,
+            true,
+            HumanReadableErrorType::Short(ColorConfig::Never),
+            false,
+        );
+
+        let span = Span::with_root_ctxt(BytePos(span.0), BytePos(span.1));
+        let handler = Handler::with_emitter(true, None, Box::new(je));
+        handler.span_err(span, "foo");
+
+        let bytes = output.lock().unwrap();
+        let actual_output = str::from_utf8(&bytes).unwrap();
+        let actual_output: TestData = decode(actual_output).unwrap();
+
+        assert_eq!(expected_output, actual_output)
+    })
+}
+
+#[test]
+fn empty() {
+    test_positions(
+        " ",
+        (0, 1),
+        SpanTestData {
+            byte_start: 0,
+            byte_end: 1,
+            line_start: 1,
+            column_start: 1,
+            line_end: 1,
+            column_end: 2,
+        },
+    )
+}
+
+#[test]
+fn bom() {
+    test_positions(
+        "\u{feff} ",
+        (0, 1),
+        SpanTestData {
+            byte_start: 3,
+            byte_end: 4,
+            line_start: 1,
+            column_start: 1,
+            line_end: 1,
+            column_end: 2,
+        },
+    )
+}
+
+#[test]
+fn lf_newlines() {
+    test_positions(
+        "\nmod foo;\nmod bar;\n",
+        (5, 12),
+        SpanTestData {
+            byte_start: 5,
+            byte_end: 12,
+            line_start: 2,
+            column_start: 5,
+            line_end: 3,
+            column_end: 3,
+        },
+    )
+}
+
+#[test]
+fn crlf_newlines() {
+    test_positions(
+        "\r\nmod foo;\r\nmod bar;\r\n",
+        (5, 12),
+        SpanTestData {
+            byte_start: 6,
+            byte_end: 14,
+            line_start: 2,
+            column_start: 5,
+            line_end: 3,
+            column_end: 3,
+        },
+    )
+}
+
+#[test]
+fn crlf_newlines_with_bom() {
+    test_positions(
+        "\u{feff}\r\nmod foo;\r\nmod bar;\r\n",
+        (5, 12),
+        SpanTestData {
+            byte_start: 9,
+            byte_end: 17,
+            line_start: 2,
+            column_start: 5,
+            line_end: 3,
+            column_end: 3,
+        },
+    )
+}
+
+#[test]
+fn span_before_crlf() {
+    test_positions(
+        "foo\r\nbar",
+        (2, 3),
+        SpanTestData {
+            byte_start: 2,
+            byte_end: 3,
+            line_start: 1,
+            column_start: 3,
+            line_end: 1,
+            column_end: 4,
+        },
+    )
+}
+
+#[test]
+fn span_on_crlf() {
+    test_positions(
+        "foo\r\nbar",
+        (3, 4),
+        SpanTestData {
+            byte_start: 3,
+            byte_end: 5,
+            line_start: 1,
+            column_start: 4,
+            line_end: 2,
+            column_end: 1,
+        },
+    )
+}
+
+#[test]
+fn span_after_crlf() {
+    test_positions(
+        "foo\r\nbar",
+        (4, 5),
+        SpanTestData {
+            byte_start: 5,
+            byte_end: 6,
+            line_start: 2,
+            column_start: 1,
+            line_end: 2,
+            column_end: 2,
+        },
+    )
+}
diff --git a/src/librustc_errors/lib.rs b/src/librustc_errors/lib.rs
index 8ee28875c62..17765ef9dee 100644
--- a/src/librustc_errors/lib.rs
+++ b/src/librustc_errors/lib.rs
@@ -18,6 +18,8 @@ use registry::Registry;
 use rustc_data_structures::sync::{self, Lrc, Lock};
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
 use rustc_data_structures::stable_hasher::StableHasher;
+use syntax_pos::source_map::SourceMap;
+use syntax_pos::{Loc, Span, MultiSpan};
 
 use std::borrow::Cow;
 use std::cell::Cell;
@@ -35,17 +37,7 @@ mod snippet;
 pub mod registry;
 mod styled_buffer;
 mod lock;
-
-use syntax_pos::{
-    BytePos,
-    FileLinesResult,
-    FileName,
-    Loc,
-    MultiSpan,
-    SourceFile,
-    Span,
-    SpanSnippetError,
-};
+pub mod json;
 
 pub type PResult<'a, T> = Result<T, DiagnosticBuilder<'a>>;
 
@@ -150,26 +142,12 @@ pub struct SubstitutionPart {
     pub snippet: String,
 }
 
-pub type SourceMapperDyn = dyn SourceMapper + sync::Send + sync::Sync;
-
-pub trait SourceMapper {
-    fn lookup_char_pos(&self, pos: BytePos) -> Loc;
-    fn span_to_lines(&self, sp: Span) -> FileLinesResult;
-    fn span_to_string(&self, sp: Span) -> String;
-    fn span_to_snippet(&self, sp: Span) -> Result<String, SpanSnippetError>;
-    fn span_to_filename(&self, sp: Span) -> FileName;
-    fn merge_spans(&self, sp_lhs: Span, sp_rhs: Span) -> Option<Span>;
-    fn call_span_if_macro(&self, sp: Span) -> Span;
-    fn ensure_source_file_source_present(&self, source_file: Lrc<SourceFile>) -> bool;
-    fn doctest_offset_line(&self, file: &FileName, line: usize) -> usize;
-}
-
 impl CodeSuggestion {
     /// Returns the assembled code suggestions, whether they should be shown with an underline
     /// and whether the substitution only differs in capitalization.
     pub fn splice_lines(
         &self,
-        cm: &SourceMapperDyn,
+        cm: &SourceMap,
     ) -> Vec<(String, Vec<SubstitutionPart>, bool)> {
         use syntax_pos::{CharPos, Pos};
 
@@ -259,36 +237,7 @@ impl CodeSuggestion {
     }
 }
 
-/// Used as a return value to signify a fatal error occurred. (It is also
-/// used as the argument to panic at the moment, but that will eventually
-/// not be true.)
-#[derive(Copy, Clone, Debug)]
-#[must_use]
-pub struct FatalError;
-
-pub struct FatalErrorMarker;
-
-// Don't implement Send on FatalError. This makes it impossible to panic!(FatalError).
-// We don't want to invoke the panic handler and print a backtrace for fatal errors.
-impl !Send for FatalError {}
-
-impl FatalError {
-    pub fn raise(self) -> ! {
-        panic::resume_unwind(Box::new(FatalErrorMarker))
-    }
-}
-
-impl fmt::Display for FatalError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "parser fatal error")
-    }
-}
-
-impl error::Error for FatalError {
-    fn description(&self) -> &str {
-        "The parser has encountered a fatal error"
-    }
-}
+pub use syntax_pos::fatal_error::{FatalError, FatalErrorMarker};
 
 /// Signifies that the compiler died with an explicit call to `.bug`
 /// or `.span_bug` rather than a failed assertion, etc.
@@ -405,7 +354,7 @@ impl Handler {
         color_config: ColorConfig,
         can_emit_warnings: bool,
         treat_err_as_bug: Option<usize>,
-        cm: Option<Lrc<SourceMapperDyn>>,
+        cm: Option<Lrc<SourceMap>>,
     ) -> Self {
         Self::with_tty_emitter_and_flags(
             color_config,
@@ -420,7 +369,7 @@ impl Handler {
 
     pub fn with_tty_emitter_and_flags(
         color_config: ColorConfig,
-        cm: Option<Lrc<SourceMapperDyn>>,
+        cm: Option<Lrc<SourceMap>>,
         flags: HandlerFlags,
     ) -> Self {
         let emitter = Box::new(EmitterWriter::stderr(