Path remapping: Make behavior of diagnostics output dependent on presence of --remap-path-prefix.

compiler/rustc_codegen_cranelift/src/debuginfo/mod.rs

@@ -66,7 +66,7 @@ impl<'tcx> DebugContext<'tcx> {
             rustc_interface::util::version_str().unwrap_or("unknown version"),
             cranelift_codegen::VERSION,
         );
-        let comp_dir = tcx.sess.opts.working_dir.to_string_lossy(false).into_owned();
+        let comp_dir = tcx.sess.opts.working_dir.to_string_lossy(FileNameDisplayPreference::Remapped).into_owned();
         let (name, file_info) = match tcx.sess.local_crate_source_file.clone() {
             Some(path) => {
                 let name = path.to_string_lossy().into_owned();

compiler/rustc_codegen_cranelift/src/lib.rs

@@ -74,7 +74,7 @@ mod vtable;
 mod prelude {
     pub(crate) use std::convert::{TryFrom, TryInto};
 
-    pub(crate) use rustc_span::Span;
+    pub(crate) use rustc_span::{Span, FileNameDisplayPreference};
 
     pub(crate) use rustc_hir::def_id::{DefId, LOCAL_CRATE};
     pub(crate) use rustc_middle::bug;

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -35,6 +35,7 @@ use rustc_middle::ty::{self, AdtKind, GeneratorSubsts, ParamEnv, Ty, TyCtxt};
 use rustc_middle::{bug, span_bug};
 use rustc_session::config::{self, DebugInfo};
 use rustc_span::symbol::{Interner, Symbol};
+use rustc_span::FileNameDisplayPreference;
 use rustc_span::{self, SourceFile, SourceFileHash, Span};
 use rustc_target::abi::{Abi, Align, HasDataLayout, Integer, LayoutOf, TagEncoding};
 use rustc_target::abi::{Int, Pointer, F32, F64};
@@ -771,7 +772,13 @@ pub fn file_metadata(cx: &CodegenCx<'ll, '_>, source_file: &SourceFile) -> &'ll
     let hash = Some(&source_file.src_hash);
     let file_name = Some(source_file.name.prefer_remapped().to_string());
     let directory = if source_file.is_real_file() && !source_file.is_imported() {
-        Some(cx.sess().opts.working_dir.to_string_lossy(false).to_string())
+        Some(
+            cx.sess()
+                .opts
+                .working_dir
+                .to_string_lossy(FileNameDisplayPreference::Remapped)
+                .to_string(),
+        )
     } else {
         // If the path comes from an upstream crate we assume it has been made
         // independent of the compiler's working directory one way or another.
@@ -999,7 +1006,7 @@ pub fn compile_unit_metadata(
     let producer = format!("clang LLVM ({})", rustc_producer);
 
     let name_in_debuginfo = name_in_debuginfo.to_string_lossy();
-    let work_dir = tcx.sess.opts.working_dir.to_string_lossy(false);
+    let work_dir = tcx.sess.opts.working_dir.to_string_lossy(FileNameDisplayPreference::Remapped);
     let flags = "\0";
     let output_filenames = tcx.output_filenames(());
     let out_dir = &output_filenames.out_directory;

compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs

@@ -126,7 +126,7 @@ impl AnnotateSnippetEmitterWriter {
             }
             // owned: line source, line index, annotations
             type Owned = (String, usize, Vec<crate::snippet::Annotation>);
-            let filename = primary_lo.file.name.prefer_local();
+            let filename = source_map.filename_for_diagnostics(&primary_lo.file.name);
             let origin = filename.to_string_lossy();
             let annotated_files: Vec<Owned> = annotated_files
                 .into_iter()

compiler/rustc_errors/src/emitter.rs

@@ -1320,7 +1320,7 @@ impl EmitterWriter {
                         buffer_msg_line_offset,
                         &format!(
                             "{}:{}:{}",
-                            loc.file.name.prefer_local(),
+                            sm.filename_for_diagnostics(&loc.file.name),
                             sm.doctest_offset_line(&loc.file.name, loc.line),
                             loc.col.0 + 1,
                         ),
@@ -1334,7 +1334,7 @@ impl EmitterWriter {
                         0,
                         &format!(
                             "{}:{}:{}: ",
-                            loc.file.name.prefer_local(),
+                            sm.filename_for_diagnostics(&loc.file.name),
                             sm.doctest_offset_line(&loc.file.name, loc.line),
                             loc.col.0 + 1,
                         ),
@@ -1362,12 +1362,12 @@ impl EmitterWriter {
                     };
                     format!(
                         "{}:{}{}",
-                        annotated_file.file.name.prefer_local(),
+                        sm.filename_for_diagnostics(&annotated_file.file.name),
                         sm.doctest_offset_line(&annotated_file.file.name, first_line.line_index),
                         col
                     )
                 } else {
-                    format!("{}", annotated_file.file.name.prefer_local())
+                    format!("{}", sm.filename_for_diagnostics(&annotated_file.file.name))
                 };
                 buffer.append(buffer_msg_line_offset + 1, &loc, Style::LineAndColumn);
                 for _ in 0..max_line_num_len {

compiler/rustc_errors/src/json.rs

@@ -464,7 +464,7 @@ impl DiagnosticSpan {
         });
 
         DiagnosticSpan {
-            file_name: start.file.name.prefer_local().to_string(),
+            file_name: je.sm.filename_for_diagnostics(&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,

compiler/rustc_expand/src/base.rs

@@ -1113,7 +1113,7 @@ impl<'a> ExtCtxt<'a> {
                         span,
                         &format!(
                             "cannot resolve relative path in non-file source `{}`",
-                            other.prefer_local()
+                            self.source_map().filename_for_diagnostics(&other)
                         ),
                     ));
                 }

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -1626,14 +1626,11 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 (TypeError::Sorts(values), extra) => {
                     let sort_string = |ty: Ty<'tcx>| match (extra, ty.kind()) {
                         (true, ty::Opaque(def_id, _)) => {
-                            let pos = self
-                                .tcx
-                                .sess
-                                .source_map()
-                                .lookup_char_pos(self.tcx.def_span(*def_id).lo());
+                            let sm = self.tcx.sess.source_map();
+                            let pos = sm.lookup_char_pos(self.tcx.def_span(*def_id).lo());
                             format!(
                                 " (opaque type at <{}:{}:{}>)",
-                                pos.file.name.prefer_local(),
+                                sm.filename_for_diagnostics(&pos.file.name),
                                 pos.line,
                                 pos.col.to_usize() + 1,
                             )

compiler/rustc_mir/src/interpret/eval_context.rs

@@ -272,11 +272,12 @@ impl<'tcx> fmt::Display for FrameInfo<'tcx> {
                 write!(f, "inside `{}`", self.instance)?;
             }
             if !self.span.is_dummy() {
-                let lo = tcx.sess.source_map().lookup_char_pos(self.span.lo());
+                let sm = tcx.sess.source_map();
+                let lo = sm.lookup_char_pos(self.span.lo());
                 write!(
                     f,
                     " at {}:{}:{}",
-                    lo.file.name.prefer_local(),
+                    sm.filename_for_diagnostics(&lo.file.name),
                     lo.line,
                     lo.col.to_usize() + 1
                 )?;

compiler/rustc_parse/src/lib.rs

@@ -190,7 +190,7 @@ pub fn maybe_file_to_stream(
     let src = source_file.src.as_ref().unwrap_or_else(|| {
         sess.span_diagnostic.bug(&format!(
             "cannot lex `source_file` without source: {}",
-            source_file.name.prefer_local()
+            sess.source_map().filename_for_diagnostics(&source_file.name)
         ));
     });
 

compiler/rustc_span/src/lib.rs

@@ -260,11 +260,12 @@ impl RealFileName {
         }
     }
 
-    pub fn to_string_lossy(&self, prefer_local: bool) -> Cow<'_, str> {
-        if prefer_local {
-            self.local_path_if_available().to_string_lossy()
-        } else {
-            self.remapped_path_if_available().to_string_lossy()
+    pub fn to_string_lossy(&self, display_pref: FileNameDisplayPreference) -> Cow<'_, str> {
+        match display_pref {
+            FileNameDisplayPreference::Local => self.local_path_if_available().to_string_lossy(),
+            FileNameDisplayPreference::Remapped => {
+                self.remapped_path_if_available().to_string_lossy()
+            }
         }
     }
 }
@@ -300,17 +301,23 @@ impl From<PathBuf> for FileName {
     }
 }
 
+#[derive(Clone, Copy, Eq, PartialEq, Hash, Debug)]
+pub enum FileNameDisplayPreference {
+    Remapped,
+    Local,
+}
+
 pub struct FileNameDisplay<'a> {
     inner: &'a FileName,
-    prefer_local: bool,
+    display_pref: FileNameDisplayPreference,
 }
 
 impl fmt::Display for FileNameDisplay<'_> {
     fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         use FileName::*;
         match *self.inner {
             Real(ref name) => {
-                write!(fmt, "{}", name.to_string_lossy(self.prefer_local))
+                write!(fmt, "{}", name.to_string_lossy(self.display_pref))
             }
             QuoteExpansion(_) => write!(fmt, "<quote expansion>"),
             MacroExpansion(_) => write!(fmt, "<macro expansion>"),
@@ -328,7 +335,7 @@ impl fmt::Display for FileNameDisplay<'_> {
 impl FileNameDisplay<'_> {
     pub fn to_string_lossy(&self) -> Cow<'_, str> {
         match self.inner {
-            FileName::Real(ref inner) => inner.to_string_lossy(self.prefer_local),
+            FileName::Real(ref inner) => inner.to_string_lossy(self.display_pref),
             _ => Cow::from(format!("{}", self)),
         }
     }
@@ -352,13 +359,17 @@ impl FileName {
     }
 
     pub fn prefer_remapped(&self) -> FileNameDisplay<'_> {
-        FileNameDisplay { inner: self, prefer_local: false }
+        FileNameDisplay { inner: self, display_pref: FileNameDisplayPreference::Remapped }
     }
 
     // This may include transient local filesystem information.
     // Must not be embedded in build outputs.
     pub fn prefer_local(&self) -> FileNameDisplay<'_> {
-        FileNameDisplay { inner: self, prefer_local: true }
+        FileNameDisplay { inner: self, display_pref: FileNameDisplayPreference::Local }
+    }
+
+    pub fn display(&self, display_pref: FileNameDisplayPreference) -> FileNameDisplay<'_> {
+        FileNameDisplay { inner: self, display_pref }
     }
 
     pub fn macro_expansion_source_code(src: &str) -> FileName {

compiler/rustc_span/src/source_map.rs

@@ -427,7 +427,7 @@ impl SourceMap {
         }
     }
 
-    fn span_to_string(&self, sp: Span, prefer_local: bool) -> String {
+    fn span_to_string(&self, sp: Span, filename_display_pref: FileNameDisplayPreference) -> String {
         if self.files.borrow().source_files.is_empty() || sp.is_dummy() {
             return "no-location".to_string();
         }
@@ -436,7 +436,7 @@ impl SourceMap {
         let hi = self.lookup_char_pos(sp.hi());
         format!(
             "{}:{}:{}: {}:{}",
-            if prefer_local { lo.file.name.prefer_local() } else { lo.file.name.prefer_remapped() },
+            lo.file.name.display(filename_display_pref),
             lo.line,
             lo.col.to_usize() + 1,
             hi.line,
@@ -446,20 +446,24 @@ impl SourceMap {
 
     /// Format the span location suitable for embedding in build artifacts
     pub fn span_to_embeddable_string(&self, sp: Span) -> String {
-        self.span_to_string(sp, false)
+        self.span_to_string(sp, FileNameDisplayPreference::Remapped)
     }
 
     /// Format the span location to be printed in diagnostics. Must not be emitted
     /// to build artifacts as this may leak local file paths. Use span_to_embeddable_string
     /// for string suitable for embedding.
     pub fn span_to_diagnostic_string(&self, sp: Span) -> String {
-        self.span_to_string(sp, true)
+        self.span_to_string(sp, self.path_mapping.filename_display_for_diagnostics)
     }
 
     pub fn span_to_filename(&self, sp: Span) -> FileName {
         self.lookup_char_pos(sp.lo()).file.name.clone()
     }
 
+    pub fn filename_for_diagnostics<'a>(&self, filename: &'a FileName) -> FileNameDisplay<'a> {
+        filename.display(self.path_mapping.filename_display_for_diagnostics)
+    }
+
     pub fn is_multiline(&self, sp: Span) -> bool {
         let lo = self.lookup_source_file_idx(sp.lo());
         let hi = self.lookup_source_file_idx(sp.hi());
@@ -1002,15 +1006,22 @@ impl SourceMap {
 #[derive(Clone)]
 pub struct FilePathMapping {
     mapping: Vec<(PathBuf, PathBuf)>,
+    filename_display_for_diagnostics: FileNameDisplayPreference,
 }
 
 impl FilePathMapping {
     pub fn empty() -> FilePathMapping {
-        FilePathMapping { mapping: vec![] }
+        FilePathMapping::new(Vec::new())
     }
 
     pub fn new(mapping: Vec<(PathBuf, PathBuf)>) -> FilePathMapping {
-        FilePathMapping { mapping }
+        let filename_display_for_diagnostics = if mapping.is_empty() {
+            FileNameDisplayPreference::Local
+        } else {
+            FileNameDisplayPreference::Remapped
+        };
+
+        FilePathMapping { mapping, filename_display_for_diagnostics }
     }
 
     /// Applies any path prefix substitution as defined by the mapping.

src/test/ui/remap-path-prefix.rs

@@ -0,0 +1,9 @@
+// compile-flags: --remap-path-prefix={{src-base}}=remapped
+
+fn main() {
+    // We cannot actually put an ERROR marker here because
+    // the file name in the error message is not what the
+    // test framework expects (since the filename gets remapped).
+    // We still test the expected error in the stderr file.
+    ferris
+}

src/test/ui/remap-path-prefix.stderr

@@ -0,0 +1,9 @@
+error[E0425]: cannot find value `ferris` in this scope
+  --> remapped/remap-path-prefix.rs:8:5
+   |
+LL |     ferris
+   |     ^^^^^^ not found in this scope
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0425`.

src/tools/clippy/clippy_lints/src/macro_use.rs

@@ -47,11 +47,8 @@ pub struct MacroRefData {
 
 impl MacroRefData {
     pub fn new(name: String, callee: Span, cx: &LateContext<'_>) -> Self {
-        let mut path = cx
-            .sess()
-            .source_map()
-            .span_to_filename(callee)
-            .prefer_local()
+        let sm = cx.sess().source_map();
+        let mut path = sm.filename_for_diagnostics(&sm.span_to_filename(callee))
             .to_string();
 
         // std lib paths are <::std::module::file type>