Fortify dummy span checking

21 files changed, 59 insertions, 59 deletions

diff --git a/src/libproc_macro/lib.rs b/src/libproc_macro/lib.rs
index e580b459196..820b0906a75 100644
--- a/src/libproc_macro/lib.rs
+++ b/src/libproc_macro/lib.rs
@@ -177,8 +177,6 @@ impl iter::FromIterator<TokenStream> for TokenStream {
 #[unstable(feature = "proc_macro", issue = "38356")]
 pub mod token_stream {
     use syntax::tokenstream;
-    use syntax_pos::DUMMY_SP;
-
     use {TokenTree, TokenStream, Delimiter};
 
     /// An iterator over `TokenStream`'s `TokenTree`s.
@@ -207,7 +205,7 @@ pub mod token_stream {
                 // need to flattened during iteration over stream's token trees.
                 // Eventually this needs to be removed in favor of keeping original token trees
                 // and not doing the roundtrip through AST.
-                if tree.span().0 == DUMMY_SP {
+                if tree.span().0.is_dummy() {
                     if let TokenTree::Group(ref group) = tree {
                         if group.delimiter() == Delimiter::None {
                             self.cursor.insert(group.stream.clone().0);
diff --git a/src/librustc/hir/map/definitions.rs b/src/librustc/hir/map/definitions.rs
index b2365e22cc6..e262c951e39 100644
--- a/src/librustc/hir/map/definitions.rs
+++ b/src/librustc/hir/map/definitions.rs
@@ -486,12 +486,7 @@ impl Definitions {
     #[inline]
     pub fn opt_span(&self, def_id: DefId) -> Option<Span> {
         if def_id.krate == LOCAL_CRATE {
-            let span = self.def_index_to_span.get(&def_id.index).cloned().unwrap_or(DUMMY_SP);
-            if span != DUMMY_SP {
-                Some(span)
-            } else {
-                None
-            }
+            self.def_index_to_span.get(&def_id.index).cloned()
         } else {
             None
         }
@@ -588,8 +583,8 @@ impl Definitions {
             self.opaque_expansions_that_defined.insert(index, expansion);
         }
 
-        // The span is added if it isn't DUMMY_SP
-        if span != DUMMY_SP {
+        // The span is added if it isn't dummy
+        if !span.is_dummy() {
             self.def_index_to_span.insert(index, span);
         }
 
diff --git a/src/librustc/middle/stability.rs b/src/librustc/middle/stability.rs
index a289a2c21ce..9bf5c4d72b7 100644
--- a/src/librustc/middle/stability.rs
+++ b/src/librustc/middle/stability.rs
@@ -20,7 +20,7 @@ use ty::{self, TyCtxt};
 use middle::privacy::AccessLevels;
 use session::DiagnosticMessageId;
 use syntax::symbol::Symbol;
-use syntax_pos::{Span, MultiSpan, DUMMY_SP};
+use syntax_pos::{Span, MultiSpan};
 use syntax::ast;
 use syntax::ast::{NodeId, Attribute};
 use syntax::feature_gate::{GateIssue, emit_feature_err, find_lang_feature_accepted_version};
@@ -687,7 +687,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                 let msp: MultiSpan = span.into();
                 let cm = &self.sess.parse_sess.codemap();
                 let span_key = msp.primary_span().and_then(|sp: Span|
-                    if sp != DUMMY_SP {
+                    if !sp.is_dummy() {
                         let file = cm.lookup_char_pos(sp.lo()).file;
                         if file.name.is_macros() {
                             None
@@ -725,7 +725,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx> {
         match item.node {
             hir::ItemExternCrate(_) => {
                 // compiler-generated `extern crate` items have a dummy span.
-                if item.span == DUMMY_SP { return }
+                if item.span.is_dummy() { return }
 
                 let def_id = self.tcx.hir.local_def_id(item.id);
                 let cnum = match self.tcx.extern_mod_stmt_cnum(def_id) {
diff --git a/src/librustc/ty/query/plumbing.rs b/src/librustc/ty/query/plumbing.rs
index e17c6fba74c..d783b9574ef 100644
--- a/src/librustc/ty/query/plumbing.rs
+++ b/src/librustc/ty/query/plumbing.rs
@@ -708,7 +708,7 @@ macro_rules! define_queries {
 
             // FIXME(eddyb) Get more valid Span's on queries.
             pub fn default_span(&self, tcx: TyCtxt<'_, $tcx, '_>, span: Span) -> Span {
-                if span != DUMMY_SP {
+                if !span.is_dummy() {
                     return span;
                 }
                 // The def_span query is used to calculate default_span,
diff --git a/src/librustc_codegen_llvm/debuginfo/metadata.rs b/src/librustc_codegen_llvm/debuginfo/metadata.rs
index 1eec57c9c87..6d727f7b048 100644
--- a/src/librustc_codegen_llvm/debuginfo/metadata.rs
+++ b/src/librustc_codegen_llvm/debuginfo/metadata.rs
@@ -1662,7 +1662,7 @@ pub fn create_global_var_metadata(cx: &CodegenCx,
     let var_scope = get_namespace_for_item(cx, def_id);
     let span = tcx.def_span(def_id);
 
-    let (file_metadata, line_number) = if span != syntax_pos::DUMMY_SP {
+    let (file_metadata, line_number) = if !span.is_dummy() {
         let loc = span_start(cx, span);
         (file_metadata(cx, &loc.file.name, LOCAL_CRATE), loc.line as c_uint)
     } else {
diff --git a/src/librustc_codegen_llvm/debuginfo/mod.rs b/src/librustc_codegen_llvm/debuginfo/mod.rs
index 803966145f7..068dd9821ac 100644
--- a/src/librustc_codegen_llvm/debuginfo/mod.rs
+++ b/src/librustc_codegen_llvm/debuginfo/mod.rs
@@ -219,7 +219,7 @@ pub fn create_function_debug_context<'a, 'tcx>(cx: &CodegenCx<'a, 'tcx>,
     let span = mir.span;
 
     // This can be the case for functions inlined from another crate
-    if span == syntax_pos::DUMMY_SP {
+    if span.is_dummy() {
         // FIXME(simulacrum): Probably can't happen; remove.
         return FunctionDebugContext::FunctionWithoutDebugInfo;
     }
diff --git a/src/librustc_errors/emitter.rs b/src/librustc_errors/emitter.rs
index 92e72fe91d3..e79a3a87738 100644
--- a/src/librustc_errors/emitter.rs
+++ b/src/librustc_errors/emitter.rs
@@ -10,7 +10,7 @@
 
 use self::Destination::*;
 
-use syntax_pos::{DUMMY_SP, FileMap, Span, MultiSpan};
+use syntax_pos::{FileMap, Span, MultiSpan};
 
 use {Level, CodeSuggestion, DiagnosticBuilder, SubDiagnostic, CodeMapperDyn, DiagnosticId};
 use snippet::{Annotation, AnnotationType, Line, MultilineAnnotation, StyledString, Style};
@@ -216,7 +216,7 @@ impl EmitterWriter {
 
         if let Some(ref cm) = self.cm {
             for span_label in msp.span_labels() {
-                if span_label.span == DUMMY_SP {
+                if span_label.span.is_dummy() {
                     continue;
                 }
 
@@ -730,7 +730,7 @@ impl EmitterWriter {
         let mut max = 0;
         if let Some(ref cm) = self.cm {
             for primary_span in msp.primary_spans() {
-                if primary_span != &DUMMY_SP {
+                if !primary_span.is_dummy() {
                     let hi = cm.lookup_char_pos(primary_span.hi());
                     if hi.line > max {
                         max = hi.line;
@@ -739,7 +739,7 @@ impl EmitterWriter {
             }
             if !self.short_message {
                 for span_label in msp.span_labels() {
-                    if span_label.span != DUMMY_SP {
+                    if !span_label.span.is_dummy() {
                         let hi = cm.lookup_char_pos(span_label.span.hi());
                         if hi.line > max {
                             max = hi.line;
@@ -778,7 +778,7 @@ impl EmitterWriter {
 
             // First, find all the spans in <*macros> and point instead at their use site
             for sp in span.primary_spans() {
-                if *sp == DUMMY_SP {
+                if sp.is_dummy() {
                     continue;
                 }
                 let call_sp = cm.call_span_if_macro(*sp);
@@ -790,7 +790,7 @@ impl EmitterWriter {
                     // Only show macro locations that are local
                     // and display them like a span_note
                     if let Some(def_site) = trace.def_site_span {
-                        if def_site == DUMMY_SP {
+                        if def_site.is_dummy() {
                             continue;
                         }
                         if always_backtrace {
@@ -830,7 +830,7 @@ impl EmitterWriter {
                 span.push_span_label(label_span, label_text);
             }
             for sp_label in span.span_labels() {
-                if sp_label.span == DUMMY_SP {
+                if sp_label.span.is_dummy() {
                     continue;
                 }
                 if cm.span_to_filename(sp_label.span.clone()).is_macros() &&
@@ -1003,7 +1003,7 @@ impl EmitterWriter {
         // Make sure our primary file comes first
         let (primary_lo, cm) = if let (Some(cm), Some(ref primary_span)) =
             (self.cm.as_ref(), msp.primary_span().as_ref()) {
-            if primary_span != &&DUMMY_SP {
+            if !primary_span.is_dummy() {
                 (cm.lookup_char_pos(primary_span.lo()), cm)
             } else {
                 emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
diff --git a/src/librustc_metadata/encoder.rs b/src/librustc_metadata/encoder.rs
index d8a224d3bad..93294075272 100644
--- a/src/librustc_metadata/encoder.rs
+++ b/src/librustc_metadata/encoder.rs
@@ -41,7 +41,7 @@ use std::u32;
 use syntax::ast::{self, CRATE_NODE_ID};
 use syntax::attr;
 use syntax::symbol::keywords;
-use syntax_pos::{self, hygiene, FileName, FileMap, Span, DUMMY_SP};
+use syntax_pos::{self, hygiene, FileName, FileMap, Span};
 
 use rustc::hir::{self, PatKind};
 use rustc::hir::itemlikevisit::ItemLikeVisitor;
@@ -147,7 +147,7 @@ impl<'a, 'tcx> SpecializedEncoder<DefIndex> for EncodeContext<'a, 'tcx> {
 
 impl<'a, 'tcx> SpecializedEncoder<Span> for EncodeContext<'a, 'tcx> {
     fn specialized_encode(&mut self, span: &Span) -> Result<(), Self::Error> {
-        if *span == DUMMY_SP {
+        if span.is_dummy() {
             return TAG_INVALID_SPAN.encode(self)
         }
 
diff --git a/src/librustc_mir/borrow_check/nll/type_check/mod.rs b/src/librustc_mir/borrow_check/nll/type_check/mod.rs
index 2da2b10edb8..9b6e3e0cab6 100644
--- a/src/librustc_mir/borrow_check/nll/type_check/mod.rs
+++ b/src/librustc_mir/borrow_check/nll/type_check/mod.rs
@@ -190,7 +190,7 @@ struct TypeVerifier<'a, 'b: 'a, 'gcx: 'b + 'tcx, 'tcx: 'b> {
 
 impl<'a, 'b, 'gcx, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'gcx, 'tcx> {
     fn visit_span(&mut self, span: &Span) {
-        if *span != DUMMY_SP {
+        if !span.is_dummy() {
             self.last_span = *span;
         }
     }
@@ -1601,7 +1601,7 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                 statement_index: 0,
             };
             for stmt in &block_data.statements {
-                if stmt.source_info.span != DUMMY_SP {
+                if !stmt.source_info.span.is_dummy() {
                     self.last_span = stmt.source_info.span;
                 }
                 self.check_stmt(mir, stmt, location);
diff --git a/src/librustc_resolve/check_unused.rs b/src/librustc_resolve/check_unused.rs
index 590ce168d5d..0c4b9a546cb 100644
--- a/src/librustc_resolve/check_unused.rs
+++ b/src/librustc_resolve/check_unused.rs
@@ -86,7 +86,7 @@ impl<'a, 'b> Visitor<'a> for UnusedImportCheckVisitor<'a, 'b> {
         // because this means that they were generated in some fashion by the
         // compiler and we don't need to consider them.
         if let ast::ItemKind::Use(..) = item.node {
-            if item.vis.node == ast::VisibilityKind::Public || item.span.source_equal(&DUMMY_SP) {
+            if item.vis.node == ast::VisibilityKind::Public || item.span.is_dummy() {
                 return;
             }
         }
@@ -129,7 +129,7 @@ pub fn check_crate(resolver: &mut Resolver, krate: &ast::Crate) {
         match directive.subclass {
             _ if directive.used.get() ||
                  directive.vis.get() == ty::Visibility::Public ||
-                 directive.span.source_equal(&DUMMY_SP) => {}
+                 directive.span.is_dummy() => {}
             ImportDirectiveSubclass::ExternCrate(_) => {
                 resolver.maybe_unused_extern_crates.push((directive.id, directive.span));
             }
diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index 640e650207e..9887abd60bf 100644
--- a/src/librustc_resolve/lib.rs
+++ b/src/librustc_resolve/lib.rs
@@ -2861,7 +2861,7 @@ impl<'a> Resolver<'a> {
                     .map(|suggestion| import_candidate_to_paths(&suggestion)).collect::<Vec<_>>();
                 enum_candidates.sort();
                 for (sp, variant_path, enum_path) in enum_candidates {
-                    if sp == DUMMY_SP {
+                    if sp.is_dummy() {
                         let msg = format!("there is an enum variant `{}`, \
                                         try using `{}`?",
                                         variant_path,
@@ -4285,7 +4285,7 @@ impl<'a> Resolver<'a> {
             let mut err = struct_span_err!(self.session, span, E0659, "`{}` is ambiguous", name);
             err.span_note(b1.span, &msg1);
             match b2.def() {
-                Def::Macro(..) if b2.span == DUMMY_SP =>
+                Def::Macro(..) if b2.span.is_dummy() =>
                     err.note(&format!("`{}` is also a builtin macro", name)),
                 _ => err.span_note(b2.span, &msg2),
             };
@@ -4398,14 +4398,14 @@ impl<'a> Resolver<'a> {
                           container));
 
         err.span_label(span, format!("`{}` re{} here", name, new_participle));
-        if old_binding.span != DUMMY_SP {
+        if !old_binding.span.is_dummy() {
             err.span_label(self.session.codemap().def_span(old_binding.span),
                            format!("previous {} of the {} `{}` here", old_noun, old_kind, name));
         }
 
         // See https://github.com/rust-lang/rust/issues/32354
         if old_binding.is_import() || new_binding.is_import() {
-            let binding = if new_binding.is_import() && new_binding.span != DUMMY_SP {
+            let binding = if new_binding.is_import() && !new_binding.span.is_dummy() {
                 new_binding
             } else {
                 old_binding
diff --git a/src/librustc_save_analysis/lib.rs b/src/librustc_save_analysis/lib.rs
index 89d30fd666a..c07db44b36c 100644
--- a/src/librustc_save_analysis/lib.rs
+++ b/src/librustc_save_analysis/lib.rs
@@ -1157,7 +1157,7 @@ fn escape(s: String) -> String {
 // Helper function to determine if a span came from a
 // macro expansion or syntax extension.
 fn generated_code(span: Span) -> bool {
-    span.ctxt() != NO_EXPANSION || span == DUMMY_SP
+    span.ctxt() != NO_EXPANSION || span.is_dummy()
 }
 
 // DefId::index is a newtype and so the JSON serialisation is ugly. Therefore
diff --git a/src/librustc_typeck/check_unused.rs b/src/librustc_typeck/check_unused.rs
index 41adde0d4a1..ae5ca5441ad 100644
--- a/src/librustc_typeck/check_unused.rs
+++ b/src/librustc_typeck/check_unused.rs
@@ -12,7 +12,7 @@ use lint;
 use rustc::ty::TyCtxt;
 
 use syntax::ast;
-use syntax_pos::{Span, DUMMY_SP};
+use syntax_pos::Span;
 
 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
 use rustc::hir::itemlikevisit::ItemLikeVisitor;
@@ -39,7 +39,7 @@ pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
 
 impl<'a, 'tcx, 'v> ItemLikeVisitor<'v> for CheckVisitor<'a, 'tcx> {
     fn visit_item(&mut self, item: &hir::Item) {
-        if item.vis == hir::Public || item.span == DUMMY_SP {
+        if item.vis == hir::Public || item.span.is_dummy() {
             return;
         }
         if let hir::ItemUse(ref path, _) = item.node {
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 23c367da48d..65babbffffe 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -3464,7 +3464,7 @@ impl Span {
 
 impl Clean<Span> for syntax_pos::Span {
     fn clean(&self, cx: &DocContext) -> Span {
-        if *self == DUMMY_SP {
+        if self.is_dummy() {
             return Span::empty();
         }
 
diff --git a/src/libsyntax/codemap.rs b/src/libsyntax/codemap.rs
index 1d5429bdf8f..ea6b39504e8 100644
--- a/src/libsyntax/codemap.rs
+++ b/src/libsyntax/codemap.rs
@@ -443,7 +443,7 @@ impl CodeMap {
     }
 
     pub fn span_to_string(&self, sp: Span) -> String {
-        if self.files.borrow().file_maps.is_empty() && sp.source_equal(&DUMMY_SP) {
+        if self.files.borrow().file_maps.is_empty() && sp.is_dummy() {
             return "no-location".to_string();
         }
 
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index e364e145593..f29bff20f3d 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -1297,7 +1297,7 @@ impl<'a, 'b> Folder for InvocationCollector<'a, 'b> {
                 // Detect if this is an inline module (`mod m { ... }` as opposed to `mod m;`).
                 // In the non-inline case, `inner` is never the dummy span (c.f. `parse_item_mod`).
                 // Thus, if `inner` is the dummy span, we know the module is inline.
-                let inline_module = item.span.contains(inner) || inner == DUMMY_SP;
+                let inline_module = item.span.contains(inner) || inner.is_dummy();
 
                 if inline_module {
                     if let Some(path) = attr::first_attr_value_str_by_name(&item.attrs, "path") {
diff --git a/src/libsyntax/ext/tt/quoted.rs b/src/libsyntax/ext/tt/quoted.rs
index 01b971976a7..82b0fae3e9c 100644
--- a/src/libsyntax/ext/tt/quoted.rs
+++ b/src/libsyntax/ext/tt/quoted.rs
@@ -14,7 +14,7 @@ use feature_gate::{self, emit_feature_err, Features, GateIssue};
 use parse::{token, ParseSess};
 use print::pprust;
 use symbol::keywords;
-use syntax_pos::{BytePos, Span, DUMMY_SP};
+use syntax_pos::{BytePos, Span};
 use tokenstream;
 
 use std::iter::Peekable;
@@ -41,8 +41,8 @@ impl Delimited {
 
     /// Return a `self::TokenTree` with a `Span` corresponding to the opening delimiter.
     pub fn open_tt(&self, span: Span) -> TokenTree {
-        let open_span = if span == DUMMY_SP {
-            DUMMY_SP
+        let open_span = if span.is_dummy() {
+            span
         } else {
             span.with_lo(span.lo() + BytePos(self.delim.len() as u32))
         };
@@ -51,8 +51,8 @@ impl Delimited {
 
     /// Return a `self::TokenTree` with a `Span` corresponding to the closing delimiter.
     pub fn close_tt(&self, span: Span) -> TokenTree {
-        let close_span = if span == DUMMY_SP {
-            DUMMY_SP
+        let close_span = if span.is_dummy() {
+            span
         } else {
             span.with_lo(span.hi() - BytePos(self.delim.len() as u32))
         };
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index cce8da1dcbd..c443f240780 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -13,7 +13,7 @@
 use rustc_data_structures::sync::{Lrc, Lock};
 use ast::{self, CrateConfig};
 use codemap::{CodeMap, FilePathMapping};
-use syntax_pos::{self, Span, FileMap, NO_EXPANSION, FileName};
+use syntax_pos::{Span, FileMap, FileName};
 use errors::{Handler, ColorConfig, DiagnosticBuilder};
 use feature_gate::UnstableFeatures;
 use parse::parser::Parser;
@@ -188,8 +188,8 @@ fn filemap_to_parser(sess: & ParseSess, filemap: Lrc<FileMap>) -> Parser {
     let end_pos = filemap.end_pos;
     let mut parser = stream_to_parser(sess, filemap_to_stream(sess, filemap, None));
 
-    if parser.token == token::Eof && parser.span == syntax_pos::DUMMY_SP {
-        parser.span = Span::new(end_pos, end_pos, NO_EXPANSION);
+    if parser.token == token::Eof && parser.span.is_dummy() {
+        parser.span = Span::new(end_pos, end_pos, parser.span.ctxt());
     }
 
     parser
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index faf2cf64e1d..96053f988fa 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -43,7 +43,7 @@ use ast::{BinOpKind, UnOp};
 use ast::{RangeEnd, RangeSyntax};
 use {ast, attr};
 use codemap::{self, CodeMap, Spanned, respan};
-use syntax_pos::{self, Span, MultiSpan, BytePos, FileName, DUMMY_SP, edition::Edition};
+use syntax_pos::{self, Span, MultiSpan, BytePos, FileName, edition::Edition};
 use errors::{self, Applicability, DiagnosticBuilder};
 use parse::{self, SeqSep, classify, token};
 use parse::lexer::TokenAndSpan;
@@ -567,7 +567,7 @@ impl<'a> Parser<'a> {
 
         if let Some(directory) = directory {
             parser.directory = directory;
-        } else if !parser.span.source_equal(&DUMMY_SP) {
+        } else if !parser.span.is_dummy() {
             if let FileName::Real(mut path) = sess.codemap().span_to_unmapped_path(parser.span) {
                 path.pop();
                 parser.directory.path = Cow::from(path);
@@ -584,7 +584,7 @@ impl<'a> Parser<'a> {
         } else {
             self.token_cursor.next()
         };
-        if next.sp == syntax_pos::DUMMY_SP {
+        if next.sp.is_dummy() {
             // Tweak the location for better diagnostics, but keep syntactic context intact.
             next.sp = self.prev_span.with_ctxt(next.sp.ctxt());
         }
@@ -6137,7 +6137,7 @@ impl<'a> Parser<'a> {
             return Err(err);
         }
 
-        let hi = if self.span == syntax_pos::DUMMY_SP {
+        let hi = if self.span.is_dummy() {
             inner_lo
         } else {
             self.prev_span
@@ -6368,7 +6368,7 @@ impl<'a> Parser<'a> {
                 }
                 let mut err = self.diagnostic().struct_span_err(id_sp,
                     "cannot declare a new module at this location");
-                if id_sp != syntax_pos::DUMMY_SP {
+                if !id_sp.is_dummy() {
                     let src_path = self.sess.codemap().span_to_filename(id_sp);
                     if let FileName::Real(src_path) = src_path {
                         if let Some(stem) = src_path.file_stem() {
diff --git a/src/libsyntax/tokenstream.rs b/src/libsyntax/tokenstream.rs
index 455cc4391dd..8736fcf9729 100644
--- a/src/libsyntax/tokenstream.rs
+++ b/src/libsyntax/tokenstream.rs
@@ -57,8 +57,8 @@ impl Delimited {
 
     /// Returns the opening delimiter as a token tree.
     pub fn open_tt(&self, span: Span) -> TokenTree {
-        let open_span = if span == DUMMY_SP {
-            DUMMY_SP
+        let open_span = if span.is_dummy() {
+            span
         } else {
             span.with_hi(span.lo() + BytePos(self.delim.len() as u32))
         };
@@ -67,8 +67,8 @@ impl Delimited {
 
     /// Returns the closing delimiter as a token tree.
     pub fn close_tt(&self, span: Span) -> TokenTree {
-        let close_span = if span == DUMMY_SP {
-            DUMMY_SP
+        let close_span = if span.is_dummy() {
+            span
         } else {
             span.with_lo(span.hi() - BytePos(self.delim.len() as u32))
         };
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index 308fb118f07..491ce720f36 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -248,6 +248,13 @@ impl Span {
         self.data().with_ctxt(ctxt)
     }
 
+    /// Returns `true` if this is a dummy span with any hygienic context.
+    #[inline]
+    pub fn is_dummy(self) -> bool {
+        let span = self.data();
+        span.lo.0 == 0 && span.hi.0 == 0
+    }
+
     /// Returns a new span representing an empty span at the beginning of this span
     #[inline]
     pub fn shrink_to_lo(self) -> Span {
@@ -263,7 +270,7 @@ impl Span {
 
     /// Returns `self` if `self` is not the dummy span, and `other` otherwise.
     pub fn substitute_dummy(self, other: Span) -> Span {
-        if self.source_equal(&DUMMY_SP) { other } else { self }
+        if self.is_dummy() { other } else { self }
     }
 
     /// Return true if `self` fully encloses `other`.