Auto merge of #43968 - petrochenkov:span2, r=michaelwoerister

Make fields of `Span` private

I actually tried to intern spans and benchmark the result<sup>*</sup>, and this was a prerequisite.
This kind of encapsulation will be a prerequisite for any other attempt to compress span's representation, so I decided to submit this change alone.

The issue #43088 seems relevant, but it looks like `SpanId` won't be able to reuse this interface, unless the tables are global (like interner that I tried) and are not a part of HIR.
r? @michaelwoerister anyway

<sup>*</sup> Interning means 2-3 times more space is required for a single span, but duplicates are free. In practice it turned out that duplicates are not *that* common, so more memory was wasted by interning rather than saved.

src/libproc_macro/lib.rs

@@ -89,10 +89,7 @@ impl FromStr for TokenStream {
             // notify the expansion info that it is unhygienic
             let mark = Mark::fresh(mark);
             mark.set_expn_info(expn_info);
-            let span = syntax_pos::Span {
-                ctxt: SyntaxContext::empty().apply_mark(mark),
-                ..call_site
-            };
+            let span = call_site.with_ctxt(SyntaxContext::empty().apply_mark(mark));
             let stream = parse::parse_stream_from_source_str(name, src, sess, Some(span));
             Ok(__internal::token_stream_wrap(stream))
         })
@@ -177,10 +174,10 @@ pub struct Span(syntax_pos::Span);
 #[unstable(feature = "proc_macro", issue = "38356")]
 impl Default for Span {
     fn default() -> Span {
-        ::__internal::with_sess(|(_, mark)| Span(syntax_pos::Span {
-            ctxt: SyntaxContext::empty().apply_mark(mark),
-            ..mark.expn_info().unwrap().call_site
-        }))
+        ::__internal::with_sess(|(_, mark)| {
+            let call_site = mark.expn_info().unwrap().call_site;
+            Span(call_site.with_ctxt(SyntaxContext::empty().apply_mark(mark)))
+        })
     }
 }
 
@@ -570,7 +567,7 @@ impl TokenTree {
                 }).into();
             },
             TokenNode::Term(symbol) => {
-                let ident = ast::Ident { name: symbol.0, ctxt: self.span.0.ctxt };
+                let ident = ast::Ident { name: symbol.0, ctxt: self.span.0.ctxt() };
                 let token =
                     if symbol.0.as_str().starts_with("'") { Lifetime(ident) } else { Ident(ident) };
                 return TokenTree::Token(self.span.0, token).into();

src/librustc/hir/lowering.rs

@@ -425,8 +425,7 @@ impl<'a> LoweringContext<'a> {
         Symbol::gensym(s)
     }
 
-    fn allow_internal_unstable(&self, reason: CompilerDesugaringKind, mut span: Span)
-        -> Span
+    fn allow_internal_unstable(&self, reason: CompilerDesugaringKind, span: Span) -> Span
     {
         let mark = Mark::fresh(Mark::root());
         mark.set_expn_info(codemap::ExpnInfo {
@@ -438,8 +437,7 @@ impl<'a> LoweringContext<'a> {
                 allow_internal_unsafe: false,
             },
         });
-        span.ctxt = SyntaxContext::empty().apply_mark(mark);
-        span
+        span.with_ctxt(SyntaxContext::empty().apply_mark(mark))
     }
 
     fn with_catch_scope<T, F>(&mut self, catch_id: NodeId, f: F) -> T
@@ -613,7 +611,7 @@ impl<'a> LoweringContext<'a> {
             TyKind::Slice(ref ty) => hir::TySlice(self.lower_ty(ty)),
             TyKind::Ptr(ref mt) => hir::TyPtr(self.lower_mt(mt)),
             TyKind::Rptr(ref region, ref mt) => {
-                let span = Span { hi: t.span.lo, ..t.span };
+                let span = t.span.with_hi(t.span.lo());
                 let lifetime = match *region {
                     Some(ref lt) => self.lower_lifetime(lt),
                     None => self.elided_lifetime(span)
@@ -1237,7 +1235,7 @@ impl<'a> LoweringContext<'a> {
             name: self.lower_ident(match f.ident {
                 Some(ident) => ident,
                 // FIXME(jseyfried) positional field hygiene
-                None => Ident { name: Symbol::intern(&index.to_string()), ctxt: f.span.ctxt },
+                None => Ident { name: Symbol::intern(&index.to_string()), ctxt: f.span.ctxt() },
             }),
             vis: self.lower_visibility(&f.vis, None),
             ty: self.lower_ty(&f.ty),

src/librustc/hir/print.rs

@@ -262,7 +262,7 @@ impl<'a> State<'a> {
                              indented: usize,
                              close_box: bool)
                              -> io::Result<()> {
-        self.maybe_print_comment(span.hi)?;
+        self.maybe_print_comment(span.hi())?;
         self.break_offset_if_not_bol(1, -(indented as isize))?;
         self.s.word("}")?;
         if close_box {
@@ -324,12 +324,12 @@ impl<'a> State<'a> {
         let len = elts.len();
         let mut i = 0;
         for elt in elts {
-            self.maybe_print_comment(get_span(elt).hi)?;
+            self.maybe_print_comment(get_span(elt).hi())?;
             op(self, elt)?;
             i += 1;
             if i < len {
                 self.s.word(",")?;
-                self.maybe_print_trailing_comment(get_span(elt), Some(get_span(&elts[i]).hi))?;
+                self.maybe_print_trailing_comment(get_span(elt), Some(get_span(&elts[i]).hi()))?;
                 self.space_if_not_bol()?;
             }
         }
@@ -368,7 +368,7 @@ impl<'a> State<'a> {
     }
 
     pub fn print_type(&mut self, ty: &hir::Ty) -> io::Result<()> {
-        self.maybe_print_comment(ty.span.lo)?;
+        self.maybe_print_comment(ty.span.lo())?;
         self.ibox(0)?;
         match ty.node {
             hir::TySlice(ref ty) => {
@@ -458,7 +458,7 @@ impl<'a> State<'a> {
 
     pub fn print_foreign_item(&mut self, item: &hir::ForeignItem) -> io::Result<()> {
         self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(item.span.lo)?;
+        self.maybe_print_comment(item.span.lo())?;
         self.print_outer_attributes(&item.attrs)?;
         match item.node {
             hir::ForeignItemFn(ref decl, ref arg_names, ref generics) => {
@@ -531,7 +531,7 @@ impl<'a> State<'a> {
     /// Pretty-print an item
     pub fn print_item(&mut self, item: &hir::Item) -> io::Result<()> {
         self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(item.span.lo)?;
+        self.maybe_print_comment(item.span.lo())?;
         self.print_outer_attributes(&item.attrs)?;
         self.ann.pre(self, NodeItem(item))?;
         match item.node {
@@ -797,7 +797,7 @@ impl<'a> State<'a> {
         self.bopen()?;
         for v in variants {
             self.space_if_not_bol()?;
-            self.maybe_print_comment(v.span.lo)?;
+            self.maybe_print_comment(v.span.lo())?;
             self.print_outer_attributes(&v.node.attrs)?;
             self.ibox(indent_unit)?;
             self.print_variant(v)?;
@@ -842,7 +842,7 @@ impl<'a> State<'a> {
             if struct_def.is_tuple() {
                 self.popen()?;
                 self.commasep(Inconsistent, struct_def.fields(), |s, field| {
-                    s.maybe_print_comment(field.span.lo)?;
+                    s.maybe_print_comment(field.span.lo())?;
                     s.print_outer_attributes(&field.attrs)?;
                     s.print_visibility(&field.vis)?;
                     s.print_type(&field.ty)
@@ -863,7 +863,7 @@ impl<'a> State<'a> {
 
             for field in struct_def.fields() {
                 self.hardbreak_if_not_bol()?;
-                self.maybe_print_comment(field.span.lo)?;
+                self.maybe_print_comment(field.span.lo())?;
                 self.print_outer_attributes(&field.attrs)?;
                 self.print_visibility(&field.vis)?;
                 self.print_name(field.name)?;
@@ -908,7 +908,7 @@ impl<'a> State<'a> {
     pub fn print_trait_item(&mut self, ti: &hir::TraitItem) -> io::Result<()> {
         self.ann.pre(self, NodeSubItem(ti.id))?;
         self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(ti.span.lo)?;
+        self.maybe_print_comment(ti.span.lo())?;
         self.print_outer_attributes(&ti.attrs)?;
         match ti.node {
             hir::TraitItemKind::Const(ref ty, default) => {
@@ -938,7 +938,7 @@ impl<'a> State<'a> {
     pub fn print_impl_item(&mut self, ii: &hir::ImplItem) -> io::Result<()> {
         self.ann.pre(self, NodeSubItem(ii.id))?;
         self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(ii.span.lo)?;
+        self.maybe_print_comment(ii.span.lo())?;
         self.print_outer_attributes(&ii.attrs)?;
         self.print_defaultness(ii.defaultness)?;
 
@@ -962,7 +962,7 @@ impl<'a> State<'a> {
     }
 
     pub fn print_stmt(&mut self, st: &hir::Stmt) -> io::Result<()> {
-        self.maybe_print_comment(st.span.lo)?;
+        self.maybe_print_comment(st.span.lo())?;
         match st.node {
             hir::StmtDecl(ref decl, _) => {
                 self.print_decl(&decl)?;
@@ -1017,7 +1017,7 @@ impl<'a> State<'a> {
             hir::PopUnsafeBlock(..) => self.word_space("pop_unsafe")?,
             hir::DefaultBlock => (),
         }
-        self.maybe_print_comment(blk.span.lo)?;
+        self.maybe_print_comment(blk.span.lo())?;
         self.ann.pre(self, NodeBlock(blk))?;
         self.bopen()?;
 
@@ -1030,7 +1030,7 @@ impl<'a> State<'a> {
             Some(ref expr) => {
                 self.space_if_not_bol()?;
                 self.print_expr(&expr)?;
-                self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi))?;
+                self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi()))?;
             }
             _ => (),
         }
@@ -1228,7 +1228,7 @@ impl<'a> State<'a> {
     }
 
     pub fn print_expr(&mut self, expr: &hir::Expr) -> io::Result<()> {
-        self.maybe_print_comment(expr.span.lo)?;
+        self.maybe_print_comment(expr.span.lo())?;
         self.print_outer_attributes(&expr.attrs)?;
         self.ibox(indent_unit)?;
         self.ann.pre(self, NodeExpr(expr))?;
@@ -1480,7 +1480,7 @@ impl<'a> State<'a> {
     }
 
     pub fn print_decl(&mut self, decl: &hir::Decl) -> io::Result<()> {
-        self.maybe_print_comment(decl.span.lo)?;
+        self.maybe_print_comment(decl.span.lo())?;
         match decl.node {
             hir::DeclLocal(ref loc) => {
                 self.space_if_not_bol()?;
@@ -1523,7 +1523,7 @@ impl<'a> State<'a> {
                       path: &hir::Path,
                       colons_before_params: bool)
                       -> io::Result<()> {
-        self.maybe_print_comment(path.span.lo)?;
+        self.maybe_print_comment(path.span.lo())?;
 
         for (i, segment) in path.segments.iter().enumerate() {
             if i > 0 {
@@ -1641,7 +1641,7 @@ impl<'a> State<'a> {
     }
 
     pub fn print_pat(&mut self, pat: &hir::Pat) -> io::Result<()> {
-        self.maybe_print_comment(pat.span.lo)?;
+        self.maybe_print_comment(pat.span.lo())?;
         self.ann.pre(self, NodePat(pat))?;
         // Pat isn't normalized, but the beauty of it
         // is that it doesn't matter
@@ -1897,7 +1897,7 @@ impl<'a> State<'a> {
         match decl.output {
             hir::Return(ref ty) => {
                 self.print_type(&ty)?;
-                self.maybe_print_comment(ty.span.lo)
+                self.maybe_print_comment(ty.span.lo())
             }
             hir::DefaultReturn(..) => unreachable!(),
         }
@@ -2074,7 +2074,7 @@ impl<'a> State<'a> {
         self.end()?;
 
         match decl.output {
-            hir::Return(ref output) => self.maybe_print_comment(output.span.lo),
+            hir::Return(ref output) => self.maybe_print_comment(output.span.lo()),
             _ => Ok(()),
         }
     }
@@ -2124,13 +2124,13 @@ impl<'a> State<'a> {
             if (*cmnt).style != comments::Trailing {
                 return Ok(());
             }
-            let span_line = cm.lookup_char_pos(span.hi);
+            let span_line = cm.lookup_char_pos(span.hi());
             let comment_line = cm.lookup_char_pos((*cmnt).pos);
             let mut next = (*cmnt).pos + BytePos(1);
             if let Some(p) = next_pos {
                 next = p;
             }
-            if span.hi < (*cmnt).pos && (*cmnt).pos < next &&
+            if span.hi() < (*cmnt).pos && (*cmnt).pos < next &&
                span_line.line == comment_line.line {
                 self.print_comment(cmnt)?;
             }

src/librustc/ich/hcx.rs

@@ -253,17 +253,17 @@ impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>> for Span {
         // If this is not an empty or invalid span, we want to hash the last
         // position that belongs to it, as opposed to hashing the first
         // position past it.
-        let span_hi = if self.hi > self.lo {
+        let span_hi = if self.hi() > self.lo() {
             // We might end up in the middle of a multibyte character here,
             // but that's OK, since we are not trying to decode anything at
             // this position.
-            self.hi - ::syntax_pos::BytePos(1)
+            self.hi() - ::syntax_pos::BytePos(1)
         } else {
-            self.hi
+            self.hi()
         };
 
         {
-            let loc1 = hcx.codemap().byte_pos_to_line_and_col(self.lo);
+            let loc1 = hcx.codemap().byte_pos_to_line_and_col(self.lo());
             let loc1 = loc1.as_ref()
                            .map(|&(ref fm, line, col)| (&fm.name[..], line, col.to_usize()))
                            .unwrap_or(("???", 0, 0));
@@ -296,7 +296,7 @@ impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>> for Span {
             }
         }
 
-        if self.ctxt == SyntaxContext::empty() {
+        if self.ctxt() == SyntaxContext::empty() {
             0u8.hash_stable(hcx, hasher);
         } else {
             1u8.hash_stable(hcx, hasher);

src/librustc/infer/error_reporting/mod.rs

@@ -118,7 +118,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         fn explain_span<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
                                         heading: &str, span: Span)
                                         -> (String, Option<Span>) {
-            let lo = tcx.sess.codemap().lookup_char_pos_adj(span.lo);
+            let lo = tcx.sess.codemap().lookup_char_pos_adj(span.lo());
             (format!("the {} at {}:{}", heading, lo.line, lo.col.to_usize() + 1),
              Some(span))
         }

src/librustc/middle/region.rs

@@ -180,7 +180,7 @@ impl CodeExtent {
                         // (This is the special case aluded to in the
                         // doc-comment for this method)
                         let stmt_span = blk.stmts[r.first_statement_index as usize].span;
-                        Some(Span { lo: stmt_span.hi, hi: blk.span.hi, ctxt: stmt_span.ctxt })
+                        Some(Span::new(stmt_span.hi(), blk.span.hi(), stmt_span.ctxt()))
                     }
                 }
             }

src/librustc_allocator/expand.rs

@@ -82,10 +82,7 @@ impl<'a> Folder for ExpandAllocatorDirectives<'a> {
                 allow_internal_unsafe: false,
             }
         });
-        let span = Span {
-            ctxt: SyntaxContext::empty().apply_mark(mark),
-            ..item.span
-        };
+        let span = item.span.with_ctxt(SyntaxContext::empty().apply_mark(mark));
         let ecfg = ExpansionConfig::default(name.to_string());
         let mut f = AllocFnFactory {
             span,

src/librustc_errors/emitter.rs

@@ -183,8 +183,8 @@ impl EmitterWriter {
                     continue;
                 }
 
-                let lo = cm.lookup_char_pos(span_label.span.lo);
-                let mut hi = cm.lookup_char_pos(span_label.span.hi);
+                let lo = cm.lookup_char_pos(span_label.span.lo());
+                let mut hi = cm.lookup_char_pos(span_label.span.hi());
 
                 // Watch out for "empty spans". If we get a span like 6..6, we
                 // want to just display a `^` at 6, so convert that to
@@ -683,15 +683,15 @@ impl EmitterWriter {
         if let Some(ref cm) = self.cm {
             for primary_span in msp.primary_spans() {
                 if primary_span != &DUMMY_SP {
-                    let hi = cm.lookup_char_pos(primary_span.hi);
+                    let hi = cm.lookup_char_pos(primary_span.hi());
                     if hi.line > max {
                         max = hi.line;
                     }
                 }
             }
             for span_label in msp.span_labels() {
                 if span_label.span != DUMMY_SP {
-                    let hi = cm.lookup_char_pos(span_label.span.hi);
+                    let hi = cm.lookup_char_pos(span_label.span.hi());
                     if hi.line > max {
                         max = hi.line;
                     }
@@ -914,7 +914,7 @@ impl EmitterWriter {
         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 {
-                (cm.lookup_char_pos(primary_span.lo), cm)
+                (cm.lookup_char_pos(primary_span.lo()), cm)
             } else {
                 emit_to_destination(&buffer.render(), level, &mut self.dst)?;
                 return Ok(());
@@ -1091,7 +1091,7 @@ impl EmitterWriter {
                                Some(Style::HeaderMsg));
 
             let suggestions = suggestion.splice_lines(cm.borrow());
-            let span_start_pos = cm.lookup_char_pos(primary_sub.span.lo);
+            let span_start_pos = cm.lookup_char_pos(primary_sub.span.lo());
             let line_start = span_start_pos.line;
             draw_col_separator_no_space(&mut buffer, 1, max_line_num_len + 1);
             let mut row_num = 2;