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 https://github.com/rust-lang/rust/issues/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.

2 files changed, 13 insertions, 17 deletions

diff --git a/src/librustc_errors/emitter.rs b/src/librustc_errors/emitter.rs
index 53d90531cc9..daa132dbf62 100644
--- a/src/librustc_errors/emitter.rs
+++ b/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
@@ -683,7 +683,7 @@ 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;
                     }
@@ -691,7 +691,7 @@ impl EmitterWriter {
             }
             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;
diff --git a/src/librustc_errors/lib.rs b/src/librustc_errors/lib.rs
index 2c756be02f1..d9b0f4ac8a6 100644
--- a/src/librustc_errors/lib.rs
+++ b/src/librustc_errors/lib.rs
@@ -148,16 +148,12 @@ impl CodeSuggestion {
 
         // Assumption: all spans are in the same file, and all spans
         // are disjoint. Sort in ascending order.
-        primary_spans.sort_by_key(|sp| sp.0.lo);
+        primary_spans.sort_by_key(|sp| sp.0.lo());
 
         // Find the bounding span.
-        let lo = primary_spans.iter().map(|sp| sp.0.lo).min().unwrap();
-        let hi = primary_spans.iter().map(|sp| sp.0.hi).min().unwrap();
-        let bounding_span = Span {
-            lo,
-            hi,
-            ctxt: NO_EXPANSION,
-        };
+        let lo = primary_spans.iter().map(|sp| sp.0.lo()).min().unwrap();
+        let hi = primary_spans.iter().map(|sp| sp.0.hi()).min().unwrap();
+        let bounding_span = Span::new(lo, hi, NO_EXPANSION);
         let lines = cm.span_to_lines(bounding_span).unwrap();
         assert!(!lines.lines.is_empty());
 
@@ -171,14 +167,14 @@ impl CodeSuggestion {
         //
         // Finally push the trailing line segment of the last span
         let fm = &lines.file;
-        let mut prev_hi = cm.lookup_char_pos(bounding_span.lo);
+        let mut prev_hi = cm.lookup_char_pos(bounding_span.lo());
         prev_hi.col = CharPos::from_usize(0);
 
         let mut prev_line = fm.get_line(lines.lines[0].line_index);
         let mut bufs = vec![(String::new(), false); self.substitutions()];
 
         for (sp, substitutes) in primary_spans {
-            let cur_lo = cm.lookup_char_pos(sp.lo);
+            let cur_lo = cm.lookup_char_pos(sp.lo());
             for (&mut (ref mut buf, ref mut underline), substitute) in bufs.iter_mut()
                                                                            .zip(substitutes) {
                 if prev_hi.line == cur_lo.line {
@@ -208,7 +204,7 @@ impl CodeSuggestion {
                 }
                 buf.push_str(substitute);
             }
-            prev_hi = cm.lookup_char_pos(sp.hi);
+            prev_hi = cm.lookup_char_pos(sp.hi());
             prev_line = fm.get_line(prev_hi.line - 1);
         }
         for &mut (ref mut buf, _) in &mut bufs {