Remove RegionHighlightMode::tcx.

It's easier to pass it in to the one method that needs it
(`highlighting_region_vid`) than to store it in the type. This means
`RegionHighlightMode` can impl `Default`.

compiler/rustc_borrowck/src/diagnostics/region_name.rs

@@ -442,8 +442,8 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
         span: Span,
         counter: usize,
     ) -> RegionNameHighlight {
-        let mut highlight = RegionHighlightMode::new(self.infcx.tcx);
+        let mut highlight = RegionHighlightMode::default();
-        highlight.highlighting_region_vid(needle_fr, counter);
+        highlight.highlighting_region_vid(self.infcx.tcx, needle_fr, counter);
         let type_name =
             self.infcx.extract_inference_diagnostics_data(ty.into(), Some(highlight)).name;
 
@@ -804,8 +804,8 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
             return None;
         }
 
-        let mut highlight = RegionHighlightMode::new(tcx);
+        let mut highlight = RegionHighlightMode::default();
-        highlight.highlighting_region_vid(fr, *self.next_region_name.try_borrow().unwrap());
+        highlight.highlighting_region_vid(tcx, fr, *self.next_region_name.try_borrow().unwrap());
         let type_name =
             self.infcx.extract_inference_diagnostics_data(yield_ty.into(), Some(highlight)).name;
 

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs

@@ -385,7 +385,7 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
 
         let highlight_trait_ref = |trait_ref| Highlighted {
             tcx: self.tcx(),
-            highlight: RegionHighlightMode::new(self.tcx()),
+            highlight: RegionHighlightMode::default(),
             value: trait_ref,
         };
 

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/trait_impl_difference.rs

@@ -67,9 +67,9 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         }
 
         impl<'tcx> HighlightBuilder<'tcx> {
-            fn build(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> RegionHighlightMode<'tcx> {
+            fn build(ty: Ty<'tcx>) -> RegionHighlightMode<'tcx> {
                 let mut builder =
-                    HighlightBuilder { highlight: RegionHighlightMode::new(tcx), counter: 1 };
+                    HighlightBuilder { highlight: RegionHighlightMode::default(), counter: 1 };
                 builder.visit_ty(ty);
                 builder.highlight
             }
@@ -85,12 +85,12 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             }
         }
 
-        let expected_highlight = HighlightBuilder::build(self.tcx(), expected);
+        let expected_highlight = HighlightBuilder::build(expected);
         let expected = self
             .cx
             .extract_inference_diagnostics_data(expected.into(), Some(expected_highlight))
             .name;
-        let found_highlight = HighlightBuilder::build(self.tcx(), found);
+        let found_highlight = HighlightBuilder::build(found);
         let found =
             self.cx.extract_inference_diagnostics_data(found.into(), Some(found_highlight)).name;
 

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -136,10 +136,8 @@ define_helper!(
 ///
 /// Regions not selected by the region highlight mode are presently
 /// unaffected.
-#[derive(Copy, Clone)]
+#[derive(Copy, Clone, Default)]
 pub struct RegionHighlightMode<'tcx> {
-    tcx: TyCtxt<'tcx>,
-
     /// If enabled, when we see the selected region, use "`'N`"
     /// instead of the ordinary behavior.
     highlight_regions: [Option<(ty::Region<'tcx>, usize)>; 3],
@@ -155,14 +153,6 @@ pub struct RegionHighlightMode<'tcx> {
 }
 
 impl<'tcx> RegionHighlightMode<'tcx> {
-    pub fn new(tcx: TyCtxt<'tcx>) -> Self {
-        Self {
-            tcx,
-            highlight_regions: Default::default(),
-            highlight_bound_region: Default::default(),
-        }
-    }
-
     /// If `region` and `number` are both `Some`, invokes
     /// `highlighting_region`.
     pub fn maybe_highlighting_region(
@@ -188,8 +178,13 @@ impl<'tcx> RegionHighlightMode<'tcx> {
     }
 
     /// Convenience wrapper for `highlighting_region`.
-    pub fn highlighting_region_vid(&mut self, vid: ty::RegionVid, number: usize) {
+    pub fn highlighting_region_vid(
-        self.highlighting_region(ty::Region::new_var(self.tcx, vid), number)
+        &mut self,
+        tcx: TyCtxt<'tcx>,
+        vid: ty::RegionVid,
+        number: usize,
+    ) {
+        self.highlighting_region(ty::Region::new_var(tcx, vid), number)
     }
 
     /// Returns `Some(n)` with the number to use for the given region, if any.
@@ -1778,7 +1773,7 @@ impl<'a, 'tcx> FmtPrinter<'a, 'tcx> {
             printed_type_count: 0,
             type_length_limit,
             truncated: false,
-            region_highlight_mode: RegionHighlightMode::new(tcx),
+            region_highlight_mode: RegionHighlightMode::default(),
             ty_infer_name_resolver: None,
             const_infer_name_resolver: None,
         }))