Move should_truncate from trait Printer to sub-trait PrettyPrinter.

It's not used in `Printer`.

Author: nnethercote

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

@@ -126,10 +126,6 @@ pub trait Printer<'tcx>: Sized {
         trait_ref: Option<ty::TraitRef<'tcx>>,
     ) -> Result<(), PrintError>;
 
-    fn should_truncate(&mut self) -> bool {
-        false
-    }
-
     // Defaults (should not be overridden):
 
     #[instrument(skip(self), level = "debug")]

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

@@ -333,6 +333,10 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         f: impl FnOnce(&mut Self) -> Result<(), PrintError>,
     ) -> Result<(), PrintError>;
 
+    fn should_truncate(&mut self) -> bool {
+        false
+    }
+
     /// Returns `true` if the region should be printed in
     /// optional positions, e.g., `&'a T` or `dyn Tr + 'b`.
     /// This is typically the case for all non-`'_` regions.
@@ -2295,10 +2299,6 @@ impl<'tcx> Printer<'tcx> for FmtPrinter<'_, 'tcx> {
         }
     }
 
-    fn should_truncate(&mut self) -> bool {
-        !self.type_length_limit.value_within_limit(self.printed_type_count)
-    }
-
     fn print_dyn_existential(
         &mut self,
         predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
@@ -2487,6 +2487,10 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
         Ok(())
     }
 
+    fn should_truncate(&mut self) -> bool {
+        !self.type_length_limit.value_within_limit(self.printed_type_count)
+    }
+
     fn should_print_region(&self, region: ty::Region<'tcx>) -> bool {
         let highlight = self.region_highlight_mode;
         if highlight.region_highlighted(region).is_some() {