rustc: support overriding type printing in ty::print::Printer.

Author: eddyb

src/librustc/infer/error_reporting/mod.rs

@@ -458,6 +458,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
             type Path = Vec<String>;
             type Region = !;
+            type Type = !;
 
             fn print_region(
                 self: PrintCx<'_, '_, '_, Self>,
@@ -466,6 +467,13 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 Err(NonTrivialPath)
             }
 
+            fn print_type<'tcx>(
+                self: PrintCx<'_, '_, 'tcx, Self>,
+                _ty: Ty<'tcx>,
+            ) -> Result<Self::Type, Self::Error> {
+                Err(NonTrivialPath)
+            }
+
             fn path_crate(
                 self: PrintCx<'_, '_, '_, Self>,
                 cnum: CrateNum,

src/librustc/ty/print.rs

@@ -252,6 +252,7 @@ pub trait Printer: Sized {
 
     type Path;
     type Region;
+    type Type;
 
     fn print_def_path(
         self: PrintCx<'_, '_, 'tcx, Self>,
@@ -278,6 +279,11 @@ pub trait Printer: Sized {
         region: ty::Region<'_>,
     ) -> Result<Self::Region, Self::Error>;
 
+    fn print_type(
+        self: PrintCx<'_, '_, 'tcx, Self>,
+        ty: Ty<'tcx>,
+    ) -> Result<Self::Type, Self::Error>;
+
     fn path_crate(
         self: PrintCx<'_, '_, '_, Self>,
         cnum: CrateNum,
@@ -317,7 +323,15 @@ pub trait Printer: Sized {
 }
 
 /// Trait for printers that pretty-print using `fmt::Write` to the printer.
-pub trait PrettyPrinter: Printer<Error = fmt::Error, Path = Self, Region = Self> + fmt::Write {
+pub trait PrettyPrinter:
+    Printer<
+        Error = fmt::Error,
+        Path = Self,
+        Region = Self,
+        Type = Self,
+    > +
+    fmt::Write
+{
     /// Enter a nested print context, for pretty-printing
     /// nested components in some larger context.
     fn nest<'a, 'gcx, 'tcx, E>(
@@ -870,8 +884,8 @@ impl<'gcx, 'tcx, P: PrettyPrinter> PrintCx<'_, 'gcx, 'tcx, P> {
                     nest!(self, |cx| ty.print_display(cx));
                 }
                 UnpackedKind::Const(ct) => {
-                    start_or_continue(self, start, ", ")?;
-                    ct.print_display(self)?;
+                    start_or_continue(&mut self, start, ", ")?;
+                    nest!(self, |cx| ct.print_display(cx));
                 }
             }
         }
@@ -901,6 +915,7 @@ impl<F: fmt::Write> Printer for FmtPrinter<F> {
 
     type Path = Self;
     type Region = Self;
+    type Type = Self;
 
     fn print_def_path(
         mut self: PrintCx<'_, '_, 'tcx, Self>,
@@ -1031,6 +1046,13 @@ impl<F: fmt::Write> Printer for FmtPrinter<F> {
         Ok(self.printer)
     }
 
+    fn print_type(
+        self: PrintCx<'_, '_, 'tcx, Self>,
+        ty: Ty<'tcx>,
+    ) -> Result<Self::Type, Self::Error> {
+        self.pretty_print_type(ty)
+    }
+
     fn path_crate(
         mut self: PrintCx<'_, '_, '_, Self>,
         cnum: CrateNum,