Use associative type defaults in {Layout,FnAbi}OfHelpers.

This avoids some repetitive boilerplate code.

Author: nnethercote

src/common.rs

@@ -309,17 +309,13 @@ pub(crate) struct FunctionCx<'m, 'clif, 'tcx: 'm> {
 }
 
 impl<'tcx> LayoutOfHelpers<'tcx> for FunctionCx<'_, '_, 'tcx> {
-    type LayoutOfResult = TyAndLayout<'tcx>;
-
     #[inline]
     fn handle_layout_err(&self, err: LayoutError<'tcx>, span: Span, ty: Ty<'tcx>) -> ! {
         RevealAllLayoutCx(self.tcx).handle_layout_err(err, span, ty)
     }
 }
 
 impl<'tcx> FnAbiOfHelpers<'tcx> for FunctionCx<'_, '_, 'tcx> {
-    type FnAbiOfResult = &'tcx FnAbi<'tcx, Ty<'tcx>>;
-
     #[inline]
     fn handle_fn_abi_err(
         &self,
@@ -450,8 +446,6 @@ impl<'tcx> FunctionCx<'_, '_, 'tcx> {
 pub(crate) struct RevealAllLayoutCx<'tcx>(pub(crate) TyCtxt<'tcx>);
 
 impl<'tcx> LayoutOfHelpers<'tcx> for RevealAllLayoutCx<'tcx> {
-    type LayoutOfResult = TyAndLayout<'tcx>;
-
     #[inline]
     fn handle_layout_err(&self, err: LayoutError<'tcx>, span: Span, ty: Ty<'tcx>) -> ! {
         if let LayoutError::SizeOverflow(_) | LayoutError::ReferencesError(_) = err {
@@ -466,8 +460,6 @@ impl<'tcx> LayoutOfHelpers<'tcx> for RevealAllLayoutCx<'tcx> {
 }
 
 impl<'tcx> FnAbiOfHelpers<'tcx> for RevealAllLayoutCx<'tcx> {
-    type FnAbiOfResult = &'tcx FnAbi<'tcx, Ty<'tcx>>;
-
     #[inline]
     fn handle_fn_abi_err(
         &self,