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

This avoids some repetitive boilerplate code.

Author: nnethercote

src/builder.rs

@@ -23,7 +23,6 @@ use rustc_middle::bug;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
 use rustc_middle::ty::layout::{
     FnAbiError, FnAbiOfHelpers, FnAbiRequest, HasParamEnv, HasTyCtxt, LayoutError, LayoutOfHelpers,
-    TyAndLayout,
 };
 use rustc_middle::ty::{Instance, ParamEnv, Ty, TyCtxt};
 use rustc_span::def_id::DefId;
@@ -473,17 +472,13 @@ impl HasDataLayout for Builder<'_, '_, '_> {
 }
 
 impl<'tcx> LayoutOfHelpers<'tcx> for Builder<'_, '_, 'tcx> {
-    type LayoutOfResult = TyAndLayout<'tcx>;
-
     #[inline]
     fn handle_layout_err(&self, err: LayoutError<'tcx>, span: Span, ty: Ty<'tcx>) -> ! {
         self.cx.handle_layout_err(err, span, ty)
     }
 }
 
 impl<'tcx> FnAbiOfHelpers<'tcx> for Builder<'_, '_, 'tcx> {
-    type FnAbiOfResult = &'tcx FnAbi<'tcx, Ty<'tcx>>;
-
     #[inline]
     fn handle_fn_abi_err(
         &self,

src/context.rs

@@ -12,13 +12,12 @@ use rustc_middle::mir::mono::CodegenUnit;
 use rustc_middle::span_bug;
 use rustc_middle::ty::layout::{
     FnAbiError, FnAbiOf, FnAbiOfHelpers, FnAbiRequest, HasParamEnv, HasTyCtxt, LayoutError,
-    LayoutOfHelpers, TyAndLayout,
+    LayoutOfHelpers,
 };
 use rustc_middle::ty::{self, Instance, ParamEnv, PolyExistentialTraitRef, Ty, TyCtxt};
 use rustc_session::Session;
 use rustc_span::source_map::respan;
 use rustc_span::{Span, DUMMY_SP};
-use rustc_target::abi::call::FnAbi;
 use rustc_target::abi::{HasDataLayout, PointeeInfo, Size, TargetDataLayout, VariantIdx};
 use rustc_target::spec::{HasTargetSpec, HasWasmCAbiOpt, Target, TlsModel, WasmCAbi};
 
@@ -572,8 +571,6 @@ impl<'gcc, 'tcx> HasWasmCAbiOpt for CodegenCx<'gcc, 'tcx> {
 }
 
 impl<'gcc, 'tcx> LayoutOfHelpers<'tcx> for CodegenCx<'gcc, '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 {
@@ -585,8 +582,6 @@ impl<'gcc, 'tcx> LayoutOfHelpers<'tcx> for CodegenCx<'gcc, 'tcx> {
 }
 
 impl<'gcc, 'tcx> FnAbiOfHelpers<'tcx> for CodegenCx<'gcc, 'tcx> {
-    type FnAbiOfResult = &'tcx FnAbi<'tcx, Ty<'tcx>>;
-
     #[inline]
     fn handle_fn_abi_err(
         &self,