Rollup merge of #69968 - eddyb:tupled-closure-captures, r=nikomatsakis

rustc: keep upvars tupled in {Closure,Generator}Substs.

Previously, each closure/generator capture's (aka "upvar") type was tracked as one "synthetic" type parameter in the closure/generator substs, and figuring out where the parent `fn`'s generics end and the synthetics start involved slicing at `tcx.generics_of(def_id).parent_count`.

Needing to query `generics_of` limited @davidtwco (who wants to compute some `TypeFlags` differently for parent generics vs upvars, and `TyCtxt` is not available there), which is how I got started on this, but it's also possible that the `generics_of` queries are slowing down `{Closure,Generator}Substs` methods.

To give an example, for a `foo::<T, U>::{closure#0}` with captures `x: X` and `y: Y`, substs are:
* before this PR: `[T, U, /*kind*/, /*signature*/, X, Y]`
* after this PR: `[T, U, /*kind*/, /*signature*/, (X, Y)]`

You can see that, with this PR, no matter how many captures, the last 3 entries in the substs (or 5 for a generator) are always the "synthetic" ones, with the last one being the tuple of capture types.

r? @nikomatsakis cc @Zoxc

1 files changed, 2 insertions, 2 deletions

diff --git a/src/librustc_codegen_llvm/debuginfo/metadata.rs b/src/librustc_codegen_llvm/debuginfo/metadata.rs
index c867d8cf3c4..d7a0acb1339 100644
--- a/src/librustc_codegen_llvm/debuginfo/metadata.rs
+++ b/src/librustc_codegen_llvm/debuginfo/metadata.rs
@@ -663,7 +663,7 @@ pub fn type_metadata(cx: &CodegenCx<'ll, 'tcx>, t: Ty<'tcx>, usage_site_span: Sp
             MetadataCreationResult::new(pointer_type_metadata(cx, t, fn_metadata), false)
         }
         ty::Closure(def_id, substs) => {
-            let upvar_tys: Vec<_> = substs.as_closure().upvar_tys(def_id, cx.tcx).collect();
+            let upvar_tys: Vec<_> = substs.as_closure().upvar_tys().collect();
             let containing_scope = get_namespace_for_item(cx, def_id);
             prepare_tuple_metadata(
                 cx,
@@ -678,7 +678,7 @@ pub fn type_metadata(cx: &CodegenCx<'ll, 'tcx>, t: Ty<'tcx>, usage_site_span: Sp
         ty::Generator(def_id, substs, _) => {
             let upvar_tys: Vec<_> = substs
                 .as_generator()
-                .prefix_tys(def_id, cx.tcx)
+                .prefix_tys()
                 .map(|t| cx.tcx.normalize_erasing_regions(ParamEnv::reveal_all(), t))
                 .collect();
             prepare_enum_metadata(cx, t, def_id, unique_type_id, usage_site_span, upvar_tys)