Revert "Deduplicate template parameter creation"

This reverts commit 6adc2c1.

(cherry picked from commit 38f7060)

Author: petrochenkov

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -1314,31 +1314,21 @@ fn build_generic_type_param_di_nodes<'ll, 'tcx>(
     ty: Ty<'tcx>,
 ) -> SmallVec<Option<&'ll DIType>> {
     if let ty::Adt(def, args) = *ty.kind() {
-        let generics = cx.tcx.generics_of(def.did());
-        return get_template_parameters(cx, generics, args);
-    }
-
-    return smallvec![];
-}
-
-pub(super) fn get_template_parameters<'ll, 'tcx>(
-    cx: &CodegenCx<'ll, 'tcx>,
-    generics: &ty::Generics,
-    args: ty::GenericArgsRef<'tcx>,
-) -> SmallVec<Option<&'ll DIType>> {
-    if args.types().next().is_some() {
-        let names = get_parameter_names(cx, generics);
-        let template_params: SmallVec<_> = iter::zip(args, names)
-            .filter_map(|(kind, name)| {
-                kind.as_type().map(|ty| {
-                    let actual_type = cx.tcx.normalize_erasing_regions(cx.typing_env(), ty);
-                    let actual_type_di_node = type_di_node(cx, actual_type);
-                    Some(cx.create_template_type_parameter(name.as_str(), actual_type_di_node))
+        if args.types().next().is_some() {
+            let generics = cx.tcx.generics_of(def.did());
+            let names = get_parameter_names(cx, generics);
+            let template_params: SmallVec<_> = iter::zip(args, names)
+                .filter_map(|(kind, name)| {
+                    kind.as_type().map(|ty| {
+                        let actual_type = cx.tcx.normalize_erasing_regions(cx.typing_env(), ty);
+                        let actual_type_di_node = type_di_node(cx, actual_type);
+                        Some(cx.create_template_type_parameter(name.as_str(), actual_type_di_node))
+                    })
                 })
-            })
-            .collect();
+                .collect();
 
-        return template_params;
+            return template_params;
+        }
     }
 
     return smallvec![];

compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs

@@ -363,7 +363,6 @@ fn build_coroutine_variant_struct_type_di_node<'ll, 'tcx>(
 
             state_specific_fields.into_iter().chain(common_fields).collect()
         },
-        // FIXME: this is a no-op. `build_generic_type_param_di_nodes` only works for Adts.
         |cx| build_generic_type_param_di_nodes(cx, coroutine_type_and_layout.ty),
     )
     .di_node

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -2,8 +2,8 @@
 
 use std::cell::{OnceCell, RefCell};
 use std::ops::Range;
-use std::ptr;
 use std::sync::Arc;
+use std::{iter, ptr};
 
 use libc::c_uint;
 use metadata::create_subroutine_type;
@@ -486,10 +486,40 @@ impl<'ll, 'tcx> DebugInfoCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             generics: &ty::Generics,
             args: GenericArgsRef<'tcx>,
         ) -> &'ll DIArray {
-            let template_params = metadata::get_template_parameters(cx, generics, args);
+            if args.types().next().is_none() {
+                return create_DIArray(DIB(cx), &[]);
+            }
+
+            // Again, only create type information if full debuginfo is enabled
+            let template_params: Vec<_> = if cx.sess().opts.debuginfo == DebugInfo::Full {
+                let names = get_parameter_names(cx, generics);
+                iter::zip(args, names)
+                    .filter_map(|(kind, name)| {
+                        kind.as_type().map(|ty| {
+                            let actual_type = cx.tcx.normalize_erasing_regions(cx.typing_env(), ty);
+                            let actual_type_metadata = type_di_node(cx, actual_type);
+                            Some(cx.create_template_type_parameter(
+                                name.as_str(),
+                                actual_type_metadata,
+                            ))
+                        })
+                    })
+                    .collect()
+            } else {
+                vec![]
+            };
+
             create_DIArray(DIB(cx), &template_params)
         }
 
+        fn get_parameter_names(cx: &CodegenCx<'_, '_>, generics: &ty::Generics) -> Vec<Symbol> {
+            let mut names = generics.parent.map_or_else(Vec::new, |def_id| {
+                get_parameter_names(cx, cx.tcx.generics_of(def_id))
+            });
+            names.extend(generics.own_params.iter().map(|param| param.name));
+            names
+        }
+
         /// Returns a scope, plus `true` if that's a type scope for "class" methods,
         /// otherwise `false` for plain namespace scopes.
         fn get_containing_scope<'ll, 'tcx>(