Make lookup_impl_method() query transparent

The bulk of the work is trait solving and cached in the trait solver's cache, and this will save memory.

src/tools/rust-analyzer/crates/hir-ty/src/consteval.rs

@@ -5,13 +5,12 @@ mod tests;
 
 use base_db::Crate;
 use hir_def::{
-    EnumVariantId, GeneralConstId,
+    EnumVariantId, GeneralConstId, HasModule, StaticId,
     expr_store::{Body, HygieneId, path::Path},
     hir::{Expr, ExprId},
     resolver::{Resolver, ValueNs},
     type_ref::LiteralConstRef,
 };
-use hir_def::{HasModule, StaticId};
 use hir_expand::Lookup;
 use rustc_type_ir::{UnevaluatedConst, inherent::IntoKind};
 use stdx::never;

src/tools/rust-analyzer/crates/hir-ty/src/db.rs

@@ -96,6 +96,7 @@ pub trait HirDatabase: DefDatabase + std::fmt::Debug {
     ) -> Result<i128, ConstEvalError<'db>>;
 
     #[salsa::invoke(crate::method_resolution::lookup_impl_method_query)]
+    #[salsa::transparent]
     fn lookup_impl_method<'db>(
         &'db self,
         env: Arc<TraitEnvironment<'db>>,