Actually get the correct ParamEnv in derive_partial_eq_without_eq

tests/ui/derive_partial_eq_without_eq.fixed

@@ -52,7 +52,7 @@ impl PartialEq for ManualPartialEqImpl {
 }
 
 // Generic fields should be properly checked for Eq-ness
-#[derive(PartialEq)]
+#[derive(PartialEq, Eq)]
 pub struct GenericNotEq<T: Eq, U: PartialEq> {
     foo: T,
     bar: U,
@@ -95,7 +95,7 @@ pub enum EnumNotEq {
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub struct RustFixWithOtherDerives;
 
-#[derive(PartialEq)]
+#[derive(PartialEq, Eq)]
 pub struct Generic<T>(T);
 
 #[derive(PartialEq, Eq)]

tests/ui/derive_partial_eq_without_eq.stderr

@@ -6,6 +6,12 @@ LL | #[derive(Debug, PartialEq)]
    |
    = note: `-D clippy::derive-partial-eq-without-eq` implied by `-D warnings`
 
+error: you are deriving `PartialEq` and can implement `Eq`
+  --> $DIR/derive_partial_eq_without_eq.rs:55:10
+   |
+LL | #[derive(PartialEq)]
+   |          ^^^^^^^^^ help: consider deriving `Eq` as well: `PartialEq, Eq`
+
 error: you are deriving `PartialEq` and can implement `Eq`
   --> $DIR/derive_partial_eq_without_eq.rs:61:10
    |
@@ -42,6 +48,12 @@ error: you are deriving `PartialEq` and can implement `Eq`
 LL | #[derive(Debug, PartialEq, Clone)]
    |                 ^^^^^^^^^ help: consider deriving `Eq` as well: `PartialEq, Eq`
 
+error: you are deriving `PartialEq` and can implement `Eq`
+  --> $DIR/derive_partial_eq_without_eq.rs:98:10
+   |
+LL | #[derive(PartialEq)]
+   |          ^^^^^^^^^ help: consider deriving `Eq` as well: `PartialEq, Eq`
+
 error: you are deriving `PartialEq` and can implement `Eq`
   --> $DIR/derive_partial_eq_without_eq.rs:105:14
    |
@@ -54,5 +66,5 @@ error: you are deriving `PartialEq` and can implement `Eq`
 LL |     #[derive(PartialEq)]
    |              ^^^^^^^^^ help: consider deriving `Eq` as well: `PartialEq, Eq`
 
-error: aborting due to 9 previous errors
+error: aborting due to 11 previous errors