move canonicalize_param_env into sub-fn

Author: lcnr

compiler/rustc_next_trait_solver/src/canonicalizer.rs

@@ -86,20 +86,11 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
         Canonical { max_universe, variables, value }
     }
 
-    /// When canonicalizing query inputs, we keep `'static` in the `param_env`
-    /// but erase it everywhere else. We generally don't want to depend on region
-    /// identity, so while it should not matter whether `'static` is kept in the
-    /// value or opaque type storage as well, this prevents us from accidentally
-    /// relying on it in the future.
-    ///
-    /// We want to keep the option of canonicalizing `'static` to an existential
-    /// variable in the future by changing the way we detect global where-bounds.
-    pub fn canonicalize_input<P: TypeFoldable<I>>(
+    fn canonicalize_param_env(
         delegate: &'a D,
         variables: &'a mut Vec<I::GenericArg>,
-        input: QueryInput<I, P>,
-    ) -> ty::Canonical<I, QueryInput<I, P>> {
-        // First canonicalize the `param_env` while keeping `'static`
+        param_env: I::ParamEnv,
+    ) -> (I::ParamEnv, HashMap<I::GenericArg, usize>, Vec<CanonicalVarKind<I>>) {
         let mut env_canonicalizer = Canonicalizer {
             delegate,
             canonicalize_mode: CanonicalizeMode::Input { keep_static: true },
@@ -111,19 +102,36 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
 
             cache: Default::default(),
         };
-        let param_env = input.goal.param_env.fold_with(&mut env_canonicalizer);
+        let param_env = param_env.fold_with(&mut env_canonicalizer);
         debug_assert_eq!(env_canonicalizer.binder_index, ty::INNERMOST);
+        (param_env, env_canonicalizer.variable_lookup_table, env_canonicalizer.var_kinds)
+    }
+
+    /// When canonicalizing query inputs, we keep `'static` in the `param_env`
+    /// but erase it everywhere else. We generally don't want to depend on region
+    /// identity, so while it should not matter whether `'static` is kept in the
+    /// value or opaque type storage as well, this prevents us from accidentally
+    /// relying on it in the future.
+    ///
+    /// We want to keep the option of canonicalizing `'static` to an existential
+    /// variable in the future by changing the way we detect global where-bounds.
+    pub fn canonicalize_input<P: TypeFoldable<I>>(
+        delegate: &'a D,
+        variables: &'a mut Vec<I::GenericArg>,
+        input: QueryInput<I, P>,
+    ) -> ty::Canonical<I, QueryInput<I, P>> {
+        // First canonicalize the `param_env` while keeping `'static`
+        let (param_env, variable_lookup_table, var_kinds) =
+            Canonicalizer::canonicalize_param_env(delegate, variables, input.goal.param_env);
         // Then canonicalize the rest of the input without keeping `'static`
         // while *mostly* reusing the canonicalizer from above.
         let mut rest_canonicalizer = Canonicalizer {
             delegate,
             canonicalize_mode: CanonicalizeMode::Input { keep_static: false },
 
-            variables: env_canonicalizer.variables,
-            // We're able to reuse the `variable_lookup_table` as whether or not
-            // it already contains an entry for `'static` does not matter.
-            variable_lookup_table: env_canonicalizer.variable_lookup_table,
-            var_kinds: env_canonicalizer.var_kinds,
+            variables,
+            variable_lookup_table,
+            var_kinds,
             binder_index: ty::INNERMOST,
 
             // We do not reuse the cache as it may contain entries whose canonicalized