Only run analyses when we are going to use their results

Currently, there are various analyses related to deriving various traits that we
unconditionally run. However, if we aren't going to derive those traits in
codegen, then computing whether or not we can derive the traits is wasteful.

Author: fitzgen

src/ir/context.rs

@@ -1790,7 +1790,9 @@ impl<'ctx> BindgenContext<'ctx> {
     /// Compute whether we can derive debug.
     fn compute_cannot_derive_debug(&mut self) {
         assert!(self.cannot_derive_debug.is_none());
-        self.cannot_derive_debug = Some(analyze::<CannotDeriveDebug>(self));
+        if self.options.derive_debug {
+            self.cannot_derive_debug = Some(analyze::<CannotDeriveDebug>(self));
+        }
     }
 
     /// Look up whether the item with `id` can
@@ -1807,7 +1809,9 @@ impl<'ctx> BindgenContext<'ctx> {
     /// Compute whether we can derive default.
     fn compute_cannot_derive_default(&mut self) {
         assert!(self.cannot_derive_default.is_none());
-        self.cannot_derive_default = Some(analyze::<CannotDeriveDefault>(self));
+        if self.options.derive_default {
+            self.cannot_derive_default = Some(analyze::<CannotDeriveDefault>(self));
+        }
     }
 
     /// Look up whether the item with `id` can
@@ -1830,7 +1834,9 @@ impl<'ctx> BindgenContext<'ctx> {
     /// Compute whether we can derive hash.
     fn compute_cannot_derive_hash(&mut self) {
         assert!(self.cannot_derive_hash.is_none());
-        self.cannot_derive_hash = Some(analyze::<CannotDeriveHash>(self));
+        if self.options.derive_hash {
+            self.cannot_derive_hash = Some(analyze::<CannotDeriveHash>(self));
+        }
     }
 
     /// Look up whether the item with `id` can