Move early needs_subst bailout to _after_ linting.

This ensures we get still get lints for generic contexts.

src/librustc_mir/transform/const_prop.rs

@@ -578,11 +578,6 @@ fn const_prop(
             return None;
         }
 
-        // FIXME we need to revisit this for #67176
-        if rvalue.needs_subst() {
-            return None;
-        }
-
         // Perform any special handling for specific Rvalue types.
         // Generally, checks here fall into one of two categories:
         //   1. Additional checking to provide useful lints to the user
@@ -623,6 +618,11 @@ fn const_prop(
             _ => {}
         }
 
+        // FIXME we need to revisit this for #67176
+        if rvalue.needs_subst() {
+            return None;
+        }
+
         self.use_ecx(|this| {
             trace!("calling eval_rvalue_into_place(rvalue = {:?}, place = {:?})", rvalue, place);
             this.ecx.eval_rvalue_into_place(rvalue, place)?;