cs & schemify: repair bad cross-module copy propagation

Closes #2732

pkgs/racket-test-core/tests/racket/module.rktl

@@ -2970,6 +2970,27 @@ case of module-leve bindings; it doesn't cover local bindings.
           (read i)))
   (test #t dynamic-require ''check-with-inlining-duplicates-by-using-submodules 'check))
 
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Check copy propagation across module boundaries
+
+(module defines-also-something-as-alias-for-something racket/base
+
+  (provide also-something)
+
+  (define something (list 1 2 3))
+  (define also-something something))
+
+
+(module uses-also-something-via-local-alias racket/base
+  (require 'defines-also-something-as-alias-for-something)
+
+  (provide v)
+
+  (define copy also-something)
+  (define v (list copy)))
+
+(test '((1 2 3)) dynamic-require ''uses-also-something-via-local-alias 'v)
+
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (report-errs)

racket/src/schemify/infer-known.rkt

@@ -59,7 +59,10 @@
                [(or (known-procedure/can-inline? known)
                     (known-literal? known))
                 known]
-               [(not defn)
+               [(or (not defn)
+                    ;; can't just return `known`; like `known-procedure/can-inline/need-imports`,
+                    ;; we'd lose track of the need to potentially propagate imports
+                    (known-copy? known))
                 (known-copy rhs)]
                [else known]))]
        [defn a-known-constant]