symbol files: fixes the logic for multi-methods

compiler/passes.nim

@@ -18,7 +18,7 @@ import
 
 type
   TPassContext* = object of RootObj # the pass's context
-    fromCache*: bool  # true if created by "openCached"
+    rd*: PRodReader  # != nil if created by "openCached"
 
   PPassContext* = ref TPassContext
 
@@ -118,7 +118,7 @@ proc openPassesCached(g: ModuleGraph; a: var TPassContextArray, module: PSym,
     if not isNil(gPasses[i].openCached):
       a[i] = gPasses[i].openCached(g, module, rd)
       if a[i] != nil:
-        a[i].fromCache = true
+        a[i].rd = rd
     else:
       a[i] = nil