Disambiguate Repeated Identifiers for data types in error messages

If, in an interactive context, you redefine a type, but then try to use functions for the previous definition, it will (as expected) give you an error message. The following code would trigger this in an interactive context:

data X = Y Int
f (Y i) = i
data X = Y Int | Z String
f (Y 3)

However the error message is not very good:

Couldn't match expected type `:Interactive.X'
            with actual type `:Interactive.X'

This is very uninformative to the user if they do not understand what's going on.

The following GHC API code can replicate this:

  runDeclsWithLocation "Interactive.hs" 1 "data X = Y Int"
  runDeclsWithLocation "Asdf.hs" 2 "f (Y i) = i"
  runDeclsWithLocation "Bloop.hs" 3 "data X = Y Int | Z String"
  runStmtWithLocation  "Test.hs" 4 "f (Y 3)" RunToCompletion

Note that varying the location given to runStmt and runDecls (the string as well as the line number) seems to have no effect upon anything. I started out with just "<interactive>" but varied it to check - no effect on anything as far as I can tell.

How can I make this error message more informative? I would ideally like something like

Couldn't match expected type `:Interactive1.X'
            with actual type `:Interactive5.X'

or really anything that caused these types to be visibly different.

Trac metadata

Trac field	Value
Version	7.6.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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