"-main-is" flag is broken for recent ghc-head

Here is a minimal reproduction:

Main.hs:

main :: IO ()
main = putStrLn "Main"

Main2.hs:

module Main2 where

import Main

main2 :: IO ()
main2 = do
  putStrLn "Main2"
  main

Run ghc with something like /home/terrorjack/.stack/programs/x86_64-linux/ghc-8.7.20181003/bin/ghc -main-is Main2.main2 Main.hs Main2.hs, and it reports the following error:

[1 of 2] Compiling Main             ( Main.hs, Main.o )

Main.hs:1:1: error:
    Not in scope: ‘main2’
    Perhaps you meant ‘main’ (line 2)
  |
1 | main :: IO ()
  | ^

Meanwhile, the exact same flags work for ghc-8.6.1, and also a previous ghc-head build on d90946ce, so some accidental breakage might be in a recent commit.

Trac metadata

Trac field	Value
Version	8.6.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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