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Given the sources:

-- A.hs --------------------
module A
--  {-# DEPRECATED "bad" #-}
    where
a = 1

-- B.hs --------------------
module B where
import A

I get the interactions:

$ ghc B
[1 of 2] Compiling A                ( A.hs, A.o )
[2 of 2] Compiling B                ( B.hs, B.o )

$ manually edit A.hs to uncomment the deprecated line

$ ghc B
[1 of 2] Compiling A                ( A.hs, A.o )

$ touch B.hs

$ ghc B
[2 of 2] Compiling B                ( B.hs, B.o )

B.hs:2:1: warning: [-Wdeprecations] Module `A' is deprecated: bad
  |
2 | import A
  | ^^^^^^^^

Observe that after editing the deprecated pragma in A.hs GHC didn't recompile B.hs, meaning that the warning only appeared after I touch'd B.hs. Turning on -Werror turns the problem from one of incorrectly missing warnings to one of incorrect compilation results.

I was also got the same results when adding a deprecated pragma to an individual function.

My guess is whatever .hi hash you take for recompilation checking should include deprecated pragmas.

Trac metadata

Trac field	Value
Version	8.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	ndmitchell@gmail.com
Operating system
Architecture