hdgarrood · Apr 4, 2020 · Mar 13, 2020
diff --git a/CONTRIBUTORS.md b/CONTRIBUTORS.md
@@ -139,6 +139,7 @@ If you would prefer to use different terms, please use the section below instead
 | [@matthew-hilty](https://github.com/matthew-hilty) | Matthew Hilty | [MIT license](http://opensource.org/licenses/MIT) |
 | [@woody88](https://github.com/woody88) | Woodson Delhia | [MIT license](http://opensource.org/licenses/MIT) |
 | [@mhmdanas](https://github.com/mhmdanas) | Mohammed Anas | [MIT license](http://opensource.org/licenses/MIT) |
+| [@kl0tl](https://github.com/kl0tl) | Cyril Sobierajewicz | [MIT license](http://opensource.org/licenses/MIT) |
 
 ### Contributors using Modified Terms
 

diff --git a/src/Language/PureScript/Errors.hs b/src/Language/PureScript/Errors.hs
@@ -63,6 +63,7 @@ data SimpleErrorMessage
   | MissingFFIImplementations ModuleName [Ident]
   | UnusedFFIImplementations ModuleName [Ident]
   | InvalidFFIIdentifier ModuleName Text
+  | DeprecatedFFIPrime ModuleName Text
   | FileIOError Text IOError -- ^ A description of what we were trying to do, and the error which occurred
   | InfiniteType SourceType
   | InfiniteKind SourceType
@@ -221,6 +222,7 @@ errorCode em = case unwrapErrorMessage em of
   MissingFFIImplementations{} -> "MissingFFIImplementations"
   UnusedFFIImplementations{} -> "UnusedFFIImplementations"
   InvalidFFIIdentifier{} -> "InvalidFFIIdentifier"
+  DeprecatedFFIPrime{} -> "DeprecatedFFIPrime"
   FileIOError{} -> "FileIOError"
   InfiniteType{} -> "InfiniteType"
   InfiniteKind{} -> "InfiniteKind"
@@ -669,6 +671,13 @@ prettyPrintSingleError (PPEOptions codeColor full level showDocs relPath) e = fl
                 , line "Note that exported identifiers in FFI modules must be valid PureScript identifiers."
                 ]
             ]
+    renderSimpleErrorMessage (DeprecatedFFIPrime mn ident) =
+      paras [ line $ "In the FFI module for " <> markCode (runModuleName mn) <> ":"
+            , indent . paras $
+                [ line $ "The identifier " <> markCode ident <> " contains a prime (" <> markCode "'" <> ")."
+                , line $ "Primes in identifiers exported from FFI modules are deprecated and won’t be supported in the future."
+                ]
+            ]
     renderSimpleErrorMessage InvalidDoBind =
       line "The last statement in a 'do' block must be an expression, but this block ends with a binder."
     renderSimpleErrorMessage InvalidDoLet =

diff --git a/src/Language/PureScript/Make/Actions.hs b/src/Language/PureScript/Make/Actions.hs
@@ -285,6 +285,11 @@ checkForeignDecls m path = do
   js <- either (errorParsingModule . Bundle.UnableToParseModule) pure $ JS.parse jsStr path
 
   foreignIdentsStrs <- either errorParsingModule pure $ getExps js
+
+  let deprecatedFFI = filter (any (== '\'')) foreignIdentsStrs
+  unless (null deprecatedFFI) $
+    warningDeprecatedForeignPrimes deprecatedFFI
+
   foreignIdents <- either
                      errorInvalidForeignIdentifiers
                      (pure . S.fromList)
@@ -315,6 +320,10 @@ checkForeignDecls m path = do
   errorInvalidForeignIdentifiers =
     throwError . mconcat . map (errorMessage . InvalidFFIIdentifier mname . T.pack)
 
+  warningDeprecatedForeignPrimes :: [String] -> Make ()
+  warningDeprecatedForeignPrimes =
+    tell . mconcat . map (errorMessage' modSS . DeprecatedFFIPrime mname . T.pack)
+
   parseIdents :: [String] -> Either [String] [Ident]
   parseIdents strs =
     case partitionEithers (map parseIdent strs) of

diff --git a/tests/purs/passing/2172.purs b/tests/purs/passing/2172.purs
diff --git a/tests/purs/passing/2172.js → tests/purs/warning/DeprecatedFFIPrime.js b/tests/purs/passing/2172.js → tests/purs/warning/DeprecatedFFIPrime.js
diff --git a/tests/purs/warning/DeprecatedFFIPrime.out b/tests/purs/warning/DeprecatedFFIPrime.out
@@ -0,0 +1,56 @@
+Error 1 of 4:
+
+  at tests/purs/warning/DeprecatedFFIPrime.purs:5:1 - 10:28 (line 5, column 1 - line 10, column 28)
+
+    In the FFI module for [33mMain[0m:
+
+      The identifier [33ma'[0m contains a prime ([33m'[0m).
+      Primes in identifiers exported from FFI modules are deprecated and won’t be supported in the future.
+
+
+
+  See https://github.com/purescript/documentation/blob/master/errors/DeprecatedFFIPrime.md for more information,
+  or to contribute content related to this error.
+
+Error 2 of 4:
+
+  at tests/purs/warning/DeprecatedFFIPrime.purs:5:1 - 10:28 (line 5, column 1 - line 10, column 28)
+
+    In the FFI module for [33mMain[0m:
+
+      The identifier [33mb'[0m contains a prime ([33m'[0m).
+      Primes in identifiers exported from FFI modules are deprecated and won’t be supported in the future.
+
+
+
+  See https://github.com/purescript/documentation/blob/master/errors/DeprecatedFFIPrime.md for more information,
+  or to contribute content related to this error.
+
+Error 3 of 4:
+
+  at tests/purs/warning/DeprecatedFFIPrime.purs:5:1 - 10:28 (line 5, column 1 - line 10, column 28)
+
+    In the FFI module for [33mMain[0m:
+
+      The identifier [33mc'[0m contains a prime ([33m'[0m).
+      Primes in identifiers exported from FFI modules are deprecated and won’t be supported in the future.
+
+
+
+  See https://github.com/purescript/documentation/blob/master/errors/DeprecatedFFIPrime.md for more information,
+  or to contribute content related to this error.
+
+Error 4 of 4:
+
+  at tests/purs/warning/DeprecatedFFIPrime.purs:5:1 - 10:28 (line 5, column 1 - line 10, column 28)
+
+    In the FFI module for [33mMain[0m:
+
+      The identifier [33md'[0m contains a prime ([33m'[0m).
+      Primes in identifiers exported from FFI modules are deprecated and won’t be supported in the future.
+
+
+
+  See https://github.com/purescript/documentation/blob/master/errors/DeprecatedFFIPrime.md for more information,
+  or to contribute content related to this error.
+
diff --git a/tests/purs/warning/DeprecatedFFIPrime.purs b/tests/purs/warning/DeprecatedFFIPrime.purs
@@ -0,0 +1,10 @@
+-- @shouldWarnWith DeprecatedFFIPrime
+-- @shouldWarnWith DeprecatedFFIPrime
+-- @shouldWarnWith DeprecatedFFIPrime
+-- @shouldWarnWith DeprecatedFFIPrime
+module Main where
+
+foreign import a' :: Number
+foreign import b' :: Number
+foreign import c' :: Number
+foreign import d' :: Number