Merge pull request #93 from inariksit/notYet-errormsg

Fix #92 (inappropriate error message)

.github/workflows/build-all-versions.yml

@@ -33,7 +33,7 @@ jobs:
     - uses: actions/checkout@v2
       if: github.event.action == 'opened' || github.event.action == 'synchronize' || github.event.ref == 'refs/heads/master'
 
-    - uses: actions/setup-haskell@v1.1.1
+    - uses: actions/setup-haskell@v1.1.4
       id: setup-haskell-cabal
       name: Setup Haskell
       with:
@@ -73,7 +73,7 @@ jobs:
     - uses: actions/checkout@v2
       if: github.event.action == 'opened' || github.event.action == 'synchronize' || github.event.ref == 'refs/heads/master'
 
-    - uses: actions/setup-haskell@v1.1
+    - uses: actions/setup-haskell@v1.1.4
       name: Setup Haskell Stack
       with:
         # ghc-version: ${{ matrix.ghc }}

src/compiler/GF/Compile/GeneratePMCFG.hs

@@ -622,7 +622,9 @@ ppbug msg = error completeMsg
  where
   originalMsg = render $ hang "Internal error in GeneratePMCFG:" 4 msg
   completeMsg =
-    unlines [originalMsg
+    case render msg of -- the error message for pattern matching a runtime string
+      "descend (CStr 0,CNil,CProj (LIdent (Id {rawId2utf8 = \"s\"})) CNil)"
+        -> unlines [originalMsg -- add more helpful output
             ,""
             ,"1) Check that you are not trying to pattern match a /runtime string/."
             ,"   These are illegal:"
@@ -633,5 +635,6 @@ ppbug msg = error completeMsg
             ,"2) Not about pattern matching? Submit a bug report and we update the error message."
             ,"     https://github.com/GrammaticalFramework/gf-core/issues"
             ]
+      _ -> originalMsg -- any other message: just print it as is
 
 ppU = ppTerm Unqualified