Fix the tcI case where there are left over arguments

typechecker/src/Tc/Gen/Expr.hs

@@ -136,13 +136,15 @@ tcHeadExpr gamma (HVar var)
       Left err | isNamedWC var -> tauToSigma . metaTyVarT <$>
                                   newMetaVarOfKindType
                | otherwise     -> throwError err
+
 -- | Rule: Head-Ann
 tcHeadExpr gamma (HAnn expr ttype) = do
   (_,sigma) <- tcInfer (tcType gamma ttype)
   tcArg gamma expr sigma
   pure sigma
 
--- | Rule: Head-Con and Head-PatSyn
+-- | Rule: Head-Con
+-- | Rule: Head-PatSyn
 tcHeadExpr gamma (HConLike kp) = do
   res <- lookupGammaTc gamma (GKP kp)
   pure (case res of

typechecker/src/Tc/Gen/Inst.hs

@@ -188,9 +188,11 @@ tcI _ (RhoSg rhor) leftovers
        pure (emptySubst, [], [], rhor)
 
   | otherwise
-  = pprPanic "tcI - shouldn't be here" $
-      vsep [pprArgs leftovers
-           ,pretty "rhor:" <+> pprRho rhor]
+  = throwError (ExpectedLessArguments $
+                vsep [pretty "Expected no more arguments:"
+                     ,indent 2 $
+                      vsep [pretty "Instantiated type of application head:" <+> pprRho rhor
+                           ,pretty "Left over arguments:" <+> pprArgs leftovers]])
 
 -- TODO: Rename this note
 {- Note [I-VarD and IVar-M]

typechecker/test/cases/should-fail/constFail-infer.hs

+constFail = const True "blah" 'c'

typechecker/test/cases/should-fail/constFail-infer.output

+[ExpectedLessArguments]
+
+Expected no more arguments:
+  Instantiated type of application head: Bool
+  Left over arguments: [VisArg (TLit LitChar)]
\ No newline at end of file