restore NoSpecialType error

Reviewed By: VLanvin, thepulkitagarwal

Differential Revision: D60451900

fbshipit-source-id: 006b381094ce4f554263d7c390fd371e668aa1a8

Author: ilya-klyuchnikov

eqwalizer/src/main/scala/com/whatsapp/eqwalizer/tc/ElabApplyOverloaded.scala

@@ -10,6 +10,7 @@ import com.whatsapp.eqwalizer.ast.Exprs.Expr
 import com.whatsapp.eqwalizer.ast.Forms.OverloadedFunSpec
 import com.whatsapp.eqwalizer.ast.RemoteId
 import com.whatsapp.eqwalizer.ast.Types.{DynamicType, FunType, NoneType, Type}
+import com.whatsapp.eqwalizer.tc.TcDiagnostics.NoSpecialType
 
 class ElabApplyOverloaded(pipelineContext: PipelineContext) {
   private lazy val check = pipelineCtx.check
@@ -18,6 +19,7 @@ class ElabApplyOverloaded(pipelineContext: PipelineContext) {
   private lazy val subtype = pipelineContext.subtype
   private val elabApply = pipelineContext.elabApply
   private val narrow = pipelineContext.narrow
+  private lazy val diagnosticsInfo = pipelineContext.diagnosticsInfo
   private implicit val pipelineCtx: PipelineContext = pipelineContext
 
   def elabOverloaded(expr: Expr, remoteId: RemoteId, args: List[Expr], env: Env): (Type, Env) = {
@@ -28,6 +30,8 @@ class ElabApplyOverloaded(pipelineContext: PipelineContext) {
         val resTy = elabApply.elabApply(check.freshen(ft), args, argTys, env1)
         (resTy, env1)
       case _ =>
+        if (pipelineCtx.overloadedSpecDynamicResult)
+          diagnosticsInfo.add(NoSpecialType(expr.pos, expr, argTys))
         (DynamicType, env1)
     }
   }

eqwalizer/src/main/scala/com/whatsapp/eqwalizer/tc/TcDiagnostics.scala

@@ -37,6 +37,13 @@ object TcDiagnostics {
     def errorName = "expected_fun_type"
     override def erroneousExpr: Option[Expr] = Some(expr)
   }
+  case class NoSpecialType(pos: Pos, expr: Expr, argTys: List[Type])(implicit val pipelineContext: PipelineContext)
+      extends TypeError {
+    private val argTysString = argTys.map(show).mkString(", ")
+    override val msg: String = s"Not enough info to branch. Arg types: $argTysString"
+    def errorName = "not_enough_info_to_branch"
+    override def erroneousExpr: Option[Expr] = Some(expr)
+  }
   case class LambdaArityMismatch(pos: Pos, expr: Expr, lambdaArity: Int, argsArity: Int) extends TypeError {
     override val msg: String = s"fun with arity $lambdaArity used as fun with $argsArity arguments"
     def errorName = "fun_arity_mismatch"