Revert "Nothing is a special bottom type; it is a subtype of every other type. The Scala compiler loves to infer Nothing as a generic type but that is almost always incorrect. Explicit type arguments should be used instead."

This reverts commit 9622a3f.

Author: halotukozak

analyzer/src/main/scala/com/avsystem/commons/analyzer/AnalyzerPlugin.scala

@@ -56,7 +56,7 @@ final class AnalyzerPlugin(val global: Global) extends Plugin { plugin =>
     new Any2StringAdd(global),
     new ThrowableObjects(global),
     new DiscardedMonixTask(global),
-    new RequireExplicitNothing(global),
+    new ThrownExceptionNotInFunction(global),
     new BadSingletonComponent(global),
     new ConstantDeclarations(global),
     new BasePackage(global),

analyzer/src/main/scala/com/avsystem/commons/analyzer/RequireExplicitNothing.scala

@@ -0,0 +1,14 @@
+package com.avsystem.commons
+package analyzer
+
+import scala.tools.nsc.Global
+
+final class ThrownExceptionNotInFunction(g: Global) extends AnalyzerRule(g, "thrownExceptionNotInFunction") {
+
+  import global.*
+
+  def analyze(unit: CompilationUnit): Unit = unit.body.foreach(analyzeTree {
+    case t@Apply(f: TypeApply, List(Throw(_))) if definitions.isFunctionType(f.tpe.params.head.tpe) =>
+      report(t.pos, "exception thrown in place of function definition")
+  })
+}

analyzer/src/main/scala/com/avsystem/commons/analyzer/ThrownExceptionNotInFunction.scala

@@ -0,0 +1,83 @@
+package com.avsystem.commons
+package analyzer
+
+import org.scalatest.funsuite.AnyFunSuite
+
+final class ThrownExceptionNotInFunctionTest extends AnyFunSuite with AnalyzerTest {
+  settings.pluginOptions.value ++= List("AVSystemAnalyzer:-discardedMonixTask")
+
+  Seq(
+    ("Option[_]", "map"),
+    ("Option[_]", "flatMap"),
+    ("List[_]", "map"),
+    ("Seq[_]", "map"),
+    ("Set[_]", "map"),
+    ("Map[_, _]", "map"),
+    ("scala.concurrent.Future[_]", "map"),
+    ("scala.concurrent.Future[_]", "flatMap"),
+    ("scala.util.Try[_]", "map"),
+    ("Either[_, _]", "map"),
+    ("monix.eval.Task[_]", "map"),
+    ("monix.eval.Task[_]", "flatMap"),
+    ("com.avsystem.commons.misc.Opt[_]", "map"),
+    ("String => Int", "andThen"),
+    ("String => Nothing", "andThen"),
+    ("Nothing => Nothing", "andThen"),
+    ("String => Int", "compose"),
+    ("Seq[_]", "foreach"),
+  ).foreach { case (tpe, function) =>
+    test(s"Testing $function of $tpe") {
+      assertErrors(10,
+        //language=Scala
+        s"""
+           |object whatever {
+           |  implicit val ec: scala.concurrent.ExecutionContext = ??? // for Future
+           |
+           |  def sth: $tpe = ???
+           |  def ex: Exception = ???
+           |
+           |  // errors from these
+           |  sth.$function(throw ex)
+           |
+           |  {
+           |    println(""); sth.$function(throw ex)
+           |  }
+           |
+           |  if (true) sth.$function(throw ex) else sth.$function(throw ex)
+           |
+           |  try sth.$function(throw ex) catch {
+           |    case _: Exception => sth.$function(throw ex)
+           |  } finally sth.$function(throw ex)
+           |
+           |  Seq(1, 2, 3).foreach(_ => sth.$function(throw ex))
+           |
+           |  while (true) sth.$function(throw ex)
+           |
+           |  do sth.$function(throw ex) while (true)
+           |
+           |  // no errors from these
+           |  sth.$function(_ => throw ex)
+           |
+           |  {
+           |    println(""); sth.$function(_ => throw ex)
+           |  }
+           |
+           |  if (true) sth.$function(_ => throw ex) else sth.$function(_ => throw ex)
+           |
+           |  try sth.$function(_ => throw ex) catch {
+           |    case _: Exception => sth.$function(_ => throw ex)
+           |  } finally sth.$function(_ => throw ex)
+           |
+           |  Seq(1, 2, 3).foreach(_ => sth.$function(_ => throw ex))
+           |
+           |  while (true) sth.$function(_ => throw ex)
+           |
+           |  do sth.$function(_ => throw ex) while (true)
+           |}
+           |
+           |""".stripMargin
+      )
+    }
+  }
+}
+