enhance CatchThrowable rule to reject catching Throwable with pattern matching and add corresponding tests

Author: halotukozak

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

@@ -25,10 +25,15 @@ class CatchThrowable(g: Global) extends AnalyzerRule(g, "catchThrowable", Level.
   def analyze(unit: CompilationUnit): Unit =
     unit.body.foreach {
       case t: Try =>
-        t.catches.foreach { case cas@CaseDef(pat, _, _) =>
-          if (pat.tpe != null && pat.tpe =:= throwableTpe && !isNonFatalPattern(pat)) {
-            report(cas.pos, "Catching Throwable is discouraged, catch specific exceptions instead")
-          }
+        t.catches.foreach {
+          case cas@CaseDef(Alternative(trees), _, _) =>
+            if (trees.exists(_.tpe =:= throwableTpe)) {
+              report(cas.pos, "Catching Throwable is discouraged, catch specific exceptions instead")
+            }
+          case cas@CaseDef(pat, _, _) =>
+            if (pat.tpe != null && pat.tpe =:= throwableTpe && !isNonFatalPattern(pat)) {
+              report(cas.pos, "Catching Throwable is discouraged, catch specific exceptions instead")
+            }
         }
       case _ =>
     }

analyzer/src/test/scala/com/avsystem/commons/analyzer/CatchThrowableTest.scala

@@ -89,4 +89,36 @@ class CatchThrowableTest extends AnyFunSuite with AnalyzerTest {
         |}
       """.stripMargin)
   }
+
+  test("catching non-Throwable with pattern match should be allowed") {
+    assertNoErrors(
+      //language=Scala
+      """
+        |object Test {
+        |  def test(): Unit = {
+        |    try {
+        |      println("test")
+        |    } catch {
+        |      case _: IndexOutOfBoundsException | _: NullPointerException => println("OK!")
+        |    }
+        |  }
+        |}
+      """.stripMargin)
+  }
+
+  test("catching Throwable with pattern match should be rejected") {
+    assertErrors(1,
+      //language=Scala
+      """
+        |object Test {
+        |  def test(): Unit = {
+        |    try {
+        |      println("test")
+        |    } catch {
+        |      case _: IndexOutOfBoundsException | _: Throwable => println("Not OK!")
+        |    }
+        |  }
+        |}
+      """.stripMargin)
+  }
 }