From 5983cfcb48f5827f01e97e2dff077153624ec7bf Mon Sep 17 00:00:00 2001
From: Pavel Fatin <pavel.fatin@jetbrains.com>
Date: Tue, 12 Dec 2017 13:07:09 +0100
Subject: [PATCH] ComparingLengthInspection: skip when n is 0, #SCL-8300,
 #SCL-13116 fixed

---
 .../ComparingLengthInspection.scala           |  9 +++-
 .../codeInspection/collections/package.scala  |  2 +
 .../collections/ComparingLengthTest.scala     | 50 ++++++++++++++++++-
 3 files changed, 58 insertions(+), 3 deletions(-)

diff --git a/scala/scala-impl/src/org/jetbrains/plugins/scala/codeInspection/collections/ComparingLengthInspection.scala b/scala/scala-impl/src/org/jetbrains/plugins/scala/codeInspection/collections/ComparingLengthInspection.scala
index 1cbbb634a30..c1f5a659fb8 100644
--- a/scala/scala-impl/src/org/jetbrains/plugins/scala/codeInspection/collections/ComparingLengthInspection.scala
+++ b/scala/scala-impl/src/org/jetbrains/plugins/scala/codeInspection/collections/ComparingLengthInspection.scala
@@ -2,6 +2,7 @@ package org.jetbrains.plugins.scala.codeInspection.collections
 
 import org.jetbrains.plugins.scala.codeInspection.InspectionBundle
 import org.jetbrains.plugins.scala.codeInspection.collections.ComparingLengthInspection._
+import org.jetbrains.plugins.scala.lang.psi.api.base.ScIntLiteral
 import org.jetbrains.plugins.scala.lang.psi.api.expr.ScExpression
 
 /**
@@ -22,10 +23,14 @@ private object ComparingLengthInspection {
       case q `.sizeOrLength` () `!=` n => (q, "!=", n)
       case q `.sizeOrLength` () `<` n => (q, "<", n)
       case q `.sizeOrLength` () `<=` n => (q, "<=", n)
-    } filter { case (q, op, n) =>
-      isSeq(q) && !isIndexedSeq(q)
+    } filter { case (q, _, n) =>
+      isNonIndexedSeq(q) && !intLiteralValue(n).contains(0)
     } map { case (q, op, n) =>
       replace(e).withText(s"${invocationText(q, "lengthCompare", n)} $op 0").highlightFrom(q)
     }
   }
+
+  private def intLiteralValue(e: ScExpression) = Some(e).collect {
+    case ScIntLiteral(n) => n
+  }
 }
\ No newline at end of file
diff --git a/scala/scala-impl/src/org/jetbrains/plugins/scala/codeInspection/collections/package.scala b/scala/scala-impl/src/org/jetbrains/plugins/scala/codeInspection/collections/package.scala
index 09112439726..42c7fe84053 100644
--- a/scala/scala-impl/src/org/jetbrains/plugins/scala/codeInspection/collections/package.scala
+++ b/scala/scala-impl/src/org/jetbrains/plugins/scala/codeInspection/collections/package.scala
@@ -394,6 +394,8 @@ package object collections {
 
   def isIndexedSeq(expr: ScExpression): Boolean = isExpressionOfType("scala.collection.IndexedSeqLike", expr)
 
+  def isNonIndexedSeq(expr: ScExpression): Boolean = isSeq(expr) && !isIndexedSeq(expr)
+
   def isMap(expr: ScExpression): Boolean = isExpressionOfType("scala.collection.GenMapLike", expr)
 
   def isSortedSet(expr: ScExpression): Boolean = isExpressionOfType("scala.collection.SortedSetLike", expr)
diff --git a/scala/scala-impl/test/org/jetbrains/plugins/scala/codeInspection/collections/ComparingLengthTest.scala b/scala/scala-impl/test/org/jetbrains/plugins/scala/codeInspection/collections/ComparingLengthTest.scala
index 10c8df725bb..c319c94cec1 100644
--- a/scala/scala-impl/test/org/jetbrains/plugins/scala/codeInspection/collections/ComparingLengthTest.scala
+++ b/scala/scala-impl/test/org/jetbrains/plugins/scala/codeInspection/collections/ComparingLengthTest.scala
@@ -64,6 +64,33 @@ class ComparingLengthTest extends OperationsOnCollectionInspectionTest {
     )
   }
 
+  def testLengthIndexedSeq(): Unit = {
+    checkTextHasNoErrors(
+      "Vector(1, 2, 3).length == 2"
+    )
+  }
+
+  def testLengthZero(): Unit = {
+    checkTextHasNoErrors(
+      "Seq(1, 2, 3).length == 0"
+    )
+    checkTextHasNoErrors(
+      "Seq(1, 2, 3).length != 0"
+    )
+    checkTextHasNoErrors(
+      "Seq(1, 2, 3).length > 0"
+    )
+    checkTextHasNoErrors(
+      "Seq(1, 2, 3).length => 0"
+    )
+    checkTextHasNoErrors(
+      "Seq(1, 2, 3).length < 0"
+    )
+    checkTextHasNoErrors(
+      "Seq(1, 2, 3).length <= 0"
+    )
+  }
+
   def testSizeEqual(): Unit = {
     doTest(
       s"Seq(1, 2, 3).${START}size == 2$END",
@@ -112,7 +139,28 @@ class ComparingLengthTest extends OperationsOnCollectionInspectionTest {
     )
   }
 
-  def testIndexedSeq(): Unit = {
+  def testSizeZero(): Unit = {
+    checkTextHasNoErrors(
+      "Seq(1, 2, 3).size == 0"
+    )
+    checkTextHasNoErrors(
+      "Seq(1, 2, 3).size != 0"
+    )
+    checkTextHasNoErrors(
+      "Seq(1, 2, 3).size > 0"
+    )
+    checkTextHasNoErrors(
+      "Seq(1, 2, 3).size => 0"
+    )
+    checkTextHasNoErrors(
+      "Seq(1, 2, 3).size < 0"
+    )
+    checkTextHasNoErrors(
+      "Seq(1, 2, 3).size <= 0"
+    )
+  }
+
+  def testSizeIndexedSeq(): Unit = {
     checkTextHasNoErrors(
       "Vector(1, 2, 3).size == 2"
     )