Added tests with redeclaration. The behavior is correct (compilation error), while diagnostic message is not ideal.

jps-plugin/testData/incremental/pureKotlin/classRedeclaration/build.log

@@ -0,0 +1,13 @@
+Compiling files:
+src/class2.kt
+End of files
+Cleaning output files:
+out/production/module/Klass.class
+End of files
+Compiling files:
+src/class1.kt
+src/class2.kt
+End of files
+COMPILATION FAILED
+Kotlin:ERROR:Redeclaration: Klass
+Kotlin:ERROR:Redeclaration: Klass

jps-plugin/testData/incremental/pureKotlin/classRedeclaration/class1.kt

@@ -0,0 +1 @@
+class Klass

jps-plugin/testData/incremental/pureKotlin/classRedeclaration/class2.kt.new

@@ -0,0 +1 @@
+class Klass

jps-plugin/testData/incremental/pureKotlin/conflictingPlatformDeclarations/build.log

@@ -0,0 +1,11 @@
+Cleaning output files:
+out/production/module/test/TestPackage$fun2$*.class
+out/production/module/test/TestPackage.class
+End of files
+Compiling files:
+src/fun2.kt
+End of files
+COMPILATION FAILED
+Kotlin:ERROR:Platform declaration clash: The following declarations have the same JVM signature (function(Ljava/util/List;)V):
+    fun function(list: kotlin.List<kotlin.Any>): kotlin.Unit
+    fun function(list: kotlin.List<kotlin.String>): kotlin.Unit

jps-plugin/testData/incremental/pureKotlin/conflictingPlatformDeclarations/fun1.kt

@@ -0,0 +1,5 @@
+package test
+
+fun function(list: List<Any>) {
+
+}

jps-plugin/testData/incremental/pureKotlin/conflictingPlatformDeclarations/fun2.kt

@@ -0,0 +1,3 @@
+package test
+
+val x = 1

jps-plugin/testData/incremental/pureKotlin/conflictingPlatformDeclarations/fun2.kt.new

@@ -0,0 +1,7 @@
+package test
+
+val x = 1
+
+fun function(list: List<String>) {
+
+}

jps-plugin/testData/incremental/pureKotlin/funRedeclaration/build.log

@@ -0,0 +1,11 @@
+Cleaning output files:
+out/production/module/test/TestPackage$fun2$*.class
+out/production/module/test/TestPackage.class
+End of files
+Compiling files:
+src/fun2.kt
+End of files
+COMPILATION FAILED
+Kotlin:ERROR:Platform declaration clash: The following declarations have the same JVM signature (function()V):
+    fun function(): kotlin.Unit
+    fun function(): kotlin.Unit

jps-plugin/testData/incremental/pureKotlin/funRedeclaration/fun1.kt

@@ -0,0 +1,5 @@
+package test
+
+fun function() {
+
+}

jps-plugin/testData/incremental/pureKotlin/funRedeclaration/fun2.kt

@@ -0,0 +1,3 @@
+package test
+
+val x = 1

jps-plugin/testData/incremental/pureKotlin/funRedeclaration/fun2.kt.new

@@ -0,0 +1,7 @@
+package test
+
+val x = 1
+
+fun function() {
+
+}

jps-plugin/testData/incremental/pureKotlin/propertyRedeclaration/build.log

@@ -0,0 +1,11 @@
+Cleaning output files:
+out/production/module/test/TestPackage$prop2$*.class
+out/production/module/test/TestPackage.class
+End of files
+Compiling files:
+src/prop2.kt
+End of files
+COMPILATION FAILED
+Kotlin:ERROR:Platform declaration clash: The following declarations have the same JVM signature (getProperty()I):
+    fun <get-property>(): kotlin.Int
+    fun <get-property>(): kotlin.Int

jps-plugin/testData/incremental/pureKotlin/propertyRedeclaration/prop1.kt

@@ -0,0 +1,3 @@
+package test
+
+val property = 1

jps-plugin/testData/incremental/pureKotlin/propertyRedeclaration/prop2.kt

@@ -0,0 +1,5 @@
+package test
+
+fun dummy() {
+
+}

jps-plugin/testData/incremental/pureKotlin/propertyRedeclaration/prop2.kt.new

@@ -0,0 +1,7 @@
+package test
+
+fun dummy() {
+
+}
+
+val property = 1