convertToDouble refactor and test

Author: Kopilov

core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/convert.kt

@@ -164,11 +164,11 @@ public fun DataColumn<String?>.convertToDouble(locale: Locale? = null): DataColu
         }
     }
 
-    if (locale != null) {
+    return if (locale != null) {
         val explicitParser = Parsers.getDoubleParser(locale)
-        return applyParser(explicitParser)
+        applyParser(explicitParser)
     } else {
-        return try {
+        try {
             val defaultParser = Parsers.getDoubleParser()
             applyParser(defaultParser)
         } catch (e: TypeConversionException) {

core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/convert.kt

@@ -14,6 +14,7 @@ import org.jetbrains.kotlinx.dataframe.exceptions.TypeConverterNotFoundException
 import org.jetbrains.kotlinx.dataframe.hasNulls
 import org.junit.Test
 import java.time.LocalTime
+import java.util.*
 import kotlin.reflect.*
 import kotlin.time.Duration.Companion.hours
 
@@ -85,6 +86,10 @@ class ConvertTests {
             columnOf("1", "10", "a").convertTo<IntClass>()
         }.row shouldBe 2
 
+        shouldThrow<CellConversionException> {
+            columnOf("1", "x", "2.5").convertToDouble()
+        }.row shouldBe 1
+
         shouldThrow<TypeConverterNotFoundException> {
             columnOf(EnumClass.A).convertTo<IntClass>()
         }