Capitalize/decapitalize only ASCII characters across project

Use {de,}capitalizeAsciiOnly and to{Lower,Upper}CaseAsciiOnly where
possible, and stdlib's functions with Locale.US everywhere else.

Otherwise, if the default system locale is Turkish, the capital latin
letter "I" is transformed in toLowerCase to "ı" (see
https://github.com/JetBrains/kotlin/blob/66bc142f92085047a1ca64f9a291f0496e33dd98/libraries/stdlib/jvm/test/text/StringJVMTest.kt#L119),
which for example breaks the codegen for `intArrayOf` in
KT-25400/KT-43405.

Similarly, lower case latin letter "i" is transformed to "İ".

 #KT-13631 Fixed
 #KT-25400 Fixed
 #KT-43405 Fixed

build-common/src/org/jetbrains/kotlin/incremental/IncrementalJsCache.kt

@@ -32,6 +32,7 @@ import org.jetbrains.kotlin.name.parentOrNull
 import org.jetbrains.kotlin.serialization.SerializerExtensionProtocol
 import org.jetbrains.kotlin.serialization.deserialization.getClassId
 import org.jetbrains.kotlin.serialization.js.JsSerializerProtocol
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.capitalizeAsciiOnly
 import java.io.DataInput
 import java.io.DataOutput
 import java.io.File
@@ -326,7 +327,7 @@ private class ProtoDataProvider(private val serializerProtocol: SerializerExtens
         proto.`package`.apply {
             val packageNameId = getExtensionOrNull(serializerProtocol.packageFqName)
             val packageFqName = packageNameId?.let { FqName(nameResolver.getPackageFqName(it)) } ?: FqName.ROOT
-            val packagePartClassId = ClassId(packageFqName, Name.identifier(sourceFile.nameWithoutExtension.capitalize() + "Kt"))
+            val packagePartClassId = ClassId(packageFqName, Name.identifier(sourceFile.nameWithoutExtension.capitalizeAsciiOnly() + "Kt"))
             classes[packagePartClassId] = PackagePartProtoData(this, nameResolver, packageFqName)
         }
 
@@ -347,7 +348,7 @@ fun getProtoData(sourceFile: File, metadata: ByteArray): Map<ClassId, ProtoData>
 
     proto.`package`.apply {
         val packageFqName = getExtensionOrNull(JsProtoBuf.packageFqName)?.let(nameResolver::getPackageFqName)?.let(::FqName) ?: FqName.ROOT
-        val packagePartClassId = ClassId(packageFqName, Name.identifier(sourceFile.nameWithoutExtension.capitalize() + "Kt"))
+        val packagePartClassId = ClassId(packageFqName, Name.identifier(sourceFile.nameWithoutExtension.capitalizeAsciiOnly() + "Kt"))
         classes[packagePartClassId] = PackagePartProtoData(this, nameResolver, packageFqName)
     }
 
@@ -412,4 +413,4 @@ private class PackageMetadataMap(storageFile: File) : BasicStringMap<ByteArray>(
     operator fun get(packageName: String) = storage[packageName]
 
     override fun dumpValue(value: ByteArray): String = "Package metadata: ${value.md5()}"
-}
+}

compiler/backend/src/org/jetbrains/kotlin/codegen/intrinsics/IntrinsicMethods.java

@@ -17,11 +17,10 @@
 package org.jetbrains.kotlin.codegen.intrinsics;
 
 import com.google.common.collect.ImmutableList;
-import kotlin.text.StringsKt;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
-import org.jetbrains.kotlin.builtins.StandardNames;
 import org.jetbrains.kotlin.builtins.PrimitiveType;
+import org.jetbrains.kotlin.builtins.StandardNames;
 import org.jetbrains.kotlin.codegen.AsmUtil;
 import org.jetbrains.kotlin.config.JvmTarget;
 import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor;
@@ -30,6 +29,7 @@ import org.jetbrains.kotlin.name.FqNameUnsafe;
 import org.jetbrains.kotlin.name.Name;
 import org.jetbrains.kotlin.resolve.jvm.JvmPrimitiveType;
 import org.jetbrains.kotlin.types.expressions.OperatorConventions;
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.CapitalizeDecapitalizeKt;
 import org.jetbrains.org.objectweb.asm.Type;
 
 import static org.jetbrains.kotlin.builtins.StandardNames.*;
@@ -122,7 +122,9 @@ public class IntrinsicMethods {
             declareIntrinsicFunction(typeFqName, "toString", 0, TO_STRING);
 
             intrinsicsMap.registerIntrinsic(
-                    BUILT_INS_PACKAGE_FQ_NAME, null, StringsKt.decapitalize(type.getArrayTypeName().asString()) + "Of", 1, new ArrayOf()
+                    BUILT_INS_PACKAGE_FQ_NAME, null,
+                    CapitalizeDecapitalizeKt.decapitalizeAsciiOnly(type.getArrayTypeName().asString()) + "Of",
+                    1, new ArrayOf()
             );
         }
 

compiler/cli/src/org/jetbrains/kotlin/cli/common/messages/PlainTextMessageRenderer.java

@@ -23,6 +23,7 @@ import org.fusesource.jansi.Ansi;
 import org.fusesource.jansi.internal.CLibrary;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.CapitalizeDecapitalizeKt;
 
 import java.util.EnumSet;
 import java.util.Set;
@@ -130,7 +131,7 @@ public abstract class PlainTextMessageRenderer implements MessageRenderer {
             return message;
         }
 
-        return StringsKt.decapitalize(message);
+        return CapitalizeDecapitalizeKt.decapitalizeAsciiOnly(message);
     }
 
     @NotNull

compiler/compiler-runner/src/org/jetbrains/kotlin/compilerRunner/CompilerOutputParser.kt

@@ -30,6 +30,7 @@ import org.xml.sax.SAXException
 import org.xml.sax.helpers.DefaultHandler
 import java.io.IOException
 import java.io.Reader
+import java.util.*
 import javax.xml.parsers.SAXParserFactory
 
 object CompilerOutputParser {
@@ -124,7 +125,7 @@ object CompilerOutputParser {
                 // We're directly inside the root tag: <MESSAGES>
                 return
             }
-            val qNameLowerCase = qName.toLowerCase()
+            val qNameLowerCase = qName.toLowerCase(Locale.US)
             var category: CompilerMessageSeverity? = CATEGORIES[qNameLowerCase]
             if (category == null) {
                 messageCollector.report(ERROR, "Unknown compiler message tag: $qName")

compiler/daemon/daemon-common/src/org/jetbrains/kotlin/daemon/common/FileSystemUtils.kt

@@ -16,6 +16,7 @@
 
 package org.jetbrains.kotlin.daemon.common
 
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.toLowerCaseAsciiOnly
 import java.io.File
 
 enum class OSKind {
@@ -25,7 +26,7 @@ enum class OSKind {
     Unknown;
 
     companion object {
-        val current: OSKind = System.getProperty("os.name").toLowerCase().let {
+        val current: OSKind = System.getProperty("os.name").toLowerCaseAsciiOnly().let {
             when {
                 // partly taken from http://www.code4copy.com/java/post/detecting-os-type-in-java
                 it.startsWith("windows") -> Windows

compiler/fir/fir2ir/jvm-backend/src/org/jetbrains/kotlin/fir/backend/jvm/FirJvmMangleComputer.kt

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.fir.visitors.FirVisitor
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.toLowerCaseAsciiOnly
 import org.jetbrains.kotlin.utils.addToStdlib.ifNotEmpty
 
 open class FirJvmMangleComputer(
@@ -210,7 +211,7 @@ open class FirJvmMangleComputer(
                             is ConeStarProjection -> appendSignature(MangleConstant.STAR_MARK)
                             is ConeKotlinTypeProjection -> {
                                 if (arg.kind != ProjectionKind.INVARIANT) {
-                                    appendSignature(arg.kind.name.toLowerCase())
+                                    appendSignature(arg.kind.name.toLowerCaseAsciiOnly())
                                     appendSignature(MangleConstant.VARIANCE_SEPARATOR)
                                 }
 

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/JavaUtils.kt

@@ -47,6 +47,7 @@ import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.types.Variance.*
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.capitalizeAsciiOnly
 import org.jetbrains.kotlin.utils.addToStdlib.runIf
 import java.lang.Deprecated
 import java.lang.annotation.Documented
@@ -140,7 +141,7 @@ internal fun JavaType?.toConeKotlinTypeWithoutEnhancement(
             val primitiveType = type
             val kotlinPrimitiveName = when (val javaName = primitiveType?.typeName?.asString()) {
                 null -> "Unit"
-                else -> javaName.capitalize()
+                else -> javaName.capitalizeAsciiOnly()
             }
 
             val classId = StandardClassIds.byName(kotlinPrimitiveName)
@@ -194,7 +195,7 @@ private fun JavaArrayType.toConeKotlinTypeWithoutEnhancement(
             )
         }
     } else {
-        val javaComponentName = componentType.type?.typeName?.asString()?.capitalize() ?: error("Array of voids")
+        val javaComponentName = componentType.type?.typeName?.asString()?.capitalizeAsciiOnly() ?: error("Array of voids")
         val classId = StandardClassIds.byName(javaComponentName + "Array")
 
         if (forAnnotationValueParameter) {

compiler/fir/jvm/src/org/jetbrains/kotlin/fir/resolve/FirJavaSyntheticNamesProvider.kt

@@ -9,6 +9,7 @@ import org.jetbrains.kotlin.fir.NoMutableState
 import org.jetbrains.kotlin.fir.resolve.calls.FirSyntheticNamesProvider
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.util.capitalizeDecapitalize.capitalizeAsciiOnly
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.decapitalizeAsciiOnly
 import org.jetbrains.kotlin.util.capitalizeDecapitalize.toUpperCaseAsciiOnly
 
 @NoMutableState
@@ -91,7 +92,7 @@ object FirJavaSyntheticNamesProvider : FirSyntheticNamesProvider() {
             else -> return emptyList()
         }
         val withoutPrefix = identifier.removePrefix(prefix)
-        val withoutPrefixName = Name.identifier(withoutPrefix.decapitalize())
+        val withoutPrefixName = Name.identifier(withoutPrefix.decapitalizeAsciiOnly())
         return if (prefix == SETTER_PREFIX) {
             listOf(withoutPrefixName, Name.identifier(IS_PREFIX + withoutPrefix))
         } else {
@@ -99,4 +100,3 @@ object FirJavaSyntheticNamesProvider : FirSyntheticNamesProvider() {
         }
     }
 }
-

compiler/fir/tree/src/org/jetbrains/kotlin/fir/FirRenderer.kt

@@ -27,6 +27,7 @@ import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.fir.visitors.FirVisitorVoid
 import org.jetbrains.kotlin.name.SpecialNames
 import org.jetbrains.kotlin.types.Variance
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.toLowerCaseAsciiOnly
 import org.jetbrains.kotlin.utils.Printer
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
@@ -226,7 +227,7 @@ class FirRenderer(builder: StringBuilder, private val mode: RenderMode = RenderM
     }
 
     private fun FirMemberDeclaration.modalityAsString(): String {
-        return modality?.name?.toLowerCase() ?: run {
+        return modality?.name?.toLowerCaseAsciiOnly() ?: run {
             if (this is FirCallableMemberDeclaration<*> && this.isOverride) {
                 "open?"
             } else {
@@ -343,7 +344,7 @@ class FirRenderer(builder: StringBuilder, private val mode: RenderMode = RenderM
         declaration.renderPhaseIfNeeded()
         print(
             when (declaration) {
-                is FirRegularClass -> declaration.classKind.name.toLowerCase().replace("_", " ")
+                is FirRegularClass -> declaration.classKind.name.toLowerCaseAsciiOnly().replace("_", " ")
                 is FirTypeAlias -> "typealias"
                 is FirSimpleFunction -> "fun"
                 is FirProperty -> {

compiler/ir/ir.interpreter/src/org/jetbrains/kotlin/ir/interpreter/Utils.kt

@@ -7,18 +7,22 @@ package org.jetbrains.kotlin.ir.interpreter
 
 import org.jetbrains.kotlin.builtins.StandardNames
 import org.jetbrains.kotlin.descriptors.ClassKind
-import org.jetbrains.kotlin.ir.interpreter.builtins.evaluateIntrinsicAnnotation
-import org.jetbrains.kotlin.ir.interpreter.stack.Variable
-import org.jetbrains.kotlin.ir.interpreter.state.*
 import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.*
 import org.jetbrains.kotlin.ir.expressions.impl.IrConstImpl
-import org.jetbrains.kotlin.ir.symbols.*
+import org.jetbrains.kotlin.ir.interpreter.builtins.evaluateIntrinsicAnnotation
+import org.jetbrains.kotlin.ir.interpreter.stack.Variable
+import org.jetbrains.kotlin.ir.interpreter.state.*
+import org.jetbrains.kotlin.ir.symbols.IrFieldSymbol
+import org.jetbrains.kotlin.ir.symbols.IrSymbol
+import org.jetbrains.kotlin.ir.symbols.IrTypeParameterSymbol
+import org.jetbrains.kotlin.ir.symbols.IrValueParameterSymbol
 import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.capitalizeAsciiOnly
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
 internal fun IrFunction.getDispatchReceiver(): IrValueParameterSymbol? = this.dispatchReceiverParameter?.symbol
@@ -202,7 +206,7 @@ internal fun State?.getCorrectReceiverByFunction(irFunction: IrFunction): State?
     return generateSequence(original) { it.superClass }.firstOrNull { it.irClass.thisReceiver == other } ?: this
 }
 
-internal fun IrFunction.getCapitalizedFileName() = this.file.name.replace(".kt", "Kt").capitalize()
+internal fun IrFunction.getCapitalizedFileName() = this.file.name.replace(".kt", "Kt").capitalizeAsciiOnly()
 
 internal fun IrType.isUnsigned() = this.isUByte() || this.isUShort() || this.isUInt() || this.isULong()
 

compiler/ir/ir.interpreter/src/org/jetbrains/kotlin/ir/interpreter/state/Wrapper.kt

@@ -17,6 +17,7 @@ import org.jetbrains.kotlin.ir.util.defaultType
 import org.jetbrains.kotlin.ir.util.fqNameForIrSerialization
 import org.jetbrains.kotlin.ir.util.fqNameWhenAvailable
 import org.jetbrains.kotlin.ir.util.parentAsClass
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.capitalizeAsciiOnly
 import java.lang.invoke.MethodHandle
 import java.lang.invoke.MethodHandles
 import java.lang.invoke.MethodType
@@ -30,7 +31,7 @@ internal class Wrapper(val value: Any, override val irClass: IrClass) : Complex(
         if (irFunction.getEvaluateIntrinsicValue()?.isEmpty() == true) return null // this method will handle IntrinsicEvaluator
         // if function is actually a getter, then use "get${property.name.capitalize()}" as method name
         val propertyName = (irFunction as? IrSimpleFunction)?.correspondingPropertySymbol?.owner?.name?.asString()
-        val propertyCall = listOfNotNull(propertyName, "get${propertyName?.capitalize()}")
+        val propertyCall = listOfNotNull(propertyName, "get${propertyName?.capitalizeAsciiOnly()}")
             .firstOrNull { receiverClass.methods.any { method -> method.name == it } }
 
         val intrinsicName = getJavaOriginalName(irFunction)
@@ -187,4 +188,4 @@ internal class Wrapper(val value: Any, override val irClass: IrClass) : Complex(
     override fun toString(): String {
         return "Wrapper(obj='$typeFqName', value=$value)"
     }
-}
+}

compiler/psi/src/org/jetbrains/kotlin/kdoc/parser/KDocKnownTag.kt

@@ -16,6 +16,8 @@
 
 package org.jetbrains.kotlin.kdoc.parser
 
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.toUpperCaseAsciiOnly
+
 enum class KDocKnownTag(val isReferenceRequired: Boolean, val isSectionStart: Boolean) {
     AUTHOR(false, false),
     THROWS(true, false),
@@ -37,7 +39,7 @@ enum class KDocKnownTag(val isReferenceRequired: Boolean, val isSectionStart: Bo
                 tagName.subSequence(1, tagName.length)
             } else tagName
             try {
-                return valueOf(name.toString().toUpperCase())
+                return valueOf(name.toString().toUpperCaseAsciiOnly())
             } catch (ignored: IllegalArgumentException) {
             }
 

compiler/psi/src/org/jetbrains/kotlin/kdoc/psi/impl/KDocImpl.kt

@@ -10,13 +10,14 @@ import com.intellij.psi.impl.source.tree.LazyParseablePsiElement
 import com.intellij.psi.tree.IElementType
 import org.jetbrains.kotlin.idea.KotlinLanguage
 import org.jetbrains.kotlin.kdoc.lexer.KDocTokens
+import org.jetbrains.kotlin.kdoc.parser.KDocKnownTag
 import org.jetbrains.kotlin.kdoc.psi.api.KDoc
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.KtDeclaration
-import org.jetbrains.kotlin.psi.psiUtil.getParentOfType
 import org.jetbrains.kotlin.psi.psiUtil.getChildOfType
 import org.jetbrains.kotlin.psi.psiUtil.getChildrenOfType
-import org.jetbrains.kotlin.kdoc.parser.KDocKnownTag
+import org.jetbrains.kotlin.psi.psiUtil.getParentOfType
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.toLowerCaseAsciiOnly
 
 class KDocImpl(buffer: CharSequence?) : LazyParseablePsiElement(KDocTokens.KDOC, buffer), KDoc {
 
@@ -37,10 +38,10 @@ class KDocImpl(buffer: CharSequence?) : LazyParseablePsiElement(KDocTokens.KDOC,
         getChildrenOfType<KDocSection>().firstOrNull { it.name == name }
 
     override fun findSectionByTag(tag: KDocKnownTag): KDocSection? =
-        findSectionByName(tag.name.toLowerCase())
+        findSectionByName(tag.name.toLowerCaseAsciiOnly())
 
     override fun findSectionByTag(tag: KDocKnownTag, subjectName: String): KDocSection? =
         getChildrenOfType<KDocSection>().firstOrNull {
-            it.name == tag.name.toLowerCase() && it.getSubjectName() == subjectName
+            it.name == tag.name.toLowerCaseAsciiOnly() && it.getSubjectName() == subjectName
         }
 }

compiler/visualizer/render-fir/src/org/jetbrains/kotlin/compiler/visualizer/FirVisualizer.kt

@@ -26,6 +26,7 @@ import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.getChildrenOfType
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.toLowerCaseAsciiOnly
 
 private typealias Stack = MutableList<Pair<String, MutableList<String>>>
 
@@ -452,7 +453,7 @@ class FirVisualizer(private val firFile: FirFile) : BaseRenderer() {
             resolvedQualifier.symbol?.let {
                 val fir = it.fir
                 if (fir is FirClass) {
-                    data.append(fir.classKind.name.toLowerCase()).append(" ")
+                    data.append(fir.classKind.name.toLowerCaseAsciiOnly()).append(" ")
                     data.append((fir as? FirRegularClass)?.name ?: Name.special("<anonymous>"))
                     if (fir.superTypeRefs.any { it.render() != "kotlin/Any" }) {
                         data.append(": ")

core/compiler.common/src/org/jetbrains/kotlin/descriptors/annotations/AnnotationUseSiteTarget.kt

@@ -16,16 +16,18 @@
 
 package org.jetbrains.kotlin.descriptors.annotations
 
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.toLowerCaseAsciiOnly
+
 enum class AnnotationUseSiteTarget(renderName: String? = null) {
-    FIELD(),
+    FIELD,
-    FILE(),
+    FILE,
-    PROPERTY(),
+    PROPERTY,
     PROPERTY_GETTER("get"),
     PROPERTY_SETTER("set"),
-    RECEIVER(),
+    RECEIVER,
     CONSTRUCTOR_PARAMETER("param"),
     SETTER_PARAMETER("setparam"),
     PROPERTY_DELEGATE_FIELD("delegate");
 
-    val renderName: String = renderName ?: name.toLowerCase()
+    val renderName: String = renderName ?: name.toLowerCaseAsciiOnly()
 }

core/descriptors/src/org/jetbrains/kotlin/builtins/ReflectionTypes.kt

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.DescriptorUtils
 import org.jetbrains.kotlin.resolve.scopes.MemberScope
 import org.jetbrains.kotlin.types.*
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.capitalizeAsciiOnly
 import kotlin.reflect.KProperty
 
 class ReflectionTypes(module: ModuleDescriptor, private val notFoundClasses: NotFoundClasses) {
@@ -35,7 +36,7 @@ class ReflectionTypes(module: ModuleDescriptor, private val notFoundClasses: Not
 
     private class ClassLookup(val numberOfTypeParameters: Int) {
         operator fun getValue(types: ReflectionTypes, property: KProperty<*>): ClassDescriptor {
-            return types.find(property.name.capitalize(), numberOfTypeParameters)
+            return types.find(property.name.capitalizeAsciiOnly(), numberOfTypeParameters)
         }
     }
 

core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererImpl.kt

@@ -25,6 +25,7 @@ import org.jetbrains.kotlin.resolve.descriptorUtil.declaresOrInheritsDefaultValu
 import org.jetbrains.kotlin.types.*
 import org.jetbrains.kotlin.types.ErrorUtils.UninferredParameterTypeConstructor
 import org.jetbrains.kotlin.types.TypeUtils.CANT_INFER_FUNCTION_PARAM_TYPE
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.toLowerCaseAsciiOnly
 import java.util.*
 
 internal class DescriptorRendererImpl(
@@ -494,7 +495,7 @@ internal class DescriptorRendererImpl(
 
     private fun renderModality(modality: Modality, builder: StringBuilder, defaultModality: Modality) {
         if (!renderDefaultModality && modality == defaultModality) return
-        renderModifier(builder, DescriptorRendererModifier.MODALITY in modifiers, modality.name.toLowerCase())
+        renderModifier(builder, DescriptorRendererModifier.MODALITY in modifiers, modality.name.toLowerCaseAsciiOnly())
     }
 
     private fun MemberDescriptor.implicitModalityWithoutExtensions(): Modality {
@@ -538,7 +539,7 @@ internal class DescriptorRendererImpl(
     private fun renderMemberKind(callableMember: CallableMemberDescriptor, builder: StringBuilder) {
         if (DescriptorRendererModifier.MEMBER_KIND !in modifiers) return
         if (verbose && callableMember.kind != CallableMemberDescriptor.Kind.DECLARATION) {
-            builder.append("/*").append(callableMember.kind.name.toLowerCase()).append("*/ ")
+            builder.append("/*").append(callableMember.kind.name.toLowerCaseAsciiOnly()).append("*/ ")
         }
     }
 

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/KDocCompletionContributor.kt

@@ -43,6 +43,7 @@ import org.jetbrains.kotlin.psi.psiUtil.getStrictParentOfType
 import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.scopes.DescriptorKindFilter
 import org.jetbrains.kotlin.resolve.scopes.utils.collectDescriptorsFiltered
+import java.util.*
 
 class KDocCompletionContributor : CompletionContributor() {
     init {
@@ -157,7 +158,7 @@ object KDocTagCompletionProvider : CompletionProvider<CompletionParameters>() {
         val resultWithPrefix = result.withPrefixMatcher(prefix)
         KDocKnownTag.values().forEach {
             if (kdocOwner == null || it.isApplicable(kdocOwner)) {
-                resultWithPrefix.addElement(LookupElementBuilder.create("@" + it.name.toLowerCase()))
+                resultWithPrefix.addElement(LookupElementBuilder.create("@" + it.name.toLowerCase(Locale.US)))
             }
         }
     }

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/VariableOrParameterNameWithTypeCompletion.kt

@@ -24,7 +24,6 @@ import com.intellij.openapi.progress.ProgressManager
 import com.intellij.openapi.util.Key
 import com.intellij.psi.PsiClass
 import com.intellij.psi.PsiElement
-import com.intellij.psi.codeStyle.CodeStyleSettingsManager
 import com.intellij.psi.codeStyle.NameUtil
 import org.jetbrains.kotlin.descriptors.ClassifierDescriptor
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
@@ -69,7 +68,7 @@ class VariableOrParameterNameWithTypeCompletion(
             prefixWords.indices.map { index -> if (index == 0) prefix else prefixWords.drop(index).joinToString("") }
 
         userPrefixes = nameSuggestionPrefixes.indices.map { prefixWords.take(it).joinToString("") }
-        classNamePrefixMatchers = nameSuggestionPrefixes.map { CamelHumpMatcher(it.capitalize(), false) }
+        classNamePrefixMatchers = nameSuggestionPrefixes.map { CamelHumpMatcher(it.capitalize(Locale.US), false) }
     }
 
     private val suggestionsByTypesAdded = HashSet<Type>()
@@ -281,4 +280,4 @@ class VariableOrParameterNameWithTypeCompletion(
     object Weigher : LookupElementWeigher("kotlin.parameterNameAndTypePriority") {
         override fun weigh(element: LookupElement, context: WeighingContext): Int = element.getUserData(PRIORITY_KEY) ?: 0
     }
-}
+}

idea/idea-core/src/org/jetbrains/kotlin/idea/core/KotlinNameSuggester.kt

@@ -164,7 +164,7 @@ object KotlinNameSuggester {
                     val argText = typeArguments.joinToString(separator = "") { it.typeReference?.typeElement?.render() ?: "" }
                     "$argText${referenceExpression?.text ?: ""}"
                 }
-                else -> text.capitalize()
+                else -> text.capitalizeAsciiOnly()
             }
         }
 

idea/idea-gradle/src/org/jetbrains/kotlin/idea/run/KotlinMPPGradleTestTasksProvider.kt

@@ -13,6 +13,7 @@ import com.intellij.openapi.module.Module
 import org.jetbrains.kotlin.config.KotlinFacetSettingsProvider
 import org.jetbrains.kotlin.idea.caches.project.isMPPModule
 import org.jetbrains.kotlin.idea.configuration.KotlinTargetData
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.capitalizeAsciiOnly
 import org.jetbrains.plugins.gradle.execution.test.runner.GradleTestTasksProvider
 import org.jetbrains.plugins.gradle.service.project.GradleProjectResolverUtil
 import org.jetbrains.plugins.gradle.util.GradleConstants
@@ -57,6 +58,6 @@ class KotlinMPPGradleTestTasksProvider : GradleTestTasksProvider {
 
     private fun getTaskNames(task: TaskData, namePrefix: String): List<String> {
         val name = task.name
-        return listOf(namePrefix + CLEAN_NAME_PREFIX + name.capitalize(), namePrefix + name)
+        return listOf(namePrefix + CLEAN_NAME_PREFIX + name.capitalizeAsciiOnly(), namePrefix + name)
     }
-}
+}

idea/idea-gradle/src/org/jetbrains/kotlin/idea/run/MultiplatformTestTasksChooser.kt

@@ -13,6 +13,7 @@ import org.jetbrains.kotlin.config.ExternalSystemRunTask
 import org.jetbrains.kotlin.config.ExternalSystemTestRunTask
 import org.jetbrains.kotlin.idea.facet.externalSystemTestRunTasks
 import org.jetbrains.kotlin.idea.util.module
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.capitalizeAsciiOnly
 import org.jetbrains.plugins.gradle.execution.test.runner.*
 import org.jetbrains.plugins.gradle.util.TasksToRun
 import java.util.*
@@ -56,7 +57,7 @@ class MultiplatformTestTasksChooser : TestTasksChooser() {
             return { it.targetName == targetName }
         }
 
-        val taskPrefix = targetName + parts[1].capitalize()
+        val taskPrefix = targetName + parts[1].capitalizeAsciiOnly()
 
         return { it.targetName == targetName && it.taskName.startsWith(taskPrefix) }
     }
@@ -119,9 +120,9 @@ class MultiplatformTestTasksChooser : TestTasksChooser() {
     }
 
     private fun getTaskNames(task: ExternalSystemRunTask): List<String> {
-        return listOf("clean" + task.taskName.capitalize(), task.taskName)
+        return listOf("clean" + task.taskName.capitalizeAsciiOnly(), task.taskName)
     }
 }
 
 private val ExternalSystemRunTask.presentableName: String
-    get() = targetName ?: (":$taskName")
+    get() = targetName ?: (":$taskName")

idea/idea-maven/src/org/jetbrains/kotlin/idea/maven/PomFile.kt

@@ -35,6 +35,7 @@ import org.jetbrains.kotlin.config.TestSourceKotlinRootType
 import org.jetbrains.kotlin.idea.configuration.RepositoryDescription
 import org.jetbrains.kotlin.idea.maven.configuration.KotlinMavenConfigurator
 import org.jetbrains.kotlin.psi.psiUtil.getChildrenOfType
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.toLowerCaseAsciiOnly
 import org.jetbrains.kotlin.utils.SmartList
 import java.util.*
 
@@ -116,7 +117,7 @@ class PomFile private constructor(private val xmlFile: XmlFile, val domModel: Ma
         dependency.classifier.stringValue = classifier
 
         if (scope != null && scope != MavenArtifactScope.COMPILE) {
-            dependency.scope.stringValue = scope.name.toLowerCase()
+            dependency.scope.stringValue = scope.name.toLowerCaseAsciiOnly()
         }
 
         if (optional) {
@@ -635,7 +636,8 @@ internal fun MavenDomDependencies.findDependencies(artifacts: List<MavenId>, sco
 }
 
 private fun MavenDomDependency.matches(artifact: MavenId, scope: MavenArtifactScope?) =
-    this.matches(artifact) && (this.scope.stringValue == scope?.name?.toLowerCase() || scope == null && this.scope.stringValue == "compile")
+    this.matches(artifact) &&
+            (this.scope.stringValue == scope?.name?.toLowerCaseAsciiOnly() || scope == null && this.scope.stringValue == "compile")
 
 private fun MavenDomArtifactCoordinates.matches(artifact: MavenId) =
     (artifact.groupId == null || groupId.stringValue == artifact.groupId)

idea/idea-new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/wizard/NewProjectWizardModuleBuilder.kt

@@ -40,6 +40,7 @@ import org.jetbrains.kotlin.tools.projectWizard.wizard.ui.firstStep.FirstWizardS
 import org.jetbrains.kotlin.tools.projectWizard.wizard.ui.runWithProgressBar
 import org.jetbrains.kotlin.tools.projectWizard.wizard.ui.secondStep.SecondStepWizardComponent
 import java.io.File
+import java.util.*
 import javax.swing.JButton
 import javax.swing.JComponent
 import com.intellij.openapi.module.Module as IdeaModule
@@ -217,7 +218,7 @@ class ModuleNewWizardFirstStep(wizard: IdeWizard) : WizardStep(wizard, Generatio
     private fun suggestGroupId(): String {
         val username = SystemProperties.getUserName() ?: return DEFAULT_GROUP_ID
         if (!username.matches("[\\w\\s]+".toRegex())) return DEFAULT_GROUP_ID
-        val usernameAsGroupId = username.trim().toLowerCase().split("\\s+".toRegex()).joinToString(separator = ".")
+        val usernameAsGroupId = username.trim().toLowerCase(Locale.US).split("\\s+".toRegex()).joinToString(separator = ".")
         return "me.$usernameAsGroupId"
     }
 

idea/idea-new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/wizard/ui/secondStep/modulesEditor/ModulesEditorToolbarDecorator.kt

@@ -13,6 +13,7 @@ import org.jetbrains.kotlin.tools.projectWizard.settings.buildsystem.Sourceset
 import org.jetbrains.kotlin.tools.projectWizard.wizard.KotlinNewProjectWizardUIBundle
 import org.jetbrains.kotlin.tools.projectWizard.wizard.ui.createPanelWithPopupHandler
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
+import java.util.*
 import javax.swing.JComponent
 
 class ModulesEditorToolbarDecorator(
@@ -72,7 +73,7 @@ class ModulesEditorToolbarDecorator(
                     null -> ""
                 }
 
-                text = KotlinNewProjectWizardUIBundle.message("editor.modules.add", moduleKindTextToAdd.capitalize())
+                text = KotlinNewProjectWizardUIBundle.message("editor.modules.add", moduleKindTextToAdd.capitalize(Locale.US))
             }
             event.presentation.isEnabled
         }
@@ -103,7 +104,7 @@ class ModulesEditorToolbarDecorator(
                 isEnabled = tree.selectedSettingItem is Module
                 text = KotlinNewProjectWizardUIBundle.message(
                     "editor.modules.remove.tooltip",
-                    selectedModuleKindText?.let { " ${it.capitalize()}" }.orEmpty()
+                    selectedModuleKindText?.let { " ${it.capitalize(Locale.US)}" }.orEmpty()
                 )
             }
             event.presentation.isEnabled

idea/jvm-debugger/jvm-debugger-util/src/org/jetbrains/kotlin/idea/debugger/FileRankingCalculator.kt

@@ -29,6 +29,7 @@ import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.DescriptorUtils
 import org.jetbrains.kotlin.resolve.descriptorUtil.varargParameterPosition
 import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.capitalizeAsciiOnly
 import org.jetbrains.kotlin.utils.keysToMap
 import kotlin.jvm.internal.FunctionBase
 
@@ -172,7 +173,7 @@ abstract class FileRankingCalculator(private val checkClassFqName: Boolean = tru
             return -MAJOR
 
         // boolean is
-        return if (methodName.drop(3) == propertyName.capitalize()) MAJOR else -NORMAL
+        return if (methodName.drop(3) == propertyName.capitalizeAsciiOnly()) MAJOR else -NORMAL
     }
 
     private fun rankingForVisibility(descriptor: DeclarationDescriptorWithVisibility, accessible: Accessible): Ranking {

idea/src/org/jetbrains/kotlin/idea/inspections/RecursivePropertyAccessorInspection.kt

@@ -21,6 +21,7 @@ import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.BindingContext.DECLARATION_TO_DESCRIPTOR
 import org.jetbrains.kotlin.resolve.BindingContext.REFERENCE_TARGET
 import org.jetbrains.kotlin.synthetic.SyntheticJavaPropertyDescriptor
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.capitalizeAsciiOnly
 
 class RecursivePropertyAccessorInspection : AbstractKotlinInspection() {
 
@@ -98,7 +99,7 @@ class RecursivePropertyAccessorInspection : AbstractKotlinInspection() {
             if (element !is KtSimpleNameExpression) return false
             val namedFunction = element.getParentOfType<KtDeclarationWithBody>(true) as? KtNamedFunction ?: return false
             val name = namedFunction.name ?: return false
-            val referencedName = element.text.capitalize()
+            val referencedName = element.text.capitalizeAsciiOnly()
             val isGetter = name == "get$referencedName"
             val isSetter = name == "set$referencedName"
             if (!isGetter && !isSetter) return false
@@ -117,4 +118,4 @@ class RecursivePropertyAccessorInspection : AbstractKotlinInspection() {
             return (context[REFERENCE_TARGET, receiver] as? ClassDescriptor)?.kind == ClassKind.OBJECT
         }
     }
-}
+}

idea/src/org/jetbrains/kotlin/idea/quickfix/AddArrayOfTypeFix.kt

@@ -15,6 +15,7 @@ import org.jetbrains.kotlin.psi.KtPsiFactory
 import org.jetbrains.kotlin.psi.createExpressionByPattern
 import org.jetbrains.kotlin.renderer.DescriptorRenderer
 import org.jetbrains.kotlin.types.KotlinType
+import java.util.*
 
 class AddArrayOfTypeFix(expression: KtExpression, expectedType: KotlinType) : KotlinQuickFixAction<KtExpression>(expression) {
 
@@ -22,7 +23,7 @@ class AddArrayOfTypeFix(expression: KtExpression, expectedType: KotlinType) : Ko
         "arrayOf"
     } else {
         val typeName = DescriptorRenderer.SHORT_NAMES_IN_TYPES.renderType(expectedType)
-        "${typeName.decapitalize()}Of"
+        "${typeName.decapitalize(Locale.US)}Of"
 
     }
 
@@ -34,4 +35,4 @@ class AddArrayOfTypeFix(expression: KtExpression, expectedType: KotlinType) : Ko
         val arrayOfExpression = KtPsiFactory(project).createExpressionByPattern("$0($1)", prefix, element)
         element.replace(arrayOfExpression)
     }
-}
+}

idea/src/org/jetbrains/kotlin/idea/refactoring/introduce/extractionEngine/extractableAnalysisUtil.kt

@@ -27,6 +27,7 @@ import org.jetbrains.kotlin.cfg.pseudocodeTraverser.traverseFollowingInstruction
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.descriptors.impl.LocalVariableDescriptor
 import org.jetbrains.kotlin.diagnostics.Errors
+import org.jetbrains.kotlin.idea.KotlinBundle
 import org.jetbrains.kotlin.idea.caches.resolve.analyzeWithContent
 import org.jetbrains.kotlin.idea.caches.resolve.findModuleDescriptor
 import org.jetbrains.kotlin.idea.caches.resolve.getResolutionFacade
@@ -34,7 +35,6 @@ import org.jetbrains.kotlin.idea.codeInsight.DescriptorToSourceUtilsIde
 import org.jetbrains.kotlin.idea.core.KotlinNameSuggester
 import org.jetbrains.kotlin.idea.core.NewDeclarationNameValidator
 import org.jetbrains.kotlin.idea.core.compareDescriptors
-import org.jetbrains.kotlin.idea.KotlinBundle
 import org.jetbrains.kotlin.idea.refactoring.createTempCopy
 import org.jetbrains.kotlin.idea.refactoring.introduce.extractionEngine.AnalysisResult.ErrorMessage
 import org.jetbrains.kotlin.idea.refactoring.introduce.extractionEngine.AnalysisResult.Status
@@ -56,6 +56,7 @@ import org.jetbrains.kotlin.resolve.calls.callUtil.getCalleeExpressionIfAny
 import org.jetbrains.kotlin.resolve.scopes.LexicalScope
 import org.jetbrains.kotlin.types.*
 import org.jetbrains.kotlin.types.typeUtil.makeNullable
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.capitalizeAsciiOnly
 import org.jetbrains.kotlin.utils.DFS.*
 import java.util.*
 
@@ -736,7 +737,7 @@ private fun ExtractionData.suggestFunctionNames(returnType: KotlinType): List<St
     expressions.singleOrNull()?.let { expr ->
         val property = expr.getStrictParentOfType<KtProperty>()
         if (property?.initializer == expr) {
-            property.name?.let { functionNames.add(KotlinNameSuggester.suggestNameByName("get" + it.capitalize(), validator)) }
+            property.name?.let { functionNames.add(KotlinNameSuggester.suggestNameByName("get" + it.capitalizeAsciiOnly(), validator)) }
         }
     }
 
@@ -834,4 +835,4 @@ fun ExtractableCodeDescriptor.validate(target: ExtractionTarget = ExtractionTarg
     )
 
     return ExtractableCodeDescriptorWithConflicts(this, conflicts)
-}
+}

idea/src/org/jetbrains/kotlin/idea/refactoring/move/moveMethod/MoveKotlinMethodProcessor.kt

@@ -40,6 +40,7 @@ import org.jetbrains.kotlin.resolve.calls.callUtil.getResolvedCall
 import org.jetbrains.kotlin.resolve.descriptorUtil.isAncestorOf
 import org.jetbrains.kotlin.resolve.scopes.receivers.ImplicitReceiver
 import org.jetbrains.kotlin.resolve.scopes.utils.getImplicitReceiversHierarchy
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.capitalizeAsciiOnly
 import org.jetbrains.kotlin.util.containingNonLocalDeclaration
 
 class MoveKotlinMethodProcessor(
@@ -197,7 +198,7 @@ class MoveKotlinMethodProcessor(
                             argumentExpression
                         } else return
                     } else {
-                        val getterName = "get${targetVariable.nameAsSafeName.identifier.capitalize()}"
+                        val getterName = "get${targetVariable.nameAsSafeName.identifier.capitalizeAsciiOnly()}"
                         JavaPsiFacade.getElementFactory(myProject).createExpressionFromText("${oldReceiver.text}.$getterName()", null)
                     }
 

idea/src/org/jetbrains/kotlin/idea/refactoring/move/moveUtils.kt

@@ -57,6 +57,7 @@ import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode
 import org.jetbrains.kotlin.resolve.scopes.receivers.ImplicitClassReceiver
 import org.jetbrains.kotlin.resolve.scopes.receivers.ImplicitReceiver
 import org.jetbrains.kotlin.types.expressions.DoubleColonLHS
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.capitalizeAsciiOnly
 import org.jetbrains.kotlin.utils.addIfNotNull
 import java.io.File
 import java.lang.System.currentTimeMillis
@@ -407,7 +408,7 @@ fun guessNewFileName(declarationsToMove: Collection<KtNamedDeclaration>): String
     val newFileName = representative?.run {
         if (containingKtFile.isScript()) "$name.kts" else "$name.${KotlinFileType.EXTENSION}"
     } ?: declarationsToMove.first().containingFile.name
-    return newFileName.capitalize()
+    return newFileName.capitalizeAsciiOnly()
 }
 
 // returns true if successful

j2k/src/org/jetbrains/kotlin/j2k/ast/Expressions.kt

@@ -22,6 +22,7 @@ import com.intellij.psi.tree.IElementType
 import org.jetbrains.kotlin.j2k.CodeBuilder
 import org.jetbrains.kotlin.j2k.append
 import org.jetbrains.kotlin.lexer.KtTokens
+import java.util.*
 
 class ArrayAccessExpression(val expression: Expression, val index: Expression, val lvalue: Boolean) : Expression() {
     override fun generateCode(builder: CodeBuilder) {
@@ -294,7 +295,7 @@ class ClassLiteralExpression(val type: Type): Expression() {
 fun createArrayInitializerExpression(arrayType: ArrayType, initializers: List<Expression>, needExplicitType: Boolean = true) : MethodCallExpression {
     val elementType = arrayType.elementType
     val createArrayFunction = when {
-        elementType is PrimitiveType -> (elementType.toNotNullType().canonicalCode() + "ArrayOf").decapitalize()
+        elementType is PrimitiveType -> (elementType.toNotNullType().canonicalCode() + "ArrayOf").decapitalize(Locale.US)
         needExplicitType -> "arrayOf<" + arrayType.elementType.canonicalCode() + ">"
         else -> "arrayOf"
     }

j2k/src/org/jetbrains/kotlin/j2k/usageProcessing/FieldToPropertyProcessing.kt

@@ -23,6 +23,7 @@ import org.jetbrains.kotlin.j2k.AccessorKind
 import org.jetbrains.kotlin.j2k.CodeConverter
 import org.jetbrains.kotlin.j2k.ast.*
 import org.jetbrains.kotlin.j2k.dot
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.capitalizeAsciiOnly
 
 class FieldToPropertyProcessing(
         private val field: PsiField,
@@ -167,5 +168,5 @@ class UseAccessorsJavaCodeProcessor(private val factory: PsiElementFactory, priv
     }
 
     private fun accessorName(kind: AccessorKind) =
-        (if (kind == AccessorKind.GETTER) "get" else "set") + propertyName.capitalize()
+        (if (kind == AccessorKind.GETTER) "get" else "set") + propertyName.capitalizeAsciiOnly()
 }

js/js.dce/src/org/jetbrains/kotlin/js/dce/util.kt

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.js.backend.ast.*
 import org.jetbrains.kotlin.js.backend.ast.metadata.SpecialFunction
 import org.jetbrains.kotlin.js.backend.ast.metadata.specialFunction
 import org.jetbrains.kotlin.js.dce.Context.Node
+import java.util.*
 
 fun Context.isObjectDefineProperty(function: JsExpression) = isObjectFunction(function, "defineProperty")
 
@@ -46,7 +47,7 @@ fun Context.isObjectFunction(function: JsExpression, functionName: String): Bool
 fun Context.isKotlinFunction(function: JsExpression, name: String): Boolean {
     if (function !is JsNameRef || function.ident != name) return false
     val receiver = (function.qualifier as? JsNameRef)?.name ?: return false
-    return receiver in nodes && receiver.ident.toLowerCase() == "kotlin"
+    return receiver in nodes && receiver.ident.toLowerCase(Locale.US) == "kotlin"
 }
 
 fun isSpecialFunction(expr: JsExpression, specialFunction: SpecialFunction): Boolean =

js/js.frontend/src/org/jetbrains/kotlin/js/config/ErrorTolerancePolicy.kt

@@ -5,6 +5,8 @@
 
 package org.jetbrains.kotlin.js.config
 
+import java.util.*
+
 enum class ErrorTolerancePolicy(val allowSyntaxErrors: Boolean, val allowSemanticErrors: Boolean) {
     NONE(false, false),
     SEMANTIC(false, true),
@@ -16,7 +18,7 @@ enum class ErrorTolerancePolicy(val allowSyntaxErrors: Boolean, val allowSemanti
         val DEFAULT = NONE
 
         fun resolvePolicy(key: String): ErrorTolerancePolicy {
-            return when (key.toUpperCase()) {
+            return when (key.toUpperCase(Locale.US)) {
                 "NONE" -> NONE
                 "SEMANTIC" -> SEMANTIC
                 "SYNTAX", "ALL" -> ALL
@@ -24,4 +26,4 @@ enum class ErrorTolerancePolicy(val allowSyntaxErrors: Boolean, val allowSemanti
             }
         }
     }
-}
+}

js/js.translator/src/org/jetbrains/kotlin/js/translate/intrinsic/functions/factories/ArrayFIF.kt

@@ -109,7 +109,7 @@ object ArrayFIF : CompositeFIF() {
     }
 
     private val PrimitiveType.lowerCaseName
-        get() = typeName.asString().toLowerCase()
+        get() = typeName.asString().toLowerCase(Locale.US)
 
     fun getTag(descriptor: CallableDescriptor, config: JsConfig): String? {
         if (descriptor !is ConstructorDescriptor) return null

libraries/tools/kotlin-main-kts/src/org/jetbrains/kotlin/mainKts/impl/directories.kt

@@ -39,7 +39,7 @@ class Directories(
     // compiler/daemon/daemon-common/src/org/jetbrains/kotlin/daemon/common/FileSystemUtils.kt
     // which in turn is based on: http://www.code4copy.com/java/post/detecting-os-type-in-java
     private val os: OSKind
-        get() = getProperty("os.name")?.toLowerCase().let { name ->
+        get() = getProperty("os.name")?.toLowerCase(Locale.US).let { name ->
             when {
                 name == null -> OSKind.Unknown
                 name.startsWith("windows") -> OSKind.Windows

libraries/tools/kotlinp/src/org/jetbrains/kotlin/kotlinp/printers.kt

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.kotlinp
 
 import kotlinx.metadata.*
 import kotlinx.metadata.jvm.*
+import java.util.*
 
 private object SpecialCharacters {
     const val TYPE_ALIAS_MARKER = '^'
@@ -309,7 +310,7 @@ private fun printType(flags: Flags, output: (String) -> Unit): KmTypeVisitor =
             printType(flags) { argumentTypeString ->
                 arguments += buildString {
                     if (variance != KmVariance.INVARIANT) {
-                        append(variance.name.toLowerCase()).append(" ")
+                        append(variance.name.toLowerCase(Locale.US)).append(" ")
                     }
                     append(argumentTypeString)
                 }
@@ -399,7 +400,7 @@ private fun printTypeParameter(
                     append("@").append(renderAnnotation(annotation)).append(" ")
                 }
                 if (variance != KmVariance.INVARIANT) {
-                    append(variance.name.toLowerCase()).append(" ")
+                    append(variance.name.toLowerCase(Locale.US)).append(" ")
                 }
                 append("T#$id")
                 if (settings.isVerbose) {

libraries/tools/new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/ir/buildsystem/SourcesetIR.kt

@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.tools.projectWizard.plugins.printer.GradlePrinter
 import org.jetbrains.kotlin.tools.projectWizard.settings.buildsystem.Sourceset
 import org.jetbrains.kotlin.tools.projectWizard.settings.buildsystem.SourcesetType
 import java.nio.file.Path
+import java.util.*
 
 
 sealed class SourcesetIR : BuildSystemIR {
@@ -55,4 +56,4 @@ data class MultiplatformSourcesetIR(
 }
 
 val MultiplatformSourcesetIR.sourcesetName
-    get() = targetName + sourcesetType.name.capitalize()
+    get() = targetName + sourcesetType.name.capitalize(Locale.US)

libraries/tools/new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/moduleConfigurators/NativeTargetConfigurator.kt

@@ -4,8 +4,6 @@ import kotlinx.collections.immutable.toPersistentList
 import org.jetbrains.annotations.NonNls
 import org.jetbrains.kotlin.tools.projectWizard.KotlinNewProjectWizardBundle
 import org.jetbrains.kotlin.tools.projectWizard.core.Reader
-
-import org.jetbrains.kotlin.tools.projectWizard.core.buildList
 import org.jetbrains.kotlin.tools.projectWizard.ir.buildsystem.BuildSystemIR
 import org.jetbrains.kotlin.tools.projectWizard.ir.buildsystem.gradle.*
 import org.jetbrains.kotlin.tools.projectWizard.ir.buildsystem.gradle.multiplatform.NonDefaultTargetConfigurationIR
@@ -13,6 +11,7 @@ import org.jetbrains.kotlin.tools.projectWizard.plugins.buildSystem.BuildSystemT
 import org.jetbrains.kotlin.tools.projectWizard.plugins.kotlin.*
 import org.jetbrains.kotlin.tools.projectWizard.plugins.printer.GradlePrinter
 import org.jetbrains.kotlin.tools.projectWizard.settings.buildsystem.Module
+import java.util.*
 
 interface NativeTargetConfigurator : TargetConfigurator {
     val isDesktopTarget: Boolean
@@ -22,7 +21,7 @@ interface NativeTargetConfigurator : TargetConfigurator {
 class RealNativeTargetConfigurator private constructor(
     override val moduleSubType: ModuleSubType
 ) : NativeTargetConfigurator, SimpleTargetConfigurator {
-    override val text: String = moduleSubType.name.capitalize()
+    override val text: String = moduleSubType.name.capitalize(Locale.US)
     override val isDesktopTarget: Boolean
         get() = moduleSubType.isNativeDesktop
 

libraries/tools/new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/mpp/mpp.kt

@@ -7,12 +7,9 @@ package org.jetbrains.kotlin.tools.projectWizard.mpp
 
 import org.jetbrains.annotations.NonNls
 import org.jetbrains.kotlin.tools.projectWizard.core.*
-import org.jetbrains.kotlin.tools.projectWizard.core.safeAs
 import org.jetbrains.kotlin.tools.projectWizard.moduleConfigurators.SimpleTargetConfigurator
 import org.jetbrains.kotlin.tools.projectWizard.moduleConfigurators.inContextOfModuleConfigurator
-import org.jetbrains.kotlin.tools.projectWizard.plugins.buildSystem.gradle.GradlePlugin
 import org.jetbrains.kotlin.tools.projectWizard.plugins.kotlin.ModuleSubType
-import org.jetbrains.kotlin.tools.projectWizard.plugins.kotlin.ModulesToIrConversionData
 import org.jetbrains.kotlin.tools.projectWizard.plugins.projectPath
 import org.jetbrains.kotlin.tools.projectWizard.plugins.templates.TemplatesPlugin
 import org.jetbrains.kotlin.tools.projectWizard.settings.JavaPackage
@@ -22,6 +19,7 @@ import org.jetbrains.kotlin.tools.projectWizard.templates.FileDescriptor
 import org.jetbrains.kotlin.tools.projectWizard.templates.FileTemplate
 import org.jetbrains.kotlin.tools.projectWizard.templates.FileTextDescriptor
 import java.nio.file.Path
+import java.util.*
 
 @DslMarker
 annotation class ExpectFileDSL
@@ -321,7 +319,7 @@ private fun pathForFileInTarget(
     sourcesetType: SourcesetType,
 ) = mppModulePath /
         Defaults.SRC_DIR /
-        "${target.name}${sourcesetType.name.capitalize()}" /
+        "${target.name}${sourcesetType.name.capitalize(Locale.US)}" /
         mppModule.configurator.kotlinDirectoryName /
         javaPackage?.asPath() /
-        filename
+        filename

libraries/tools/new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/plugins/kotlin/ModulesToIRsConverter.kt

@@ -16,6 +16,7 @@ import org.jetbrains.kotlin.tools.projectWizard.plugins.buildSystem.isGradle
 import org.jetbrains.kotlin.tools.projectWizard.plugins.templates.TemplatesPlugin
 import org.jetbrains.kotlin.tools.projectWizard.settings.buildsystem.*
 import java.nio.file.Path
+import java.util.*
 
 data class ModulesToIrConversionData(
     val rootModules: List<Module>,
@@ -265,7 +266,7 @@ class ModulesToIRsConverter(
         val (moduleDependencies) = createModuleDependencies(target)
         mutateProjectStructureByModuleConfigurator(target, modulePath)
         val sourcesetss = target.sourcesets.map { sourceset ->
-            val sourcesetName = target.name + sourceset.sourcesetType.name.capitalize()
+            val sourcesetName = target.name + sourceset.sourcesetType.name.capitalize(Locale.US)
             MultiplatformSourcesetIR(
                 sourceset.sourcesetType,
                 modulePath / Defaults.SRC_DIR / sourcesetName,

libraries/tools/new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/plugins/templates/TemplatesPlugin.kt

@@ -9,8 +9,8 @@ import org.jetbrains.kotlin.tools.projectWizard.core.entity.settings.PluginSetti
 import org.jetbrains.kotlin.tools.projectWizard.core.service.TemplateEngineService
 import org.jetbrains.kotlin.tools.projectWizard.ir.buildsystem.*
 import org.jetbrains.kotlin.tools.projectWizard.moduleConfigurators.ModuleConfiguratorWithTests
-import org.jetbrains.kotlin.tools.projectWizard.moduleConfigurators.MppModuleConfigurator.runArbitraryTask
 import org.jetbrains.kotlin.tools.projectWizard.moduleConfigurators.isPresent
+import org.jetbrains.kotlin.tools.projectWizard.moduleConfigurators.settingValue
 import org.jetbrains.kotlin.tools.projectWizard.phases.GenerationPhase
 import org.jetbrains.kotlin.tools.projectWizard.plugins.buildSystem.BuildSystemPlugin
 import org.jetbrains.kotlin.tools.projectWizard.plugins.kotlin.KotlinPlugin
@@ -21,8 +21,8 @@ import org.jetbrains.kotlin.tools.projectWizard.templates.*
 import org.jetbrains.kotlin.tools.projectWizard.transformers.interceptors.InterceptionPoint
 import org.jetbrains.kotlin.tools.projectWizard.transformers.interceptors.TemplateInterceptionApplicationState
 import org.jetbrains.kotlin.tools.projectWizard.transformers.interceptors.applyAll
-import org.jetbrains.kotlin.tools.projectWizard.moduleConfigurators.settingValue
 import java.nio.file.Path
+import java.util.*
 
 class TemplatesPlugin(context: Context) : Plugin(context) {
     override val path = pluginPath
@@ -174,7 +174,7 @@ class TemplatesPlugin(context: Context) : Plugin(context) {
                         is SrcFilePath -> moduleConfigurator.kotlinDirectoryName
                         is ResourcesFilePath -> moduleConfigurator.resourcesDirectoryName
                     }
-                    SRC_DIR / "${module.name}${filePath.sourcesetType.name.capitalize()}" / directory
+                    SRC_DIR / "${module.name}${filePath.sourcesetType.name.capitalize(Locale.US)}" / directory
                 }
                 is FakeMultiplatformModuleIR -> error("Not supported for FakeMultiplatformModuleIR")
             }
@@ -193,4 +193,4 @@ class TemplatesPlugin(context: Context) : Plugin(context) {
             templates,
             fileTemplatesToRender
         )
-}
+}

libraries/tools/new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/templates/KtorServerTemplate.kt

@@ -7,6 +7,11 @@ package org.jetbrains.kotlin.tools.projectWizard.templates
 
 
 import org.jetbrains.annotations.NonNls
+import org.jetbrains.kotlin.tools.projectWizard.KotlinNewProjectWizardBundle
+import org.jetbrains.kotlin.tools.projectWizard.Versions
+import org.jetbrains.kotlin.tools.projectWizard.WizardGradleRunConfiguration
+import org.jetbrains.kotlin.tools.projectWizard.WizardRunConfiguration
+import org.jetbrains.kotlin.tools.projectWizard.core.Reader
 import org.jetbrains.kotlin.tools.projectWizard.core.Writer
 import org.jetbrains.kotlin.tools.projectWizard.core.asPath
 import org.jetbrains.kotlin.tools.projectWizard.core.buildList
@@ -15,20 +20,19 @@ import org.jetbrains.kotlin.tools.projectWizard.ir.buildsystem.*
 import org.jetbrains.kotlin.tools.projectWizard.ir.buildsystem.gradle.multiplatform.TargetConfigurationIR
 import org.jetbrains.kotlin.tools.projectWizard.ir.buildsystem.gradle.multiplatform.addWithJavaIntoJvmTarget
 import org.jetbrains.kotlin.tools.projectWizard.library.MavenArtifact
-import org.jetbrains.kotlin.tools.projectWizard.phases.GenerationPhase
-import org.jetbrains.kotlin.tools.projectWizard.plugins.kotlin.ModuleType
-import org.jetbrains.kotlin.tools.projectWizard.settings.DisplayableSettingItem
-import org.jetbrains.kotlin.tools.projectWizard.transformers.interceptors.InterceptionPoint
-import org.jetbrains.kotlin.tools.projectWizard.KotlinNewProjectWizardBundle
-import org.jetbrains.kotlin.tools.projectWizard.Versions
-import org.jetbrains.kotlin.tools.projectWizard.WizardGradleRunConfiguration
-import org.jetbrains.kotlin.tools.projectWizard.WizardRunConfiguration
-import org.jetbrains.kotlin.tools.projectWizard.core.Reader
 import org.jetbrains.kotlin.tools.projectWizard.moduleConfigurators.moduleType
+import org.jetbrains.kotlin.tools.projectWizard.phases.GenerationPhase
 import org.jetbrains.kotlin.tools.projectWizard.plugins.kotlin.KotlinPlugin
+import org.jetbrains.kotlin.tools.projectWizard.plugins.kotlin.ModuleType
 import org.jetbrains.kotlin.tools.projectWizard.plugins.kotlin.ProjectKind
-import org.jetbrains.kotlin.tools.projectWizard.settings.buildsystem.*
+import org.jetbrains.kotlin.tools.projectWizard.settings.DisplayableSettingItem
+import org.jetbrains.kotlin.tools.projectWizard.settings.buildsystem.DefaultRepository
+import org.jetbrains.kotlin.tools.projectWizard.settings.buildsystem.Module
+import org.jetbrains.kotlin.tools.projectWizard.settings.buildsystem.Repositories
+import org.jetbrains.kotlin.tools.projectWizard.settings.buildsystem.SourcesetType
 import org.jetbrains.kotlin.tools.projectWizard.settings.version.Version
+import org.jetbrains.kotlin.tools.projectWizard.transformers.interceptors.InterceptionPoint
+import java.util.*
 
 class KtorServerTemplate : Template() {
     override val title: String = KotlinNewProjectWizardBundle.message("module.template.ktor.server.title")
@@ -110,5 +114,5 @@ enum class KtorServerEngine(val engineName: String, val dependencyName: String)
         get() = engineName.capitalize()
 
     val import: String
-        get() = "io.ktor.server.${engineName.decapitalize()}.${engineName.capitalize()}"
+        get() = "io.ktor.server.${engineName.decapitalize(Locale.US)}.${engineName.capitalize(Locale.US)}"
-}
+}

libraries/tools/new-project-wizard/src/org/jetbrains/kotlin/tools/projectWizard/templates/Template.kt

@@ -1,12 +1,14 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
 package org.jetbrains.kotlin.tools.projectWizard.templates
 
 import org.jetbrains.kotlin.tools.projectWizard.Identificator
 import org.jetbrains.kotlin.tools.projectWizard.SettingsOwner
 import org.jetbrains.kotlin.tools.projectWizard.WizardRunConfiguration
-
-
 import org.jetbrains.kotlin.tools.projectWizard.core.*
-
 import org.jetbrains.kotlin.tools.projectWizard.core.entity.settings.*
 import org.jetbrains.kotlin.tools.projectWizard.enumSettingImpl
 import org.jetbrains.kotlin.tools.projectWizard.ir.buildsystem.*
@@ -14,8 +16,6 @@ import org.jetbrains.kotlin.tools.projectWizard.ir.buildsystem.gradle.multiplatf
 import org.jetbrains.kotlin.tools.projectWizard.phases.GenerationPhase
 import org.jetbrains.kotlin.tools.projectWizard.plugins.RunConfigurationsPlugin
 import org.jetbrains.kotlin.tools.projectWizard.plugins.StructurePlugin
-import org.jetbrains.kotlin.tools.projectWizard.plugins.kotlin.ModuleType
-import org.jetbrains.kotlin.tools.projectWizard.plugins.kotlin.ModulesToIrConversionData
 import org.jetbrains.kotlin.tools.projectWizard.plugins.kotlin.ProjectKind
 import org.jetbrains.kotlin.tools.projectWizard.settings.DisplayableSettingItem
 import org.jetbrains.kotlin.tools.projectWizard.settings.buildsystem.Module
@@ -23,6 +23,7 @@ import org.jetbrains.kotlin.tools.projectWizard.settings.version.Version
 import org.jetbrains.kotlin.tools.projectWizard.transformers.interceptors.InterceptionPoint
 import org.jetbrains.kotlin.tools.projectWizard.transformers.interceptors.TemplateInterceptor
 import java.nio.file.Path
+import java.util.*
 import kotlin.properties.ReadOnlyProperty
 
 interface TemplateEnvironment {
@@ -163,7 +164,7 @@ abstract class Template : SettingsOwner, EntitiesOwnerDescriptor, DisplayableSet
 
 
     private fun Reader.createDefaultSettings() = mapOf(
-        "projectName" to StructurePlugin.name.settingValue.capitalize()
+        "projectName" to StructurePlugin.name.settingValue.capitalize(Locale.US)
     )
 
     override fun equals(other: Any?): Boolean =
@@ -331,4 +332,4 @@ operator fun TemplateApplicationResult.plus(other: TemplateApplicationResult) =
         irsToAddToBuildFile + other.irsToAddToBuildFile,
         updateTarget andThen other.updateTarget,
         updateModuleIR andThen other.updateModuleIR,
-    )
+    )

native/utils/src/org/jetbrains/kotlin/konan/target/utils.kt

@@ -5,6 +5,8 @@
 
 package org.jetbrains.kotlin.konan.target
 
+import java.util.*
+
 /**
  * Name of a preset used in the 'kotlin-multiplatform' Gradle plugin to represent this target.
  */
@@ -19,5 +21,5 @@ val KonanTarget.presetName: String
 
 private fun evaluatePresetName(targetName: String): String {
     val nameParts = targetName.split('_').mapNotNull { it.takeIf(String::isNotEmpty) }
-    return nameParts.asSequence().drop(1).joinToString("", nameParts.firstOrNull().orEmpty(), transform = String::capitalize)
+    return nameParts.asSequence().drop(1).joinToString("", nameParts.firstOrNull().orEmpty()) { it.capitalize(Locale.US) }
 }

nj2k/nj2k-services/src/org/jetbrains/kotlin/nj2k/postProcessing/processings/ConvertGettersAndSettersToPropertyProcessing.kt

@@ -52,6 +52,7 @@ import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.checker.KotlinTypeChecker
 import org.jetbrains.kotlin.types.isError
 import org.jetbrains.kotlin.types.typeUtil.isUnit
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.decapitalizeAsciiOnly
 import org.jetbrains.kotlin.util.isJavaDescriptor
 import org.jetbrains.kotlin.utils.addToStdlib.cast
 import org.jetbrains.kotlin.utils.addToStdlib.firstIsInstanceOrNull
@@ -369,7 +370,7 @@ private class ConvertGettersAndSettersToPropertyStatefulProcessing(
         return declarations
             .asSequence()
             .mapNotNull { it.asPropertyAccessor() }
-            .groupBy { it.name.removePrefix("is").decapitalize() }
+            .groupBy { it.name.removePrefix("is").decapitalizeAsciiOnly() }
             .values
             .mapNotNull { group ->
                 val realGetter = group.firstIsInstanceOrNull<RealGetter>()

nj2k/src/org/jetbrains/kotlin/nj2k/ConversionsRunner.kt

@@ -21,6 +21,7 @@ import org.jetbrains.kotlin.nj2k.tree.JKLambdaExpression
 import org.jetbrains.kotlin.nj2k.tree.JKParameter
 import org.jetbrains.kotlin.nj2k.tree.JKTreeRoot
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
+import java.util.*
 
 object ConversionsRunner {
     private fun createConversions(context: NewJ2kConverterContext) = listOf(
@@ -105,7 +106,7 @@ object ConversionsRunner {
 
     private fun Conversion.description(): String {
         val conversionName = this::class.simpleName
-        val words = conversionName?.let { wordRegex.findAll(conversionName).map { it.value.decapitalize() }.toList() }
+        val words = conversionName?.let { wordRegex.findAll(conversionName).map { it.value.decapitalize(Locale.US) }.toList() }
         return when {
             conversionName == null -> "Converting..."
             conversionName.endsWith("Conversion") -> "Converting ${words!!.dropLast(1).joinToString(" ")}"
@@ -114,4 +115,4 @@ object ConversionsRunner {
     }
 
     private val wordRegex = "[A-Z][a-z0-9]+".toRegex()
-}
+}

nj2k/src/org/jetbrains/kotlin/nj2k/conversions/BoxedTypeOperationsConversion.kt

@@ -8,7 +8,7 @@ package org.jetbrains.kotlin.nj2k.conversions
 import org.jetbrains.kotlin.nj2k.NewJ2kConverterContext
 import org.jetbrains.kotlin.nj2k.tree.*
 import org.jetbrains.kotlin.nj2k.types.primitiveTypes
-
+import java.util.*
 
 class BoxedTypeOperationsConversion(context: NewJ2kConverterContext) : RecursiveApplicableConversionBase(context) {
     override fun applyToElement(element: JKTreeElement): JKTreeElement {
@@ -40,7 +40,7 @@ class BoxedTypeOperationsConversion(context: NewJ2kConverterContext) : Recursive
         if (operationType !in primitiveTypeNames) return null
         return JKCallExpressionImpl(
             symbolProvider.provideMethodSymbol(
-                "kotlin.${primitiveTypeName.capitalize()}.to${operationType.capitalize()}"
+                "kotlin.${primitiveTypeName.capitalize(Locale.US)}.to${operationType.capitalize(Locale.US)}"
             ),
             JKArgumentList()
         ).withFormattingFrom(methodCallExpression)
@@ -59,4 +59,4 @@ class BoxedTypeOperationsConversion(context: NewJ2kConverterContext) : Recursive
         private val primitiveTypeUnwrapRegexp =
             """([\w.]+)\.(\w+)Value""".toRegex()
     }
-}
+}

nj2k/src/org/jetbrains/kotlin/nj2k/conversions/ImplicitCastsConversion.kt

@@ -15,6 +15,7 @@ import org.jetbrains.kotlin.nj2k.types.*
 
 import org.jetbrains.kotlin.resolve.jvm.JvmPrimitiveType
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
+import java.util.*
 
 class ImplicitCastsConversion(context: NewJ2kConverterContext) : RecursiveApplicableConversionBase(context) {
     override fun applyToElement(element: JKTreeElement): JKTreeElement {
@@ -138,8 +139,8 @@ class ImplicitCastsConversion(context: NewJ2kConverterContext) : RecursiveApplic
             }
         }
 
-        val initialTypeName = expressionTypeAsPrimitive.jvmPrimitiveType.javaKeywordName.capitalize()
+        val initialTypeName = expressionTypeAsPrimitive.jvmPrimitiveType.javaKeywordName.capitalize(Locale.US)
-        val conversionFunctionName = "to${toTypeAsPrimitive.jvmPrimitiveType.javaKeywordName.capitalize()}"
+        val conversionFunctionName = "to${toTypeAsPrimitive.jvmPrimitiveType.javaKeywordName.capitalize(Locale.US)}"
         return JKQualifiedExpression(
             copyTreeAndDetach().parenthesizeIfBinaryExpression(),
             JKCallExpressionImpl(
@@ -164,4 +165,4 @@ class ImplicitCastsConversion(context: NewJ2kConverterContext) : RecursiveApplic
         val lastArrayType = realParameterTypes.lastOrNull()?.arrayInnerType() ?: return realParameterTypes
         return realParameterTypes.subList(0, realParameterTypes.lastIndex) + lastArrayType
     }
-}
+}

nj2k/src/org/jetbrains/kotlin/nj2k/utils.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.nj2k
 import org.jetbrains.kotlin.lexer.KtKeywordToken
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.load.java.JvmAbi
+import org.jetbrains.kotlin.util.capitalizeDecapitalize.decapitalizeAsciiOnly
 
 fun <T> List<T>.replace(element: T, replacer: T): List<T> {
     val mutableList = toMutableList()
@@ -22,14 +23,14 @@ fun String.asGetterName() =
         ?.takeIf {
             it.isNotEmpty() && it.first().isUpperCase()
                     || it.startsWith("is") && it.length > 2 && it[2].isUpperCase()
-        }?.decapitalize()
+        }?.decapitalizeAsciiOnly()
         ?.escaped()
 
 fun String.asSetterName() =
     takeIf { JvmAbi.isSetterName(it) }
         ?.removePrefix("set")
         ?.takeIf { it.isNotEmpty() && it.first().isUpperCase() }
-        ?.decapitalize()
+        ?.decapitalizeAsciiOnly()
         ?.escaped()
 
 fun String.isPossiblyGetterOrSetterName() =
@@ -40,4 +41,4 @@ private val KEYWORDS = KtTokens.KEYWORDS.types.map { (it as KtKeywordToken).valu
 
 fun String.escaped() =
     if (this in KEYWORDS || '$' in this) "`$this`"
-    else this
+    else this

plugins/kapt3/kapt3-base/src/org/jetbrains/kotlin/kapt3/base/incremental/incrementalProcessors.kt

@@ -9,6 +9,7 @@ import com.sun.tools.javac.code.Symbol
 import org.jetbrains.kotlin.kapt3.base.util.KaptLogger
 import java.io.File
 import java.net.URI
+import java.util.*
 import javax.annotation.processing.Filer
 import javax.annotation.processing.ProcessingEnvironment
 import javax.annotation.processing.Processor
@@ -49,7 +50,7 @@ class IncrementalProcessor(private val processor: Processor, private val kind: D
             if (fromOptions == null) {
                 RuntimeProcType.NON_INCREMENTAL
             } else {
-                val declaredType = fromOptions.drop("org.gradle.annotation.processing.".length).toUpperCase()
+                val declaredType = fromOptions.drop("org.gradle.annotation.processing.".length).toUpperCase(Locale.US)
                 if (ALLOWED_RUNTIME_TYPES.contains(declaredType)) {
                     enumValueOf(declaredType)
                 } else {
@@ -251,4 +252,4 @@ enum class RuntimeProcType(val isIncremental: Boolean) {
     AGGREGATING(true),
     ISOLATING(true),
     NON_INCREMENTAL(false),
-}
+}

plugins/kapt3/kapt3-idea/src/org/jetbrains/kotlin/kapt/idea/KaptGradleProjectImportHandler.kt

@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.idea.configuration.GradleProjectImportHandler
 import org.jetbrains.kotlin.idea.facet.KotlinFacet
 import org.jetbrains.plugins.gradle.model.data.GradleSourceSetData
 import java.io.File
+import java.util.*
 
 class KaptGradleProjectImportHandler : GradleProjectImportHandler {
     override fun importBySourceSet(facet: KotlinFacet, sourceSetNode: DataNode<GradleSourceSetData>) {
@@ -42,7 +43,7 @@ class KaptGradleProjectImportHandler : GradleProjectImportHandler {
 
     private fun isKaptCompilerPluginPath(path: String): Boolean {
         val lastIndexOfFile = path.lastIndexOfAny(charArrayOf('/', File.separatorChar)).takeIf { it >= 0 } ?: return false
-        val fileName = path.drop(lastIndexOfFile + 1).toLowerCase()
+        val fileName = path.drop(lastIndexOfFile + 1).toLowerCase(Locale.US)
         return fileName.matches("kotlin\\-annotation\\-processing(\\-gradle)?\\-[0-9].*\\.jar".toRegex())
     }
-}
+}