Migrate compiler, idea and others to new case conversion api

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/context/AbstractBuilderConfigurator.kt

@@ -131,7 +131,7 @@ abstract class AbstractBuilderConfigurator<T : AbstractFirTreeBuilder>(val firTr
             thisRef: Nothing?,
             prop: KProperty<*>
         ): ReadOnlyProperty<Nothing?, IntermediateBuilder> {
-            val name = name ?: "Fir${prop.name.capitalize()}"
+            val name = name ?: "Fir${prop.name.replaceFirstChar(Char::uppercaseChar)}"
             builder = IntermediateBuilder(name).apply {
                 firTreeBuilder.intermediateBuilders += this
                 IntermediateBuilderConfigurationContext(this).block()

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/context/AbstractFieldConfigurator.kt

@@ -22,7 +22,7 @@ abstract class AbstractFieldConfigurator<T : AbstractFirTreeBuilder>(private val
 
         fun generateBooleanFields(vararg names: String) {
             names.forEach {
-                +booleanField("is${it.capitalize()}")
+                +booleanField("is${it.replaceFirstChar(Char::uppercaseChar)}")
             }
         }
 

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/model/ElementUtils.kt

@@ -27,7 +27,7 @@ fun field(name: String, typeWithArgs: Pair<Type, List<Importable>>, nullable: Bo
 }
 
 fun field(type: Type, nullable: Boolean = false, withReplace: Boolean = false): Field {
-    return SimpleField(type.type.decapitalize(), type.typeWithArguments, type.packageName, null, nullable, withReplace)
+    return SimpleField(type.type.replaceFirstChar(Char::lowercaseChar), type.typeWithArguments, type.packageName, null, nullable, withReplace)
 }
 
 fun booleanField(name: String, withReplace: Boolean = false): Field {
@@ -57,7 +57,7 @@ fun field(name: String, element: AbstractElement, nullable: Boolean = false, wit
 }
 
 fun field(element: Element, nullable: Boolean = false, withReplace: Boolean = false): Field {
-    return FirField(element.name.decapitalize(), element, nullable, withReplace)
+    return FirField(element.name.replaceFirstChar(Char::lowercaseChar), element, nullable, withReplace)
 }
 
 // ----------- Field list -----------
@@ -67,7 +67,7 @@ fun fieldList(name: String, type: Importable, withReplace: Boolean = false): Fie
 }
 
 fun fieldList(element: Element, withReplace: Boolean = false): Field {
-    return FieldList(element.name.decapitalize() + "s", element, withReplace)
+    return FieldList(element.name.replaceFirstChar(Char::lowercaseChar) + "s", element, withReplace)
 }
 
 // ----------- Field set -----------

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/printer/implementation.kt

@@ -228,7 +228,7 @@ fun SmartPrinter.printImplementation(implementation: Implementation) {
 
                             field.needsSeparateTransform -> {
                                 if (!(element.needTransformOtherChildren && field.needTransformInOtherChildren)) {
-                                    println("transform${field.name.capitalize()}(transformer, data)")
+                                    println("transform${field.name.replaceFirstChar(Char::uppercaseChar)}(transformer, data)")
                                 }
                             }
 
@@ -297,7 +297,7 @@ fun SmartPrinter.printImplementation(implementation: Implementation) {
                                 field.transform()
                             }
                             if (field.needTransformInOtherChildren) {
-                                println("transform${field.name.capitalize()}(transformer, data)")
+                                println("transform${field.name.replaceFirstChar(Char::uppercaseChar)}(transformer, data)")
                             }
                         }
                         println("return this")
@@ -335,7 +335,7 @@ fun SmartPrinter.printImplementation(implementation: Implementation) {
             }
 
             for (field in allFields.filter { it.withReplace }) {
-                val capitalizedFieldName = field.name.capitalize()
+                val capitalizedFieldName = field.name.replaceFirstChar(Char::uppercaseChar)
                 val newValue = "new$capitalizedFieldName"
                 generateReplace(field, forceNullable = field.useNullableForReplace) {
                     when {

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/printer/utils.kt

@@ -96,7 +96,7 @@ val Field.isVal: Boolean get() = this is FieldList || (this is FieldWithDefault
 
 
 fun Field.transformFunctionDeclaration(returnType: String): String {
-    return transformFunctionDeclaration(name.capitalize(), returnType)
+    return transformFunctionDeclaration(name.replaceFirstChar(Char::uppercaseChar), returnType)
 }
 
 fun transformFunctionDeclaration(transformName: String, returnType: String): String {
@@ -104,7 +104,7 @@ fun transformFunctionDeclaration(transformName: String, returnType: String): Str
 }
 
 fun Field.replaceFunctionDeclaration(overridenType: Importable? = null, forceNullable: Boolean = false): String {
-    val capName = name.capitalize()
+    val capName = name.replaceFirstChar(Char::uppercaseChar)
     val type = overridenType?.typeWithArguments ?: typeWithArguments
 
     val typeWithNullable = if (forceNullable && !type.endsWith("?")) "$type?" else type
@@ -136,7 +136,7 @@ fun Implementation.Kind?.braces(): String = when (this) {
     else -> throw IllegalStateException(this.toString())
 }
 
-val Element.safeDecapitalizedName: String get() = if (name == "Class") "klass" else name.decapitalize()
+val Element.safeDecapitalizedName: String get() = if (name == "Class") "klass" else name.replaceFirstChar(Char::lowercaseChar)
 
 val Importable.typeWithArguments: String
     get() = when (this) {