[IR] Add doc comments for KotlinMangleComputer and its inheritors

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

@@ -25,6 +25,9 @@ import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.fir.visitors.FirVisitorVoid
 
+/**
+ * A mangle computer that generates a mangled name for a Kotlin declaration represented by [FirDeclaration].
+ */
 class FirJvmMangleComputer(
     builder: StringBuilder,
     mode: MangleMode,

compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/mangle/KotlinMangleComputer.kt

@@ -5,9 +5,28 @@
 
 package org.jetbrains.kotlin.backend.common.serialization.mangle
 
-interface KotlinMangleComputer<D : Any> {
+/**
+ * Something capable of producing a mangled name for a Kotlin declaration.
+ *
+ * @param Declaration A class representing a Kotlin declaration.
+ */
+interface KotlinMangleComputer<Declaration : Any> {
 
-    fun computeMangle(declaration: D): String
+    /**
+     * Computes the mangled name of [declaration].
+     *
+     * @param declaration The Kotlin declaration to compute a mangle name for.
+     * @return The mangled name of [declaration].
+     */
+    fun computeMangle(declaration: Declaration): String
 
-    fun copy(newMode: MangleMode): KotlinMangleComputer<D>
-}
+    /**
+     * Creates a copy of this mangle computer with a different mangle mode but otherwise the same state.
+     *
+     * Useful for temporarily switching the mangle mode.
+     *
+     * @param newMode The mangle mode to use in the new mangle computer.
+     * @return A copy of this mangle computer.
+     */
+    fun copy(newMode: MangleMode): KotlinMangleComputer<Declaration>
+}

compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/mangle/descriptor/DescriptorMangleComputer.kt

@@ -15,6 +15,9 @@ import org.jetbrains.kotlin.types.checker.SimpleClassicTypeSystemContext
 import org.jetbrains.kotlin.types.model.TypeSystemContext
 import org.jetbrains.kotlin.types.typeUtil.isUnit
 
+/**
+ * The descriptor-based mangle computer. Used to compute a mangled name for a declaration given its [DeclarationDescriptor].
+ */
 abstract class DescriptorMangleComputer(builder: StringBuilder, mode: MangleMode) :
     BaseKotlinMangleComputer<
             /*Declaration=*/DeclarationDescriptor,

compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/mangle/ir/IrMangleComputer.kt

@@ -16,6 +16,9 @@ import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
 import org.jetbrains.kotlin.ir.visitors.acceptVoid
 
+/**
+ * A mangle computer that generates a mangled name for a Kotlin declaration represented by [IrDeclaration].
+ */
 abstract class IrMangleComputer(
     builder: StringBuilder,
     mode: MangleMode,