Add comments for generators about data/inline class (in psi2ir and fir2ir) and annotations (fir2ir).

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/DataClassMembersGenerator.kt

@@ -30,6 +30,12 @@ import org.jetbrains.kotlin.psi.psiUtil.startOffset
 import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.DescriptorToSourceUtils
 
+/**
+ * A generator that generates synthetic members of data class as well as part of inline class.
+ *
+ * This one uses [DataClassMethodGenerator] to determine which members are needed to generate; uses [DataClassMembersGenerator] to generate
+ * function bodies; and provides ways to declare functions or parameters based on descriptors and binding context.
+ */
 class DataClassMembersGenerator(
     declarationGenerator: DeclarationGenerator
 ) : DeclarationGeneratorExtension(declarationGenerator) {

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/DataClassMembersGenerator.kt

@@ -27,6 +27,12 @@ import org.jetbrains.kotlin.types.checker.KotlinTypeChecker
 import org.jetbrains.kotlin.types.isNullable
 import org.jetbrains.kotlin.types.typeUtil.representativeUpperBound
 
+/**
+ * A platform-, frontend-independent logic for generating synthetic members of data class: equals, hashCode, toString, componentN, and copy.
+ * Different front-ends may need to define how to declare functions, parameters, etc., or simply provide predefined ones.
+ *
+ * Generating synthetic members of inline class can use this as well, in particular, members from Any: equals, hashCode, and toString.
+ */
 abstract class DataClassMembersGenerator(
     val context: IrGeneratorContext,
     val symbolTable: SymbolTable,