KT-29862 startOffset of class declaration

NB startOffset of primary class constructor declaration should still
point to the 'class' keyword (because of debugger requirements).

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

@@ -54,7 +54,7 @@ class ClassGenerator(
 
     fun generateClass(ktClassOrObject: KtPureClassOrObject): IrClass {
         val classDescriptor = ktClassOrObject.findClassDescriptor(this.context.bindingContext)
-        val startOffset = ktClassOrObject.getStartOffsetOfClassDeclarationKeywordOrNull() ?: ktClassOrObject.pureStartOffset
+        val startOffset = ktClassOrObject.getStartOffsetOfClassDeclarationOrNull() ?: ktClassOrObject.pureStartOffset
         val endOffset = ktClassOrObject.pureEndOffset
 
         return context.symbolTable.declareClass(

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

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.psi2ir.generators
 import com.intellij.psi.tree.TokenSet
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.psi.psiUtil.startOffsetSkippingComments
 import org.jetbrains.kotlin.psi2ir.getChildTokenStartOffsetOrNull
 
 private val FUNCTION_DECL_TOKENS = TokenSet.create(KtTokens.FUN_KEYWORD)
@@ -26,9 +27,9 @@ internal fun KtPureElement.getStartOffsetOfFunctionDeclarationKeywordOrNull(): I
         else -> null
     }
 
-internal fun KtPureClassOrObject.getStartOffsetOfClassDeclarationKeywordOrNull(): Int? =
+internal fun KtPureClassOrObject.getStartOffsetOfClassDeclarationOrNull(): Int? =
     when (this) {
-        is KtClassOrObject -> getChildTokenStartOffsetOrNull(CLASS_DECL_TOKENS)
+        is KtClassOrObject -> startOffsetSkippingComments
         else -> null
     }