[fir2ir] Support stub-based FIR declarations

In the IDE, FIR declarations for libraries are built on top of binary
stubs. This helps to improve memory usage significantly, as Protobuf
metadata isn't loaded all the time. However, the containing file type
for stubs is different.

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/ConversionUtils.kt

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.fir.backend
 
 import com.intellij.psi.PsiCompiledElement
+import com.intellij.psi.PsiElement
 import com.intellij.psi.tree.IElementType
 import org.jetbrains.kotlin.*
 import org.jetbrains.kotlin.backend.common.actualizer.IrActualizedResult
@@ -55,6 +56,7 @@ import org.jetbrains.kotlin.ir.util.functions
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.name.SpecialNames
 import org.jetbrains.kotlin.name.StandardClassIds
+import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.psi.psiUtil.startOffsetSkippingComments
 import org.jetbrains.kotlin.types.ConstantValueKind
 import org.jetbrains.kotlin.types.Variance
@@ -76,7 +78,7 @@ internal inline fun <T : IrElement> KtSourceElement?.convertWithOffsets(f: (star
     val startOffset: Int
     val endOffset: Int
 
-    if (psi is PsiCompiledElement) {
+    if (isCompiledElement(psi)) {
         startOffset = UNDEFINED_OFFSET
         endOffset = UNDEFINED_OFFSET
     } else {
@@ -101,7 +103,7 @@ internal inline fun <T : IrElement> FirStatement.convertWithOffsets(
 ): T {
     val startOffset: Int
     val endOffset: Int
-    if (psi is PsiCompiledElement) {
+    if (isCompiledElement(psi)) {
         startOffset = UNDEFINED_OFFSET
         endOffset = UNDEFINED_OFFSET
     } else {
@@ -111,6 +113,19 @@ internal inline fun <T : IrElement> FirStatement.convertWithOffsets(
     return f(startOffset, endOffset)
 }
 
+private fun isCompiledElement(element: PsiElement?): Boolean {
+    if (element == null) {
+        return false
+    }
+
+    if (element is PsiCompiledElement) {
+        return true
+    }
+
+    val containingFile = element.containingFile
+    return containingFile !is KtFile || containingFile.isCompiled
+}
+
 internal fun createErrorType(): IrErrorType = IrErrorTypeImpl(null, emptyList(), Variance.INVARIANT)
 
 enum class ConversionTypeOrigin(val forSetter: Boolean) {