Enable eliding function bodies in header mode.

^KT-78422

Author: aviroop-123

compiler/fir/raw-fir/light-tree2fir/src/org/jetbrains/kotlin/fir/lightTree/converter/LightTreeRawFirDeclarationBuilder.kt

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.fir.lightTree.converter
 
 import com.intellij.lang.LighterASTNode
 import com.intellij.psi.TokenType
+import com.intellij.util.containers.addIfNotNull
 import com.intellij.util.diff.FlyweightCapableTreeStructure
 import org.jetbrains.kotlin.*
 import org.jetbrains.kotlin.ElementTypeUtils.isExpression
@@ -1923,7 +1924,7 @@ class LightTreeRawFirDeclarationBuilder(
     /**
      * @see org.jetbrains.kotlin.parsing.KotlinParsing.parseFunction
      */
-    fun convertFunctionDeclaration(functionDeclaration: LighterASTNode): FirStatement {
+    fun convertFunctionDeclaration(functionDeclaration: LighterASTNode, generateHeaders: Boolean = false): FirStatement {
         var modifiers: ModifierList? = null
         var identifier: String? = null
         var valueParametersList: LighterASTNode? = null
@@ -1940,6 +1941,8 @@ class LightTreeRawFirDeclarationBuilder(
             identifier = it.asText
         }
 
+        var headerMode = generateHeaders
+
         val isLocal = isCallableLocal(functionDeclaration) { getParent() }
         val functionSource = functionDeclaration.toFirSourceElement()
         val isAnonymousFunction = identifier == null && isLocal
@@ -1971,6 +1974,11 @@ class LightTreeRawFirDeclarationBuilder(
 
             val calculatedModifiers = modifiers ?: ModifierList()
 
+            if (calculatedModifiers.hasInline()) {
+                // We need to disable header mode for inline functions.
+                headerMode = false
+            }
+
             if (returnType == null) {
                 returnType =
                     if (block != null || !hasEqToken) implicitUnitType
@@ -2066,7 +2074,7 @@ class LightTreeRawFirDeclarationBuilder(
 
                     val allowLegacyContractDescription = outerContractDescription == null
                     val bodyWithContractDescription = withForcedLocalContext {
-                        convertFunctionBody(block, expression, allowLegacyContractDescription)
+                        convertFunctionBody(block, expression, allowLegacyContractDescription, headerMode)
                     }
                     this.body = bodyWithContractDescription.first
                     val contractDescription = outerContractDescription ?: bodyWithContractDescription.second
@@ -2103,11 +2111,12 @@ class LightTreeRawFirDeclarationBuilder(
     private fun convertFunctionBody(
         blockNode: LighterASTNode?,
         expression: LighterASTNode?,
-        allowLegacyContractDescription: Boolean
+        allowLegacyContractDescription: Boolean,
+        generateHeaders: Boolean = false,
     ): Pair<FirBlock?, FirContractDescription?> {
         return when {
             blockNode != null -> {
-                val block = convertBlock(blockNode)
+                val block = convertBlock(blockNode) // We might be able to process only the contract statement in the body.
                 val contractDescription = runIf(allowLegacyContractDescription) {
                     val blockSource = block.source
                     val diagnostic = when {
@@ -2117,7 +2126,11 @@ class LightTreeRawFirDeclarationBuilder(
                     }
                     processLegacyContractDescription(block, diagnostic)
                 }
-                block to contractDescription
+                if (generateHeaders) {
+                    null to contractDescription // We want to preserve the contract info when processing as headers.
+                } else {
+                    block to contractDescription
+                }
             }
             expression != null -> FirSingleExpressionBlock(
                 expressionConverter.getAsFirExpression<FirExpression>(expression, "Function has no body (but should)").toReturn()