[analysis api] fix ISE: No conversion was found for SYNTAX

^KT-51786 fixed

compiler/fir/raw-fir/raw-fir.common/build.gradle.kts

@@ -22,7 +22,10 @@ dependencies {
 }
 
 sourceSets {
-    "main" { projectDefault() }
+    "main" {
+        projectDefault()
+        java.srcDir("gen")
+    }
     "test" { none() }
 }
 

compiler/fir/raw-fir/raw-fir.common/gen/org/jetbrains/kotlin/fir/builder/FirSyntaxErrors.kt

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.builder
+
+import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.diagnostics.*
+import org.jetbrains.kotlin.diagnostics.rendering.RootDiagnosticRendererFactory
+
+/*
+ * This file was generated automatically
+ * DO NOT MODIFY IT MANUALLY
+ */
+
+object FirSyntaxErrors {
+    // Syntax
+    val SYNTAX by error0<PsiElement>()
+
+    init {
+        RootDiagnosticRendererFactory.registerFactory(FirSyntaxErrorsDefaultMessages)
+    }
+}

compiler/fir/raw-fir/raw-fir.common/src/org/jetbrains/kotlin/fir/builder/FirSyntaxErrorsDefaultMessages.kt

@@ -5,24 +5,11 @@
 
 package org.jetbrains.kotlin.fir.builder
 
-import com.intellij.psi.PsiElement
 import org.jetbrains.kotlin.diagnostics.KtDiagnosticFactoryToRendererMap
-import org.jetbrains.kotlin.diagnostics.error0
 import org.jetbrains.kotlin.diagnostics.rendering.BaseDiagnosticRendererFactory
-import org.jetbrains.kotlin.diagnostics.rendering.RootDiagnosticRendererFactory
-
-object FirSyntaxErrors {
-
-    val SYNTAX by error0<PsiElement>()
-
-    init {
-        RootDiagnosticRendererFactory.registerFactory(FirSyntaxErrorsDefaultMessages)
-    }
-}
 
 @Suppress("unused")
 object FirSyntaxErrorsDefaultMessages : BaseDiagnosticRendererFactory() {
-
     override val MAP = KtDiagnosticFactoryToRendererMap("FIR").also { map ->
         map.put(FirSyntaxErrors.SYNTAX, "Syntax error")
     }