[FIR2IR] Run constant evaluation before IR extensions

Test `constValInSerialName` in serialization still fails but because of
  different reason

^KT-54994 Fixed

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrConverter.kt

@@ -98,6 +98,8 @@ class Fir2IrConverter(
             }
         }
 
+        evaluateConstants(irModuleFragment)
+
         if (irGenerationExtensions.isNotEmpty()) {
             val pluginContext = Fir2IrPluginContext(components, irModuleFragment.descriptor)
             for (extension in irGenerationExtensions) {
@@ -106,8 +108,6 @@ class Fir2IrConverter(
         }
 
         irModuleFragment.acceptVoid(ExternalPackageParentPatcher(components, fir2IrExtensions))
-
-        evaluateConstants(irModuleFragment)
     }
 
     fun bindFakeOverridesOrPostpone(declarations: List<IrDeclaration>) {

plugins/kotlinx-serialization/testData/boxIr/constValInSerialName.kt

@@ -0,0 +1,20 @@
+// WITH_STDLIB
+// ISSUE: KT-54994
+
+import kotlinx.serialization.*
+import kotlinx.serialization.json.*
+import kotlinx.serialization.internal.*
+
+const val prefix = "foo"
+
+@Serializable
+data class Bar(@SerialName("$prefix.bar") val bar: String)
+
+fun box(): String {
+    val expectedBar = Bar("hello")
+    val json = Json.encodeToString(Bar.serializer(), expectedBar)
+    if (json != """{"foo.bar":"hello"}""") return "Fail: $json"
+    val actualBar = Json.decodeFromString(Bar.serializer(), json)
+    if (expectedBar != actualBar) return "Fail: $actualBar"
+    return "OK"
+}

plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationFirBlackBoxTestGenerated.java

@@ -39,6 +39,12 @@ public class SerializationFirBlackBoxTestGenerated extends AbstractSerialization
             runTest("plugins/kotlinx-serialization/testData/boxIr/classSerializerAsObject.kt");
         }
 
+        @Test
+        @TestMetadata("constValInSerialName.kt")
+        public void testConstValInSerialName() throws Exception {
+            runTest("plugins/kotlinx-serialization/testData/boxIr/constValInSerialName.kt");
+        }
+
         @Test
         @TestMetadata("contextualByDefault.kt")
         public void testContextualByDefault() throws Exception {

plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationIrBoxTestGenerated.java

@@ -37,6 +37,12 @@ public class SerializationIrBoxTestGenerated extends AbstractSerializationIrBoxT
         runTest("plugins/kotlinx-serialization/testData/boxIr/classSerializerAsObject.kt");
     }
 
+    @Test
+    @TestMetadata("constValInSerialName.kt")
+    public void testConstValInSerialName() throws Exception {
+        runTest("plugins/kotlinx-serialization/testData/boxIr/constValInSerialName.kt");
+    }
+
     @Test
     @TestMetadata("contextualByDefault.kt")
     public void testContextualByDefault() throws Exception {