FIR: introduce RETURN_FOR_BUILT_IN_SUSPEND diagnostic

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDataClassConverters.kt

@@ -3180,6 +3180,12 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.RETURN_FOR_BUILT_IN_SUSPEND) { firDiagnostic ->
+        ReturnForBuiltInSuspendImpl(
+            firDiagnostic as FirPsiDiagnostic,
+            token,
+        )
+    }
     add(FirJvmErrors.CONFLICTING_JVM_DECLARATIONS) { firDiagnostic ->
         ConflictingJvmDeclarationsImpl(
             firDiagnostic as FirPsiDiagnostic,

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnostics.kt

@@ -2223,6 +2223,10 @@ sealed class KtFirDiagnostic<PSI : PsiElement> : KtDiagnosticWithPsi<PSI> {
         override val diagnosticClass get() = ModifierFormForNonBuiltInSuspend::class
     }
 
+    abstract class ReturnForBuiltInSuspend : KtFirDiagnostic<KtReturnExpression>() {
+        override val diagnosticClass get() = ReturnForBuiltInSuspend::class
+    }
+
     abstract class ConflictingJvmDeclarations : KtFirDiagnostic<PsiElement>() {
         override val diagnosticClass get() = ConflictingJvmDeclarations::class
     }

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnosticsImpl.kt

@@ -3589,6 +3589,13 @@ internal class ModifierFormForNonBuiltInSuspendImpl(
     override val firDiagnostic: FirPsiDiagnostic by weakRef(firDiagnostic)
 }
 
+internal class ReturnForBuiltInSuspendImpl(
+    firDiagnostic: FirPsiDiagnostic,
+    override val token: ValidityToken,
+) : KtFirDiagnostic.ReturnForBuiltInSuspend(), KtAbstractFirDiagnostic<KtReturnExpression> {
+    override val firDiagnostic: FirPsiDiagnostic by weakRef(firDiagnostic)
+}
+
 internal class ConflictingJvmDeclarationsImpl(
     firDiagnostic: FirPsiDiagnostic,
     override val token: ValidityToken,