PSI2IR: Support suspend conversion for function references

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/ExpressionCodegen.kt

@@ -689,7 +689,8 @@ class ExpressionCodegen(
     override fun visitElement(element: IrElement, data: BlockInfo) =
         throw AssertionError(
             "Unexpected IR element found during code generation. Either code generation for it " +
-                    "is not implemented, or it should have been lowered: ${element.render()}"
+                    "is not implemented, or it should have been lowered:\n" +
+                    element.render()
         )
 
     override fun visitClass(declaration: IrClass, data: BlockInfo): PromisedValue {

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/ReflectionReferencesGenerator.kt

@@ -77,10 +77,12 @@ class ReflectionReferencesGenerator(statementGenerator: StatementGenerator) : St
 
         val callBuilder = unwrapCallableDescriptorAndTypeArguments(resolvedCall, context.extensions.samConversion)
 
+        val callableReferenceType = getTypeInferredByFrontendOrFail(ktCallableReference)
         if (resolvedCall.valueArguments.isNotEmpty() ||
-            requiresCoercionToUnit(resolvedDescriptor, getTypeInferredByFrontendOrFail(ktCallableReference))
+            requiresCoercionToUnit(resolvedDescriptor, callableReferenceType) ||
+            requiresSuspendConversion(resolvedDescriptor, callableReferenceType)
         ) {
-            return generateAdaptedCallableReference(ktCallableReference, callBuilder)
+            return generateAdaptedCallableReference(ktCallableReference, callBuilder, callableReferenceType)
         }
 
         return statementGenerator.generateCallReceiver(
@@ -91,7 +93,7 @@ class ReflectionReferencesGenerator(statementGenerator: StatementGenerator) : St
         ).call { dispatchReceiverValue, extensionReceiverValue ->
             generateCallableReference(
                 ktCallableReference,
-                getTypeInferredByFrontendOrFail(ktCallableReference),
+                callableReferenceType,
                 callBuilder.descriptor,
                 callBuilder.typeArguments
             ).also { irCallableReference ->
@@ -106,9 +108,15 @@ class ReflectionReferencesGenerator(statementGenerator: StatementGenerator) : St
         return KotlinBuiltIns.isUnit(ktExpectedReturnType) && !KotlinBuiltIns.isUnit(descriptor.returnType!!)
     }
 
+    private fun requiresSuspendConversion(descriptor: CallableDescriptor, callableReferenceType: KotlinType): Boolean =
+        descriptor is FunctionDescriptor &&
+                !descriptor.isSuspend &&
+                callableReferenceType.isKSuspendFunctionType
+
     private fun generateAdaptedCallableReference(
         ktCallableReference: KtCallableReferenceExpression,
-        callBuilder: CallBuilder
+        callBuilder: CallBuilder,
+        callableReferenceType: KotlinType
     ): IrExpression {
         val adapteeDescriptor = callBuilder.descriptor
         if (adapteeDescriptor !is FunctionDescriptor) {
@@ -128,7 +136,7 @@ class ReflectionReferencesGenerator(statementGenerator: StatementGenerator) : St
         val ktExpectedParameterTypes = ktFunctionalTypeArguments.take(ktFunctionalTypeArguments.size - 1).map { it.type }
 
         val irAdapterFun =
-            createAdapterFun(startOffset, endOffset, adapteeDescriptor, ktExpectedParameterTypes, ktExpectedReturnType, callBuilder)
+            createAdapterFun(startOffset, endOffset, adapteeDescriptor, ktExpectedParameterTypes, ktExpectedReturnType, callBuilder, callableReferenceType)
         val irCall = createAdapteeCall(startOffset, endOffset, adapteeSymbol, callBuilder, irAdapterFun)
 
         irAdapterFun.body = IrBlockBodyImpl(startOffset, endOffset).apply {
@@ -326,9 +334,13 @@ class ReflectionReferencesGenerator(statementGenerator: StatementGenerator) : St
         ktExpectedParameterTypes: List<KotlinType>,
         ktExpectedReturnType: KotlinType,
         callBuilder: CallBuilder,
+        callableReferenceType: KotlinType
     ): IrSimpleFunction {
         val adapterFunctionDescriptor = WrappedSimpleFunctionDescriptor()
 
+        val hasSuspendConversion = !adapteeDescriptor.isSuspend &&
+                callableReferenceType.isKSuspendFunctionType
+
         return context.symbolTable.declareSimpleFunction(
             startOffset, endOffset,
             IrDeclarationOrigin.ADAPTER_FOR_CALLABLE_REFERENCE,
@@ -345,7 +357,7 @@ class ReflectionReferencesGenerator(statementGenerator: StatementGenerator) : St
                 isInline = adapteeDescriptor.isInline, // TODO ?
                 isExternal = false,
                 isTailrec = false,
-                isSuspend = adapteeDescriptor.isSuspend, // TODO ?
+                isSuspend = adapteeDescriptor.isSuspend || hasSuspendConversion,
                 isOperator = adapteeDescriptor.isOperator, // TODO ?
                 isExpect = false,
                 isFakeOverride = false