Do not generate fields for unused suspend lambda parameters

This also allows us to not spill them in the lambda.
But, disable this optimization for local named functions.

 #KT-16222 In progress

compiler/backend/src/org/jetbrains/kotlin/codegen/ExpressionCodegen.java

@@ -52,7 +52,6 @@ import org.jetbrains.kotlin.descriptors.impl.TypeAliasConstructorDescriptor;
 import org.jetbrains.kotlin.diagnostics.Errors;
 import org.jetbrains.kotlin.lexer.KtTokens;
 import org.jetbrains.kotlin.load.java.JvmAbi;
-import org.jetbrains.kotlin.resolve.sam.SamConstructorDescriptor;
 import org.jetbrains.kotlin.load.kotlin.MethodSignatureMappingKt;
 import org.jetbrains.kotlin.load.kotlin.TypeSignatureMappingKt;
 import org.jetbrains.kotlin.name.Name;
@@ -77,6 +76,7 @@ import org.jetbrains.kotlin.resolve.jvm.diagnostics.JvmDeclarationOriginKt;
 import org.jetbrains.kotlin.resolve.jvm.jvmSignature.JvmMethodParameterKind;
 import org.jetbrains.kotlin.resolve.jvm.jvmSignature.JvmMethodParameterSignature;
 import org.jetbrains.kotlin.resolve.jvm.jvmSignature.JvmMethodSignature;
+import org.jetbrains.kotlin.resolve.sam.SamConstructorDescriptor;
 import org.jetbrains.kotlin.resolve.scopes.receivers.*;
 import org.jetbrains.kotlin.synthetic.SyntheticJavaPropertyDescriptor;
 import org.jetbrains.kotlin.types.*;

compiler/backend/src/org/jetbrains/kotlin/codegen/coroutines/CoroutineCodegen.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.codegen.coroutines
 import com.intellij.util.ArrayUtil
 import org.jetbrains.kotlin.backend.common.CodegenUtil
 import org.jetbrains.kotlin.builtins.isSuspendFunctionTypeOrSubtype
+import org.jetbrains.kotlin.cfg.index
 import org.jetbrains.kotlin.codegen.*
 import org.jetbrains.kotlin.codegen.binding.CalculatedClosure
 import org.jetbrains.kotlin.codegen.binding.CodegenBinding
@@ -22,6 +23,7 @@ import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.config.isReleaseCoroutines
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.descriptors.annotations.Annotations
+import org.jetbrains.kotlin.descriptors.impl.AnonymousFunctionDescriptor
 import org.jetbrains.kotlin.descriptors.impl.SimpleFunctionDescriptorImpl
 import org.jetbrains.kotlin.descriptors.impl.ValueParameterDescriptorImpl
 import org.jetbrains.kotlin.incremental.components.NoLookupLocation
@@ -229,6 +231,7 @@ class CoroutineCodegenForLambda private constructor(
 
     override fun generateClosureBody() {
         for (parameter in allFunctionParameters()) {
+            if (parameter.isUnused()) continue
             val fieldInfo = parameter.getFieldInfoForCoroutineLambdaParameter()
             v.newField(
                 OtherOrigin(parameter),
@@ -241,6 +244,10 @@ class CoroutineCodegenForLambda private constructor(
         generateResumeImpl()
     }
 
+    private fun ParameterDescriptor.isUnused(): Boolean =
+        originalSuspendFunctionDescriptor is AnonymousFunctionDescriptor &&
+                bindingContext[BindingContext.SUSPEND_LAMBDA_PARAMETER_USED, originalSuspendFunctionDescriptor to index()] != true
+
     private val generateErasedCreate: Boolean = allFunctionParameters().size <= 1
 
     private val doNotGenerateInvokeBridge: Boolean = !originalSuspendFunctionDescriptor.isLocalSuspendFunctionNotSuspendLambda()
@@ -398,39 +405,41 @@ class CoroutineCodegenForLambda private constructor(
             var index = 1
             for (parameter in allFunctionParameters()) {
                 val fieldInfoForCoroutineLambdaParameter = parameter.getFieldInfoForCoroutineLambdaParameter()
-                if (isBigArity) {
-                    load(cloneIndex, fieldInfoForCoroutineLambdaParameter.ownerType)
-                    load(1, AsmTypes.OBJECT_TYPE)
-                    iconst(index - 1)
-                    aload(AsmTypes.OBJECT_TYPE)
-                    StackValue.coerce(
-                        AsmTypes.OBJECT_TYPE, builtIns.nullableAnyType,
-                        fieldInfoForCoroutineLambdaParameter.fieldType, fieldInfoForCoroutineLambdaParameter.fieldKotlinType,
-                        this
-                    )
-                    putfield(
-                        fieldInfoForCoroutineLambdaParameter.ownerInternalName,
-                        fieldInfoForCoroutineLambdaParameter.fieldName,
-                        fieldInfoForCoroutineLambdaParameter.fieldType.descriptor
-                    )
-                } else {
-                    if (generateErasedCreate) {
-                        load(index, AsmTypes.OBJECT_TYPE)
+                if (!parameter.isUnused()) {
+                    if (isBigArity) {
+                        load(cloneIndex, fieldInfoForCoroutineLambdaParameter.ownerType)
+                        load(1, AsmTypes.OBJECT_TYPE)
+                        iconst(index - 1)
+                        aload(AsmTypes.OBJECT_TYPE)
                         StackValue.coerce(
                             AsmTypes.OBJECT_TYPE, builtIns.nullableAnyType,
                             fieldInfoForCoroutineLambdaParameter.fieldType, fieldInfoForCoroutineLambdaParameter.fieldKotlinType,
                             this
                         )
+                        putfield(
+                            fieldInfoForCoroutineLambdaParameter.ownerInternalName,
+                            fieldInfoForCoroutineLambdaParameter.fieldName,
+                            fieldInfoForCoroutineLambdaParameter.fieldType.descriptor
+                        )
                     } else {
-                        load(index, fieldInfoForCoroutineLambdaParameter.fieldType)
+                        if (generateErasedCreate) {
+                            load(index, AsmTypes.OBJECT_TYPE)
+                            StackValue.coerce(
+                                AsmTypes.OBJECT_TYPE, builtIns.nullableAnyType,
+                                fieldInfoForCoroutineLambdaParameter.fieldType, fieldInfoForCoroutineLambdaParameter.fieldKotlinType,
+                                this
+                            )
+                        } else {
+                            load(index, fieldInfoForCoroutineLambdaParameter.fieldType)
+                        }
+                        AsmUtil.genAssignInstanceFieldFromParam(
+                            fieldInfoForCoroutineLambdaParameter,
+                            index,
+                            this,
+                            cloneIndex,
+                            generateErasedCreate
+                        )
                     }
-                    AsmUtil.genAssignInstanceFieldFromParam(
-                        fieldInfoForCoroutineLambdaParameter,
-                        index,
-                        this,
-                        cloneIndex,
-                        generateErasedCreate
-                    )
                 }
                 index += if (isBigArity || generateErasedCreate) 1 else fieldInfoForCoroutineLambdaParameter.fieldType.size
             }
@@ -442,6 +451,7 @@ class CoroutineCodegenForLambda private constructor(
 
     private fun ExpressionCodegen.initializeCoroutineParameters() {
         for (parameter in allFunctionParameters()) {
+            if (parameter.isUnused()) continue
             val fieldStackValue =
                 StackValue.field(
                     parameter.getFieldInfoForCoroutineLambdaParameter(), generateThisOrOuter(context.thisDescriptor, false)
@@ -463,7 +473,11 @@ class CoroutineCodegenForLambda private constructor(
             v.visitLocalVariable(name, mappedType.descriptor, null, label, endLabel, newIndex)
         }
 
-        initializeVariablesForDestructuredLambdaParameters(this, originalSuspendFunctionDescriptor.valueParameters, endLabel)
+        initializeVariablesForDestructuredLambdaParameters(
+            this,
+            originalSuspendFunctionDescriptor.valueParameters.filter { !it.isUnused() },
+            endLabel
+        )
     }
 
     private fun allFunctionParameters(): List<ParameterDescriptor> =