Do not write version requirements for suspend functions

Coroutines are a stable feature since 1.3. Version requirement on
suspend functions, or functions mentioning suspend function types in the
signature, was needed to prevent older compilers from reading metadata
that they can't properly use. It's not needed anymore because a newer
metadata version prevents older compilers from reading any metadata
altogether.

Also, computing isSuspendOrHasSuspendTypesInSignature took ~0.5% of
backend time on compilation of intellij (related to KT-48233).

compiler/serialization/src/org/jetbrains/kotlin/serialization/DescriptorSerializer.kt

@@ -8,7 +8,6 @@ package org.jetbrains.kotlin.serialization
 import com.intellij.openapi.project.Project
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.builtins.isSuspendFunctionType
-import org.jetbrains.kotlin.builtins.isSuspendFunctionTypeOrSubtype
 import org.jetbrains.kotlin.builtins.transformSuspendFunctionToRuntimeFunctionType
 import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.descriptors.*
@@ -331,10 +330,6 @@ class DescriptorSerializer private constructor(
         versionRequirementTable?.run {
             builder.addAllVersionRequirement(serializeVersionRequirements(descriptor))
 
-            if (descriptor.isSuspendOrHasSuspendTypesInSignature()) {
-                builder.addVersionRequirement(writeVersionRequirementDependingOnCoroutinesVersion())
-            }
-
             if (descriptor.hasInlineClassTypesInSignature()) {
                 builder.addVersionRequirement(writeVersionRequirement(LanguageFeature.InlineClasses))
             }
@@ -429,10 +424,6 @@ class DescriptorSerializer private constructor(
         versionRequirementTable?.run {
             builder.addAllVersionRequirement(serializeVersionRequirements(descriptor))
 
-            if (descriptor.isSuspendOrHasSuspendTypesInSignature()) {
-                builder.addVersionRequirement(writeVersionRequirementDependingOnCoroutinesVersion())
-            }
-
             if (descriptor.hasInlineClassTypesInSignature()) {
                 builder.addVersionRequirement(writeVersionRequirement(LanguageFeature.InlineClasses))
             }
@@ -473,10 +464,6 @@ class DescriptorSerializer private constructor(
         versionRequirementTable?.run {
             builder.addAllVersionRequirement(serializeVersionRequirements(descriptor))
 
-            if (descriptor.isSuspendOrHasSuspendTypesInSignature()) {
-                builder.addVersionRequirement(writeVersionRequirementDependingOnCoroutinesVersion())
-            }
-
             if (descriptor.hasInlineClassTypesInSignature()) {
                 builder.addVersionRequirement(writeVersionRequirement(LanguageFeature.InlineClasses))
             }
@@ -491,15 +478,6 @@ class DescriptorSerializer private constructor(
         return builder
     }
 
-    private fun MutableVersionRequirementTable.writeVersionRequirementDependingOnCoroutinesVersion(): Int =
-        writeVersionRequirement(LanguageFeature.ReleaseCoroutines)
-
-    private fun CallableMemberDescriptor.isSuspendOrHasSuspendTypesInSignature(): Boolean {
-        if (this is FunctionDescriptor && isSuspend) return true
-
-        return allTypesFromSignature().any { type -> type.contains(UnwrappedType::isSuspendFunctionTypeOrSubtype) }
-    }
-
     private fun CallableMemberDescriptor.hasInlineClassTypesInSignature(): Boolean {
         return allTypesFromSignature().any { type -> type.contains(UnwrappedType::isInlineClassType) }
     }

compiler/testData/versionRequirement/nestedClassMembers.kt

@@ -12,8 +12,6 @@ class Outer {
 
             @RequireKotlin("1.3")
             val x = ""
-
-            suspend fun s() {}
         }
     }
 

compiler/testData/versionRequirement/suspendFun.kt

@@ -1,16 +0,0 @@
-package test
-
-suspend fun topLevel() {}
-
-class Foo {
-    constructor(block: suspend () -> Unit)
-
-    suspend fun member() {}
-}
-
-fun async1(block: suspend () -> Unit) {}
-fun (suspend () -> Unit).async2() {}
-fun async3(): suspend () -> Unit = null!!
-fun async4(): Map<Int, suspend () -> Unit>? = null
-
-val (suspend () -> Unit).asyncVal: () -> Unit get() = {}

compiler/tests/org/jetbrains/kotlin/serialization/AbstractVersionRequirementTest.kt

@@ -124,23 +124,6 @@ abstract class AbstractVersionRequirementTest : TestCaseWithTmpdir() {
 
     protected abstract fun loadModule(directory: File): ModuleDescriptor
 
-    fun testSuspendFun() {
-        doTest(
-            VersionRequirement.Version(1, 3), DeprecationLevel.ERROR, null, ProtoBuf.VersionRequirement.VersionKind.LANGUAGE_VERSION, null,
-            customLanguageVersion = LanguageVersion.KOTLIN_1_3,
-            fqNamesWithRequirements = listOf(
-                "test.topLevel",
-                "test.Foo.member",
-                "test.Foo.<init>",
-                "test.async1",
-                "test.async2",
-                "test.async3",
-                "test.async4",
-                "test.asyncVal"
-            )
-        )
-    }
-
     fun testDefinitelyNotNull() {
         doTest(
             VersionRequirement.Version(1, 7), DeprecationLevel.ERROR, null, ProtoBuf.VersionRequirement.VersionKind.LANGUAGE_VERSION, null,
@@ -221,7 +204,6 @@ abstract class AbstractVersionRequirementTest : TestCaseWithTmpdir() {
                 "test.Outer.Inner.Deep.<init>",
                 "test.Outer.Inner.Deep.f",
                 "test.Outer.Inner.Deep.x",
-                "test.Outer.Inner.Deep.s",
                 "test.Outer.Nested.g",
                 "test.Outer.Companion"
             )

libraries/tools/kotlinp/testData/SimpleClass.txt

@@ -8,7 +8,6 @@ public final class SimpleClass<in T#0 /* A */> : kotlin/Any {
   // signature: <init>(I)V
   public constructor(p: kotlin/Int /* = ... */)
 
-  // requires language version 1.3.0 (level=ERROR)
   // signature: g(Lkotlin/jvm/functions/Function0;Lkotlin/jvm/functions/Function1;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
   protected final inline suspend fun <reified T#1 /* T */> g(crossinline a: kotlin/Function0<T#0>, noinline b: suspend kotlin/Function1<kotlin/coroutines/Continuation<T#1>, kotlin/Any?>): kotlin/Unit
 

libraries/tools/kotlinp/testData/ValueClass.txt

@@ -31,7 +31,6 @@ public final value class A : kotlin/Any {
 // requires language version 1.3.0 (level=ERROR)
 public final value class B : kotlin/Any {
 
-  // requires language version 1.3.0 (level=ERROR)
   // requires language version 1.3.0 (level=ERROR)
   // signature: constructor-impl(Lkotlin/jvm/functions/Function1;)Lkotlin/jvm/functions/Function1;
   public constructor(f: suspend kotlin/Function1<kotlin/coroutines/Continuation<kotlin/Unit>, kotlin/Any?>)
@@ -45,7 +44,6 @@ public final value class B : kotlin/Any {
   // signature: toString-impl(Lkotlin/jvm/functions/Function1;)Ljava/lang/String;
   public open /* synthesized */ fun toString(): kotlin/String
 
-  // requires language version 1.3.0 (level=ERROR)
   // field: f:Lkotlin/jvm/functions/Function1;
   private final val f: suspend kotlin/Function1<kotlin/coroutines/Continuation<kotlin/Unit>, kotlin/Any?>
     private final get