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Add .NET 11 runtime async/await interop
Adds first-class async/await support for ClojureCLR targeting .NET 11's runtime async feature. The compiler emits MethodImplAttributes.Async (0x2000) and calls AsyncHelpers.Await — the runtime handles suspension, resumption, and local hoisting. No state machine generation needed. Compiler changes: - New AwaitExpr AST node with await* special form - ^:async metadata on defn sets the async flag on generated methods - FnMethod emits invokeAsync() with 0x2000 flag, invoke() delegates to it - Compile-time validation: await outside ^:async fn, await in catch/finally - ^:async + primitive type hints rejected at compile time Async interface support for gen-class and proxy: - Methods returning Task/Task<T>/ValueTask/ValueTask<T> get 0x2000 flag - Stubs await the IFn result and cast to the interface return type - Enables implementing IAsyncDisposable, custom async interfaces, etc. New Clojure namespace clojure.async.task: - t/await — macro expanding to await* special form - t/async — immediately-invoked async lambda block - t/await-all — parallel await via Task.WhenAll - t/->task, t/task? — helpers All async code is gated behind #if NET11_0_OR_GREATER. Existing targets (net6.0 through net10.0, net462, net481) are unaffected. Includes 14 NUnit tests covering: basic async defn, args, closures across await, chaining, void Task, async blocks, Task<T>, compile errors (outside async, in catch, prim hints), C# interop, deftype async interface.
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‎Clojure/Clojure.Source/Clojure.Source.csproj‎

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<EmbeddedResource Include="clojure\core\server.clj">
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<CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
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</EmbeddedResource>
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<EmbeddedResource Include="clojure\async\task.clj">
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<CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
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</EmbeddedResource>
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</ItemGroup>
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</Project>

‎Clojure/Clojure.Source/clojure/async/task.clj‎

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(ns clojure.async.task
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"Task-based async/await interop for .NET 11+ runtime async.
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Requires .NET 11 Preview 1 or later."
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(:refer-clojure :exclude [await]))
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(defmacro await
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"Suspends the current ^:async function until the given Task completes.
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Returns the task's result value. Only valid inside a ^:async defn
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or an (async ...) block.
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Usage:
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(t/await (.ReadAllTextAsync System.IO.File path))
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(t/await some-task)"
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[task-expr]
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`(await* ~task-expr))
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(defmacro async
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"Executes body in an async context, returning a Task<object>.
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The body may use (t/await ...) to suspend on Tasks.
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Usage:
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(t/async
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(let [data (t/await (fetch url))]
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(process data)))"
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[& body]
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`((^:async fn* [] ~@body)))
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(defmacro await-all
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"Awaits multiple tasks in parallel. Returns a vector of results.
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Usage:
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(let [[a b c] (t/await-all (task1) (task2) (task3))]
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...)"
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[& task-exprs]
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(let [tasks-sym (gensym "tasks")]
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`(let [~tasks-sym (into-array System.Threading.Tasks.Task [~@task-exprs])]
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(await* (System.Threading.Tasks.Task/WhenAll ~tasks-sym))
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(mapv (fn [t#] (.Result ^|System.Threading.Tasks.Task`1[System.Object]| t#)) ~tasks-sym))))
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(defn ->task
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"Wraps a value in a completed Task<object>.
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Uses an immediately-invoked async fn to wrap the value."
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[value]
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((^:async fn* [] value)))
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(defn task?
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"Returns true if x is a Task."
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[x]
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(instance? System.Threading.Tasks.Task x))

‎Clojure/Clojure.Source/clojure/core.clj‎

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;;todo - restore propagation of fn name
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;;must figure out how to convey primitive hints to self calls first
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;;(cons `fn fdecl)
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(with-meta (cons `fn fdecl) {:rettag (:tag m)})))))
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(with-meta (cons `fn fdecl) (if (:async m) {:rettag (:tag m) :async true} {:rettag (:tag m)}))))))
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(. (var defn) (setMacro))
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‎Clojure/Clojure/CljCompiler/Ast/AwaitExpr.cs‎

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/**
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* Copyright (c) Rich Hickey. All rights reserved.
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* The use and distribution terms for this software are covered by the
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* Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
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* which can be found in the file epl-v10.html at the root of this distribution.
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* By using this software in any fashion, you are agreeing to be bound by
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* the terms of this license.
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* You must not remove this notice, or any other, from this software.
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**/
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#if NET11_0_OR_GREATER
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using System;
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using System.Reflection;
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using System.Reflection.Emit;
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using System.Threading.Tasks;
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using clojure.lang.CljCompiler.Context;
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namespace clojure.lang.CljCompiler.Ast
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{
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public class AwaitExpr : Expr
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{
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#region Data
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readonly Expr _taskExpr;
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public Expr TaskExpr => _taskExpr;
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readonly Type _resultType;
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readonly MethodInfo _awaitMethod;
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#endregion
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#region Ctors
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public AwaitExpr(Expr taskExpr, Type resultType, MethodInfo awaitMethod)
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{
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_taskExpr = taskExpr;
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_resultType = resultType;
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_awaitMethod = awaitMethod;
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}
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#endregion
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#region Type mangling
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public bool HasClrType => true;
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public Type ClrType => _resultType == typeof(void) ? typeof(object) : _resultType;
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#endregion
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#region Parsing
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public sealed class Parser : IParser
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{
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public Expr Parse(ParserContext pcon, object frm)
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{
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ISeq form = (ISeq)frm;
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if (!Compiler.RuntimeAsyncAvailable)
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throw new ParseException(
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"(await* ...) requires .NET 11+ with runtime async support");
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if (!Compiler.AsyncMethodCache.IsSupported)
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throw new ParseException(
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"(await* ...) requires System.Runtime.CompilerServices.AsyncHelpers");
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if (RT.count(form) != 2)
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throw new ParseException(
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"Wrong number of arguments to await*, expected: (await* expr)");
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ObjMethod method = (ObjMethod)Compiler.MethodVar.deref();
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if (method == null)
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throw new ParseException(
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"(await* ...) must appear inside a function body");
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if (Compiler.InCatchFinallyVar.deref() is not null)
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throw new ParseException(
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"(await* ...) cannot appear inside a catch, finally, or fault handler");
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if (!method.IsAsync)
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throw new ParseException(
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"(await* ...) can only be used inside a ^:async function or (async ...) block");
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if (pcon.Rhc == RHC.Eval)
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return Compiler.Analyze(pcon,
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RT.list(RT.list(Compiler.FnOnceSym, PersistentVector.EMPTY, form)),
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"await__" + RT.nextID());
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Expr taskExpr = Compiler.Analyze(
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pcon.SetRhc(RHC.Expression).SetAssign(false),
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RT.second(form));
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Type taskType;
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if (taskExpr.HasClrType)
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{
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taskType = taskExpr.ClrType;
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bool isTaskType =
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taskType == typeof(Task)
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|| taskType == typeof(ValueTask)
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|| (taskType.IsGenericType &&
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(taskType.GetGenericTypeDefinition() == typeof(Task<>)
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|| taskType.GetGenericTypeDefinition() == typeof(ValueTask<>)));
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if (!isTaskType)
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{
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if (taskType == typeof(object))
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taskType = typeof(Task<object>);
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else
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throw new ParseException(
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$"(await* ...) requires a Task, Task<T>, ValueTask, or ValueTask<T>, got: {taskType.FullName}");
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}
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}
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else
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{
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taskType = typeof(Task<object>);
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}
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MethodInfo awaitMethod =
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Compiler.AsyncMethodCache.ResolveAwaitMethod(taskType, out Type resultType);
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if (awaitMethod == null)
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throw new ParseException(
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"Failed to resolve AsyncHelpers.Await method for type: " + taskType.FullName);
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method.HasAwait = true;
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return new AwaitExpr(taskExpr, resultType, awaitMethod);
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}
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}
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#endregion
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#region eval
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public object Eval()
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{
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throw new InvalidOperationException("Can't eval await*");
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}
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#endregion
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#region Code generation
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public void Emit(RHC rhc, ObjExpr objx, CljILGen ilg)
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{
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_taskExpr.Emit(RHC.Expression, objx, ilg);
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if (_taskExpr.HasClrType && _taskExpr.ClrType == typeof(object))
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{
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ilg.Emit(OpCodes.Castclass, typeof(Task<object>));
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}
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ilg.Emit(OpCodes.Call, _awaitMethod);
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if (_resultType != typeof(void))
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{
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if (rhc == RHC.Statement)
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ilg.Emit(OpCodes.Pop);
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else if (_resultType.IsValueType)
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ilg.Emit(OpCodes.Box, _resultType);
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}
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else
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{
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if (rhc != RHC.Statement)
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ilg.Emit(OpCodes.Ldnull);
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}
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}
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public bool HasNormalExit() => true;
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#endregion
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}
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}
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#endif

‎Clojure/Clojure/CljCompiler/Ast/FnExpr.cs‎

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static readonly Keyword KW_ONCE = Keyword.intern(null, "once");
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#if NET11_0_OR_GREATER
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static readonly Keyword KW_ASYNC = Keyword.intern(null, "async");
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public bool IsAsync { get; private set; }
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#endif
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FnMethod _variadicMethod = null;
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public FnMethod VariadicMethod => _variadicMethod;
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bool IsVariadic => _variadicMethod is not null;
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if (((IMeta)form.first()).meta() is not null)
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{
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fn.OnceOnly = RT.booleanCast(RT.get(RT.meta(form.first()), KW_ONCE));
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#if NET11_0_OR_GREATER
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fn.IsAsync = RT.booleanCast(RT.get(RT.meta(form.first()), KW_ASYNC));
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#endif
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}
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#if NET11_0_OR_GREATER
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// Also check metadata on the form itself (propagated by defn -> fn macro)
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if (!fn.IsAsync && RT.meta(form) is IPersistentMap formMeta)
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{
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fn.IsAsync = RT.booleanCast(RT.get(formMeta, KW_ASYNC));
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}
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#endif
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fn.ComputeNames(form, name);
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