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Add EmittedIL tests for reflection-free record and union ToString
Locks in the IL emitted under --reflectionfree: each field is boxed and rendered through Operators.ToString with a null guard, and the parts are joined with String.Concat (array form for the record, 3-arg form for the single-field union case). Nullary union cases return the bare case name. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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‎tests/FSharp.Compiler.ComponentTests/EmittedIL/ReflectionFreeToString.fs‎

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// Copyright (c) Microsoft Corporation. All Rights Reserved. See License.txt in the project root for license information.
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namespace EmittedIL
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open Xunit
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open FSharp.Test.Compiler
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module ``ReflectionFreeToString`` =
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// Under --reflectionfree the reflective sprintf "%+A" ToString is replaced by a structurally
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// generated one. These tests lock in the emitted IL: a match/field-read that boxes each field,
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// renders it through Operators.ToString (the `string` operator) with a null guard, and joins the
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// parts with String.Concat. No PrintfFormat is constructed.
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[<Fact>]
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let ``Record ToString is generated structurally without printf`` () =
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FSharp """
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module ReflectionFreeToString
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type Point = { X: int; Y: int }
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"""
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|> withOptions [ "--reflectionfree" ]
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|> compile
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|> shouldSucceed
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|> verifyIL ["""
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.method public strict virtual instance string ToString() cil managed
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{
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.custom instance void [runtime]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 )
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.maxstack 6
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.locals init (int32 V_0)
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IL_0000: ldc.i4.7
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IL_0001: newarr [runtime]System.String
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IL_0006: dup
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IL_0007: ldc.i4.0
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IL_0008: ldstr "{ "
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IL_000d: stelem [runtime]System.String
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IL_0012: dup
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IL_0013: ldc.i4.1
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IL_0014: ldstr "X = "
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IL_0019: stelem [runtime]System.String
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IL_001e: dup
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IL_001f: ldc.i4.2
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IL_0020: ldarg.0
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IL_0021: ldfld int32 ReflectionFreeToString/Point::X@
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IL_0026: stloc.0
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IL_0027: ldloc.0
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IL_0028: call object [FSharp.Core]Microsoft.FSharp.Core.Operators::Box<int32>(!!0)
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IL_002d: brfalse.s IL_0037
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IL_002f: ldloc.0
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IL_0030: call string [FSharp.Core]Microsoft.FSharp.Core.Operators::ToString<int32>(!!0)
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IL_0035: br.s IL_003c
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IL_0037: ldstr "null"
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IL_003c: stelem [runtime]System.String
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IL_0041: dup
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IL_0042: ldc.i4.3
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IL_0043: ldstr "; "
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IL_0048: stelem [runtime]System.String
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IL_004d: dup
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IL_004e: ldc.i4.4
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IL_004f: ldstr "Y = "
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IL_0054: stelem [runtime]System.String
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IL_0059: dup
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IL_005a: ldc.i4.5
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IL_005b: ldarg.0
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IL_005c: ldfld int32 ReflectionFreeToString/Point::Y@
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IL_0061: stloc.0
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IL_0062: ldloc.0
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IL_0063: call object [FSharp.Core]Microsoft.FSharp.Core.Operators::Box<int32>(!!0)
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IL_0068: brfalse.s IL_0072
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IL_006a: ldloc.0
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IL_006b: call string [FSharp.Core]Microsoft.FSharp.Core.Operators::ToString<int32>(!!0)
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IL_0070: br.s IL_0077
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IL_0072: ldstr "null"
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IL_0077: stelem [runtime]System.String
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IL_007c: dup
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IL_007d: ldc.i4.6
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IL_007e: ldstr " }"
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IL_0083: stelem [runtime]System.String
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IL_0088: call string [runtime]System.String::Concat(string[])
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IL_008d: ret
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}"""]
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[<Fact>]
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let ``Union ToString is generated structurally without printf`` () =
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FSharp """
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module ReflectionFreeToString
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type Color = | Red | Custom of int
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"""
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|> withOptions [ "--reflectionfree" ]
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|> compile
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|> shouldSucceed
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|> verifyIL ["""
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.method public strict virtual instance string ToString() cil managed
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{
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.custom instance void [runtime]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 )
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.maxstack 5
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.locals init (class ReflectionFreeToString/Color/Custom V_0,
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int32 V_1)
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IL_0000: ldarg.0
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IL_0001: isinst ReflectionFreeToString/Color/_Red
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IL_0006: brfalse.s IL_000e
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IL_0008: ldstr "Red"
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IL_000d: ret
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IL_000e: ldarg.0
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IL_000f: castclass ReflectionFreeToString/Color/Custom
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IL_0014: stloc.0
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IL_0015: ldstr "Custom("
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IL_001a: ldloc.0
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IL_001b: ldfld int32 ReflectionFreeToString/Color/Custom::item
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IL_0020: stloc.1
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IL_0021: ldloc.1
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IL_0022: call object [FSharp.Core]Microsoft.FSharp.Core.Operators::Box<int32>(!!0)
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IL_0027: brfalse.s IL_0031
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IL_0029: ldloc.1
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IL_002a: call string [FSharp.Core]Microsoft.FSharp.Core.Operators::ToString<int32>(!!0)
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IL_002f: br.s IL_0036
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IL_0031: ldstr "null"
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IL_0036: ldstr ")"
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IL_003b: call string [runtime]System.String::Concat(string,
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string,
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string)
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IL_0040: ret
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}"""]

‎tests/FSharp.Compiler.ComponentTests/FSharp.Compiler.ComponentTests.fsproj‎

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<Compile Include="EmittedIL\RealInternalSignature\RealInternalSignature.fs" />
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<Compile Include="EmittedIL\SkipLocalsInit.fs" />
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<Compile Include="EmittedIL\StringFormatAndInterpolation.fs" />
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<Compile Include="EmittedIL\ReflectionFreeToString.fs" />
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<!--<Compile Include="EmittedIL\StructGettersReadOnly.fs" />-->
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<Compile Include="EmittedIL\TailCalls.fs" />
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<Compile Include="EmittedIL\TupleElimination.fs" />

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