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Fix null coalescing operator emit with span conversion #75103

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Oct 2, 2024
Merged

Fix null coalescing operator emit with span conversion #75103

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6029531
Fix null coalescing operator emit with span conversion
jjonescz Sep 13, 2024
b535653
Simplify check
jjonescz Sep 19, 2024
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2 changes: 1 addition & 1 deletion src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_NullCoalescingOperator.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -89,7 +89,7 @@ private BoundExpression MakeNullCoalescingOperator(
// we can apply conversion before doing the null check that allows for a more efficient IL emit.
Debug.Assert(rewrittenLeft.Type is { });
if (rewrittenLeft.Type.IsReferenceType &&
BoundNode.GetConversion(leftConversion, leftPlaceholder) is { IsImplicit: true, IsUserDefined: false })
BoundNode.GetConversion(leftConversion, leftPlaceholder) is { Kind: ConversionKind.Identity or ConversionKind.ImplicitReference })
{
rewrittenLeft = ApplyConversionIfNotIdentity(leftConversion, leftPlaceholder, rewrittenLeft);

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101 changes: 101 additions & 0 deletions src/Compilers/CSharp/Test/Emit3/FirstClassSpanTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -6694,6 +6694,107 @@ ReadOnlySpan<object> M()
Diagnostic(ErrorCode.ERR_EscapeVariable, "x").WithArguments("x").WithLocation(7, 16));
}

[Theory, MemberData(nameof(LangVersions))]
public void Conversion_Array_Span_Coalesce(LanguageVersion langVersion)
{
var source = """
using System;
class C
{
void M1(int[] a)
{
M2(a ?? Span<int>.Empty);
}
void M2(Span<int> s) => throw null;
}
""";
var comp = CreateCompilationWithSpanAndMemoryExtensions(source,
parseOptions: TestOptions.Regular.WithLanguageVersion(langVersion));
var verifier = CompileAndVerify(comp);
verifier.VerifyDiagnostics();
verifier.VerifyIL("C.M1", """
{
// Code size 25 (0x19)
.maxstack 2
.locals init (int[] V_0)
IL_0000: ldarg.0
IL_0001: ldarg.1
IL_0002: stloc.0
IL_0003: ldloc.0
IL_0004: brtrue.s IL_000d
IL_0006: call "System.Span<int> System.Span<int>.Empty.get"
IL_000b: br.s IL_0013
IL_000d: ldloc.0
IL_000e: call "System.Span<int> System.Span<int>.op_Implicit(int[])"
IL_0013: call "void C.M2(System.Span<int>)"
IL_0018: ret
}
""");
}

[Fact]
public void Conversion_string_ReadOnlySpan_Coalesce()
{
var source = """
using System;
class C
{
void M1(string s)
{
M2(s ?? ReadOnlySpan<char>.Empty);
}
void M2(ReadOnlySpan<char> s) => throw null;
}
""";
var comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.Regular13);
var verifier = CompileAndVerify(comp);
verifier.VerifyDiagnostics();
var owner = ExecutionConditionUtil.IsCoreClr ? "string" : "System.ReadOnlySpan<char>";
verifier.VerifyIL("C.M1", $$"""
{
// Code size 25 (0x19)
.maxstack 2
.locals init (string V_0)
IL_0000: ldarg.0
IL_0001: ldarg.1
IL_0002: stloc.0
IL_0003: ldloc.0
IL_0004: brtrue.s IL_000d
IL_0006: call "System.ReadOnlySpan<char> System.ReadOnlySpan<char>.Empty.get"
IL_000b: br.s IL_0013
IL_000d: ldloc.0
IL_000e: call "System.ReadOnlySpan<char> {{owner}}.op_Implicit(string)"
IL_0013: call "void C.M2(System.ReadOnlySpan<char>)"
IL_0018: ret
}
""");

var expectedIl = """
{
// Code size 25 (0x19)
.maxstack 2
.locals init (string V_0)
IL_0000: ldarg.0
IL_0001: ldarg.1
IL_0002: stloc.0
IL_0003: ldloc.0
IL_0004: brtrue.s IL_000d
IL_0006: call "System.ReadOnlySpan<char> System.ReadOnlySpan<char>.Empty.get"
IL_000b: br.s IL_0013
IL_000d: ldloc.0
IL_000e: call "System.ReadOnlySpan<char> System.MemoryExtensions.AsSpan(string)"
IL_0013: call "void C.M2(System.ReadOnlySpan<char>)"
IL_0018: ret
}
""";

comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.RegularNext);
CompileAndVerify(comp).VerifyDiagnostics().VerifyIL("C.M1", expectedIl);

comp = CreateCompilationWithSpanAndMemoryExtensions(source);
CompileAndVerify(comp).VerifyDiagnostics().VerifyIL("C.M1", expectedIl);
}

[Fact]
public void OverloadResolution_SpanVsIEnumerable()
{
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4 changes: 4 additions & 0 deletions src/Compilers/Test/Utilities/CSharp/TestSources.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,8 @@ public Span(T[] arr, int start, int length)
this.Length = length;
}

public static Span<T> Empty => default;

public void CopyTo(Span<T> other)
{
Array.Copy(arr, start, other.arr, other.start, Length);
Expand Down Expand Up @@ -130,6 +132,8 @@ public ReadOnlySpan(T[] arr, int start, int length)
this.Length = length;
}

public static ReadOnlySpan<T> Empty => default;

public void CopyTo(Span<T> other)
{
Array.Copy(arr, start, other.arr, other.start, Length);
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