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Prefer array to ReadOnlySpan over Span #75853

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merged 5 commits into from
Nov 21, 2024
Merged

Prefer array to ReadOnlySpan over Span #75853

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cce4d0b
Prefer array to ROS over Span
jjonescz Nov 11, 2024
745ca79
Update tests
jjonescz Nov 11, 2024
946ec84
Add more tests
jjonescz Nov 11, 2024
cdeb600
Test ambiguity
jjonescz Nov 12, 2024
514b583
Merge branch 'main' into FirstClassSpan-27-BetterROS
jjonescz Nov 21, 2024
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13 changes: 13 additions & 0 deletions src/Compilers/CSharp/Portable/Binder/Semantics/OverloadResolution/OverloadResolution.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2980,6 +2980,19 @@ private BetterResult BetterConversionFromExpression(BoundExpression node, TypeSy
switch ((conv1.Kind, conv2.Kind))
{
case (ConversionKind.ImplicitSpan, ConversionKind.ImplicitSpan):
// If the expression is of an array type, prefer ReadOnlySpan over Span (to avoid ArrayTypeMismatchExceptions).
if (node.Type is ArrayTypeSymbol)
{
if (t1.IsReadOnlySpan() && t2.IsSpan())
{
return BetterResult.Left;
}

if (t1.IsSpan() && t2.IsReadOnlySpan())
{
return BetterResult.Right;
}
}
break;
case (_, ConversionKind.ImplicitSpan):
return BetterResult.Right;
Expand Down
162 changes: 156 additions & 6 deletions src/Compilers/CSharp/Test/Emit3/FirstClassSpanTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -458,6 +458,37 @@ static class C
CompileAndVerify(comp, expectedOutput: expectedOutput).VerifyDiagnostics();
}

[Fact]
public void BreakingChange_TypeInference_SpanVsIEnumerable_02_BothSpanAndReadOnlySpan()
{
var source = """
using System;
using System.Collections.Generic;

string[] s = new[] { "a" };
object[] o = s;

C.R(o);

static class C
{
public static void R<T>(IEnumerable<T> e) => Console.Write(1);
public static void R<T>(ReadOnlySpan<T> s) => Console.Write(2);
public static void R<T>(Span<T> s) => Console.Write(3);
}
""";
var comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.Regular13);
CompileAndVerify(comp, expectedOutput: "1").VerifyDiagnostics();

var expectedOutput = "2";

comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.RegularNext);
CompileAndVerify(comp, expectedOutput: expectedOutput).VerifyDiagnostics();

comp = CreateCompilationWithSpanAndMemoryExtensions(source);
CompileAndVerify(comp, expectedOutput: expectedOutput).VerifyDiagnostics();
}

[Fact]
public void BreakingChange_Conversion_SpanVsIEnumerable()
{
Expand Down Expand Up @@ -518,6 +549,37 @@ static class E
CompileAndVerify(comp, expectedOutput: expectedOutput).VerifyDiagnostics();
}

[Fact]
public void BreakingChange_Conversion_SpanVsIEnumerable_BothSpanAndReadOnlySpan()
{
var source = """
using System;
using System.Collections.Generic;

string[] s = new[] { "a" };
object[] o = s;

o.R<object>();

static class E
{
public static void R<T>(this IEnumerable<T> e) => Console.Write(1);
public static void R<T>(this ReadOnlySpan<T> s) => Console.Write(2);
public static void R<T>(this Span<T> s) => Console.Write(3);
}
""";
var comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.Regular13);
CompileAndVerify(comp, expectedOutput: "1").VerifyDiagnostics();

var expectedOutput = "2";

comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.RegularNext);
CompileAndVerify(comp, expectedOutput: expectedOutput).VerifyDiagnostics();

comp = CreateCompilationWithSpanAndMemoryExtensions(source);
CompileAndVerify(comp, expectedOutput: expectedOutput).VerifyDiagnostics();
}

[Fact]
public void BreakingChange_Conversion_SpanVsArray()
{
Expand Down Expand Up @@ -631,6 +693,36 @@ static class C
CreateCompilationWithSpanAndMemoryExtensions(source).VerifyDiagnostics(expectedDiagnostics);
}

[Fact]
public void BreakingChange_OverloadResolution_Betterness_01()
{
var source = """
using System;
using System.Collections.Generic;

var x = new int[0];
C.M(x, x);

static class C
{
public static void M(IEnumerable<int> a, ReadOnlySpan<int> b) => Console.Write(1);
public static void M(Span<int> a, Span<int> b) => Console.Write(2);
}
""";
var comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.Regular13);
CompileAndVerify(comp, expectedOutput: "2").VerifyDiagnostics();

var expectedDiagnostics = new[]
{
// (5,3): error CS0121: The call is ambiguous between the following methods or properties: 'C.M(IEnumerable<int>, ReadOnlySpan<int>)' and 'C.M(Span<int>, Span<int>)'
// C.M(x, x);
Diagnostic(ErrorCode.ERR_AmbigCall, "M").WithArguments("C.M(System.Collections.Generic.IEnumerable<int>, System.ReadOnlySpan<int>)", "C.M(System.Span<int>, System.Span<int>)").WithLocation(5, 3)
};

CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.RegularNext).VerifyDiagnostics(expectedDiagnostics);
CreateCompilationWithSpanAndMemoryExtensions(source).VerifyDiagnostics(expectedDiagnostics);
}

[Theory, CombinatorialData]
public void Conversion_Array_Span_Implicit(
[CombinatorialLangVersions] LanguageVersion langVersion,
Expand Down Expand Up @@ -7857,8 +7949,8 @@ static class C
CompileAndVerify(comp, expectedOutput: expectedOutput).VerifyDiagnostics();
}

[Theory, MemberData(nameof(LangVersions))]
public void OverloadResolution_SpanVsReadOnlySpan_01(LanguageVersion langVersion)
[Fact]
public void OverloadResolution_SpanVsReadOnlySpan_01()
{
var source = """
using System;
Expand All @@ -7873,8 +7965,16 @@ static class C
public static void M(ReadOnlySpan<int> arg) => Console.Write(2);
}
""";
var comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.Regular.WithLanguageVersion(langVersion));
var comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.Regular13);
CompileAndVerify(comp, expectedOutput: "112").VerifyDiagnostics();

var expectedOutput = "212";

comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.RegularNext);
CompileAndVerify(comp, expectedOutput: expectedOutput).VerifyDiagnostics();

comp = CreateCompilationWithSpanAndMemoryExtensions(source);
CompileAndVerify(comp, expectedOutput: expectedOutput).VerifyDiagnostics();
}

[Fact]
Expand All @@ -7898,7 +7998,7 @@ static class C
var comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.Regular13);
CompileAndVerify(comp, expectedOutput: ExecutionConditionUtil.IsCoreClr ? "1123" : "1121").VerifyDiagnostics();

var expectedOutput = "1122";
var expectedOutput = "2122";

comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.RegularNext);
CompileAndVerify(comp, expectedOutput: expectedOutput).VerifyDiagnostics();
Expand Down Expand Up @@ -7939,6 +8039,31 @@ static class C
CompileAndVerify(comp, expectedOutput: expectedOutput).VerifyDiagnostics();
}

[Fact]
public void OverloadResolution_SpanVsReadOnlySpan_04()
{
var source = """
using System;

C.M1(new object[0]);
C.M1(new string[0]);

C.M2(new object[0]);
C.M2(new string[0]);

static class C
{
public static void M1(Span<string> arg) => Console.Write(1);
public static void M1(ReadOnlySpan<object> arg) => Console.Write(2);

public static void M2(Span<object> arg) => Console.Write(1);
public static void M2(ReadOnlySpan<string> arg) => Console.Write(2);
}
""";
var comp = CreateCompilationWithSpanAndMemoryExtensions(source);
CompileAndVerify(comp, expectedOutput: "2212").VerifyDiagnostics();
}

[Fact]
public void OverloadResolution_SpanVsReadOnlySpan_ExtensionMethodReceiver_01()
{
Expand All @@ -7958,7 +8083,7 @@ static class C
// (new int[0]).E();
Diagnostic(ErrorCode.ERR_BadInstanceArgType, "new int[0]").WithArguments("int[]", "E", "C.E(System.Span<int>)", "System.Span<int>").WithLocation(3, 2));

var expectedOutput = "1";
var expectedOutput = "2";

var comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.RegularNext);
CompileAndVerify(comp, expectedOutput: expectedOutput).VerifyDiagnostics();
Expand Down Expand Up @@ -8009,7 +8134,7 @@ static class C
// (new string[0]).E();
Diagnostic(ErrorCode.ERR_BadInstanceArgType, "new object[0]").WithArguments("object[]", "E", "C.E(System.Span<object>)", "System.Span<object>").WithLocation(4, 2));

var expectedOutput = "21";
var expectedOutput = "22";

var comp = CreateCompilationWithSpanAndMemoryExtensions(source, parseOptions: TestOptions.RegularNext);
CompileAndVerify(comp, expectedOutput: expectedOutput).VerifyDiagnostics();
Expand Down Expand Up @@ -8050,6 +8175,31 @@ static class C
CompileAndVerify(comp, expectedOutput: expectedOutput).VerifyDiagnostics();
}

[Fact]
public void OverloadResolution_SpanVsReadOnlySpan_ExtensionMethodReceiver_05()
{
var source = """
using System;

(new object[0]).M1();
(new string[0]).M1();

(new object[0]).M2();
(new string[0]).M2();

static class E
{
public static void M1(this Span<string> arg) => Console.Write(1);
public static void M1(this ReadOnlySpan<object> arg) => Console.Write(2);

public static void M2(this Span<object> arg) => Console.Write(1);
public static void M2(this ReadOnlySpan<string> arg) => Console.Write(2);
}
""";
var comp = CreateCompilationWithSpanAndMemoryExtensions(source);
CompileAndVerify(comp, expectedOutput: "2212").VerifyDiagnostics();
}

[Fact]
public void OverloadResolution_ReadOnlySpanVsReadOnlySpan()
{
Expand Down
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