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Field-backed properties: recognize field in interpolated string (#75566)
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@cston
cston authored Oct 23, 2024
1 parent ba0c208 commit 0c28435
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Showing 3 changed files with 778 additions and 2 deletions.
6 changes: 4 additions & 2 deletions src/Compilers/CSharp/Portable/Parser/LanguageParser_InterpolatedString.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -109,7 +109,7 @@ CodeAnalysis.Syntax.InternalSyntax.SyntaxList<InterpolatedStringContentSyntax> g
originalTextSpan[currentContentStart..interpolation.OpenBraceRange.Start]));

// Now parse the interpolation itself.
var interpolationNode = ParseInterpolation(this.Options, originalText, interpolation, kind);
var interpolationNode = ParseInterpolation(this.Options, originalText, interpolation, kind, IsInFieldKeywordContext);

// Make sure the interpolation starts at the right location.
var indentationError = getInterpolationIndentationError(indentationWhitespace, interpolation);
Expand Down Expand Up @@ -361,7 +361,8 @@ private static InterpolationSyntax ParseInterpolation(
CSharpParseOptions options,
string text,
Lexer.Interpolation interpolation,
Lexer.InterpolatedStringKind kind)
Lexer.InterpolatedStringKind kind,
bool isInFieldKeywordContext)
{
// Grab the text from after the { all the way to the start of the } (or the start of the : if present). This
// will be used to parse out the expression of the interpolation.
Expand All @@ -377,6 +378,7 @@ private static InterpolationSyntax ParseInterpolation(

// Now create a parser to actually handle the expression portion of the interpolation
using var tempParser = new LanguageParser(tempLexer, oldTree: null, changes: null);
using var _ = new FieldKeywordContext(tempParser, isInFieldKeywordContext);

var result = tempParser.ParseInterpolation(
text, interpolation, kind,
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293 changes: 293 additions & 0 deletions src/Compilers/CSharp/Test/Emit3/FieldKeywordTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -10171,6 +10171,299 @@ partial class B
VerifyMergedProperties(actualProperties, actualFields);
}

[Theory]
[CombinatorialData]
public void InterpolatedString(
[CombinatorialValues(LanguageVersion.CSharp13, LanguageVersionFacts.CSharpNext)] LanguageVersion languageVersion)
{
string source = $$"""
using System;
class C
{
public object P1 => $"P1: {field is null}";
public object P2 { get; set { field = value; field = $"{field}"; } }
}
class Program
{
static void Main()
{
var c = new C();
c.P2 = 2;
Console.WriteLine(c.P1);
Console.WriteLine(c.P2);
}
}
""";
var comp = CreateCompilation(
source,
parseOptions: TestOptions.Regular.WithLanguageVersion(languageVersion),
options: TestOptions.ReleaseExe,
targetFramework: TargetFramework.Net80);

if (languageVersion == LanguageVersion.CSharp13)
{
comp.VerifyEmitDiagnostics(
// (4,32): error CS0103: The name 'field' does not exist in the current context
// public object P1 => $"P1: {field is null}";
Diagnostic(ErrorCode.ERR_NameNotInContext, "field").WithArguments("field").WithLocation(4, 32),
// (5,19): error CS8652: The feature 'field keyword' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
// public object P2 { get; set { field = value; field = $"{field}"; } }
Diagnostic(ErrorCode.ERR_FeatureInPreview, "P2").WithArguments("field keyword").WithLocation(5, 19),
// (5,35): error CS0103: The name 'field' does not exist in the current context
// public object P2 { get; set { field = value; field = $"{field}"; } }
Diagnostic(ErrorCode.ERR_NameNotInContext, "field").WithArguments("field").WithLocation(5, 35),
// (5,50): error CS0103: The name 'field' does not exist in the current context
// public object P2 { get; set { field = value; field = $"{field}"; } }
Diagnostic(ErrorCode.ERR_NameNotInContext, "field").WithArguments("field").WithLocation(5, 50),
// (5,61): error CS0103: The name 'field' does not exist in the current context
// public object P2 { get; set { field = value; field = $"{field}"; } }
Diagnostic(ErrorCode.ERR_NameNotInContext, "field").WithArguments("field").WithLocation(5, 61));
}
else
{
var verifier = CompileAndVerify(comp, verify: Verification.Skipped, expectedOutput: IncludeExpectedOutput("""
P1: True
2
"""));
verifier.VerifyDiagnostics();
verifier.VerifyIL("C.P1.get", """
{
// Code size 45 (0x2d)
.maxstack 3
.locals init (System.Runtime.CompilerServices.DefaultInterpolatedStringHandler V_0)
IL_0000: ldloca.s V_0
IL_0002: ldc.i4.4
IL_0003: ldc.i4.1
IL_0004: call "System.Runtime.CompilerServices.DefaultInterpolatedStringHandler..ctor(int, int)"
IL_0009: ldloca.s V_0
IL_000b: ldstr "P1: "
IL_0010: call "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendLiteral(string)"
IL_0015: ldloca.s V_0
IL_0017: ldarg.0
IL_0018: ldfld "object C.<P1>k__BackingField"
IL_001d: ldnull
IL_001e: ceq
IL_0020: call "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendFormatted<bool>(bool)"
IL_0025: ldloca.s V_0
IL_0027: call "string System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.ToStringAndClear()"
IL_002c: ret
}
""");
verifier.VerifyIL("C.P2.set", """
{
// Code size 43 (0x2b)
.maxstack 4
.locals init (System.Runtime.CompilerServices.DefaultInterpolatedStringHandler V_0)
IL_0000: ldarg.0
IL_0001: ldarg.1
IL_0002: stfld "object C.<P2>k__BackingField"
IL_0007: ldarg.0
IL_0008: ldloca.s V_0
IL_000a: ldc.i4.0
IL_000b: ldc.i4.1
IL_000c: call "System.Runtime.CompilerServices.DefaultInterpolatedStringHandler..ctor(int, int)"
IL_0011: ldloca.s V_0
IL_0013: ldarg.0
IL_0014: ldfld "object C.<P2>k__BackingField"
IL_0019: call "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendFormatted<object>(object)"
IL_001e: ldloca.s V_0
IL_0020: call "string System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.ToStringAndClear()"
IL_0025: stfld "object C.<P2>k__BackingField"
IL_002a: ret
}
""");
}
}

[Theory]
[CombinatorialData]
public void InterpolatedString_Alignment(
[CombinatorialValues(LanguageVersion.CSharp13, LanguageVersionFacts.CSharpNext)] LanguageVersion languageVersion)
{
string source = $$"""
using System;
class C
{
int x = 42;
const int field = 5;
public int P1 { get { Console.WriteLine($"{x,field}"); return 1; } }
}
class Program
{
static void Main()
{
var c = new C();
Console.WriteLine(c.P1);
}
}
""";
var comp = CreateCompilation(
source,
parseOptions: TestOptions.Regular.WithLanguageVersion(languageVersion),
options: TestOptions.ReleaseExe,
targetFramework: TargetFramework.Net80);

if (languageVersion == LanguageVersion.CSharp13)
{
var verifier = CompileAndVerify(comp, verify: Verification.Skipped, expectedOutput: IncludeExpectedOutput("""
42
1
"""));
verifier.VerifyDiagnostics();
verifier.VerifyIL("C.P1.get", """
{
// Code size 37 (0x25)
.maxstack 3
.locals init (System.Runtime.CompilerServices.DefaultInterpolatedStringHandler V_0)
IL_0000: ldloca.s V_0
IL_0002: ldc.i4.0
IL_0003: ldc.i4.1
IL_0004: call "System.Runtime.CompilerServices.DefaultInterpolatedStringHandler..ctor(int, int)"
IL_0009: ldloca.s V_0
IL_000b: ldarg.0
IL_000c: ldfld "int C.x"
IL_0011: ldc.i4.5
IL_0012: call "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendFormatted<int>(int, int)"
IL_0017: ldloca.s V_0
IL_0019: call "string System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.ToStringAndClear()"
IL_001e: call "void System.Console.WriteLine(string)"
IL_0023: ldc.i4.1
IL_0024: ret
}
""");
}
else
{
comp.VerifyEmitDiagnostics(
// (6,50): warning CS9258: In language version preview, the 'field' keyword binds to a synthesized backing field for the property. To avoid generating a synthesized backing field, and to refer to the existing member, use 'this.field' or '@field' instead.
// public int P1 { get { Console.WriteLine($"{x,field}"); return 1; } }
Diagnostic(ErrorCode.WRN_FieldIsAmbiguous, "field").WithArguments("preview").WithLocation(6, 50),
// (6,50): error CS0150: A constant value is expected
// public int P1 { get { Console.WriteLine($"{x,field}"); return 1; } }
Diagnostic(ErrorCode.ERR_ConstantExpected, "field").WithLocation(6, 50));
}

var containingType = comp.GetMember<NamedTypeSymbol>("C");
var actualFields = containingType.GetMembers().OfType<FieldSymbol>().Where(f => f.IsImplicitlyDeclared).ToImmutableArray();
if (languageVersion == LanguageVersion.CSharp13)
{
Assert.Empty(actualFields.ToTestDisplayStrings());
}
else
{
var expectedFields = new[]
{
"System.Int32 C.<P1>k__BackingField",
};
AssertEx.Equal(expectedFields, actualFields.ToTestDisplayStrings());
}

var actualProperties = containingType.GetMembers().OfType<PropertySymbol>().ToImmutableArray();
Assert.Equal(1, actualProperties.Length);
if (languageVersion == LanguageVersion.CSharp13)
{
Assert.True(actualProperties[0] is SourcePropertySymbol { Name: "P1", IsAutoProperty: false, UsesFieldKeyword: false, BackingField: null });
}
else
{
Assert.True(actualProperties[0] is SourcePropertySymbol { Name: "P1", IsAutoProperty: false, UsesFieldKeyword: true, BackingField: { } });
}

VerifyMergedProperties(actualProperties, actualFields);
}

[Theory]
[CombinatorialData]
public void InterpolatedString_Format(
[CombinatorialValues(LanguageVersion.CSharp13, LanguageVersionFacts.CSharpNext)] LanguageVersion languageVersion)
{
string source = $$"""
using System;
class C
{
int x = 42;
const int y = 3;
const int field = 5;
public int P2 { get { Console.WriteLine($"{x:field}"); return 2; } }
public int P3 { get { Console.WriteLine($"{x,y:field}"); return 3; } }
}
class Program
{
static void Main()
{
var c = new C();
Console.WriteLine((c.P2, c.P3));
}
}
""";
var comp = CreateCompilation(
source,
parseOptions: TestOptions.Regular.WithLanguageVersion(languageVersion),
options: TestOptions.ReleaseExe,
targetFramework: TargetFramework.Net80);

var verifier = CompileAndVerify(comp, verify: Verification.Skipped, expectedOutput: IncludeExpectedOutput("""
field
field
(2, 3)
"""));
verifier.VerifyDiagnostics();
verifier.VerifyIL("C.P2.get", """
{
// Code size 41 (0x29)
.maxstack 3
.locals init (System.Runtime.CompilerServices.DefaultInterpolatedStringHandler V_0)
IL_0000: ldloca.s V_0
IL_0002: ldc.i4.0
IL_0003: ldc.i4.1
IL_0004: call "System.Runtime.CompilerServices.DefaultInterpolatedStringHandler..ctor(int, int)"
IL_0009: ldloca.s V_0
IL_000b: ldarg.0
IL_000c: ldfld "int C.x"
IL_0011: ldstr "field"
IL_0016: call "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendFormatted<int>(int, string)"
IL_001b: ldloca.s V_0
IL_001d: call "string System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.ToStringAndClear()"
IL_0022: call "void System.Console.WriteLine(string)"
IL_0027: ldc.i4.2
IL_0028: ret
}
""");
verifier.VerifyIL("C.P3.get", """
{
// Code size 42 (0x2a)
.maxstack 4
.locals init (System.Runtime.CompilerServices.DefaultInterpolatedStringHandler V_0)
IL_0000: ldloca.s V_0
IL_0002: ldc.i4.0
IL_0003: ldc.i4.1
IL_0004: call "System.Runtime.CompilerServices.DefaultInterpolatedStringHandler..ctor(int, int)"
IL_0009: ldloca.s V_0
IL_000b: ldarg.0
IL_000c: ldfld "int C.x"
IL_0011: ldc.i4.3
IL_0012: ldstr "field"
IL_0017: call "void System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.AppendFormatted<int>(int, int, string)"
IL_001c: ldloca.s V_0
IL_001e: call "string System.Runtime.CompilerServices.DefaultInterpolatedStringHandler.ToStringAndClear()"
IL_0023: call "void System.Console.WriteLine(string)"
IL_0028: ldc.i4.3
IL_0029: ret
}
""");

var containingType = comp.GetMember<NamedTypeSymbol>("C");
var actualFields = containingType.GetMembers().OfType<FieldSymbol>().Where(f => f.IsImplicitlyDeclared).ToImmutableArray();
Assert.Empty(actualFields.ToTestDisplayStrings());

var actualProperties = containingType.GetMembers().OfType<PropertySymbol>().ToImmutableArray();
Assert.Equal(2, actualProperties.Length);
Assert.True(actualProperties[0] is SourcePropertySymbol { Name: "P2", IsAutoProperty: false, UsesFieldKeyword: false, BackingField: null });
Assert.True(actualProperties[1] is SourcePropertySymbol { Name: "P3", IsAutoProperty: false, UsesFieldKeyword: false, BackingField: null });

VerifyMergedProperties(actualProperties, actualFields);
}

[Theory]
[InlineData("{ get; }")]
[InlineData("{ get; set; }")]
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