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Handle field reference from semantic model in non-field-backed property #75904

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merged 3 commits into from
Nov 14, 2024
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Handle field reference from semantic model in non-field-backed property #75904

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95ac0db
Handle field reference from semantic model in non-field-backed property
cston Nov 13, 2024
51da949
Update test
cston Nov 13, 2024
e66b853
Add test with existing backing field
cston Nov 14, 2024
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5 changes: 4 additions & 1 deletion src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1465,9 +1465,12 @@ private BoundExpression BindFieldExpression(FieldExpressionSyntax node, BindingD
}
}

// Field will be null when binding a field expression in a speculative
// semantic model when the property does not have a backing field.
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@AlekseyTs AlekseyTs Nov 14, 2024 •
edited by cston
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in a speculative semantic model when the property does not have a backing field.

Consider if we could assert the fact. At least partially. #Resolved

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It wasn't obvious what to assert here since the Binder is not specific to the semantic model (IsSemanticModelBinder == false), even when called from that code path.

if (field is null)
{
throw ExceptionUtilities.UnexpectedValue(ContainingMember());
diagnostics.Add(ErrorCode.ERR_NoSuchMember, node, ContainingMember(), "field");
return BadExpression(node);
}

var implicitReceiver = field.IsStatic ? null : ThisReference(node, field.ContainingType, wasCompilerGenerated: true);
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68 changes: 68 additions & 0 deletions src/Compilers/CSharp/Test/Emit3/FieldKeywordTests.cs
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Expand Up @@ -10464,6 +10464,74 @@ .locals init (System.Runtime.CompilerServices.DefaultInterpolatedStringHandler V
VerifyMergedProperties(actualProperties, actualFields);
}

[WorkItem("https://github.com/dotnet/roslyn/issues/75893")]
[Theory]
[CombinatorialData]
public void SpeculativeSemanticModel_01(bool includeLocal)
{
string source = $$"""
class C
{
object P
{
get
{
{{(includeLocal ? "object field = null;" : "")}}
return null;
}
}
}
""";

var parseOptions = TestOptions.RegularPreview;
var comp = CreateCompilation(source, parseOptions: parseOptions);
var tree = comp.SyntaxTrees.Single();
var model = comp.GetSemanticModel(tree);
var previousAccessor = tree.GetRoot().DescendantNodes().OfType<AccessorDeclarationSyntax>().Single();

var modifiedTree = SyntaxFactory.ParseSyntaxTree(source.Replace("return null;", "return field;"), parseOptions);
var modifiedAccessor = modifiedTree.GetRoot().DescendantNodes().OfType<AccessorDeclarationSyntax>().Single();
Assert.True(model.TryGetSpeculativeSemanticModelForMethodBody(previousAccessor.Body.SpanStart, modifiedAccessor, out var speculativeModel));
var expr = modifiedAccessor.DescendantNodes().OfType<FieldExpressionSyntax>().Single();
Assert.Equal("return field;", expr.Parent.ToString());
var symbolInfo = speculativeModel.GetSymbolInfo(expr);
Assert.Null(symbolInfo.Symbol);
}

[Theory]
[CombinatorialData]
public void SpeculativeSemanticModel_02(bool includeLocal)
{
string source = $$"""
class C
{
object P
{
get
{
{{(includeLocal ? "object field = null;" : "")}}
return null;
}
set;
}
}
""";

var parseOptions = TestOptions.RegularPreview;
var comp = CreateCompilation(source, parseOptions: parseOptions);
var tree = comp.SyntaxTrees.Single();
var model = comp.GetSemanticModel(tree);
var previousAccessor = tree.GetRoot().DescendantNodes().OfType<AccessorDeclarationSyntax>().First();

var modifiedTree = SyntaxFactory.ParseSyntaxTree(source.Replace("return null;", "return field;"), parseOptions);
var modifiedAccessor = modifiedTree.GetRoot().DescendantNodes().OfType<AccessorDeclarationSyntax>().First();
Assert.True(model.TryGetSpeculativeSemanticModelForMethodBody(previousAccessor.Body.SpanStart, modifiedAccessor, out var speculativeModel));
var expr = modifiedAccessor.DescendantNodes().OfType<FieldExpressionSyntax>().Single();
Assert.Equal("return field;", expr.Parent.ToString());
var symbolInfo = speculativeModel.GetSymbolInfo(expr);
Assert.Equal("System.Object C.<P>k__BackingField", symbolInfo.Symbol.ToTestDisplayString());
}

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