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Fix NRE in WTG1010 when analyzing conditional invoke expressions #238

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Fix NRE in WTG1010 when analyzing conditional invoke expressions #238

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Copilot May 26, 2026
f90995f
Fix NRE in WTG1010 when analyzing conditional invoke expressions
Copilot May 26, 2026
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9 changes: 6 additions & 3 deletions src/WTG.Analyzers.Test/TestData/VarAnalyzer/Out/Diagnostics.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -19,12 +19,15 @@
<location>Test0.cs: (10,52-58)</location>
</diagnostic>
<diagnostic>
<location>Test0.cs: (12,40-43)</location>
<location>Test0.cs: (11,53-59)</location>
</diagnostic>
<diagnostic>
<location>Test0.cs: (12,56-59)</location>
<location>Test0.cs: (13,40-43)</location>
</diagnostic>
<diagnostic>
<location>Test0.cs: (12,72-76)</location>
<location>Test0.cs: (13,56-59)</location>
</diagnostic>
<diagnostic>
<location>Test0.cs: (13,72-76)</location>
</diagnostic>
</diagnostics>
3 changes: 2 additions & 1 deletion src/WTG.Analyzers.Test/TestData/VarAnalyzer/Out/Result.cs
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Expand Up @@ -8,6 +8,7 @@ public class Bob
public void V3() => Generic(1, out var value);
public void V4() => Generic(TryGet("key", out var value1), out var value2);
public void V5() => Lookup.TryGetValue("key", out var value);
public void V6() => Lookup?.TryGetValue("key", out var value);

public void S4() => SemiAmbiguous(out var value1, out int value2, out var value3); // value1 and value2 cannot both be var as that would make it ambiguous.

Expand All @@ -30,5 +31,5 @@ public void N()
void Generic<T>(out T value) where T : struct => value = default(T);
void Generic<T>(T inValue, out T outValue) => outValue = inValue;
bool TryGet(string key, out string value) => (value = key) != null;
Dictionary<string, string> Lookup { get; } = new Dictionary<string, string>();
Dictionary<string, string>? Lookup { get; } = new Dictionary<string, string>();
}
3 changes: 2 additions & 1 deletion src/WTG.Analyzers.Test/TestData/VarAnalyzer/Out/Source.cs
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Expand Up @@ -8,6 +8,7 @@ public class Bob
public void V3() => Generic(1, out int value);
public void V4() => Generic(TryGet("key", out string value1), out bool value2);
public void V5() => Lookup.TryGetValue("key", out string value);
public void V6() => Lookup?.TryGetValue("key", out string value);

public void S4() => SemiAmbiguous(out int value1, out int value2, out bool value3); // value1 and value2 cannot both be var as that would make it ambiguous.

Expand All @@ -30,5 +31,5 @@ public void N()
void Generic<T>(out T value) where T : struct => value = default(T);
void Generic<T>(T inValue, out T outValue) => outValue = inValue;
bool TryGet(string key, out string value) => (value = key) != null;
Dictionary<string, string> Lookup { get; } = new Dictionary<string, string>();
Dictionary<string, string>? Lookup { get; } = new Dictionary<string, string>();
}
27 changes: 25 additions & 2 deletions src/WTG.Analyzers/Analyzers/Var/VarAnalyzer.cs
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Expand Up @@ -168,8 +168,31 @@ static void AnalyzeInvoke(SyntaxNodeAnalysisContext context, FileDetailCache cac
}
}

var proposedSyntax = invoke.ReplaceNode(type, SyntaxFactory.IdentifierName("var").WithTriviaFrom(type));
var symbol = context.SemanticModel.GetSpeculativeSymbolInfo(invoke.SpanStart, proposedSyntax, SpeculativeBindingOption.BindAsExpression).Symbol;
var proposedInvoke = invoke.ReplaceNode(type, SyntaxFactory.IdentifierName("var").WithTriviaFrom(type));

ExpressionSyntax speculativeExpression;
int speculativePosition;

if (invoke.Expression is MemberBindingExpressionSyntax memberBinding
&& invoke.Parent is ConditionalAccessExpressionSyntax conditionalAccess)
{
// For conditional access (e.g. obj?.Method(out Type x)), the invocation node alone
// does not have enough context for speculative binding (NRE). Rewrite as a regular
// member access expression using the conditional access target.
var memberAccess = SyntaxFactory.MemberAccessExpression(
SyntaxKind.SimpleMemberAccessExpression,
conditionalAccess.Expression,
memberBinding.Name);
speculativeExpression = proposedInvoke.WithExpression(memberAccess);
speculativePosition = conditionalAccess.SpanStart;
}
else
{
speculativeExpression = proposedInvoke;
speculativePosition = invoke.SpanStart;
}

var symbol = context.SemanticModel.GetSpeculativeSymbolInfo(speculativePosition, speculativeExpression, SpeculativeBindingOption.BindAsExpression).Symbol;

if (SymbolEqualityComparer.Default.Equals(knownMethod, symbol))
{
Expand Down
22 changes: 21 additions & 1 deletion src/WTG.Analyzers/Analyzers/Var/VarFixAllProvider.cs
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Expand Up @@ -78,7 +78,27 @@ static InvocationExpressionSyntax ReplaceTypes(SemanticModel model, InvocationEx
{
index = GetIndex(originalArguments, types[i]);
var proposedInvoke = VarifyOutTypeAtIndex(targetInvoke, index);
var actualSymbol = (IMethodSymbol?)model.GetSpeculativeSymbolInfo(originalInvoke.SpanStart, proposedInvoke, SpeculativeBindingOption.BindAsExpression).Symbol;

ExpressionSyntax speculativeExpression;
int speculativePosition;

if (originalInvoke.Expression is MemberBindingExpressionSyntax memberBinding
&& originalInvoke.Parent is ConditionalAccessExpressionSyntax conditionalAccess)
{
var memberAccess = SyntaxFactory.MemberAccessExpression(
SyntaxKind.SimpleMemberAccessExpression,
conditionalAccess.Expression,
memberBinding.Name);
speculativeExpression = proposedInvoke.WithExpression(memberAccess);
speculativePosition = conditionalAccess.SpanStart;
}
else
{
speculativeExpression = proposedInvoke;
speculativePosition = originalInvoke.SpanStart;
}

var actualSymbol = (IMethodSymbol?)model.GetSpeculativeSymbolInfo(speculativePosition, speculativeExpression, SpeculativeBindingOption.BindAsExpression).Symbol;

if (SymbolEqualityComparer.Default.Equals(requiredSymbol, actualSymbol))
{
Expand Down
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