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Caller of an async local function cannot expect any of the callee’s code to execute #64482

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merged 6 commits into from
Oct 27, 2022
Merged

Caller of an async local function cannot expect any of the callee’s code to execute #64482

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d3ee505
Caller of an async local function cannot expect any of the callee’s c…
AlekseyTs Oct 4, 2022
cc83c79
Merge remote-tracking branch 'dotnet/main' into Issue43697
AlekseyTs Oct 12, 2022
d3416e3
Document a breaking change
AlekseyTs Oct 12, 2022
c7fcfb0
Merge remote-tracking branch 'dotnet/main' into Issue43697
AlekseyTs Oct 13, 2022
8569782
Update the breaking change description
AlekseyTs Oct 13, 2022
3d34864
Merge branch 'main' into Issue43697
AlekseyTs Oct 27, 2022
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6 changes: 5 additions & 1 deletion src/Compilers/CSharp/Portable/FlowAnalysis/AbstractFlowPass.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1320,7 +1320,11 @@ protected virtual void VisitLocalFunctionUse(
if (isCall)
{
Join(ref State, ref localFunctionState.StateFromBottom);
Meet(ref State, ref localFunctionState.StateFromTop);

if (!symbol.IsAsync)
{
Meet(ref State, ref localFunctionState.StateFromTop);
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Should we have a follow-up issue to track the decision to also perform this Meet when the call is "immediately awaited"?

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Should we have a follow-up issue to track the decision to also perform this Meet when the call is "immediately awaited"?

That is a language design change that I am not planning to champion at the moment.

}
}
localFunctionState.Visited = true;
}
Expand Down
3 changes: 3 additions & 0 deletions src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAwaitUsingTests.cs
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Expand Up @@ -1481,6 +1481,9 @@ async void L1()
}
}" + IAsyncDisposableDefinition);
comp.VerifyDiagnostics(
// (9,9): error CS0165: Use of unassigned local variable 'x'
// x++;
Diagnostic(ErrorCode.ERR_UseDefViolation, "x").WithArguments("x").WithLocation(9, 9),
// (10,9): error CS0165: Use of unassigned local variable 'y'
// y++;
Diagnostic(ErrorCode.ERR_UseDefViolation, "y").WithArguments("y").WithLocation(10, 9),
Expand Down
3 changes: 3 additions & 0 deletions src/Compilers/CSharp/Test/Emit2/FlowAnalysis/LocalFunctions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -428,6 +428,9 @@ async void L1()
}
}");
comp.VerifyDiagnostics(
// (11,9): error CS0165: Use of unassigned local variable 'x'
// x++;
Diagnostic(ErrorCode.ERR_UseDefViolation, "x").WithArguments("x").WithLocation(11, 9),
// (12,9): error CS0165: Use of unassigned local variable 'y'
// y++;
Diagnostic(ErrorCode.ERR_UseDefViolation, "y").WithArguments("y").WithLocation(12, 9),
Expand Down
184 changes: 184 additions & 0 deletions src/Compilers/CSharp/Test/Semantic/Semantics/LocalFunctionTests.cs
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Expand Up @@ -10072,5 +10072,189 @@ int P

Assert.Null(model.GetSymbolInfo(node).Symbol);
}

[Fact, WorkItem(43697, "https://github.com/dotnet/roslyn/issues/43697")]
public void DefiniteAssignment_01()
{
var text = @"
using System;
using System.Threading.Tasks;

#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed. Consider applying the 'await' operator to the result of the call.
#pragma warning disable CS1998 // This async method lacks 'await' operators and will run synchronously. Consider using the 'await' operator to await non-blocking API calls, or 'await Task.Run(...)' to do CPU-bound work on a background thread.

public class C
{
public void M()
{
bool a;
M1();
Console.WriteLine(a);
async Task M1()
{
if ("""" == String.Empty)
{
throw new Exception();
}
else
{
a = true;
}
}
}
}
";
CreateCompilation(text).VerifyDiagnostics(
// (14,27): error CS0165: Use of unassigned local variable 'a'
// Console.WriteLine(a);
Diagnostic(ErrorCode.ERR_UseDefViolation, "a").WithArguments("a").WithLocation(14, 27)
);
}

[Fact, WorkItem(43697, "https://github.com/dotnet/roslyn/issues/43697")]
public void DefiniteAssignment_02()
{
var text = @"
using System;
using System.Threading.Tasks;

public class C
{
public void M()
{
bool a;
M1();
Console.WriteLine(a);
Task M1()
{
if ("""" == String.Empty)
{
throw new Exception();
}
else
{
a = true;
}

return null;
}
}
}
";
CreateCompilation(text).VerifyDiagnostics();
}

[Fact, WorkItem(43697, "https://github.com/dotnet/roslyn/issues/43697")]
public void DefiniteAssignment_03()
{
var text = @"
using System;
using System.Threading.Tasks;

#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed. Consider applying the 'await' operator to the result of the call.

public class C
{
public void M()
{
bool a;
M1();
Console.WriteLine(a);
async Task M1()
{
await Task.Yield();

if ("""" == String.Empty)
{
throw new Exception();
}
else
{
a = true;
}
}
}
}
";
CreateCompilation(text).VerifyDiagnostics(
// (13,27): error CS0165: Use of unassigned local variable 'a'
// Console.WriteLine(a);
Diagnostic(ErrorCode.ERR_UseDefViolation, "a").WithArguments("a").WithLocation(13, 27)
);
}

[Fact, WorkItem(43697, "https://github.com/dotnet/roslyn/issues/43697")]
public void DefiniteAssignment_04()
{
var text = @"
using System;
using System.Threading.Tasks;

#pragma warning disable CS1998 // This async method lacks 'await' operators and will run synchronously. Consider using the 'await' operator to await non-blocking API calls, or 'await Task.Run(...)' to do CPU-bound work on a background thread.

public class C
{
public async Task M()
{
bool a;
await M1();
Console.WriteLine(a);
async Task M1()
{
if ("""" == String.Empty)
{
throw new Exception();
}
else
{
a = true;
}
}
}
}
";
CreateCompilation(text).VerifyDiagnostics(
// (13,27): error CS0165: Use of unassigned local variable 'a'
// Console.WriteLine(a);
Diagnostic(ErrorCode.ERR_UseDefViolation, "a").WithArguments("a").WithLocation(13, 27)
);
}

[Fact, WorkItem(43697, "https://github.com/dotnet/roslyn/issues/43697")]
public void DefiniteAssignment_05()
{
var text = @"
using System;
using System.Threading.Tasks;

public class C
{
public async Task M()
{
bool a;
await M1();
Console.WriteLine(a);
async Task M1()
{
await Task.Yield();

if ("""" == String.Empty)
{
throw new Exception();
}
else
{
a = true;
}
}
}
}
";
CreateCompilation(text).VerifyDiagnostics(
// (11,27): error CS0165: Use of unassigned local variable 'a'
// Console.WriteLine(a);
Diagnostic(ErrorCode.ERR_UseDefViolation, "a").WithArguments("a").WithLocation(11, 27)
);
}
}
}