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Support for ref-readonly locals #22269

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merged 4 commits into from
Sep 23, 2017
Merged

Support for ref-readonly locals #22269

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cb6f875
Add support for ref-readonly locals
agocke Sep 20, 2017
a8a1fa4
Respond to PR comments
agocke Sep 22, 2017
7fd5722
Add some tests around conversions and language version
agocke Sep 22, 2017
eac83bd
Respond to PR comments
agocke Sep 23, 2017
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20 changes: 7 additions & 13 deletions src/Compilers/CSharp/Portable/Binder/Binder_Statements.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -773,7 +773,10 @@ protected BoundExpression BindInferredVariableInitializer(DiagnosticBag diagnost
}
else
{
valueKind = BindValueKind.RefOrOut;
valueKind = variableRefKind == RefKind.RefReadOnly
? BindValueKind.ReadonlyRef
: BindValueKind.RefOrOut;

if (initializer == null)
{
Error(diagnostics, ErrorCode.ERR_ByReferenceVariableMustBeInitialized, node);
Expand Down Expand Up @@ -836,19 +839,10 @@ protected BoundExpression BindInferredVariableInitializer(DiagnosticBag diagnost
// might own nested scope.
bool hasErrors = localSymbol.ScopeBinder.ValidateDeclarationNameConflictsInScope(localSymbol, diagnostics);

if (localSymbol.RefKind == RefKind.RefReadOnly)
{
Debug.Assert(typeSyntax.Parent is RefTypeSyntax);
var refKeyword = typeSyntax.Parent.GetFirstToken();
diagnostics.Add(ErrorCode.ERR_UnexpectedToken, refKeyword.GetLocation(), refKeyword.ToString());
}
else
var containingMethod = this.ContainingMemberOrLambda as MethodSymbol;
if (containingMethod != null && containingMethod.IsAsync && localSymbol.RefKind != RefKind.None)
{
var containingMethod = this.ContainingMemberOrLambda as MethodSymbol;
if (containingMethod != null && containingMethod.IsAsync && localSymbol.RefKind != RefKind.None)
{
Error(diagnostics, ErrorCode.ERR_BadAsyncLocalType, declarator);
}
Error(diagnostics, ErrorCode.ERR_BadAsyncLocalType, declarator);
}

EqualsValueClauseSyntax equalsClauseSyntax = declarator.Initializer;
Expand Down
43 changes: 33 additions & 10 deletions src/Compilers/CSharp/Portable/CodeGen/EmitAddress.cs
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Expand Up @@ -40,13 +40,11 @@ private LocalDefinition EmitAddress(BoundExpression expression, AddressKind addr
break;

case BoundKind.Local:
EmitLocalAddress((BoundLocal)expression);
break;
return EmitLocalAddress((BoundLocal)expression, addressKind);

case BoundKind.Dup:
Debug.Assert(((BoundDup)expression).RefKind != RefKind.None, "taking address of a stack value?");
_builder.EmitOpCode(ILOpCode.Dup);
break;
return EmitDupAddress((BoundDup)expression, addressKind);

case BoundKind.ConditionalReceiver:
// do nothing receiver ref must be already pushed
Expand Down Expand Up @@ -213,10 +211,18 @@ private void EmitComplexConditionalReceiverAddress(BoundComplexConditionalReceiv
_builder.MarkLabel(doneLabel);
}

private void EmitLocalAddress(BoundLocal localAccess)
/// <summary>
/// May introduce a temp which it will return. (otherwise returns null)
/// </summary>
private LocalDefinition EmitLocalAddress(BoundLocal localAccess, AddressKind addressKind)
{
var local = localAccess.LocalSymbol;

if (!HasHome(localAccess, addressKind != AddressKind.ReadOnly))
{
return EmitAddressOfTempClone(localAccess);
}

if (IsStackLocal(local))
{
if (local.RefKind != RefKind.None)
Expand All @@ -234,6 +240,21 @@ private void EmitLocalAddress(BoundLocal localAccess)
{
_builder.EmitLocalAddress(GetLocal(localAccess));
}
return null;
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nit: new line

}

/// <summary>
/// May introduce a temp which it will return. (otherwise returns null)
/// </summary>
private LocalDefinition EmitDupAddress(BoundDup dup, AddressKind addressKind)
{
if (!HasHome(dup, addressKind != AddressKind.ReadOnly))
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Consider using a named argument for the second parm here. Makes it more readable.

{
return EmitAddressOfTempClone(dup);
}

_builder.EmitOpCode(ILOpCode.Dup);
return null;
}

private void EmitPseudoVariableAddress(BoundPseudoVariable expression)
Expand Down Expand Up @@ -345,9 +366,11 @@ private bool HasHome(BoundExpression expression, bool needWriteable)
((BoundParameter)expression).ParameterSymbol.RefKind != RefKind.RefReadOnly;

case BoundKind.Local:
// locals have home unless they are byval stack locals
// locals have home unless they are byval stack locals or ref-readonly
// locals in a mutating call
var local = ((BoundLocal)expression).LocalSymbol;
return !IsStackLocal(local) || local.RefKind != RefKind.None;
return !((IsStackLocal(local) && local.RefKind == RefKind.None) ||
(needWriteable && local.RefKind == RefKind.RefReadOnly));
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Is needWritable protecting the local or the value?

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The local. It's specifying that you must be able to write to the local pointed to by the address.

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Then why is the last condition only checking ref readonly

In reply to: 140599487 [](ancestors = 140599487)

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i am wrong

In reply to: 140600043 [](ancestors = 140600043,140599487)


case BoundKind.Call:
var methodRefKind = ((BoundCall)expression).Method.RefKind;
Expand All @@ -356,9 +379,9 @@ private bool HasHome(BoundExpression expression, bool needWriteable)

case BoundKind.Dup:
//NB: Dup represents locals that do not need IL slot
// ref locals are currently always writeable, so we do not need to care about "needWriteable"
Debug.Assert(((BoundDup)expression).RefKind != RefKind.RefReadOnly);
return ((BoundDup)expression).RefKind != RefKind.None;
var dupRefKind = ((BoundDup)expression).RefKind;
return dupRefKind == RefKind.Ref ||
(!needWriteable && dupRefKind == RefKind.RefReadOnly);

case BoundKind.FieldAccess:
return HasHome((BoundFieldAccess)expression, needWriteable);
Expand Down
19 changes: 18 additions & 1 deletion src/Compilers/CSharp/Portable/CodeGen/Optimizer.cs
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Expand Up @@ -971,7 +971,23 @@ private static bool IsIndirectAssignment(BoundAssignmentOperator node)
{
var lhs = node.Left;

Debug.Assert(node.RefKind == RefKind.None || (lhs as BoundLocal)?.LocalSymbol.RefKind == RefKind.Ref,
bool IsAssignable(RefKind lhsKind, RefKind rhsKind)
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IsAssignable [](start = 17, length = 12)

if this is only for asserting, I'd suggest inlining into the Assert call and simply returning false otherwise. Throwing here will not trigger the Debug window while debugging, and will route it to the VS fault handler.

{
switch (lhsKind)
{
case RefKind.None:
case RefKind.Ref:
return lhsKind == rhsKind;
case RefKind.RefReadOnly:
return rhsKind == RefKind.RefReadOnly || rhsKind == RefKind.Ref;
default:
throw ExceptionUtilities.UnexpectedValue(lhsKind);
}
}

Debug.Assert(node.RefKind == RefKind.None ||
lhs is BoundLocal local &&
IsAssignable(local.LocalSymbol.RefKind, node.RefKind),
"only ref locals can be a target of a ref assignment");

switch (lhs.Kind)
Expand Down Expand Up @@ -1034,6 +1050,7 @@ private static bool IsIndirectAssignment(BoundAssignmentOperator node)
throw ExceptionUtilities.UnexpectedValue(lhs.Kind);
}
}

private static bool IsIndirectOrInstanceFieldAssignment(BoundAssignmentOperator node)
{
var lhs = node.Left;
Expand Down
2 changes: 1 addition & 1 deletion src/Compilers/CSharp/Portable/Symbols/LocalSymbol.cs
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Expand Up @@ -268,7 +268,7 @@ internal virtual bool IsWritable
case LocalDeclarationKind.UsingVariable:
return false;
default:
return true;
return RefKind != RefKind.RefReadOnly;
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The local is still assignable. Is that not what is being tracked here?

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So what do you expect to happen with the following code?

int x = 0;
ref readonly int xr = ref x;
xr++;

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Same thing that happens if xr is a readonly static

In reply to: 140599254 [](ancestors = 140599254)

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can we explicitly state the true cases, and throw otherwise?

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I don't understand why you would want to ever throw here. Ref variables are meaningful, ref-readonly variables are meaningful, and "non-ref" variables are meaningful.

}
}
}
Expand Down
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