Prototype for "default": semantic model, constant value and more tests #16425

jcouv · 2017-01-11T06:23:53Z

Continuing prototyping for #13602

Adding some tests for semantic model
Allow target-typed literal to be seen as a constant
Adding tests corresponding to scenarios where null gets special treatment (throw null, null == null, null as Some Type, ...)

As a refresher, the first part of this prototype work was in PR #13603

CC @dotnet/roslyn-compiler for review. This is for features/default branch. No rush.

jcouv · 2017-01-27T21:36:34Z

@dotnet/roslyn-compiler for review (post-RTM change).

jcouv · 2017-02-01T21:53:44Z

@gafter Could you do the first review, when you get some time?

gafter · 2017-02-02T01:27:47Z

Yes

gafter

The set of changes in this PR look good to me. However, it appears to be adding to an existing prototype that I haven't reviewed.

gafter · 2017-02-02T18:45:56Z

src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs

@@ -553,7 +553,7 @@ private BoundExpression BindExpressionInternal(ExpressionSyntax node, Diagnostic
 return BindDefaultExpression((DefaultExpressionSyntax)node, diagnostics);

 case SyntaxKind.DefaultLiteral:
- return new BoundDefaultOperator((DefaultLiteralSyntax)node);
+ return new BoundDefaultOperator((DefaultLiteralSyntax)node, ConstantValue.DefaultLiteral, type: null);


Please extract into method BindDefaultLiteral for consistency (all other expression forms delegate to a separate bind method).

Also, BoundDefaultOperator should probably be named BoundDefaultLiteral.

gafter · 2017-02-02T19:00:48Z

src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs

@@ -4834,7 +4832,6 @@ private bool IsUsingAliasInScope(string name)
 return BadExpression(node, boundLeft);
 }

- // PROTOTYPE(default) unify with case above
 // No member accesses on default
 if (boundLeft.IsLiteralDefault())


I wonder if these two cases (default and unbound lambda) can be combined by testingfor (object)leftType == null and in that case report the diagnostic using boundLeft.Display.

I addressed your other feedback in latest commit, but I couldn't quite see how to factor as you suggested here.

gafter · 2017-02-02T19:04:51Z

src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionsBase.cs

@@ -975,7 +975,7 @@ internal static bool HasImplicitConstantExpressionConversion(BoundExpression sou
 {
 var constantValue = source.ConstantValue;

- if (constantValue == null)
+ if (constantValue == null || constantValue.IsDefaultLiteral)


Perhaps change constantValue.IsDefaultLiteral to (object)source.Type == null?

jcouv · 2017-02-08T18:18:22Z

@cston I was hoping you could do the second review, since you had reviewed the first part of this prototype work. Thanks

cston · 2017-02-08T18:39:13Z

src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs

+ private static BoundExpression BindDefaultLiteral(DefaultLiteralSyntax node)
+ {
+ return new BoundDefaultLiteral(node, ConstantValue.DefaultLiteral, type: null);
+ }


Is (T)default a constant? Is const object o = (T)default; legal?

I will check. I have a test for int x = (short)default; (legal), but not with a generic cast.
My expectation is that (T)default should behave the same as default(T).

What about scenarios when it is of type user-defined struct? Is it supposed to have constant value then?

cston · 2017-02-08T18:56:04Z

src/Compilers/CSharp/Portable/Lowering/DiagnosticsPass_ExpressionTrees.cs

@@ -588,7 +588,7 @@ public override BoundNode VisitNameOfOperator(BoundNameOfOperator node)

 public override BoundNode VisitNullCoalescingOperator(BoundNullCoalescingOperator node)
 {
- if (_inExpressionLambda && node.LeftOperand.IsLiteralNull())
+ if (_inExpressionLambda && (node.LeftOperand.IsLiteralNull() || node.LeftOperand.IsLiteralDefault()))
 {
 Error(ErrorCode.ERR_ExpressionTreeContainsBadCoalesce, node.LeftOperand);


Is there a test for default?

Yes. All the tests are in TargetTypedDefaultTests.cs, which is updated as part of this PR (although GitHub doesn't expand it by default).

cston · 2017-02-08T20:41:35Z

src/Compilers/CSharp/Test/Semantic/Semantics/TargetTypedDefaultTests.cs

+ var def = nodes.OfType<DefaultLiteralSyntax>().Single();
+ Assert.Null(model.GetTypeInfo(def).Type);
+ Assert.Null(model.GetSymbolInfo(def).Symbol);
+ Assert.Null(model.GetSymbolInfo(def).Symbol);


Duplicated line.

cston · 2017-02-08T20:44:40Z

src/Compilers/CSharp/Test/Semantic/Semantics/TargetTypedDefaultTests.cs

+ comp.VerifyDiagnostics(
+ // (6,27): error CS0446: Foreach cannot operate on a 'default'. Did you intend to invoke the 'default'?
+ // foreach (int x in default) { }
+ Diagnostic(ErrorCode.ERR_AnonMethGrpInForEach, "default").WithArguments("default").WithLocation(6, 27),


Did you intend to invoke the 'default'? seems odd.

cston · 2017-02-08T20:45:26Z

src/Compilers/CSharp/Test/Semantic/Semantics/TargetTypedDefaultTests.cs

+ compilation.VerifyDiagnostics(
+ // (5,35): error CS0186: Use of null is not valid in this context
+ // var q = from x in default select x;
+ Diagnostic(ErrorCode.ERR_NullNotValid, "select x").WithLocation(5, 35)


Should the message be Use of default is not valid ...?

Should this be ERR_DefaultNotValid?

cston · 2017-02-08T20:52:46Z

src/Compilers/CSharp/Test/Semantic/Semantics/TargetTypedDefaultTests.cs

+ // (6,30): error CS0077: The as operator must be used with a reference type or nullable type ('long' is a non-nullable value type)
+ // System.Console.Write(default as long);
+ Diagnostic(ErrorCode.ERR_AsMustHaveReferenceType, "default as long").WithArguments("long").WithLocation(6, 30)
+ );


Are there tests for default as C and default is C?

Are we testing nameof(default)?

Test for yield return default;?

InvocationOnDefault has nameof(default) (illegal). DefaultInAsOperator has default as long (illegal).
I'll add tests for the other suggestions.

cston · 2017-02-08T20:57:28Z

src/Compilers/CSharp/Test/Semantic/Semantics/TargetTypedDefaultTests.cs

+ var def = nodes.OfType<DefaultLiteralSyntax>().Single();
+ Assert.Null(model.GetTypeInfo(def).Type);
+ Assert.Null(model.GetSymbolInfo(def).Symbol);
+ Assert.Null(model.GetSymbolInfo(def).Symbol);


Duplicated line.

gafter · 2017-02-09T20:42:03Z

@jcouv This needs a specification, please.

jcouv · 2017-02-13T20:31:27Z

Filed issue #17111 for writing a spec.

cston · 2017-02-13T21:52:27Z

src/Compilers/CSharp/Test/Semantic/Semantics/TargetTypedDefaultTests.cs

+ // (8,15): error CS0283: The type 'S' cannot be declared const
+ // const S y = (S)default;
+ Diagnostic(ErrorCode.ERR_BadConstType, "S").WithArguments("S").WithLocation(8, 15)
+ );


Are const object y = (T)default; or const object y = (S)default; allowed?

cston · 2017-02-13T21:54:54Z

src/Compilers/CSharp/Test/Semantic/Semantics/TargetTypedDefaultTests.cs

+";
+ var comp = CreateCompilationWithMscorlib(source, parseOptions: TestOptions.ExperimentalParseOptions);
+ comp.VerifyDiagnostics();
+ }


Consider testing IEnumerable as well.

cston · 2017-02-13T21:59:37Z

src/Compilers/CSharp/Test/Semantic/Semantics/TargetTypedDefaultTests.cs

+ }
+
+ [Fact]
+ public void CS0403ERR_TypeVarCanBeDefault()


The name of the method refers to an error, although no errors are reported.

cston · 2017-02-13T22:02:12Z

src/Compilers/CSharp/Test/Semantic/Semantics/TargetTypedDefaultTests.cs

+ var conversion = nodes.OfType<CastExpressionSyntax>().Single();
+ var conversionTypeInfo = model.GetTypeInfo(conversion);
+ Assert.Equal("System.Int16", conversionTypeInfo.Type.ToTestDisplayString());
+ Assert.Equal("System.Int32", conversionTypeInfo.ConvertedType.ToTestDisplayString());


Is new object[default] supported?

Yes, see IndexingIntoArray which has x[default] (legal).

Oops, sorry, I misunderstood. I tested access, but not array construction. I'll add.

jcouv · 2017-02-13T23:17:23Z

Thanks for the test suggestions. I pushed another batch.

cston · 2017-02-14T18:14:27Z

LGTM

jcouv · 2017-02-14T18:30:11Z

Thanks for the review and feedback. I think this completes the implementation of the prototype.
I'll make sure to follow-up with a spec document.

dotnet#16425) Conflicts: src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs src/Compilers/CSharp/Portable/Binder/Binder_Query.cs src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs src/Compilers/CSharp/Portable/Errors/ErrorCode.cs

jcouv added the Area-Compilers label Jan 11, 2017

jcouv self-assigned this Jan 11, 2017

dnfclas added the cla-already-signed label Jan 11, 2017

jcouv force-pushed the more-default branch from f4cb8f6 to c1ee4f7 Compare January 17, 2017 03:57

Test for semantic model, constant value and more tests for default

4dc80f1

jcouv force-pushed the more-default branch from c1ee4f7 to 4dc80f1 Compare January 20, 2017 03:38

jcouv requested a review from gafter January 23, 2017 23:01

jcouv assigned jcouv and gafter and unassigned jcouv Jan 27, 2017

gafter approved these changes Feb 2, 2017

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jcouv mentioned this pull request Feb 2, 2017

Prototype: target typed "default" #13603

Merged

gafter removed their assignment Feb 3, 2017

PR feedback (1)

79effee

jcouv force-pushed the more-default branch from 1beae53 to 79effee Compare February 7, 2017 00:05

cston reviewed Feb 8, 2017

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jcouv added the 4 - In Review A fix for the issue is submitted for review. label Feb 11, 2017

PR feedback (2)

89b5d07

cston reviewed Feb 13, 2017

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jcouv closed this Feb 14, 2017

jcouv reopened this Feb 14, 2017

dnfclas added the cla-already-signed label Feb 14, 2017

More tests from feedback

28dba9e

jcouv force-pushed the more-default branch from 0f2b604 to 28dba9e Compare February 14, 2017 17:19

jcouv added 2 commits February 14, 2017 09:23

Adding test for array construction

79353be

Using wrong error message for default in query

af7bb3d

jcouv merged commit 582255b into dotnet:features/default Feb 14, 2017

jcouv deleted the more-default branch February 14, 2017 18:30

Prototype for "default": semantic model, constant value and more tests #16425

Prototype for "default": semantic model, constant value and more tests #16425

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jcouv commented Jan 11, 2017 • edited Loading

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gafter commented Feb 9, 2017

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jcouv commented Feb 13, 2017

cston commented Feb 14, 2017

jcouv commented Feb 14, 2017

jcouv commented Jan 11, 2017 •

edited

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