Use default tuple fields in deconstruction since fields from inferred names are marked not usable in C#7 #21029
Conversation
|
@dotnet/roslyn-compiler please review. |
cston
force-pushed
the
21028
branch
3 times, most recently
from
d4db4ff
to
1297886
Compare
cston
changed the title
|
@dotnet/roslyn-compiler please review this small change, thanks. |
| @@ -223,6 +223,10 @@ private static bool IsTupleExpression(BoundKind kind) | |||
| { | |||
| var field = fields[i]; | |||
|
|
|||
| // Use default field rather than implicitly named fields since | |||
| // fields from inferred names are not usable in C# 7.0. | |||
| field = field.CorrespondingTupleField ?? field; | |||
There was a problem hiding this comment.
When would CorrespondingTupleField ever be non-null here?
Also can you give an example of when the use site diagnostic check below would ever get hit with this change?
There was a problem hiding this comment.
CorrespondingTupleField is null for the default (unnamed) fields, and non null for named (explicitly or inferred) fields.
The use-site diagnostic check should still be hit for use-site errors on the default fields, although I have not found a test case yet.
There was a problem hiding this comment.
use-site diagnostic here is likely for cases with broken/malformed ValueTuple - like when the corresponding field is missing or inaccessible for other reasons, we should produce an error not a crash or something like that.
There was a problem hiding this comment.
Thanks @VSadov, an inaccessible tuple field hits this code path. I've added a use-site test.
… names are marked not usable in C#7
|
retest windows_release_vs-integration_prtest please |
|
@dotnet-bot test windows_release_vs-integration_prtest please |
Customer scenario
Create a deconstruction assignment where the RHS contains two or more tuple literals with different types and inferred names.
Bugs this fixes:
#21028
Workarounds, if any
Rewrite the RHS to avoid multiple tuple literals with different types and inferred names.
Risk
Low.
Performance impact
None.
Is this a regression from a previous update?
Regression resulting from inferred tuple names.
How was the bug found?
Customer reported.