dotnet/roslyn

Deconstruction: infer variable types even if the right-hand-side is not fully typed

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#14,037 opened on Sep 23, 2016

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Area-CompilersBugConcept-Diagnostic ClarityFeature - Tupleshelp wanted

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Description

var (x, y) = (1, null); The type inference fails both for x and y, but it should succeed for x.

See CodeGenDeconstructTests.UnassignedUsedInDeconstructionInScript and this discussion https://github.com/dotnet/roslyn/pull/13957/files#r80320718

FYI for @AlekseyTs

Contributor guide

Research direction
Look at the failing test 'CodeGenDeconstructTests.UnassignedUsedInDeconstructionInScript' and the discussion at https://github.com/dotnet/roslyn/pull/13957/files#r80320718 to understand the expected behavior for type inference in deconstruction when the right hand side is partially untyped. Then inspect the type inference logic in Roslyn's binder for deconstruction patterns.
Tech stack
csharp
Domain
compilers
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
C#
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50