work items remaining for wildcards

Specs

• Gather together a specification document
  • Language behavior (e.g. this and this and this)
  • SemanticModel behavior (see also here)
  • Warnings (for expression variables declared but not used)
  • Debugging (value discarded is not visible in debugger)

Compiler

• Syntax model changes
• Symbol changes
• Parsing for the short-form wildcard pattern _
• Implement binding of wildcards
  • In a pattern
  • In a deconstruction declaration
  • In a deconstruction assignment expression
  • In an out argument (in every argument context)
  • Both the long form var _ and the short form _
• Type inference for wildcards in each context
• Implement semantic model changes
  • GetTypeInfo of a wildcard expression _ should be the type of the discarded value
  • GetSymbolInfo of a wildcard expression _ should be an IDiscardedSymbol
• Implement lowering of wildcards
  • In a pattern
  • In a deconstruction declaration
  • In a deconstruction assignment expression
  • In an out argument (in each argument context)

Testing

• Symbol tests
• Syntax tests
• SemanticModel tests
• Language static semantic tests
• Runtime behavioral tests
• PDB tests
• Scripting tests
• EE tests
• In a pattern context
• In a deconstruction declaration context
• In a deconstruction assignment expression context
• In an out argument (in every argument context)
• Both the long form var _ and the short form _, where permitted
• In the long/short form when there is/not a conflicting name in scope