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branching: if when case

TLDR

• new scopes are introduced immediately aftered the keywords (e.g. if, elif, etc)
  • except for when statements/expressions
• use whens for completely removing sections of code at compile time
• all can be used as expressions and the result assigned to a var
• case statement branches should be listed in order of most expected

branching TODOs

• likely
• unlikely
• an example of using when (and if?) inside an object constructor
  • there are examples in the doc where when is used to optionally define props
  • e.g. this file: https://github.com/nim-lang/Nim/blob/devel/lib/std/private/threadtypes.nim

when

• a compile time if statement
• the condition MUST be a constant expression
• does not open a new scope
• only the first truthy value is compiled

case

• similar to if, but represents a multi-branch selection
• supports strings, ordinal types and integers
  • ints/ordinals can also use ranges
  • the of part must match the value type
• can also use elif, else branches

checks whether x can be compiled without any semantic error. useful to verify whether a type supports some operation:whether x is declared at compile timechecks current scope at compile time