What does a programming language need? Here is a list of everything I could come up with, with no details.

Mostly in order:

• Basic datatypes
  • Numbers
    • Integer
    • Float
  • Boolean
  • String
  • Null
• Comments
  • Single line
  • Multiline
• Operators
  • +, -
  • *, /, **
  • %
  • ==, !=
  • and, or (with short-circuiting)
  • bitwise operators: &, |, ~, ^
  • <, >, <=, >=
• Variables
  • Declaration
  • (Re)assignment
  • Referencing
• Conditionals
  • If
  • While
  • Repeat-until
  • For
  • Continue, break
  • Switch/case/when
  • Goto (it has valid uses)
• Scoping
  • Lexical scope
  • Block statement
• Functions
  • With parameters
  • With return value
  • Closures
  • Anonymous functions
    • Ruby-style blocks
  • Named arguments
• Constants
• Garbage collection
• Structure types
  • Struct
  • Classes
    • Methods
    • Traits, mixins
    • Accessors
    • Inheritance (maybe)
• Equality and comparison
• Collection types
  • Array/List
  • Dictionary/Map/Hash
  • Set
  • Range
  • Tuple
• Collection syntax/methods
  • Iteration
  • map/collect
  • filter/select/reject
  • fold/reduce/inject
• Native functions
  • IO
    • Write
    • Read
    • Formatted print
• Standard library
  • ???
  • IO
  • Parsing
    • JSON
    • CSV
    • …
• Further
  • String interpolation
  • Modules
  • Testing
  • Source code formatting
• Maybe
  • List comprehensions
  • Destructuring
  • Pattern matching
  • Concurrency
  • Type system
  • Extension methods
  • Comptime
  • Macros
  • Build system
  • Package manager
  • LSP
  • Code/test coverage

See also

• Language Checklist (Nicholas Yang)