[Amendment] SE-0368: StaticBigInt

Evolution Proposal Reviews
12

I believe this is because, after parsing and during AST construction, negative numeric literals have special treatment; the prefix - is wiped away and the literal itself is flagged as negative, so there's no "operator" involved anymore during type checking:

$ echo '-5' | swiftc -dump-ast -
(source_file "<stdin>"
  (top_level_code_decl range=[<stdin>:1:1 - line:1:2]
    (brace_stmt implicit range=[<stdin>:1:1 - line:1:2]
      (integer_literal_expr type='Int' location=<stdin>:1:1 range=[<stdin>:1:1 - line:1:2] negative value=5 builtin_initializer=Swift.(file).Int.init(_builtinIntegerLiteral:) initializer=**NULL**))))

With unary +, on the other hand, the operator remains as an explicit invocation:

$ echo '+5' | swiftc -dump-ast -
(source_file "<stdin>"
  (top_level_code_decl range=[<stdin>:1:1 - line:1:2]
    (brace_stmt implicit range=[<stdin>:1:1 - line:1:2]
      (prefix_unary_expr type='Int' location=<stdin>:1:1 range=[<stdin>:1:1 - line:1:2] nothrow
        (dot_syntax_call_expr implicit type='(Int) -> Int' location=<stdin>:1:1 range=[<stdin>:1:1 - line:1:1] nothrow
          (declref_expr type='(Int.Type) -> (Int) -> Int' location=<stdin>:1:1 range=[<stdin>:1:1 - line:1:1] decl=Swift.(file).AdditiveArithmetic extension.+ [with (substitution_map generic_signature=<Self where Self : AdditiveArithmetic> (substitution Self -> Int))] function_ref=single)
          (argument_list implicit
            (argument
              (type_expr implicit type='Int.Type' location=<stdin>:1:1 range=[<stdin>:1:1 - line:1:1] typerepr='Int'))
          ))
        (argument_list implicit
          (argument
            (integer_literal_expr type='Int' location=<stdin>:1:2 range=[<stdin>:1:2 - line:1:2] value=5 builtin_initializer=Swift.(file).Int.init(_builtinIntegerLiteral:) initializer=**NULL**))
        )))))
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