[swift-dev] Role of Brace-Stmt in Swift AST

[Toni Suter]

Hi,

I am trying to understand the Swift AST by looking at output produced from swiftc -dump-ast <file>.
Most of it makes sense to me, but there are some things that I don’t understand. For example, consider
the following code:

var x = 42

This produces the following output:

(source_file
  (top_level_code_decl
    (brace_stmt
      (pattern_binding_decl
        (pattern_named type='Int' 'x')
        (call_expr implicit type='Int' location=test.swift:1:9 range=[test.swift:1:9 - line:1:9] nothrow
          (constructor_ref_call_expr implicit type='(_builtinIntegerLiteral: Int2048) -> Int' location=test.swift:1:9 range=[test.swift:1:9 - line:1:9] nothrow
            (declref_expr implicit type='Int.Type -> (_builtinIntegerLiteral: Int2048) -> Int' location=test.swift:1:9 range=[test.swift:1:9 - line:1:9] decl=Swift.(file).Int.init(_builtinIntegerLiteral:) specialized=no)
            (type_expr implicit type='Int.Type' location=test.swift:1:9 range=[test.swift:1:9 - line:1:9] typerepr='Int'))
          (tuple_expr implicit type='(_builtinIntegerLiteral: Int2048)' location=test.swift:1:9 range=[test.swift:1:9 - line:1:9] names=_builtinIntegerLiteral
            (integer_literal_expr type='Int2048' location=test.swift:1:9 range=[test.swift:1:9 - line:1:9] value=42))))
))
  (var_decl "x" type='Int' access=internal storage_kind=stored))

Intuitively, I would have expected that the initializer is part of the var_decl. Also, why is there a brace_stmt involved?
As far as I have seen, the term brace statement doesn’t appear anywhere in the Swift Language Reference. Is it the
same as code-block <https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Declarations.html#//apple_ref/swift/grammar/code-block>?

Thanks in advance!

Best regards,
Toni
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