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This is an example of documentation generated by ZigDoc, an alternative to Zig's built-in Auto Doc feature. See also examples in other modes/formats. The project being documented here (as the example) is the Zig standard library. Public Struct

Node

Public Struct
std.zig.Ast.Node
pub const Node = struct

Fields

tag: Tag
main_token: TokenIndex
data: Data

Structs

Types

File

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pub const Node = struct {
    tag: Tag,
    main_token: TokenIndex,
    data: Data,

    /// Index into `nodes`.
    pub const Index = enum(u32) {
        root = 0,
        _,

        pub fn toOptional(i: Index) OptionalIndex {
            const result: OptionalIndex = @fromBackingInt(@intCast(@backingInt(i)));
            assert(result != .none);
            return result;
        }

        pub fn toOffset(base: Index, destination: Index) Offset {
            const base_i64: i64 = @backingInt(base);
            const destination_i64: i64 = @backingInt(destination);
            return @fromBackingInt(@intCast(destination_i64 - base_i64));
        }
    };

    /// Index into `nodes`, or null.
    pub const OptionalIndex = enum(u32) {
        root = 0,
        none = std.math.maxInt(u32),
        _,

        pub fn unwrap(oi: OptionalIndex) ?Index {
            return if (oi == .none) null else @fromBackingInt(@intCast(@backingInt(oi)));
        }

        pub fn fromOptional(oi: ?Index) OptionalIndex {
            return if (oi) |i| i.toOptional() else .none;
        }
    };

    /// A relative node index.
    pub const Offset = enum(i32) {
        zero = 0,
        _,

        pub fn toOptional(o: Offset) OptionalOffset {
            const result: OptionalOffset = @fromBackingInt(@intCast(@backingInt(o)));
            assert(result != .none);
            return result;
        }

        pub fn toAbsolute(offset: Offset, base: Index) Index {
            return @fromBackingInt(@intCast(@as(i64, @backingInt(base)) + @backingInt(offset)));
        }
    };

    /// A relative node index, or null.
    pub const OptionalOffset = enum(i32) {
        none = std.math.maxInt(i32),
        _,

        pub fn unwrap(oo: OptionalOffset) ?Offset {
            return if (oo == .none) null else @fromBackingInt(@intCast(@backingInt(oo)));
        }
    };

    comptime {
        // Goal is to keep this under one byte for efficiency.
        assert(@sizeOf(Tag) == 1);

        if (!std.debug.runtime_safety) {
            assert(@sizeOf(Data) == 8);
        }
    }

    /// The FooComma/FooSemicolon variants exist to ease the implementation of
    /// `Ast.lastToken()`
    pub const Tag = enum {
        /// The root node which is guaranteed to be at `Node.Index.root`.
        /// The meaning of the `data` field depends on whether it is a `.zig` or
        /// `.zon` file.
        ///
        /// The `main_token` field is the first token for the source file.
        root,
        /// `test {}`,
        /// `test "name" {}`,
        /// `test identifier {}`.
        ///
        /// The `data` field is a `.opt_token_and_node`:
        ///   1. a `OptionalTokenIndex` to the test name token (must be string literal or identifier), if any.
        ///   2. a `Node.Index` to the block.
        ///
        /// The `main_token` field is the `test` token.
        test_decl,
        /// The `data` field is a `.extra_and_opt_node`:
        ///   1. a `ExtraIndex` to `GlobalVarDecl`.
        ///   2. a `Node.OptionalIndex` to the initialization expression.
        ///
        /// The `main_token` field is the `var` or `const` token.
        ///
        /// The initialization expression can't be `.none` unless it is part of
        /// a `assign_destructure` node or a parsing error occured.
        global_var_decl,
        /// `var a: b align(c) = d`.
        /// `const main_token: type_node align(align_node) = init_expr`.
        ///
        /// The `data` field is a `.extra_and_opt_node`:
        ///   1. a `ExtraIndex` to `LocalVarDecl`.
        ///   2. a `Node.OptionalIndex` to the initialization expression-
        ///
        /// The `main_token` field is the `var` or `const` token.
        ///
        /// The initialization expression can't be `.none` unless it is part of
        /// a `assign_destructure` node or a parsing error occured.
        local_var_decl,
        /// `var a: b = c`.
        /// `const name_token: type_expr = init_expr`.
        /// Can be local or global.
        ///
        /// The `data` field is a `.opt_node_and_opt_node`:
        ///   1. a `Node.OptionalIndex` to the type expression, if any.
        ///   2. a `Node.OptionalIndex` to the initialization expression.
        ///
        /// The `main_token` field is the `var` or `const` token.
        ///
        /// The initialization expression can't be `.none` unless it is part of
        /// a `assign_destructure` node or a parsing error occured.
        simple_var_decl,
        /// `var a align(b) = c`.
        /// `const name_token align(align_expr) = init_expr`.
        /// Can be local or global.
        ///
        /// The `data` field is a `.node_and_opt_node`:
        ///   1. a `Node.Index` to the alignment expression.
        ///   2. a `Node.OptionalIndex` to the initialization expression.
        ///
        /// The `main_token` field is the `var` or `const` token.
        ///
        /// The initialization expression can't be `.none` unless it is part of
        /// a `assign_destructure` node or a parsing error occured.
        aligned_var_decl,
        /// `errdefer expr`,
        ///
        /// The `data` field is a `.node` to the deferred expression.
        ///
        /// The `main_token` field is the `errdefer` token.
        @"errdefer",
        /// `defer expr`.
        ///
        /// The `data` field is a `.node` to the deferred expression.
        ///
        /// The `main_token` field is the `defer` token.
        @"defer",
        /// `lhs catch rhs`,
        /// `lhs catch |err| rhs`.
        ///
        /// The `main_token` field is the `catch` token.
        ///
        /// The error payload is determined by looking at the next token after
        /// the `catch` token.
        @"catch",
        /// `lhs.a`.
        ///
        /// The `data` field is a `.node_and_token`:
        ///   1. a `Node.Index` to the left side of the field access.
        ///   2. a `TokenIndex` to the field name identifier.
        ///
        /// The `main_token` field is the `.` token.
        field_access,
        /// `lhs.?`.
        ///
        /// The `data` field is a `.node_and_token`:
        ///   1. a `Node.Index` to the left side of the optional unwrap.
        ///   2. a `TokenIndex` to the `?` token.
        ///
        /// The `main_token` field is the `.` token.
        unwrap_optional,
        /// `lhs == rhs`. The `main_token` field is the `==` token.
        equal_equal,
        /// `lhs != rhs`. The `main_token` field is the `!=` token.
        bang_equal,
        /// `lhs < rhs`. The `main_token` field is the `<` token.
        less_than,
        /// `lhs > rhs`. The `main_token` field is the `>` token.
        greater_than,
        /// `lhs <= rhs`. The `main_token` field is the `<=` token.
        less_or_equal,
        /// `lhs >= rhs`. The `main_token` field is the `>=` token.
        greater_or_equal,
        /// `lhs *= rhs`. The `main_token` field is the `*=` token.
        assign_mul,
        /// `lhs /= rhs`. The `main_token` field is the `/=` token.
        assign_div,
        /// `lhs %= rhs`. The `main_token` field is the `%=` token.
        assign_mod,
        /// `lhs += rhs`. The `main_token` field is the `+=` token.
        assign_add,
        /// `lhs -= rhs`. The `main_token` field is the `-=` token.
        assign_sub,
        /// `lhs <<= rhs`. The `main_token` field is the `<<=` token.
        assign_shl,
        /// `lhs <<|= rhs`. The `main_token` field is the `<<|=` token.
        assign_shl_sat,
        /// `lhs >>= rhs`. The `main_token` field is the `>>=` token.
        assign_shr,
        /// `lhs &= rhs`. The `main_token` field is the `&=` token.
        assign_bit_and,
        /// `lhs ^= rhs`. The `main_token` field is the `^=` token.
        assign_bit_xor,
        /// `lhs |= rhs`. The `main_token` field is the `|=` token.
        assign_bit_or,
        /// `lhs *%= rhs`. The `main_token` field is the `*%=` token.
        assign_mul_wrap,
        /// `lhs +%= rhs`. The `main_token` field is the `+%=` token.
        assign_add_wrap,
        /// `lhs -%= rhs`. The `main_token` field is the `-%=` token.
        assign_sub_wrap,
        /// `lhs *|= rhs`. The `main_token` field is the `*%=` token.
        assign_mul_sat,
        /// `lhs +|= rhs`. The `main_token` field is the `+|=` token.
        assign_add_sat,
        /// `lhs -|= rhs`. The `main_token` field is the `-|=` token.
        assign_sub_sat,
        /// `lhs = rhs`. The `main_token` field is the `=` token.
        assign,
        /// `a, b, ... = rhs`.
        ///
        /// The `data` field is a `.extra_and_node`:
        ///   1. a `ExtraIndex`. Further explained below.
        ///   2. a `Node.Index` to the initialization expression.
        ///
        /// The `main_token` field is the `=` token.
        ///
        /// The `ExtraIndex` stores the following data:
        /// ```
        /// elem_count: u32,
        /// variables: [elem_count]Node.Index,
        /// ```
        ///
        /// Each node in `variables` has one of the following tags:
        ///   - `global_var_decl`
        ///   - `local_var_decl`
        ///   - `simple_var_decl`
        ///   - `aligned_var_decl`
        ///   - Any expression node
        ///
        /// The first 4 tags correspond to a `var` or `const` lhs node (note
        /// that their initialization expression is always `.none`).
        /// An expression node corresponds to a standard assignment LHS (which
        /// must be evaluated as an lvalue). There may be a preceding
        /// `comptime` token, which does not create a corresponding `comptime`
        /// node so must be manually detected.
        assign_destructure,
        /// `lhs || rhs`. The `main_token` field is the `||` token.
        merge_error_sets,
        /// `lhs * rhs`. The `main_token` field is the `*` token.
        mul,
        /// `lhs / rhs`. The `main_token` field is the `/` token.
        div,
        /// `lhs % rhs`. The `main_token` field is the `%` token.
        mod,
        /// `lhs *% rhs`. The `main_token` field is the `*%` token.
        mul_wrap,
        /// `lhs *| rhs`. The `main_token` field is the `*|` token.
        mul_sat,
        /// `lhs + rhs`. The `main_token` field is the `+` token.
        add,
        /// `lhs - rhs`. The `main_token` field is the `-` token.
        sub,
        /// `lhs ++ rhs`. The `main_token` field is the `++` token.
        array_cat,
        /// `lhs +% rhs`. The `main_token` field is the `+%` token.
        add_wrap,
        /// `lhs -% rhs`. The `main_token` field is the `-%` token.
        sub_wrap,
        /// `lhs +| rhs`. The `main_token` field is the `+|` token.
        add_sat,
        /// `lhs -| rhs`. The `main_token` field is the `-|` token.
        sub_sat,
        /// `lhs << rhs`. The `main_token` field is the `<<` token.
        shl,
        /// `lhs <<| rhs`. The `main_token` field is the `<<|` token.
        shl_sat,
        /// `lhs >> rhs`. The `main_token` field is the `>>` token.
        shr,
        /// `lhs & rhs`. The `main_token` field is the `&` token.
        bit_and,
        /// `lhs ^ rhs`. The `main_token` field is the `^` token.
        bit_xor,
        /// `lhs | rhs`. The `main_token` field is the `|` token.
        bit_or,
        /// `lhs orelse rhs`. The `main_token` field is the `orelse` token.
        @"orelse",
        /// `lhs and rhs`. The `main_token` field is the `and` token.
        bool_and,
        /// `lhs or rhs`. The `main_token` field is the `or` token.
        bool_or,
        /// `!expr`. The `main_token` field is the `!` token.
        bool_not,
        /// `-expr`. The `main_token` field is the `-` token.
        negation,
        /// `~expr`. The `main_token` field is the `~` token.
        bit_not,
        /// `-%expr`. The `main_token` field is the `-%` token.
        negation_wrap,
        /// `&expr`. The `main_token` field is the `&` token.
        address_of,
        /// `try expr`. The `main_token` field is the `try` token.
        @"try",
        /// `?expr`. The `main_token` field is the `?` token.
        optional_type,
        /// `[lhs]rhs`. The `main_token` field is the `[` token.
        array_type,
        /// `[lhs:a]b`.
        ///
        /// The `data` field is a `.node_and_extra`:
        ///   1. a `Node.Index` to the length expression.
        ///   2. a `ExtraIndex` to `ArrayTypeSentinel`.
        ///
        /// The `main_token` field is the `[` token.
        array_type_sentinel,
        /// `[*]align(lhs) rhs`,
        /// `*align(lhs) rhs`,
        /// `[]rhs`.
        ///
        /// The `data` field is a `.opt_node_and_node`:
        ///   1. a `Node.OptionalIndex` to the alignment expression, if any.
        ///   2. a `Node.Index` to the element type expression.
        ///
        /// The `main_token` is the asterisk if a single item pointer or the
        /// lbracket if a slice, many-item pointer, or C-pointer.
        ptr_type_aligned,
        /// `[*:lhs]rhs`,
        /// `*rhs`,
        /// `[:lhs]rhs`.
        ///
        /// The `data` field is a `.opt_node_and_node`:
        ///   1. a `Node.OptionalIndex` to the sentinel expression, if any.
        ///   2. a `Node.Index` to the element type expression.
        ///
        /// The `main_token` is the asterisk if a single item pointer or the
        /// lbracket if a slice, many-item pointer, or C-pointer.
        ptr_type_sentinel,
        /// The `data` field is a `.extra_and_node`:
        ///   1. a `ExtraIndex` to `PtrType`.
        ///   2. a `Node.Index` to the element type expression.
        ///
        /// The `main_token` is the asterisk if a single item pointer or the
        /// lbracket if a slice, many-item pointer, or C-pointer.
        ptr_type,
        /// The `data` field is a `.extra_and_node`:
        ///   1. a `ExtraIndex` to `PtrTypeBitRange`.
        ///   2. a `Node.Index` to the element type expression.
        ///
        /// The `main_token` is the asterisk if a single item pointer or the
        /// lbracket if a slice, many-item pointer, or C-pointer.
        ptr_type_bit_range,
        /// `lhs[rhs..]`
        ///
        /// The `main_token` field is the `[` token.
        slice_open,
        /// `sliced[start..end]`.
        ///
        /// The `data` field is a `.node_and_extra`:
        ///   1. a `Node.Index` to the sliced expression.
        ///   2. a `ExtraIndex` to `Slice`.
        ///
        /// The `main_token` field is the `[` token.
        slice,
        /// `sliced[start..end :sentinel]`,
        /// `sliced[start.. :sentinel]`.
        ///
        /// The `data` field is a `.node_and_extra`:
        ///   1. a `Node.Index` to the sliced expression.
        ///   2. a `ExtraIndex` to `SliceSentinel`.
        ///
        /// The `main_token` field is the `[` token.
        slice_sentinel,
        /// `expr.*`.
        ///
        /// The `data` field is a `.node` to expr.
        ///
        /// The `main_token` field is the `*` token.
        deref,
        /// `lhs[rhs]`.
        ///
        /// The `main_token` field is the `[` token.
        array_access,
        /// `lhs{rhs}`.
        ///
        /// The `main_token` field is the `{` token.
        array_init_one,
        /// Same as `array_init_one` except there is known to be a trailing
        /// comma before the final rbrace.
        array_init_one_comma,
        /// `.{a}`,
        /// `.{a, b}`.
        ///
        /// The `data` field is a `.opt_node_and_opt_node`:
        ///   1. a `Node.OptionalIndex` to the first element. Never `.none`
        ///   2. a `Node.OptionalIndex` to the second element, if any.
        ///
        /// The `main_token` field is the `{` token.
        array_init_dot_two,
        /// Same as `array_init_dot_two` except there is known to be a trailing
        /// comma before the final rbrace.
        array_init_dot_two_comma,
        /// `.{a, b, c}`.
        ///
        /// The `data` field is a `.extra_range` that stores a `Node.Index` for
        /// each element.
        ///
        /// The `main_token` field is the `{` token.
        array_init_dot,
        /// Same as `array_init_dot` except there is known to be a trailing
        /// comma before the final rbrace.
        array_init_dot_comma,
        /// `a{b, c}`.
        ///
        /// The `data` field is a `.node_and_extra`:
        ///   1. a `Node.Index` to the type expression.
        ///   2. a `ExtraIndex` to a `SubRange` that stores a `Node.Index` for
        ///      each element.
        ///
        /// The `main_token` field is the `{` token.
        array_init,
        /// Same as `array_init` except there is known to be a trailing comma
        /// before the final rbrace.
        array_init_comma,
        /// `a{.x = b}`, `a{}`.
        ///
        /// The `data` field is a `.node_and_opt_node`:
        ///   1. a `Node.Index` to the type expression.
        ///   2. a `Node.OptionalIndex` to the first field initialization, if any.
        ///
        /// The `main_token` field is the `{` token.
        ///
        /// The field name is determined by looking at the tokens preceding the
        /// field initialization.
        struct_init_one,
        /// Same as `struct_init_one` except there is known to be a trailing comma
        /// before the final rbrace.
        struct_init_one_comma,
        /// `.{.x = a, .y = b}`.
        ///
        /// The `data` field is a `.opt_node_and_opt_node`:
        ///   1. a `Node.OptionalIndex` to the first field initialization. Never `.none`
        ///   2. a `Node.OptionalIndex` to the second field initialization, if any.
        ///
        /// The `main_token` field is the '{' token.
        ///
        /// The field name is determined by looking at the tokens preceding the
        /// field initialization.
        struct_init_dot_two,
        /// Same as `struct_init_dot_two` except there is known to be a trailing
        /// comma before the final rbrace.
        struct_init_dot_two_comma,
        /// `.{.x = a, .y = b, .z = c}`.
        ///
        /// The `data` field is a `.extra_range` that stores a `Node.Index` for
        /// each field initialization.
        ///
        /// The `main_token` field is the `{` token.
        ///
        /// The field name is determined by looking at the tokens preceding the
        /// field initialization.
        struct_init_dot,
        /// Same as `struct_init_dot` except there is known to be a trailing
        /// comma before the final rbrace.
        struct_init_dot_comma,
        /// `a{.x = b, .y = c}`.
        ///
        /// The `data` field is a `.node_and_extra`:
        ///   1. a `Node.Index` to the type expression.
        ///   2. a `ExtraIndex` to a `SubRange` that stores a `Node.Index` for
        ///      each field initialization.
        ///
        /// The `main_token` field is the `{` token.
        ///
        /// The field name is determined by looking at the tokens preceding the
        /// field initialization.
        struct_init,
        /// Same as `struct_init` except there is known to be a trailing comma
        /// before the final rbrace.
        struct_init_comma,
        /// `a(b)`, `a()`.
        ///
        /// The `data` field is a `.node_and_opt_node`:
        ///   1. a `Node.Index` to the function expression.
        ///   2. a `Node.OptionalIndex` to the first argument, if any.
        ///
        /// The `main_token` field is the `(` token.
        call_one,
        /// Same as `call_one` except there is known to be a trailing comma
        /// before the final rparen.
        call_one_comma,
        /// `a(b, c, d)`.
        ///
        /// The `data` field is a `.node_and_extra`:
        ///   1. a `Node.Index` to the function expression.
        ///   2. a `ExtraIndex` to a `SubRange` that stores a `Node.Index` for
        ///      each argument.
        ///
        /// The `main_token` field is the `(` token.
        call,
        /// Same as `call` except there is known to be a trailing comma before
        /// the final rparen.
        call_comma,
        /// `switch(a) {}`.
        ///
        /// The `data` field is a `.node_and_extra`:
        ///   1. a `Node.Index` to the switch operand.
        ///   2. a `ExtraIndex` to a `SubRange` that stores a `Node.Index` for
        ///      each switch case.
        ///
        /// `The `main_token` field` is the identifier of a preceding label, if any; otherwise `switch`.
        @"switch",
        /// Same as `switch` except there is known to be a trailing comma before
        /// the final rbrace.
        switch_comma,
        /// `a => b`,
        /// `else => b`.
        ///
        /// The `data` field is a `.opt_node_and_node`:
        ///   1. a `Node.OptionalIndex` where `.none` means `else`.
        ///   2. a `Node.Index` to the target expression.
        ///
        /// The `main_token` field is the `=>` token.
        switch_case_one,
        /// Same as `switch_case_one` but the case is inline.
        switch_case_inline_one,
        /// `a, b, c => d`.
        ///
        /// The `data` field is a `.extra_and_node`:
        ///   1. a `ExtraIndex` to a `SubRange` that stores a `Node.Index` for
        ///      each switch item.
        ///   2. a `Node.Index` to the target expression.
        ///
        /// The `main_token` field is the `=>` token.
        switch_case,
        /// Same as `switch_case` but the case is inline.
        switch_case_inline,
        /// `lhs...rhs`.
        ///
        /// The `main_token` field is the `...` token.
        switch_range,
        /// `while (a) b`,
        /// `while (a) |x| b`.
        while_simple,
        /// `while (a) : (b) c`,
        /// `while (a) |x| : (b) c`.
        while_cont,
        /// `while (a) : (b) c else d`,
        /// `while (a) |x| : (b) c else d`,
        /// `while (a) |x| : (b) c else |y| d`.
        /// The continue expression part `: (b)` may be omitted.
        @"while",
        /// `for (a) b`.
        for_simple,
        /// `for (lhs[0..inputs]) lhs[inputs + 1] else lhs[inputs + 2]`. `For[rhs]`.
        @"for",
        /// `lhs..rhs`, `lhs..`.
        for_range,
        /// `if (a) b`.
        /// `if (b) |x| b`.
        if_simple,
        /// `if (a) b else c`.
        /// `if (a) |x| b else c`.
        /// `if (a) |x| b else |y| d`.
        @"if",
        /// `suspend expr`.
        ///
        /// The `data` field is a `.node` to expr.
        ///
        /// The `main_token` field is the `suspend` token.
        @"suspend",
        /// `resume expr`.
        ///
        /// The `data` field is a `.node` to expr.
        ///
        /// The `main_token` field is the `resume` token.
        @"resume",
        /// `continue :label expr`,
        /// `continue expr`,
        /// `continue :label`,
        /// `continue`.
        ///
        /// The `data` field is a `.opt_token_and_opt_node`:
        ///   1. a `OptionalTokenIndex` to the label identifier, if any.
        ///   2. a `Node.OptionalIndex` to the target expression, if any.
        ///
        /// The `main_token` field is the `continue` token.
        @"continue",
        /// `break :label expr`,
        /// `break expr`,
        /// `break :label`,
        /// `break`.
        ///
        /// The `data` field is a `.opt_token_and_opt_node`:
        ///   1. a `OptionalTokenIndex` to the label identifier, if any.
        ///   2. a `Node.OptionalIndex` to the target expression, if any.
        ///
        /// The `main_token` field is the `break` token.
        @"break",
        /// `return expr`, `return`.
        ///
        /// The `data` field is a `.opt_node` to the return value, if any.
        ///
        /// The `main_token` field is the `return` token.
        @"return",
        /// `fn (a: type_expr) return_type`.
        ///
        /// The `data` field is a `.opt_node_and_opt_node`:
        ///   1. a `Node.OptionalIndex` to the first parameter type expression, if any.
        ///   2. a `Node.OptionalIndex` to the return type expression. Can't be
        ///      `.none` unless a parsing error occured.
        ///
        /// The `main_token` field is the `fn` token.
        ///
        /// `anytype` and `...` parameters are omitted from the AST tree.
        /// Extern function declarations use this tag.
        fn_proto_simple,
        /// `fn (a: b, c: d) return_type`.
        ///
        /// The `data` field is a `.extra_and_opt_node`:
        ///   1. a `ExtraIndex` to a `SubRange` that stores a `Node.Index` for
        ///      each parameter type expression.
        ///   2. a `Node.OptionalIndex` to the return type expression. Can't be
        ///      `.none` unless a parsing error occured.
        ///
        /// The `main_token` field is the `fn` token.
        ///
        /// `anytype` and `...` parameters are omitted from the AST tree.
        /// Extern function declarations use this tag.
        fn_proto_multi,
        /// `fn (a: b) addrspace(e) linksection(f) callconv(g) return_type`.
        /// zero or one parameters.
        ///
        /// The `data` field is a `.extra_and_opt_node`:
        ///   1. a `Node.ExtraIndex` to `FnProtoOne`.
        ///   2. a `Node.OptionalIndex` to the return type expression. Can't be
        ///      `.none` unless a parsing error occured.
        ///
        /// The `main_token` field is the `fn` token.
        ///
        /// `anytype` and `...` parameters are omitted from the AST tree.
        /// Extern function declarations use this tag.
        fn_proto_one,
        /// `fn (a: b, c: d) addrspace(e) linksection(f) callconv(g) return_type`.
        ///
        /// The `data` field is a `.extra_and_opt_node`:
        ///   1. a `Node.ExtraIndex` to `FnProto`.
        ///   2. a `Node.OptionalIndex` to the return type expression. Can't be
        ///      `.none` unless a parsing error occured.
        ///
        /// The `main_token` field is the `fn` token.
        ///
        /// `anytype` and `...` parameters are omitted from the AST tree.
        /// Extern function declarations use this tag.
        fn_proto,
        /// Extern function declarations use the fn_proto tags rather than this one.
        ///
        /// The `data` field is a `.node_and_node`:
        ///   1. a `Node.Index` to `fn_proto_*`.
        ///   2. a `Node.Index` to function body block.
        ///
        /// The `main_token` field is the `fn` token.
        fn_decl,
        /// `anyframe->return_type`.
        ///
        /// The `data` field is a `.token_and_node`:
        ///   1. a `TokenIndex` to the `->` token.
        ///   2. a `Node.Index` to the function frame return type expression.
        ///
        /// The `main_token` field is the `anyframe` token.
        anyframe_type,
        /// The `data` field is unused.
        anyframe_literal,
        /// The `data` field is unused.
        char_literal,
        /// The `data` field is unused.
        number_literal,
        /// The `data` field is unused.
        unreachable_literal,
        /// The `data` field is unused.
        ///
        /// Most identifiers will not have explicit AST nodes, however for
        /// expressions which could be one of many different kinds of AST nodes,
        /// there will be an identifier AST node for it.
        identifier,
        /// `.foo`.
        ///
        /// The `data` field is unused.
        ///
        /// The `main_token` field is the identifier.
        enum_literal,
        /// The `data` field is unused.
        ///
        /// The `main_token` field is the string literal token.
        string_literal,
        /// The `data` field is a `.token_and_token`:
        ///   1. a `TokenIndex` to the first `.multiline_string_literal_line` token.
        ///   2. a `TokenIndex` to the last `.multiline_string_literal_line` token.
        ///
        /// The `main_token` field is the first token index (redundant with `data`).
        multiline_string_literal,
        /// `(expr)`.
        ///
        /// The `data` field is a `.node_and_token`:
        ///   1. a `Node.Index` to the sub-expression
        ///   2. a `TokenIndex` to the `)` token.
        ///
        /// The `main_token` field is the `(` token.
        grouped_expression,
        /// `@a(b, c)`.
        ///
        /// The `data` field is a `.opt_node_and_opt_node`:
        ///   1. a `Node.OptionalIndex` to the first argument, if any.
        ///   2. a `Node.OptionalIndex` to the second argument, if any.
        ///
        /// The `main_token` field is the builtin token.
        builtin_call_two,
        /// Same as `builtin_call_two` except there is known to be a trailing comma
        /// before the final rparen.
        builtin_call_two_comma,
        /// `@a(b, c, d)`.
        ///
        /// The `data` field is a `.extra_range` that stores a `Node.Index` for
        /// each argument.
        ///
        /// The `main_token` field is the builtin token.
        builtin_call,
        /// Same as `builtin_call` except there is known to be a trailing comma
        /// before the final rparen.
        builtin_call_comma,
        /// `error{a, b}`.
        ///
        /// The `data` field is a `.token_and_token`:
        ///   1. a `TokenIndex` to the `{` token.
        ///   2. a `TokenIndex` to the `}` token.
        ///
        /// The `main_token` field is the `error`.
        error_set_decl,
        /// `struct {}`, `union {}`, `opaque {}`, `enum {}`.
        ///
        /// The `data` field is a `.extra_range` that stores a `Node.Index` for
        /// each container member.
        ///
        /// The `main_token` field is the `struct`, `union`, `opaque` or `enum` token.
        container_decl,
        /// Same as `container_decl` except there is known to be a trailing
        /// comma before the final rbrace.
        container_decl_trailing,
        /// `struct {lhs, rhs}`, `union {lhs, rhs}`, `opaque {lhs, rhs}`, `enum {lhs, rhs}`.
        ///
        /// The `data` field is a `.opt_node_and_opt_node`:
        ///   1. a `Node.OptionalIndex` to the first container member, if any.
        ///   2. a `Node.OptionalIndex` to the second container member, if any.
        ///
        /// The `main_token` field is the `struct`, `union`, `opaque` or `enum` token.
        container_decl_two,
        /// Same as `container_decl_two` except there is known to be a trailing
        /// comma before the final rbrace.
        container_decl_two_trailing,
        /// `struct(arg)`, `union(arg)`, `enum(arg)`.
        ///
        /// The `data` field is a `.node_and_extra`:
        ///   1. a `Node.Index` to arg.
        ///   2. a `ExtraIndex` to a `SubRange` that stores a `Node.Index` for
        ///      each container member.
        ///
        /// The `main_token` field is the `struct`, `union` or `enum` token.
        container_decl_arg,
        /// Same as `container_decl_arg` except there is known to be a trailing
        /// comma before the final rbrace.
        container_decl_arg_trailing,
        /// `union(enum) {}`.
        ///
        /// The `data` field is a `.extra_range` that stores a `Node.Index` for
        /// each container member.
        ///
        /// The `main_token` field is the `union` token.
        ///
        /// A tagged union with explicitly provided enums will instead be
        /// represented by `container_decl_arg`.
        tagged_union,
        /// Same as `tagged_union` except there is known to be a trailing comma
        /// before the final rbrace.
        tagged_union_trailing,
        /// `union(enum) {lhs, rhs}`.
        ///
        /// The `data` field is a `.opt_node_and_opt_node`:
        ///   1. a `Node.OptionalIndex` to the first container member, if any.
        ///   2. a `Node.OptionalIndex` to the second container member, if any.
        ///
        /// The `main_token` field is the `union` token.
        ///
        /// A tagged union with explicitly provided enums will instead be
        /// represented by `container_decl_arg`.
        tagged_union_two,
        /// Same as `tagged_union_two` except there is known to be a trailing
        /// comma before the final rbrace.
        tagged_union_two_trailing,
        /// `union(enum(arg)) {}`.
        ///
        /// The `data` field is a `.node_and_extra`:
        ///   1. a `Node.Index` to arg.
        ///   2. a `ExtraIndex` to a `SubRange` that stores a `Node.Index` for
        ///      each container member.
        ///
        /// The `main_token` field is the `union` token.
        tagged_union_enum_tag,
        /// Same as `tagged_union_enum_tag` except there is known to be a
        /// trailing comma before the final rbrace.
        tagged_union_enum_tag_trailing,
        /// `a: lhs = rhs,`,
        /// `a: lhs,`.
        ///
        /// The `data` field is a `.node_and_opt_node`:
        ///   1. a `Node.Index` to the field type expression.
        ///   2. a `Node.OptionalIndex` to the default value expression, if any.
        ///
        /// The `main_token` field is the field name identifier.
        ///
        /// `lastToken()` does not include the possible trailing comma.
        container_field_init,
        /// `a: lhs align(rhs),`.
        ///
        /// The `data` field is a `.node_and_node`:
        ///   1. a `Node.Index` to the field type expression.
        ///   2. a `Node.Index` to the alignment expression.
        ///
        /// The `main_token` field is the field name identifier.
        ///
        /// `lastToken()` does not include the possible trailing comma.
        container_field_align,
        /// `a: lhs align(c) = d,`.
        ///
        /// The `data` field is a `.node_and_extra`:
        ///   1. a `Node.Index` to the field type expression.
        ///   2. a `ExtraIndex` to `ContainerField`.
        ///
        /// The `main_token` field is the field name identifier.
        ///
        /// `lastToken()` does not include the possible trailing comma.
        container_field,
        /// `comptime expr`.
        ///
        /// The `data` field is a `.node` to expr.
        ///
        /// The `main_token` field is the `comptime` token.
        @"comptime",
        /// `nosuspend expr`.
        ///
        /// The `data` field is a `.node` to expr.
        ///
        /// The `main_token` field is the `nosuspend` token.
        @"nosuspend",
        /// `{lhs rhs}`.
        ///
        /// The `data` field is a `.opt_node_and_opt_node`:
        ///   1. a `Node.OptionalIndex` to the first statement, if any.
        ///   2. a `Node.OptionalIndex` to the second statement, if any.
        ///
        /// The `main_token` field is the `{` token.
        block_two,
        /// Same as `block_two` except there is known to be a trailing
        /// comma before the final rbrace.
        block_two_semicolon,
        /// `{a b}`.
        ///
        /// The `data` field is a `.extra_range` that stores a `Node.Index` for
        /// each statement.
        ///
        /// The `main_token` field is the `{` token.
        block,
        /// Same as `block` except there is known to be a trailing comma before
        /// the final rbrace.
        block_semicolon,
        /// `asm(a)`.
        ///
        /// The `main_token` field is the `asm` token.
        asm_simple,
        /// `asm(a, b)`.
        ///
        /// The `data` field is a `.node_and_extra`:
        ///   1. a `Node.Index` to a.
        ///   2. a `ExtraIndex` to `Asm`.
        ///
        /// The `main_token` field is the `asm` token.
        @"asm",
        /// `[a] "b" (c)`.
        /// `[a] "b" (-> lhs)`.
        ///
        /// The `data` field is a `.opt_node_and_token`:
        ///   1. a `Node.OptionalIndex` to lhs, if any.
        ///   2. a `TokenIndex` to the `)` token.
        ///
        /// The `main_token` field is `a`.
        asm_output,
        /// `[a] "b" (lhs)`.
        ///
        /// The `data` field is a `.node_and_token`:
        ///   1. a `Node.Index` to lhs.
        ///   2. a `TokenIndex` to the `)` token.
        ///
        /// The `main_token` field is `a`.
        asm_input,
        /// `error.a`.
        ///
        /// The `data` field is unused.
        ///
        /// The `main_token` field is `error` token.
        error_value,
        /// `lhs!rhs`.
        ///
        /// The `main_token` field is the `!` token.
        error_union,

        pub fn isContainerField(tag: Tag) bool {
            return switch (tag) {
                .container_field_init,
                .container_field_align,
                .container_field,
                => true,

                else => false,
            };
        }
    };

    pub const Data = union {
        node: Index,
        opt_node: OptionalIndex,
        token: TokenIndex,
        node_and_node: struct { Index, Index },
        opt_node_and_opt_node: struct { OptionalIndex, OptionalIndex },
        node_and_opt_node: struct { Index, OptionalIndex },
        opt_node_and_node: struct { OptionalIndex, Index },
        node_and_extra: struct { Index, ExtraIndex },
        extra_and_node: struct { ExtraIndex, Index },
        extra_and_opt_node: struct { ExtraIndex, OptionalIndex },
        node_and_token: struct { Index, TokenIndex },
        token_and_node: struct { TokenIndex, Index },
        token_and_token: struct { TokenIndex, TokenIndex },
        opt_node_and_token: struct { OptionalIndex, TokenIndex },
        opt_token_and_node: struct { OptionalTokenIndex, Index },
        opt_token_and_opt_node: struct { OptionalTokenIndex, OptionalIndex },
        opt_token_and_opt_token: struct { OptionalTokenIndex, OptionalTokenIndex },
        @"for": struct { ExtraIndex, For },
        extra_range: SubRange,
    };

    pub const LocalVarDecl = struct {
        type_node: Index,
        align_node: Index,
    };

    pub const ArrayTypeSentinel = struct {
        sentinel: Index,
        elem_type: Index,
    };

    pub const PtrType = struct {
        sentinel: OptionalIndex,
        align_node: OptionalIndex,
        addrspace_node: OptionalIndex,
    };

    pub const PtrTypeBitRange = struct {
        sentinel: OptionalIndex,
        align_node: Index,
        addrspace_node: OptionalIndex,
        bit_range_start: Index,
        bit_range_end: Index,
    };

    pub const SubRange = struct {
        /// Index into extra_data.
        start: ExtraIndex,
        /// Index into extra_data.
        end: ExtraIndex,
    };

    pub const If = struct {
        then_expr: Index,
        else_expr: Index,
    };

    pub const ContainerField = struct {
        align_expr: Index,
        value_expr: Index,
    };

    pub const GlobalVarDecl = struct {
        /// Populated if there is an explicit type ascription.
        type_node: OptionalIndex,
        /// Populated if align(A) is present.
        align_node: OptionalIndex,
        /// Populated if addrspace(A) is present.
        addrspace_node: OptionalIndex,
        /// Populated if linksection(A) is present.
        section_node: OptionalIndex,
    };

    pub const Slice = struct {
        start: Index,
        end: Index,
    };

    pub const SliceSentinel = struct {
        start: Index,
        /// May be .none if the slice is "open"
        end: OptionalIndex,
        sentinel: Index,
    };

    pub const While = struct {
        cont_expr: OptionalIndex,
        then_expr: Index,
        else_expr: Index,
    };

    pub const WhileCont = struct {
        cont_expr: Index,
        then_expr: Index,
    };

    pub const For = packed struct(u32) {
        inputs: u31,
        has_else: bool,
    };

    pub const FnProtoOne = struct {
        /// Populated if there is exactly 1 parameter. Otherwise there are 0 parameters.
        param: OptionalIndex,
        /// Populated if align(A) is present.
        align_expr: OptionalIndex,
        /// Populated if addrspace(A) is present.
        addrspace_expr: OptionalIndex,
        /// Populated if linksection(A) is present.
        section_expr: OptionalIndex,
        /// Populated if callconv(A) is present.
        callconv_expr: OptionalIndex,
    };

    pub const FnProto = struct {
        params_start: ExtraIndex,
        params_end: ExtraIndex,
        /// Populated if align(A) is present.
        align_expr: OptionalIndex,
        /// Populated if addrspace(A) is present.
        addrspace_expr: OptionalIndex,
        /// Populated if linksection(A) is present.
        section_expr: OptionalIndex,
        /// Populated if callconv(A) is present.
        callconv_expr: OptionalIndex,
    };

    pub const Asm = struct {
        items_start: ExtraIndex,
        items_end: ExtraIndex,
        clobbers: OptionalIndex,
        /// Needed to make lastToken() work.
        rparen: TokenIndex,
    };
}