Enum rustc_expand::base::SyntaxExtensionKind

pub enum SyntaxExtensionKind {
    Bang(Box<dyn BangProcMacro + DynSync + DynSend>),
    LegacyBang(Box<dyn TTMacroExpander + DynSync + DynSend>),
    Attr(Box<dyn AttrProcMacro + DynSync + DynSend>),
    LegacyAttr(Box<dyn MultiItemModifier + DynSync + DynSend>),
    NonMacroAttr,
    Derive(Box<dyn MultiItemModifier + DynSync + DynSend>),
    LegacyDerive(Box<dyn MultiItemModifier + DynSync + DynSend>),
}

A syntax extension kind.

Variants

Bang(Box<dyn BangProcMacro + DynSync + DynSend>)

Tuple Fields

0: Box<dyn BangProcMacro + DynSync + DynSend>

An expander with signature TokenStream -> TokenStream.

A token-based function-like macro.

LegacyBang(Box<dyn TTMacroExpander + DynSync + DynSend>)

Tuple Fields

0: Box<dyn TTMacroExpander + DynSync + DynSend>

An expander with signature TokenStream -> AST.

An AST-based function-like macro.

Attr(Box<dyn AttrProcMacro + DynSync + DynSend>)

Tuple Fields

0: Box<dyn AttrProcMacro + DynSync + DynSend>

An expander with signature (TokenStream, TokenStream) -> TokenStream. The first TokenStream is the attribute itself, the second is the annotated item. The produced TokenStream replaces the input TokenStream.

A token-based attribute macro.

LegacyAttr(Box<dyn MultiItemModifier + DynSync + DynSend>)

Tuple Fields

0: Box<dyn MultiItemModifier + DynSync + DynSend>

An expander with signature (AST, AST) -> AST. The first AST fragment is the attribute itself, the second is the annotated item. The produced AST fragment replaces the input AST fragment.

An AST-based attribute macro.

NonMacroAttr

A trivial attribute “macro” that does nothing, only keeps the attribute and marks it as inert, thus making it ineligible for further expansion.

Derive(Box<dyn MultiItemModifier + DynSync + DynSend>)

Tuple Fields

0: Box<dyn MultiItemModifier + DynSync + DynSend>

An expander with signature TokenStream -> TokenStream. The produced TokenStream is appended to the input TokenStream.

FIXME: The text above describes how this should work. Currently it is handled identically to LegacyDerive. It should be migrated to a token-based representation like Bang and Attr, instead of using MultiItemModifier.

A token-based derive macro.

LegacyDerive(Box<dyn MultiItemModifier + DynSync + DynSend>)

Tuple Fields

0: Box<dyn MultiItemModifier + DynSync + DynSend>

An expander with signature AST -> AST. The produced AST fragment is appended to the input AST fragment.

An AST-based derive macro.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 24 bytes

Size for each variant:

• Bang: 16 bytes
• LegacyBang: 16 bytes
• Attr: 16 bytes
• LegacyAttr: 16 bytes
• NonMacroAttr: 0 bytes
• Derive: 16 bytes
• LegacyDerive: 16 bytes