Enum rustc_expand::base::SyntaxExtensionKind

pub enum SyntaxExtensionKind {
    Bang(Box<dyn ProcMacro + Sync + Send>),
    LegacyBang(Box<dyn TTMacroExpander + Sync + Send>),
    Attr(Box<dyn AttrProcMacro + Sync + Send>),
    LegacyAttr(Box<dyn MultiItemModifier + Sync + Send>),
    NonMacroAttr,
    Derive(Box<dyn MultiItemModifier + Sync + Send>),
    LegacyDerive(Box<dyn MultiItemModifier + Sync + Send>),
}

A syntax extension kind.

Variants

Bang(Box<dyn ProcMacro + Sync + Send>)

A token-based function-like macro.

Tuple Fields of Bang

0: Box<dyn ProcMacro + Sync + Send>

An expander with signature TokenStream -> TokenStream.

LegacyBang(Box<dyn TTMacroExpander + Sync + Send>)

An AST-based function-like macro.

Tuple Fields of LegacyBang

0: Box<dyn TTMacroExpander + Sync + Send>

An expander with signature TokenStream -> AST.

Attr(Box<dyn AttrProcMacro + Sync + Send>)

A token-based attribute macro.

Tuple Fields of Attr

0: Box<dyn AttrProcMacro + Sync + Send>

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

LegacyAttr(Box<dyn MultiItemModifier + Sync + Send>)

An AST-based attribute macro.

Tuple Fields of LegacyAttr

0: Box<dyn MultiItemModifier + Sync + Send>

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.

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 + Sync + Send>)

A token-based derive macro.

Tuple Fields of Derive

0: Box<dyn MultiItemModifier + Sync + Send>

An expander with signature TokenStream -> TokenStream (not yet). The produced TokenSteam is appended to the input TokenSteam.

LegacyDerive(Box<dyn MultiItemModifier + Sync + Send>)

An AST-based derive macro.

Tuple Fields of LegacyDerive

0: Box<dyn MultiItemModifier + Sync + Send>

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

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