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use super::*;
ast_struct! {
/// A braced block containing Rust statements.
#[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
pub struct Block {
pub brace_token: token::Brace,
/// Statements in a block
pub stmts: Vec<Stmt>,
}
}
ast_enum! {
/// A statement, usually ending in a semicolon.
#[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
pub enum Stmt {
/// A local (let) binding.
Local(Local),
/// An item definition.
Item(Item),
/// Expression, with or without trailing semicolon.
Expr(Expr, Option<Token![;]>),
/// A macro invocation in statement position.
///
/// Syntactically it's ambiguous which other kind of statement this
/// macro would expand to. It can be any of local variable (`let`),
/// item, or expression.
Macro(StmtMacro),
}
}
ast_struct! {
/// A local `let` binding: `let x: u64 = s.parse()?`.
#[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
pub struct Local {
pub attrs: Vec<Attribute>,
pub let_token: Token![let],
pub pat: Pat,
pub init: Option<LocalInit>,
pub semi_token: Token![;],
}
}
ast_struct! {
/// The expression assigned in a local `let` binding, including optional
/// diverging `else` block.
///
/// `LocalInit` represents `= s.parse()?` in `let x: u64 = s.parse()?` and
/// `= r else { return }` in `let Ok(x) = r else { return }`.
#[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
pub struct LocalInit {
pub eq_token: Token![=],
pub expr: Box<Expr>,
pub diverge: Option<(Token![else], Box<Expr>)>,
}
}
ast_struct! {
/// A macro invocation in statement position.
///
/// Syntactically it's ambiguous which other kind of statement this macro
/// would expand to. It can be any of local variable (`let`), item, or
/// expression.
#[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
pub struct StmtMacro {
pub attrs: Vec<Attribute>,
pub mac: Macro,
pub semi_token: Option<Token![;]>,
}
}
#[cfg(feature = "parsing")]
pub(crate) mod parsing {
use super::*;
use crate::parse::discouraged::Speculative as _;
use crate::parse::{Parse, ParseStream, Result};
use proc_macro2::TokenStream;
struct AllowNoSemi(bool);
impl Block {
/// Parse the body of a block as zero or more statements, possibly
/// including one trailing expression.
///
/// # Example
///
/// ```
/// use syn::{braced, token, Attribute, Block, Ident, Result, Stmt, Token};
/// use syn::parse::{Parse, ParseStream};
///
/// // Parse a function with no generics or parameter list.
/// //
/// // fn playground {
/// // let mut x = 1;
/// // x += 1;
/// // println!("{}", x);
/// // }
/// struct MiniFunction {
/// attrs: Vec<Attribute>,
/// fn_token: Token![fn],
/// name: Ident,
/// brace_token: token::Brace,
/// stmts: Vec<Stmt>,
/// }
///
/// impl Parse for MiniFunction {
/// fn parse(input: ParseStream) -> Result<Self> {
/// let outer_attrs = input.call(Attribute::parse_outer)?;
/// let fn_token: Token![fn] = input.parse()?;
/// let name: Ident = input.parse()?;
///
/// let content;
/// let brace_token = braced!(content in input);
/// let inner_attrs = content.call(Attribute::parse_inner)?;
/// let stmts = content.call(Block::parse_within)?;
///
/// Ok(MiniFunction {
/// attrs: {
/// let mut attrs = outer_attrs;
/// attrs.extend(inner_attrs);
/// attrs
/// },
/// fn_token,
/// name,
/// brace_token,
/// stmts,
/// })
/// }
/// }
/// ```
#[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
pub fn parse_within(input: ParseStream) -> Result<Vec<Stmt>> {
let mut stmts = Vec::new();
loop {
while let semi @ Some(_) = input.parse()? {
stmts.push(Stmt::Expr(Expr::Verbatim(TokenStream::new()), semi));
}
if input.is_empty() {
break;
}
let stmt = parse_stmt(input, AllowNoSemi(true))?;
let requires_semicolon = match &stmt {
Stmt::Expr(stmt, None) => expr::requires_terminator(stmt),
Stmt::Macro(stmt) => {
stmt.semi_token.is_none() && !stmt.mac.delimiter.is_brace()
}
Stmt::Local(_) | Stmt::Item(_) | Stmt::Expr(_, Some(_)) => false,
};
stmts.push(stmt);
if input.is_empty() {
break;
} else if requires_semicolon {
return Err(input.error("unexpected token, expected `;`"));
}
}
Ok(stmts)
}
}
#[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
impl Parse for Block {
fn parse(input: ParseStream) -> Result<Self> {
let content;
Ok(Block {
brace_token: braced!(content in input),
stmts: content.call(Block::parse_within)?,
})
}
}
#[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
impl Parse for Stmt {
fn parse(input: ParseStream) -> Result<Self> {
let allow_nosemi = AllowNoSemi(false);
parse_stmt(input, allow_nosemi)
}
}
fn parse_stmt(input: ParseStream, allow_nosemi: AllowNoSemi) -> Result<Stmt> {
let begin = input.fork();
let attrs = input.call(Attribute::parse_outer)?;
// brace-style macros; paren and bracket macros get parsed as
// expression statements.
let ahead = input.fork();
let mut is_item_macro = false;
if let Ok(path) = ahead.call(Path::parse_mod_style) {
if ahead.peek(Token![!]) {
if ahead.peek2(Ident) || ahead.peek2(Token![try]) {
is_item_macro = true;
} else if ahead.peek2(token::Brace)
&& !(ahead.peek3(Token![.]) || ahead.peek3(Token![?]))
{
input.advance_to(&ahead);
return stmt_mac(input, attrs, path).map(Stmt::Macro);
}
}
}
if input.peek(Token![let]) && !input.peek(token::Group) {
stmt_local(input, attrs).map(Stmt::Local)
} else if input.peek(Token![pub])
|| input.peek(Token![crate]) && !input.peek2(Token![::])
|| input.peek(Token![extern])
|| input.peek(Token![use])
|| input.peek(Token![static])
&& (input.peek2(Token![mut])
|| input.peek2(Ident)
&& !(input.peek2(Token![async])
&& (input.peek3(Token![move]) || input.peek3(Token![|]))))
|| input.peek(Token![const])
&& !(input.peek2(token::Brace)
|| input.peek2(Token![static])
|| input.peek2(Token![async])
&& !(input.peek3(Token![unsafe])
|| input.peek3(Token![extern])
|| input.peek3(Token![fn]))
|| input.peek2(Token![move])
|| input.peek2(Token![|]))
|| input.peek(Token![unsafe]) && !input.peek2(token::Brace)
|| input.peek(Token![async])
&& (input.peek2(Token![unsafe])
|| input.peek2(Token![extern])
|| input.peek2(Token![fn]))
|| input.peek(Token![fn])
|| input.peek(Token![mod])
|| input.peek(Token![type])
|| input.peek(Token![struct])
|| input.peek(Token![enum])
|| input.peek(Token![union]) && input.peek2(Ident)
|| input.peek(Token![auto]) && input.peek2(Token![trait])
|| input.peek(Token![trait])
|| input.peek(Token![default])
&& (input.peek2(Token![unsafe]) || input.peek2(Token![impl]))
|| input.peek(Token![impl])
|| input.peek(Token![macro])
|| is_item_macro
{
let item = item::parsing::parse_rest_of_item(begin, attrs, input)?;
Ok(Stmt::Item(item))
} else {
stmt_expr(input, allow_nosemi, attrs)
}
}
fn stmt_mac(input: ParseStream, attrs: Vec<Attribute>, path: Path) -> Result<StmtMacro> {
let bang_token: Token![!] = input.parse()?;
let (delimiter, tokens) = mac::parse_delimiter(input)?;
let semi_token: Option<Token![;]> = input.parse()?;
Ok(StmtMacro {
attrs,
mac: Macro {
path,
bang_token,
delimiter,
tokens,
},
semi_token,
})
}
fn stmt_local(input: ParseStream, attrs: Vec<Attribute>) -> Result<Local> {
let let_token: Token![let] = input.parse()?;
let mut pat = Pat::parse_single(input)?;
if input.peek(Token![:]) {
let colon_token: Token![:] = input.parse()?;
let ty: Type = input.parse()?;
pat = Pat::Type(PatType {
attrs: Vec::new(),
pat: Box::new(pat),
colon_token,
ty: Box::new(ty),
});
}
let init = if let Some(eq_token) = input.parse()? {
let eq_token: Token![=] = eq_token;
let expr: Expr = input.parse()?;
let diverge = if let Some(else_token) = input.parse()? {
let else_token: Token![else] = else_token;
let diverge = ExprBlock {
attrs: Vec::new(),
label: None,
block: input.parse()?,
};
Some((else_token, Box::new(Expr::Block(diverge))))
} else {
None
};
Some(LocalInit {
eq_token,
expr: Box::new(expr),
diverge,
})
} else {
None
};
let semi_token: Token![;] = input.parse()?;
Ok(Local {
attrs,
let_token,
pat,
init,
semi_token,
})
}
fn stmt_expr(
input: ParseStream,
allow_nosemi: AllowNoSemi,
mut attrs: Vec<Attribute>,
) -> Result<Stmt> {
let mut e = expr::parsing::expr_early(input)?;
let mut attr_target = &mut e;
loop {
attr_target = match attr_target {
Expr::Assign(e) => &mut e.left,
Expr::Binary(e) => &mut e.left,
Expr::Cast(e) => &mut e.expr,
Expr::Array(_)
| Expr::Async(_)
| Expr::Await(_)
| Expr::Block(_)
| Expr::Break(_)
| Expr::Call(_)
| Expr::Closure(_)
| Expr::Const(_)
| Expr::Continue(_)
| Expr::Field(_)
| Expr::ForLoop(_)
| Expr::Group(_)
| Expr::If(_)
| Expr::Index(_)
| Expr::Infer(_)
| Expr::Let(_)
| Expr::Lit(_)
| Expr::Loop(_)
| Expr::Macro(_)
| Expr::Match(_)
| Expr::MethodCall(_)
| Expr::Paren(_)
| Expr::Path(_)
| Expr::Range(_)
| Expr::Reference(_)
| Expr::Repeat(_)
| Expr::Return(_)
| Expr::Struct(_)
| Expr::Try(_)
| Expr::TryBlock(_)
| Expr::Tuple(_)
| Expr::Unary(_)
| Expr::Unsafe(_)
| Expr::While(_)
| Expr::Yield(_)
| Expr::Verbatim(_) => break,
};
}
attrs.extend(attr_target.replace_attrs(Vec::new()));
attr_target.replace_attrs(attrs);
let semi_token: Option<Token![;]> = input.parse()?;
match e {
Expr::Macro(ExprMacro { attrs, mac })
if semi_token.is_some() || mac.delimiter.is_brace() =>
{
return Ok(Stmt::Macro(StmtMacro {
attrs,
mac,
semi_token,
}));
}
_ => {}
}
if semi_token.is_some() {
Ok(Stmt::Expr(e, semi_token))
} else if allow_nosemi.0 || !expr::requires_terminator(&e) {
Ok(Stmt::Expr(e, None))
} else {
Err(input.error("expected semicolon"))
}
}
}
#[cfg(feature = "printing")]
mod printing {
use super::*;
use proc_macro2::TokenStream;
use quote::{ToTokens, TokenStreamExt};
#[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
impl ToTokens for Block {
fn to_tokens(&self, tokens: &mut TokenStream) {
self.brace_token.surround(tokens, |tokens| {
tokens.append_all(&self.stmts);
});
}
}
#[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
impl ToTokens for Stmt {
fn to_tokens(&self, tokens: &mut TokenStream) {
match self {
Stmt::Local(local) => local.to_tokens(tokens),
Stmt::Item(item) => item.to_tokens(tokens),
Stmt::Expr(expr, semi) => {
expr.to_tokens(tokens);
semi.to_tokens(tokens);
}
Stmt::Macro(mac) => mac.to_tokens(tokens),
}
}
}
#[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
impl ToTokens for Local {
fn to_tokens(&self, tokens: &mut TokenStream) {
expr::printing::outer_attrs_to_tokens(&self.attrs, tokens);
self.let_token.to_tokens(tokens);
self.pat.to_tokens(tokens);
if let Some(init) = &self.init {
init.eq_token.to_tokens(tokens);
init.expr.to_tokens(tokens);
if let Some((else_token, diverge)) = &init.diverge {
else_token.to_tokens(tokens);
diverge.to_tokens(tokens);
}
}
self.semi_token.to_tokens(tokens);
}
}
#[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
impl ToTokens for StmtMacro {
fn to_tokens(&self, tokens: &mut TokenStream) {
expr::printing::outer_attrs_to_tokens(&self.attrs, tokens);
self.mac.to_tokens(tokens);
self.semi_token.to_tokens(tokens);
}
}
}