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Diffstat (limited to 'syn/src/stmt.rs')
| -rw-r--r-- | syn/src/stmt.rs | 333 |
1 files changed, 333 insertions, 0 deletions
diff --git a/syn/src/stmt.rs b/syn/src/stmt.rs new file mode 100644 index 0000000..acee5a3 --- /dev/null +++ b/syn/src/stmt.rs @@ -0,0 +1,333 @@ +use super::*; + +ast_struct! { + /// A braced block containing Rust statements. + /// + /// *This type is available if Syn is built with the `"full"` feature.* + 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. + /// + /// *This type is available if Syn is built with the `"full"` feature.* + pub enum Stmt { + /// A local (let) binding. + Local(Local), + + /// An item definition. + Item(Item), + + /// Expr without trailing semicolon. + Expr(Expr), + + /// Expression with trailing semicolon. + Semi(Expr, Token![;]), + } +} + +ast_struct! { + /// A local `let` binding: `let x: u64 = s.parse()?`. + /// + /// *This type is available if Syn is built with the `"full"` feature.* + pub struct Local { + pub attrs: Vec<Attribute>, + pub let_token: Token![let], + pub pat: Pat, + pub init: Option<(Token![=], Box<Expr>)>, + pub semi_token: Token![;], + } +} + +#[cfg(feature = "parsing")] +pub mod parsing { + use super::*; + + use crate::parse::discouraged::Speculative; + use crate::parse::{Parse, ParseStream, Result}; + use crate::punctuated::Punctuated; + use proc_macro2::TokenStream; + + impl Block { + /// Parse the body of a block as zero or more statements, possibly + /// including one trailing expression. + /// + /// *This function is available if Syn is built with the `"parsing"` + /// feature.* + /// + /// # 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, + /// }) + /// } + /// } + /// ``` + pub fn parse_within(input: ParseStream) -> Result<Vec<Stmt>> { + let mut stmts = Vec::new(); + loop { + while let Some(semi) = input.parse::<Option<Token![;]>>()? { + stmts.push(Stmt::Semi(Expr::Verbatim(TokenStream::new()), semi)); + } + if input.is_empty() { + break; + } + let s = parse_stmt(input, true)?; + let requires_semicolon = if let Stmt::Expr(s) = &s { + expr::requires_terminator(s) + } else { + false + }; + stmts.push(s); + if input.is_empty() { + break; + } else if requires_semicolon { + return Err(input.error("unexpected token")); + } + } + Ok(stmts) + } + } + + 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)?, + }) + } + } + + impl Parse for Stmt { + fn parse(input: ParseStream) -> Result<Self> { + parse_stmt(input, false) + } + } + + fn parse_stmt(input: ParseStream, allow_nosemi: bool) -> Result<Stmt> { + let mut attrs = input.call(Attribute::parse_outer)?; + + // brace-style macros; paren and bracket macros get parsed as + // expression statements. + let ahead = input.fork(); + if let Ok(path) = ahead.call(Path::parse_mod_style) { + if ahead.peek(Token![!]) && (ahead.peek2(token::Brace) || ahead.peek2(Ident)) { + input.advance_to(&ahead); + return stmt_mac(input, attrs, path); + } + } + + if input.peek(Token![let]) { + 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.peek2(Token![::]) + || input.peek(Token![use]) + || input.peek(Token![static]) && (input.peek2(Token![mut]) || input.peek2(Ident)) + || input.peek(Token![const]) + || 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(item::parsing::existential) && input.peek2(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]) + { + let mut item: Item = input.parse()?; + attrs.extend(item.replace_attrs(Vec::new())); + item.replace_attrs(attrs); + Ok(Stmt::Item(item)) + } else { + stmt_expr(input, allow_nosemi, attrs) + } + } + + fn stmt_mac(input: ParseStream, attrs: Vec<Attribute>, path: Path) -> Result<Stmt> { + let bang_token: Token![!] = input.parse()?; + let ident: Option<Ident> = input.parse()?; + let (delimiter, tokens) = mac::parse_delimiter(input)?; + let semi_token: Option<Token![;]> = input.parse()?; + + Ok(Stmt::Item(Item::Macro(ItemMacro { + attrs, + ident, + mac: Macro { + path, + bang_token, + delimiter, + tokens, + }, + semi_token, + }))) + } + + fn stmt_local(input: ParseStream, attrs: Vec<Attribute>) -> Result<Local> { + Ok(Local { + attrs, + let_token: input.parse()?, + pat: { + let leading_vert: Option<Token![|]> = input.parse()?; + let mut pat: Pat = input.parse()?; + if leading_vert.is_some() + || input.peek(Token![|]) && !input.peek(Token![||]) && !input.peek(Token![|=]) + { + let mut cases = Punctuated::new(); + cases.push_value(pat); + while input.peek(Token![|]) + && !input.peek(Token![||]) + && !input.peek(Token![|=]) + { + let punct = input.parse()?; + cases.push_punct(punct); + let pat: Pat = input.parse()?; + cases.push_value(pat); + } + pat = Pat::Or(PatOr { + attrs: Vec::new(), + leading_vert, + cases, + }); + } + 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), + }); + } + pat + }, + init: { + if input.peek(Token![=]) { + let eq_token: Token![=] = input.parse()?; + let init: Expr = input.parse()?; + Some((eq_token, Box::new(init))) + } else { + None + } + }, + semi_token: input.parse()?, + }) + } + + fn stmt_expr( + input: ParseStream, + allow_nosemi: bool, + mut attrs: Vec<Attribute>, + ) -> Result<Stmt> { + let mut e = expr::parsing::expr_early(input)?; + + attrs.extend(e.replace_attrs(Vec::new())); + e.replace_attrs(attrs); + + if input.peek(Token![;]) { + return Ok(Stmt::Semi(e, input.parse()?)); + } + + if allow_nosemi || !expr::requires_terminator(&e) { + Ok(Stmt::Expr(e)) + } else { + Err(input.error("expected semicolon")) + } + } +} + +#[cfg(feature = "printing")] +mod printing { + use super::*; + + use proc_macro2::TokenStream; + use quote::{ToTokens, TokenStreamExt}; + + impl ToTokens for Block { + fn to_tokens(&self, tokens: &mut TokenStream) { + self.brace_token.surround(tokens, |tokens| { + tokens.append_all(&self.stmts); + }); + } + } + + 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) => expr.to_tokens(tokens), + Stmt::Semi(expr, semi) => { + expr.to_tokens(tokens); + semi.to_tokens(tokens); + } + } + } + } + + 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((eq_token, init)) = &self.init { + eq_token.to_tokens(tokens); + init.to_tokens(tokens); + } + self.semi_token.to_tokens(tokens); + } + } +} |