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use crate::ast;
use crate::parsing::Opaque;
use crate::{Id, Parse, ParseError, Parser, Spanned, ToTokens};
/// A block of expressions.
///
/// ```rust
/// use rune::{testing, ast};
///
/// let expr = testing::roundtrip::<ast::ExprBlock>("{}");
/// assert_eq!(expr.block.statements.len(), 0);
///
/// let expr = testing::roundtrip::<ast::ExprBlock>("{ 42 }");
/// assert_eq!(expr.block.statements.len(), 1);
///
/// let expr = testing::roundtrip::<ast::ExprBlock>("#[retry] { 42 }");
/// assert_eq!(expr.block.statements.len(), 1);
/// assert_eq!(expr.attributes.len(), 1);
/// ```
#[derive(Debug, Clone, PartialEq, Eq, ToTokens, Spanned)]
pub struct Block {
/// The unique identifier for the block expression.
#[rune(id)]
pub id: Option<Id>,
/// The close brace.
pub open: T!['{'],
/// Statements in the block.
pub statements: Vec<ast::Stmt>,
/// The close brace.
pub close: T!['}'],
}
impl Opaque for Block {
fn id(&self) -> Option<Id> {
self.id
}
}
impl Block {
/// Test if the block produces nothing.
pub fn produces_nothing(&self) -> bool {
let mut it = self.statements.iter();
while let Some(ast::Stmt::Expr(_, semi)) = it.next_back() {
return semi.is_some();
}
true
}
}
/// Parse implementation for a block.
///
/// # Examples
///
/// ```rust
/// use rune::{testing, ast};
///
/// let block = testing::roundtrip::<ast::Block>("{}");
/// assert_eq!(block.statements.len(), 0);
/// assert!(block.produces_nothing());
///
/// let block = testing::roundtrip::<ast::Block>("{ foo }");
/// assert_eq!(block.statements.len(), 1);
/// assert!(!block.produces_nothing());
///
/// let block = testing::roundtrip::<ast::Block>("{ foo; }");
/// assert_eq!(block.statements.len(), 1);
/// assert!(block.produces_nothing());
///
/// let block = testing::roundtrip::<ast::Block>(r#"
/// {
/// let foo = 42;
/// let bar = "string";
/// baz
/// }
/// "#);
///
/// assert_eq!(block.statements.len(), 3);
/// ```
impl Parse for Block {
fn parse(parser: &mut Parser<'_>) -> Result<Self, ParseError> {
let mut statements = Vec::new();
let open = parser.parse()?;
while !parser.peek::<T!['}']>()? {
statements.push(parser.parse()?);
}
let close = parser.parse()?;
Ok(Block {
id: Default::default(),
open,
statements,
close,
})
}
}