40 lines
1.4 KiB
Rust
40 lines
1.4 KiB
Rust
//! Routines the parser uses to classify AST nodes
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// Predicates on exprs and stmts that the pretty-printer and parser use
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use crate::ast;
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/// Does this expression require a semicolon to be treated
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/// as a statement? The negation of this: 'can this expression
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/// be used as a statement without a semicolon' -- is used
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/// as an early-bail-out in the parser so that, for instance,
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/// if true {...} else {...}
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/// |x| 5
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/// isn't parsed as (if true {...} else {...} | x) | 5
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pub fn expr_requires_semi_to_be_stmt(e: &ast::Expr) -> bool {
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match e.node {
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ast::ExprKind::If(..) |
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ast::ExprKind::IfLet(..) |
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ast::ExprKind::Match(..) |
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ast::ExprKind::Block(..) |
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ast::ExprKind::While(..) |
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ast::ExprKind::WhileLet(..) |
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ast::ExprKind::Loop(..) |
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ast::ExprKind::ForLoop(..) |
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ast::ExprKind::TryBlock(..) => false,
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_ => true,
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}
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}
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/// this statement requires a semicolon after it.
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/// note that in one case (`stmt_semi`), we've already
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/// seen the semicolon, and thus don't need another.
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pub fn stmt_ends_with_semi(stmt: &ast::StmtKind) -> bool {
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match *stmt {
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ast::StmtKind::Local(_) => true,
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ast::StmtKind::Expr(ref e) => expr_requires_semi_to_be_stmt(e),
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ast::StmtKind::Item(_) |
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ast::StmtKind::Semi(..) |
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ast::StmtKind::Mac(..) => false,
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}
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}
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