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//! Lots of helpers for dealing with SWC, particularly from unist, and for
//! building its ES AST.
use swc_core::common::{BytePos, Span, SyntaxContext, DUMMY_SP};
use swc_core::ecma::visit::{noop_visit_mut_type, VisitMut};
/// Visitor to fix SWC byte positions by removing a prefix.
///
/// > 👉 **Note**: SWC byte positions are offset by one: they are `0` when they
/// > are missing or incremented by `1` when valid.
#[derive(Debug, Default, Clone)]
pub struct RewritePrefixContext {
/// Size of prefix considered outside this tree.
pub prefix_len: u32,
}
impl VisitMut for RewritePrefixContext {
noop_visit_mut_type!();
/// Rewrite spans.
fn visit_mut_span(&mut self, span: &mut Span) {
let mut result = DUMMY_SP;
if span.lo.0 > self.prefix_len && span.hi.0 > self.prefix_len {
result = create_span(span.lo.0 - self.prefix_len, span.hi.0 - self.prefix_len);
}
*span = result;
}
}
/// Generate a span.
pub fn create_span(lo: u32, hi: u32) -> Span {
Span {
lo: BytePos(lo),
hi: BytePos(hi),
ctxt: SyntaxContext::default(),
}
}
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