61 lines
2.0 KiB
Rust
61 lines
2.0 KiB
Rust
//! When specifying SSR rule, you generally want to map one *kind* of thing to
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//! the same kind of thing: path to path, expression to expression, type to
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//! type.
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//!
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//! The problem is, while this *kind* is generally obvious to the human, the ide
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//! needs to determine it somehow. We do this in a stupid way -- by pasting SSR
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//! rule into different contexts and checking what works.
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use syntax::{ast, AstNode, SyntaxNode};
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pub(crate) fn ty(s: &str) -> Result<SyntaxNode, ()> {
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fragment::<ast::Type>("type T = {};", s)
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}
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pub(crate) fn item(s: &str) -> Result<SyntaxNode, ()> {
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fragment::<ast::Item>("{}", s)
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}
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pub(crate) fn pat(s: &str) -> Result<SyntaxNode, ()> {
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fragment::<ast::Pat>("const _: () = {let {} = ();};", s)
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}
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pub(crate) fn expr(s: &str) -> Result<SyntaxNode, ()> {
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fragment::<ast::Expr>("const _: () = {};", s)
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}
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pub(crate) fn stmt(s: &str) -> Result<SyntaxNode, ()> {
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let template = "const _: () = { {}; };";
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let input = template.replace("{}", s);
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let parse = syntax::SourceFile::parse(&input, syntax::Edition::CURRENT);
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if !parse.errors().is_empty() {
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return Err(());
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}
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let mut node =
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parse.tree().syntax().descendants().skip(2).find_map(ast::Stmt::cast).ok_or(())?;
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if !s.ends_with(';') && node.to_string().ends_with(';') {
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node = node.clone_for_update();
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if let Some(it) = node.syntax().last_token() {
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it.detach()
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}
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}
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if node.to_string() != s {
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return Err(());
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}
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Ok(node.syntax().clone_subtree())
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}
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fn fragment<T: AstNode>(template: &str, s: &str) -> Result<SyntaxNode, ()> {
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let s = s.trim();
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let input = template.replace("{}", s);
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let parse = syntax::SourceFile::parse(&input, syntax::Edition::CURRENT);
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if !parse.errors().is_empty() {
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return Err(());
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}
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let node = parse.tree().syntax().descendants().find_map(T::cast).ok_or(())?;
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if node.syntax().text() != s {
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return Err(());
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}
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Ok(node.syntax().clone_subtree())
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}
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