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//! `AstTransformer`s are functions that replace nodes in an AST and can be easily combined.
use rustc_hash::FxHashMap;
use hir::{HirDisplay, PathResolution, SemanticsScope};
use syntax::{
algo::SyntaxRewriter,
ast::{self, AstNode},
};
pub fn apply<'a, N: AstNode>(transformer: &dyn AstTransform<'a>, node: N) -> N {
SyntaxRewriter::from_fn(|element| match element {
syntax::SyntaxElement::Node(n) => {
let replacement = transformer.get_substitution(&n)?;
Some(replacement.into())
}
_ => None,
})
.rewrite_ast(&node)
}
/// `AstTransform` helps with applying bulk transformations to syntax nodes.
///
/// This is mostly useful for IDE code generation. If you paste some existing
/// code into a new context (for example, to add method overrides to an `impl`
/// block), you generally want to appropriately qualify the names, and sometimes
/// you might want to substitute generic parameters as well:
///
/// ```
/// mod x {
/// pub struct A;
/// pub trait T<U> { fn foo(&self, _: U) -> A; }
/// }
///
/// mod y {
/// use x::T;
///
/// impl T<()> for () {
/// // If we invoke **Add Missing Members** here, we want to copy-paste `foo`.
/// // But we want a slightly-modified version of it:
/// fn foo(&self, _: ()) -> x::A {}
/// }
/// }
/// ```
///
/// So, a single `AstTransform` describes such function from `SyntaxNode` to
/// `SyntaxNode`. Note that the API here is a bit too high-order and high-brow.
/// We'd want to somehow express this concept simpler, but so far nobody got to
/// simplifying this!
pub trait AstTransform<'a> {
fn get_substitution(&self, node: &syntax::SyntaxNode) -> Option<syntax::SyntaxNode>;
fn chain_before(self, other: Box<dyn AstTransform<'a> + 'a>) -> Box<dyn AstTransform<'a> + 'a>;
fn or<T: AstTransform<'a> + 'a>(self, other: T) -> Box<dyn AstTransform<'a> + 'a>
where
Self: Sized + 'a,
{
self.chain_before(Box::new(other))
}
}
struct NullTransformer;
impl<'a> AstTransform<'a> for NullTransformer {
fn get_substitution(&self, _node: &syntax::SyntaxNode) -> Option<syntax::SyntaxNode> {
None
}
fn chain_before(self, other: Box<dyn AstTransform<'a> + 'a>) -> Box<dyn AstTransform<'a> + 'a> {
other
}
}
pub struct SubstituteTypeParams<'a> {
source_scope: &'a SemanticsScope<'a>,
substs: FxHashMap<hir::TypeParam, ast::Type>,
previous: Box<dyn AstTransform<'a> + 'a>,
}
impl<'a> SubstituteTypeParams<'a> {
pub fn for_trait_impl(
source_scope: &'a SemanticsScope<'a>,
// FIXME: there's implicit invariant that `trait_` and `source_scope` match...
trait_: hir::Trait,
impl_def: ast::Impl,
) -> SubstituteTypeParams<'a> {
let substs = get_syntactic_substs(impl_def).unwrap_or_default();
let generic_def: hir::GenericDef = trait_.into();
let substs_by_param: FxHashMap<_, _> = generic_def
.params(source_scope.db)
.into_iter()
// this is a trait impl, so we need to skip the first type parameter -- this is a bit hacky
.skip(1)
// The actual list of trait type parameters may be longer than the one
// used in the `impl` block due to trailing default type parameters.
// For that case we extend the `substs` with an empty iterator so we
// can still hit those trailing values and check if they actually have
// a default type. If they do, go for that type from `hir` to `ast` so
// the resulting change can be applied correctly.
.zip(substs.into_iter().map(Some).chain(std::iter::repeat(None)))
.filter_map(|(k, v)| match v {
Some(v) => Some((k, v)),
None => {
let default = k.default(source_scope.db)?;
Some((
k,
ast::make::ty(
&default
.display_source_code(source_scope.db, source_scope.module()?.into())
.ok()?,
),
))
}
})
.collect();
return SubstituteTypeParams {
source_scope,
substs: substs_by_param,
previous: Box::new(NullTransformer),
};
// FIXME: It would probably be nicer if we could get this via HIR (i.e. get the
// trait ref, and then go from the types in the substs back to the syntax).
fn get_syntactic_substs(impl_def: ast::Impl) -> Option<Vec<ast::Type>> {
let target_trait = impl_def.trait_()?;
let path_type = match target_trait {
ast::Type::PathType(path) => path,
_ => return None,
};
let generic_arg_list = path_type.path()?.segment()?.generic_arg_list()?;
let mut result = Vec::new();
for generic_arg in generic_arg_list.generic_args() {
match generic_arg {
ast::GenericArg::TypeArg(type_arg) => result.push(type_arg.ty()?),
ast::GenericArg::AssocTypeArg(_)
| ast::GenericArg::LifetimeArg(_)
| ast::GenericArg::ConstArg(_) => (),
}
}
Some(result)
}
}
fn get_substitution_inner(&self, node: &syntax::SyntaxNode) -> Option<syntax::SyntaxNode> {
let type_ref = ast::Type::cast(node.clone())?;
let path = match &type_ref {
ast::Type::PathType(path_type) => path_type.path()?,
_ => return None,
};
let resolution = self.source_scope.speculative_resolve(&path)?;
match resolution {
hir::PathResolution::TypeParam(tp) => Some(self.substs.get(&tp)?.syntax().clone()),
_ => None,
}
}
}
impl<'a> AstTransform<'a> for SubstituteTypeParams<'a> {
fn get_substitution(&self, node: &syntax::SyntaxNode) -> Option<syntax::SyntaxNode> {
self.get_substitution_inner(node).or_else(|| self.previous.get_substitution(node))
}
fn chain_before(self, other: Box<dyn AstTransform<'a> + 'a>) -> Box<dyn AstTransform<'a> + 'a> {
Box::new(SubstituteTypeParams { previous: other, ..self })
}
}
pub struct QualifyPaths<'a> {
target_scope: &'a SemanticsScope<'a>,
source_scope: &'a SemanticsScope<'a>,
previous: Box<dyn AstTransform<'a> + 'a>,
}
impl<'a> QualifyPaths<'a> {
pub fn new(target_scope: &'a SemanticsScope<'a>, source_scope: &'a SemanticsScope<'a>) -> Self {
Self { target_scope, source_scope, previous: Box::new(NullTransformer) }
}
fn get_substitution_inner(&self, node: &syntax::SyntaxNode) -> Option<syntax::SyntaxNode> {
// FIXME handle value ns?
let from = self.target_scope.module()?;
let p = ast::Path::cast(node.clone())?;
if p.segment().and_then(|s| s.param_list()).is_some() {
// don't try to qualify `Fn(Foo) -> Bar` paths, they are in prelude anyway
return None;
}
let resolution = self.source_scope.speculative_resolve(&p)?;
match resolution {
PathResolution::Def(def) => {
let found_path = from.find_use_path(self.source_scope.db.upcast(), def)?;
let mut path = path_to_ast(found_path);
let type_args = p
.segment()
.and_then(|s| s.generic_arg_list())
.map(|arg_list| apply(self, arg_list));
if let Some(type_args) = type_args {
let last_segment = path.segment().unwrap();
path = path.with_segment(last_segment.with_generic_args(type_args))
}
Some(path.syntax().clone())
}
PathResolution::Local(_)
| PathResolution::TypeParam(_)
| PathResolution::SelfType(_) => None,
PathResolution::Macro(_) => None,
PathResolution::AssocItem(_) => None,
}
}
}
impl<'a> AstTransform<'a> for QualifyPaths<'a> {
fn get_substitution(&self, node: &syntax::SyntaxNode) -> Option<syntax::SyntaxNode> {
self.get_substitution_inner(node).or_else(|| self.previous.get_substitution(node))
}
fn chain_before(self, other: Box<dyn AstTransform<'a> + 'a>) -> Box<dyn AstTransform<'a> + 'a> {
Box::new(QualifyPaths { previous: other, ..self })
}
}
pub(crate) fn path_to_ast(path: hir::ModPath) -> ast::Path {
let parse = ast::SourceFile::parse(&path.to_string());
parse
.tree()
.syntax()
.descendants()
.find_map(ast::Path::cast)
.unwrap_or_else(|| panic!("failed to parse path {:?}, `{}`", path, path))
}
|
