214 lines
7.7 KiB
Rust
214 lines
7.7 KiB
Rust
//! `AstTransformer`s are functions that replace nodes in an AST and can be easily combined.
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use hir::{HirDisplay, PathResolution, SemanticsScope};
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use ide_db::helpers::mod_path_to_ast;
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use rustc_hash::FxHashMap;
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use syntax::{
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algo::SyntaxRewriter,
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ast::{self, AstNode},
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SyntaxNode,
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};
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pub fn apply<'a, N: AstNode>(transformer: &dyn AstTransform<'a>, node: N) -> N {
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SyntaxRewriter::from_fn(|element| match element {
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syntax::SyntaxElement::Node(n) => {
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let replacement = transformer.get_substitution(&n, transformer)?;
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Some(replacement.into())
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}
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_ => None,
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})
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.rewrite_ast(&node)
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}
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/// `AstTransform` helps with applying bulk transformations to syntax nodes.
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///
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/// This is mostly useful for IDE code generation. If you paste some existing
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/// code into a new context (for example, to add method overrides to an `impl`
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/// block), you generally want to appropriately qualify the names, and sometimes
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/// you might want to substitute generic parameters as well:
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///
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/// ```
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/// mod x {
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/// pub struct A;
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/// pub trait T<U> { fn foo(&self, _: U) -> A; }
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/// }
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///
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/// mod y {
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/// use x::T;
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///
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/// impl T<()> for () {
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/// // If we invoke **Add Missing Members** here, we want to copy-paste `foo`.
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/// // But we want a slightly-modified version of it:
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/// fn foo(&self, _: ()) -> x::A {}
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/// }
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/// }
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/// ```
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///
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/// So, a single `AstTransform` describes such function from `SyntaxNode` to
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/// `SyntaxNode`. Note that the API here is a bit too high-order and high-brow.
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/// We'd want to somehow express this concept simpler, but so far nobody got to
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/// simplifying this!
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pub trait AstTransform<'a> {
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fn get_substitution(
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&self,
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node: &SyntaxNode,
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recur: &dyn AstTransform<'a>,
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) -> Option<SyntaxNode>;
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fn or<T: AstTransform<'a> + 'a>(self, other: T) -> Box<dyn AstTransform<'a> + 'a>
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where
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Self: Sized + 'a,
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{
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Box::new(Or(Box::new(self), Box::new(other)))
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}
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}
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struct Or<'a>(Box<dyn AstTransform<'a> + 'a>, Box<dyn AstTransform<'a> + 'a>);
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impl<'a> AstTransform<'a> for Or<'a> {
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fn get_substitution(
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&self,
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node: &SyntaxNode,
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recur: &dyn AstTransform<'a>,
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) -> Option<SyntaxNode> {
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self.0.get_substitution(node, recur).or_else(|| self.1.get_substitution(node, recur))
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}
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}
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pub struct SubstituteTypeParams<'a> {
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source_scope: &'a SemanticsScope<'a>,
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substs: FxHashMap<hir::TypeParam, ast::Type>,
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}
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impl<'a> SubstituteTypeParams<'a> {
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pub fn for_trait_impl(
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source_scope: &'a SemanticsScope<'a>,
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// FIXME: there's implicit invariant that `trait_` and `source_scope` match...
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trait_: hir::Trait,
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impl_def: ast::Impl,
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) -> SubstituteTypeParams<'a> {
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let substs = get_syntactic_substs(impl_def).unwrap_or_default();
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let generic_def: hir::GenericDef = trait_.into();
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let substs_by_param: FxHashMap<_, _> = generic_def
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.type_params(source_scope.db)
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.into_iter()
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// this is a trait impl, so we need to skip the first type parameter -- this is a bit hacky
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.skip(1)
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// The actual list of trait type parameters may be longer than the one
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// used in the `impl` block due to trailing default type parameters.
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// For that case we extend the `substs` with an empty iterator so we
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// can still hit those trailing values and check if they actually have
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// a default type. If they do, go for that type from `hir` to `ast` so
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// the resulting change can be applied correctly.
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.zip(substs.into_iter().map(Some).chain(std::iter::repeat(None)))
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.filter_map(|(k, v)| match v {
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Some(v) => Some((k, v)),
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None => {
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let default = k.default(source_scope.db)?;
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Some((
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k,
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ast::make::ty(
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&default
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.display_source_code(source_scope.db, source_scope.module()?.into())
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.ok()?,
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),
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))
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}
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})
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.collect();
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return SubstituteTypeParams { source_scope, substs: substs_by_param };
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// FIXME: It would probably be nicer if we could get this via HIR (i.e. get the
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// trait ref, and then go from the types in the substs back to the syntax).
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fn get_syntactic_substs(impl_def: ast::Impl) -> Option<Vec<ast::Type>> {
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let target_trait = impl_def.trait_()?;
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let path_type = match target_trait {
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ast::Type::PathType(path) => path,
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_ => return None,
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};
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let generic_arg_list = path_type.path()?.segment()?.generic_arg_list()?;
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let mut result = Vec::new();
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for generic_arg in generic_arg_list.generic_args() {
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match generic_arg {
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ast::GenericArg::TypeArg(type_arg) => result.push(type_arg.ty()?),
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ast::GenericArg::AssocTypeArg(_)
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| ast::GenericArg::LifetimeArg(_)
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| ast::GenericArg::ConstArg(_) => (),
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}
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}
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Some(result)
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}
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}
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}
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impl<'a> AstTransform<'a> for SubstituteTypeParams<'a> {
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fn get_substitution(
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&self,
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node: &SyntaxNode,
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_recur: &dyn AstTransform<'a>,
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) -> Option<SyntaxNode> {
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let type_ref = ast::Type::cast(node.clone())?;
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let path = match &type_ref {
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ast::Type::PathType(path_type) => path_type.path()?,
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_ => return None,
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};
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let resolution = self.source_scope.speculative_resolve(&path)?;
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match resolution {
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hir::PathResolution::TypeParam(tp) => Some(self.substs.get(&tp)?.syntax().clone()),
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_ => None,
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}
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}
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}
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pub struct QualifyPaths<'a> {
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target_scope: &'a SemanticsScope<'a>,
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source_scope: &'a SemanticsScope<'a>,
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}
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impl<'a> QualifyPaths<'a> {
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pub fn new(target_scope: &'a SemanticsScope<'a>, source_scope: &'a SemanticsScope<'a>) -> Self {
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Self { target_scope, source_scope }
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}
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}
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impl<'a> AstTransform<'a> for QualifyPaths<'a> {
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fn get_substitution(
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&self,
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node: &SyntaxNode,
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recur: &dyn AstTransform<'a>,
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) -> Option<SyntaxNode> {
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// FIXME handle value ns?
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let from = self.target_scope.module()?;
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let p = ast::Path::cast(node.clone())?;
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if p.segment().and_then(|s| s.param_list()).is_some() {
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// don't try to qualify `Fn(Foo) -> Bar` paths, they are in prelude anyway
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return None;
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}
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let resolution = self.source_scope.speculative_resolve(&p)?;
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match resolution {
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PathResolution::Def(def) => {
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let found_path = from.find_use_path(self.source_scope.db.upcast(), def)?;
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let mut path = mod_path_to_ast(&found_path);
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let type_args = p
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.segment()
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.and_then(|s| s.generic_arg_list())
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.map(|arg_list| apply(recur, arg_list));
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if let Some(type_args) = type_args {
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let last_segment = path.segment().unwrap();
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path = path.with_segment(last_segment.with_generic_args(type_args))
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}
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Some(path.syntax().clone())
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}
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PathResolution::Local(_)
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| PathResolution::TypeParam(_)
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| PathResolution::SelfType(_)
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| PathResolution::ConstParam(_) => None,
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PathResolution::Macro(_) => None,
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PathResolution::AssocItem(_) => None,
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}
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}
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}
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