1 files changed, 331 insertions, 0 deletions

diff --git a/crates/syntax/src/ast.rs b/crates/syntax/src/ast.rs
new file mode 100644
index 000000000..d536bb1e7
--- /dev/null
+++ b/crates/syntax/src/ast.rs
@@ -0,0 +1,331 @@
+//! Abstract Syntax Tree, layered on top of untyped `SyntaxNode`s
+
+mod generated;
+mod traits;
+mod token_ext;
+mod node_ext;
+mod expr_ext;
+pub mod edit;
+pub mod make;
+
+use std::marker::PhantomData;
+
+use crate::{
+    syntax_node::{SyntaxNode, SyntaxNodeChildren, SyntaxToken},
+    SmolStr, SyntaxKind,
+};
+
+pub use self::{
+    expr_ext::{ArrayExprKind, BinOp, Effect, ElseBranch, LiteralKind, PrefixOp, RangeOp},
+    generated::*,
+    node_ext::{
+        AttrKind, FieldKind, NameOrNameRef, PathSegmentKind, SelfParamKind, SlicePatComponents,
+        StructKind, TypeBoundKind, VisibilityKind,
+    },
+    token_ext::*,
+    traits::*,
+};
+
+/// The main trait to go from untyped `SyntaxNode`  to a typed ast. The
+/// conversion itself has zero runtime cost: ast and syntax nodes have exactly
+/// the same representation: a pointer to the tree root and a pointer to the
+/// node itself.
+pub trait AstNode {
+    fn can_cast(kind: SyntaxKind) -> bool
+    where
+        Self: Sized;
+
+    fn cast(syntax: SyntaxNode) -> Option<Self>
+    where
+        Self: Sized;
+
+    fn syntax(&self) -> &SyntaxNode;
+}
+
+/// Like `AstNode`, but wraps tokens rather than interior nodes.
+pub trait AstToken {
+    fn can_cast(token: SyntaxKind) -> bool
+    where
+        Self: Sized;
+
+    fn cast(syntax: SyntaxToken) -> Option<Self>
+    where
+        Self: Sized;
+
+    fn syntax(&self) -> &SyntaxToken;
+
+    fn text(&self) -> &SmolStr {
+        self.syntax().text()
+    }
+}
+
+/// An iterator over `SyntaxNode` children of a particular AST type.
+#[derive(Debug, Clone)]
+pub struct AstChildren<N> {
+    inner: SyntaxNodeChildren,
+    ph: PhantomData<N>,
+}
+
+impl<N> AstChildren<N> {
+    fn new(parent: &SyntaxNode) -> Self {
+        AstChildren { inner: parent.children(), ph: PhantomData }
+    }
+}
+
+impl<N: AstNode> Iterator for AstChildren<N> {
+    type Item = N;
+    fn next(&mut self) -> Option<N> {
+        self.inner.find_map(N::cast)
+    }
+}
+
+mod support {
+    use super::{AstChildren, AstNode, SyntaxKind, SyntaxNode, SyntaxToken};
+
+    pub(super) fn child<N: AstNode>(parent: &SyntaxNode) -> Option<N> {
+        parent.children().find_map(N::cast)
+    }
+
+    pub(super) fn children<N: AstNode>(parent: &SyntaxNode) -> AstChildren<N> {
+        AstChildren::new(parent)
+    }
+
+    pub(super) fn token(parent: &SyntaxNode, kind: SyntaxKind) -> Option<SyntaxToken> {
+        parent.children_with_tokens().filter_map(|it| it.into_token()).find(|it| it.kind() == kind)
+    }
+}
+
+#[test]
+fn assert_ast_is_object_safe() {
+    fn _f(_: &dyn AstNode, _: &dyn NameOwner) {}
+}
+
+#[test]
+fn test_doc_comment_none() {
+    let file = SourceFile::parse(
+        r#"
+        // non-doc
+        mod foo {}
+        "#,
+    )
+    .ok()
+    .unwrap();
+    let module = file.syntax().descendants().find_map(Module::cast).unwrap();
+    assert!(module.doc_comment_text().is_none());
+}
+
+#[test]
+fn test_doc_comment_of_items() {
+    let file = SourceFile::parse(
+        r#"
+        //! doc
+        // non-doc
+        mod foo {}
+        "#,
+    )
+    .ok()
+    .unwrap();
+    let module = file.syntax().descendants().find_map(Module::cast).unwrap();
+    assert_eq!("doc", module.doc_comment_text().unwrap());
+}
+
+#[test]
+fn test_doc_comment_of_statics() {
+    let file = SourceFile::parse(
+        r#"
+        /// Number of levels
+        static LEVELS: i32 = 0;
+        "#,
+    )
+    .ok()
+    .unwrap();
+    let st = file.syntax().descendants().find_map(Static::cast).unwrap();
+    assert_eq!("Number of levels", st.doc_comment_text().unwrap());
+}
+
+#[test]
+fn test_doc_comment_preserves_indents() {
+    let file = SourceFile::parse(
+        r#"
+        /// doc1
+        /// ```
+        /// fn foo() {
+        ///     // ...
+        /// }
+        /// ```
+        mod foo {}
+        "#,
+    )
+    .ok()
+    .unwrap();
+    let module = file.syntax().descendants().find_map(Module::cast).unwrap();
+    assert_eq!("doc1\n```\nfn foo() {\n    // ...\n}\n```", module.doc_comment_text().unwrap());
+}
+
+#[test]
+fn test_doc_comment_preserves_newlines() {
+    let file = SourceFile::parse(
+        r#"
+        /// this
+        /// is
+        /// mod
+        /// foo
+        mod foo {}
+        "#,
+    )
+    .ok()
+    .unwrap();
+    let module = file.syntax().descendants().find_map(Module::cast).unwrap();
+    assert_eq!("this\nis\nmod\nfoo", module.doc_comment_text().unwrap());
+}
+
+#[test]
+fn test_doc_comment_single_line_block_strips_suffix() {
+    let file = SourceFile::parse(
+        r#"
+        /** this is mod foo*/
+        mod foo {}
+        "#,
+    )
+    .ok()
+    .unwrap();
+    let module = file.syntax().descendants().find_map(Module::cast).unwrap();
+    assert_eq!("this is mod foo", module.doc_comment_text().unwrap());
+}
+
+#[test]
+fn test_doc_comment_single_line_block_strips_suffix_whitespace() {
+    let file = SourceFile::parse(
+        r#"
+        /** this is mod foo */
+        mod foo {}
+        "#,
+    )
+    .ok()
+    .unwrap();
+    let module = file.syntax().descendants().find_map(Module::cast).unwrap();
+    assert_eq!("this is mod foo ", module.doc_comment_text().unwrap());
+}
+
+#[test]
+fn test_doc_comment_multi_line_block_strips_suffix() {
+    let file = SourceFile::parse(
+        r#"
+        /**
+        this
+        is
+        mod foo
+        */
+        mod foo {}
+        "#,
+    )
+    .ok()
+    .unwrap();
+    let module = file.syntax().descendants().find_map(Module::cast).unwrap();
+    assert_eq!(
+        "        this\n        is\n        mod foo\n        ",
+        module.doc_comment_text().unwrap()
+    );
+}
+
+#[test]
+fn test_comments_preserve_trailing_whitespace() {
+    let file = SourceFile::parse(
+        "\n/// Representation of a Realm.   \n/// In the specification these are called Realm Records.\nstruct Realm {}",
+    )
+    .ok()
+    .unwrap();
+    let def = file.syntax().descendants().find_map(Struct::cast).unwrap();
+    assert_eq!(
+        "Representation of a Realm.   \nIn the specification these are called Realm Records.",
+        def.doc_comment_text().unwrap()
+    );
+}
+
+#[test]
+fn test_four_slash_line_comment() {
+    let file = SourceFile::parse(
+        r#"
+        //// too many slashes to be a doc comment
+        /// doc comment
+        mod foo {}
+        "#,
+    )
+    .ok()
+    .unwrap();
+    let module = file.syntax().descendants().find_map(Module::cast).unwrap();
+    assert_eq!("doc comment", module.doc_comment_text().unwrap());
+}
+
+#[test]
+fn test_where_predicates() {
+    fn assert_bound(text: &str, bound: Option<TypeBound>) {
+        assert_eq!(text, bound.unwrap().syntax().text().to_string());
+    }
+
+    let file = SourceFile::parse(
+        r#"
+fn foo()
+where
+   T: Clone + Copy + Debug + 'static,
+   'a: 'b + 'c,
+   Iterator::Item: 'a + Debug,
+   Iterator::Item: Debug + 'a,
+   <T as Iterator>::Item: Debug + 'a,
+   for<'a> F: Fn(&'a str)
+{}
+        "#,
+    )
+    .ok()
+    .unwrap();
+    let where_clause = file.syntax().descendants().find_map(WhereClause::cast).unwrap();
+
+    let mut predicates = where_clause.predicates();
+
+    let pred = predicates.next().unwrap();
+    let mut bounds = pred.type_bound_list().unwrap().bounds();
+
+    assert!(pred.for_token().is_none());
+    assert!(pred.generic_param_list().is_none());
+    assert_eq!("T", pred.ty().unwrap().syntax().text().to_string());
+    assert_bound("Clone", bounds.next());
+    assert_bound("Copy", bounds.next());
+    assert_bound("Debug", bounds.next());
+    assert_bound("'static", bounds.next());
+
+    let pred = predicates.next().unwrap();
+    let mut bounds = pred.type_bound_list().unwrap().bounds();
+
+    assert_eq!("'a", pred.lifetime_token().unwrap().text());
+
+    assert_bound("'b", bounds.next());
+    assert_bound("'c", bounds.next());
+
+    let pred = predicates.next().unwrap();
+    let mut bounds = pred.type_bound_list().unwrap().bounds();
+
+    assert_eq!("Iterator::Item", pred.ty().unwrap().syntax().text().to_string());
+    assert_bound("'a", bounds.next());
+
+    let pred = predicates.next().unwrap();
+    let mut bounds = pred.type_bound_list().unwrap().bounds();
+
+    assert_eq!("Iterator::Item", pred.ty().unwrap().syntax().text().to_string());
+    assert_bound("Debug", bounds.next());
+    assert_bound("'a", bounds.next());
+
+    let pred = predicates.next().unwrap();
+    let mut bounds = pred.type_bound_list().unwrap().bounds();
+
+    assert_eq!("<T as Iterator>::Item", pred.ty().unwrap().syntax().text().to_string());
+    assert_bound("Debug", bounds.next());
+    assert_bound("'a", bounds.next());
+
+    let pred = predicates.next().unwrap();
+    let mut bounds = pred.type_bound_list().unwrap().bounds();
+
+    assert!(pred.for_token().is_some());
+    assert_eq!("<'a>", pred.generic_param_list().unwrap().syntax().text().to_string());
+    assert_eq!("F", pred.ty().unwrap().syntax().text().to_string());
+    assert_bound("Fn(&'a str)", bounds.next());
+}