Scale back to only two traits

crates/ra_assists/src/handlers/introduce_variable.rs

@@ -1,5 +1,5 @@
 use ra_syntax::{
-    ast::{self, AstElement, AstNode},
+    ast::{self, AstNode},
     SyntaxKind::{
         BLOCK_EXPR, BREAK_EXPR, COMMENT, LAMBDA_EXPR, LOOP_EXPR, MATCH_ARM, PATH_EXPR, RETURN_EXPR,
         WHITESPACE,
@@ -124,7 +124,7 @@ fn anchor_stmt(expr: ast::Expr) -> Option<(SyntaxNode, bool)> {
             }
         }
 
-        if ast::Stmt::cast_element(node.clone().into()).is_some() {
+        if ast::Stmt::cast(node.clone().into()).is_some() {
             return Some((node, false));
         }
 

crates/ra_hir_def/src/body/lower.rs

@@ -492,7 +492,6 @@ impl ExprCollector<'_> {
                 ast::Stmt::ExprStmt(stmt) => {
                     Some(Statement::Expr(self.collect_expr_opt(stmt.expr())))
                 }
-                ast::Stmt::ModuleItem(_) => None,
             })
             .collect();
         let tail = block.expr().map(|e| self.collect_expr(e));

crates/ra_syntax/src/ast.rs

@@ -64,6 +64,22 @@ pub trait AstToken {
     }
 }
 
+mod support {
+    use super::{AstChildren, AstNode, AstToken, SyntaxNode};
+
+    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<T: AstToken>(parent: &SyntaxNode) -> Option<T> {
+        parent.children_with_tokens().filter_map(|it| it.into_token()).find_map(T::cast)
+    }
+}
+
 /// An iterator over `SyntaxNode` children of a particular AST type.
 #[derive(Debug, Clone)]
 pub struct AstChildren<N> {

crates/ra_syntax/src/ast/extensions.rs

@@ -5,8 +5,7 @@ use itertools::Itertools;
 
 use crate::{
     ast::{
-        self, child_opt, child_token_opt, children, AstElement, AstNode, AstToken, AttrInput,
+        self, child_opt, children, support, AstNode, AstToken, AttrInput, NameOwner, SyntaxNode,
-        NameOwner, SyntaxNode,
     },
     SmolStr, SyntaxElement,
     SyntaxKind::*,
@@ -437,7 +436,7 @@ impl ast::TypeBound {
                 .skip_while(|it| it.kind() != T![const])
                 .find_map(ast::Question::cast)
         } else {
-            child_token_opt(self)
+            support::token(&self.syntax)
         }
     }
 }
@@ -509,7 +508,7 @@ impl ast::RangePat {
     pub fn start(&self) -> Option<ast::Pat> {
         self.syntax()
             .children_with_tokens()
-            .take_while(|it| !ast::RangeSeparator::can_cast_element(it.kind()))
+            .take_while(|it| !ast::RangeSeparator::can_cast(it.kind()))
             .filter_map(|it| it.into_node())
             .find_map(ast::Pat::cast)
     }
@@ -517,7 +516,7 @@ impl ast::RangePat {
     pub fn end(&self) -> Option<ast::Pat> {
         self.syntax()
             .children_with_tokens()
-            .skip_while(|it| !ast::RangeSeparator::can_cast_element(it.kind()))
+            .skip_while(|it| !ast::RangeSeparator::can_cast(it.kind()))
             .filter_map(|it| it.into_node())
             .find_map(ast::Pat::cast)
     }
@@ -525,10 +524,10 @@ impl ast::RangePat {
 
 impl ast::TokenTree {
     pub fn left_delimiter(&self) -> Option<ast::LeftDelimiter> {
-        self.syntax().first_child_or_token().and_then(ast::LeftDelimiter::cast_element)
+        self.syntax().first_child_or_token()?.into_token().and_then(ast::LeftDelimiter::cast)
     }
 
     pub fn right_delimiter(&self) -> Option<ast::RightDelimiter> {
-        self.syntax().last_child_or_token().and_then(ast::RightDelimiter::cast_element)
+        self.syntax().last_child_or_token()?.into_token().and_then(ast::RightDelimiter::cast)
     }
 }

crates/ra_syntax/src/ast/traits.rs

@@ -4,9 +4,9 @@
 
 use itertools::Itertools;
 
-use crate::ast::{
+use crate::{
-    self, child_elements, child_opt, child_token_opt, child_tokens, children, AstChildElements,
+    ast::{self, child_opt, children, support, AstChildren, AstNode, AstToken},
-    AstChildTokens, AstChildren, AstNode, AstToken,
+    syntax_node::SyntaxElementChildren,
 };
 
 pub trait TypeAscriptionOwner: AstNode {
@@ -71,7 +71,7 @@ pub trait TypeBoundsOwner: AstNode {
     }
 
     fn colon(&self) -> Option<ast::Colon> {
-        child_token_opt(self)
+        support::token(self.syntax())
     }
 }
 
@@ -82,14 +82,11 @@ pub trait AttrsOwner: AstNode {
     fn has_atom_attr(&self, atom: &str) -> bool {
         self.attrs().filter_map(|x| x.as_simple_atom()).any(|x| x == atom)
     }
-    fn attr_or_comments(&self) -> AstChildElements<ast::AttrOrComment> {
-        child_elements(self)
-    }
 }
 
 pub trait DocCommentsOwner: AstNode {
-    fn doc_comments(&self) -> AstChildTokens<ast::Comment> {
+    fn doc_comments(&self) -> CommentIter {
-        child_tokens(self)
+        CommentIter { iter: self.syntax().children_with_tokens() }
     }
 
     /// Returns the textual content of a doc comment block as a single string.
@@ -134,3 +131,14 @@ pub trait DocCommentsOwner: AstNode {
         }
     }
 }
+
+pub struct CommentIter {
+    iter: SyntaxElementChildren,
+}
+
+impl Iterator for CommentIter {
+    type Item = ast::Comment;
+    fn next(&mut self) -> Option<ast::Comment> {
+        self.iter.by_ref().find_map(|el| el.into_token().and_then(ast::Comment::cast))
+    }
+}

xtask/src/ast_src.rs

@@ -549,7 +549,6 @@ pub(crate) const AST_SRC: AstSrc = AstSrc {
         struct Block: AttrsOwner, ModuleItemOwner {
             LCurly,
             statements: [Stmt],
-            statements_or_semi: [StmtOrSemi],
             Expr,
             RCurly,
         }
@@ -749,12 +748,10 @@ pub(crate) const AST_SRC: AstSrc = AstSrc {
 
         enum AttrInput { Literal, TokenTree }
         enum Stmt {
-            ModuleItem,
             LetStmt,
             ExprStmt,
             // macro calls are parsed as expression statements */
         }
-        enum StmtOrSemi {Stmt, Semi}
 
         enum LeftDelimiter { LParen, LBrack, LCurly }
         enum RightDelimiter { RParen, RBrack, RCurly }
@@ -825,10 +822,5 @@ pub(crate) const AST_SRC: AstSrc = AstSrc {
             RecordFieldDefList,
             TupleFieldDefList,
         }
-
-        enum AttrOrComment {
-            Attr,
-            Comment
-        }
     },
 };

xtask/src/codegen/gen_syntax.rs

@@ -146,14 +146,23 @@ fn generate_ast(kinds: KindsSrc<'_>, grammar: AstSrc<'_>) -> Result<String> {
                 FieldSrc::Many(_) => {
                     quote! {
                         pub fn #method_name(&self) -> AstChildren<#ty> {
-                            AstChildren::new(&self.syntax)
+                            support::children(&self.syntax)
                         }
                     }
                 }
                 FieldSrc::Optional(_) | FieldSrc::Shorthand => {
+                    let is_token = element_kinds_map[&ty.to_string()].has_tokens;
+                    if is_token {
                         quote! {
                             pub fn #method_name(&self) -> Option<#ty> {
-                            AstChildren::new(&self.syntax).next()
+                                support::token(&self.syntax)
+                            }
+                        }
+                    } else {
+                        quote! {
+                            pub fn #method_name(&self) -> Option<#ty> {
+                                support::child(&self.syntax)
+                            }
                         }
                     }
                 }
@@ -205,6 +214,48 @@ fn generate_ast(kinds: KindsSrc<'_>, grammar: AstSrc<'_>) -> Result<String> {
             quote!(impl ast::#trait_name for #name {})
         });
 
+        let element_kinds = &element_kinds_map[&en.name.to_string()];
+        assert!(
+            element_kinds.has_nodes ^ element_kinds.has_tokens,
+            "{}: {:#?}",
+            name,
+            element_kinds
+        );
+        let specific_ast_trait = {
+            let (ast_trait, syntax_type) = if element_kinds.has_tokens {
+                (quote!(AstToken), quote!(SyntaxToken))
+            } else {
+                (quote!(AstNode), quote!(SyntaxNode))
+            };
+
+            quote! {
+                impl #ast_trait for #name {
+                    fn can_cast(kind: SyntaxKind) -> bool {
+                        match kind {
+                            #(#kinds)|* => true,
+                            _ => false,
+                        }
+                    }
+                    fn cast(syntax: #syntax_type) -> Option<Self> {
+                        let res = match syntax.kind() {
+                            #(
+                            #kinds => #name::#variants(#variants { syntax }),
+                            )*
+                            _ => return None,
+                        };
+                        Some(res)
+                    }
+                    fn syntax(&self) -> &#syntax_type {
+                        match self {
+                            #(
+                            #name::#variants(it) => &it.syntax,
+                            )*
+                        }
+                    }
+                }
+            }
+        };
+
         quote! {
             #[derive(Debug, Clone, PartialEq, Eq, Hash)]
             pub enum #name {
@@ -225,30 +276,8 @@ fn generate_ast(kinds: KindsSrc<'_>, grammar: AstSrc<'_>) -> Result<String> {
                 }
             }
 
-            impl AstNode for #name {
+            #specific_ast_trait
-                fn can_cast(kind: SyntaxKind) -> bool {
+
-                    match kind {
-                        #(#kinds)|* => true,
-                        _ => false,
-                    }
-                }
-                fn cast(syntax: SyntaxNode) -> Option<Self> {
-                    let res = match syntax.kind() {
-                        #(
-                        #kinds => #name::#variants(#variants { syntax }),
-                        )*
-                        _ => return None,
-                    };
-                    Some(res)
-                }
-                fn syntax(&self) -> &SyntaxNode {
-                    match self {
-                        #(
-                        #name::#variants(it) => &it.syntax,
-                        )*
-                    }
-                }
-            }
             #(#traits)*
         }
     });
@@ -268,7 +297,7 @@ fn generate_ast(kinds: KindsSrc<'_>, grammar: AstSrc<'_>) -> Result<String> {
         #[allow(unused_imports)]
         use crate::{
             SyntaxNode, SyntaxToken, SyntaxElement, NodeOrToken, SyntaxKind::{self, *},
-            ast::{self, AstNode, AstToken, AstChildren},
+            ast::{self, AstNode, AstToken, AstChildren, support},
         };
 
         #(#tokens)*