Merge #1088

1088: add minimal comments r=matklad a=matklad



Co-authored-by: Aleksey Kladov <[email protected]>

9 files changed, 612 insertions, 582 deletions

diff --git a/crates/ra_assists/src/replace_if_let_with_match.rs b/crates/ra_assists/src/replace_if_let_with_match.rs
index 230573499..2b451f08d 100644
--- a/crates/ra_assists/src/replace_if_let_with_match.rs
+++ b/crates/ra_assists/src/replace_if_let_with_match.rs
@@ -11,8 +11,8 @@ pub(crate) fn replace_if_let_with_match(mut ctx: AssistCtx<impl HirDatabase>) ->
     let expr = cond.expr()?;
     let then_block = if_expr.then_branch()?;
     let else_block = match if_expr.else_branch()? {
-        ast::ElseBranchFlavor::Block(it) => it,
-        ast::ElseBranchFlavor::IfExpr(_) => return None,
+        ast::ElseBranch::Block(it) => it,
+        ast::ElseBranch::IfExpr(_) => return None,
     };
 
     ctx.add_action(AssistId("replace_if_let_with_match"), "replace with match", |edit| {
diff --git a/crates/ra_hir/src/adt.rs b/crates/ra_hir/src/adt.rs
index 78ea8976b..e027eedd9 100644
--- a/crates/ra_hir/src/adt.rs
+++ b/crates/ra_hir/src/adt.rs
@@ -6,7 +6,7 @@ use std::sync::Arc;
 use ra_arena::{RawId, Arena, impl_arena_id};
 use ra_syntax::{
     TreeArc,
-    ast::{self, NameOwner, StructFlavor, TypeAscriptionOwner}
+    ast::{self, NameOwner, StructKind, TypeAscriptionOwner}
 };
 
 use crate::{
@@ -47,7 +47,7 @@ pub struct StructData {
 impl StructData {
     fn new(struct_def: &ast::StructDef) -> StructData {
         let name = struct_def.name().map(|n| n.as_name());
-        let variant_data = VariantData::new(struct_def.flavor());
+        let variant_data = VariantData::new(struct_def.kind());
         let variant_data = Arc::new(variant_data);
         StructData { name, variant_data }
     }
@@ -94,7 +94,7 @@ impl EnumData {
         let variants = variants(&*enum_def)
             .map(|var| EnumVariantData {
                 name: var.name().map(|it| it.as_name()),
-                variant_data: Arc::new(VariantData::new(var.flavor())),
+                variant_data: Arc::new(VariantData::new(var.kind())),
             })
             .collect();
         Arc::new(EnumData { name, variants })
@@ -143,9 +143,9 @@ impl VariantData {
 }
 
 impl VariantData {
-    fn new(flavor: StructFlavor) -> Self {
+    fn new(flavor: StructKind) -> Self {
         let inner = match flavor {
-            ast::StructFlavor::Tuple(fl) => {
+            ast::StructKind::Tuple(fl) => {
                 let fields = fl
                     .fields()
                     .enumerate()
@@ -156,7 +156,7 @@ impl VariantData {
                     .collect();
                 VariantDataInner::Tuple(fields)
             }
-            ast::StructFlavor::Named(fl) => {
+            ast::StructKind::Named(fl) => {
                 let fields = fl
                     .fields()
                     .map(|fd| StructFieldData {
@@ -166,7 +166,7 @@ impl VariantData {
                     .collect();
                 VariantDataInner::Struct(fields)
             }
-            ast::StructFlavor::Unit => VariantDataInner::Unit,
+            ast::StructKind::Unit => VariantDataInner::Unit,
         };
         VariantData(inner)
     }
@@ -200,27 +200,27 @@ impl StructField {
         let fields = var_data.fields().unwrap();
         let ss;
         let es;
-        let (file_id, struct_flavor) = match self.parent {
+        let (file_id, struct_kind) = match self.parent {
             VariantDef::Struct(s) => {
                 let (file_id, source) = s.source(db);
                 ss = source;
-                (file_id, ss.flavor())
+                (file_id, ss.kind())
             }
             VariantDef::EnumVariant(e) => {
                 let (file_id, source) = e.source(db);
                 es = source;
-                (file_id, es.flavor())
+                (file_id, es.kind())
             }
         };
 
-        let field_sources = match struct_flavor {
-            ast::StructFlavor::Tuple(fl) => {
+        let field_sources = match struct_kind {
+            ast::StructKind::Tuple(fl) => {
                 fl.fields().map(|it| FieldSource::Pos(it.to_owned())).collect()
             }
-            ast::StructFlavor::Named(fl) => {
+            ast::StructKind::Named(fl) => {
                 fl.fields().map(|it| FieldSource::Named(it.to_owned())).collect()
             }
-            ast::StructFlavor::Unit => Vec::new(),
+            ast::StructKind::Unit => Vec::new(),
         };
         let field = field_sources
             .into_iter()
diff --git a/crates/ra_hir/src/code_model_impl/function.rs b/crates/ra_hir/src/code_model_impl/function.rs
index 334cb302b..f8bd0f784 100644
--- a/crates/ra_hir/src/code_model_impl/function.rs
+++ b/crates/ra_hir/src/code_model_impl/function.rs
@@ -20,12 +20,12 @@ impl FnSignature {
                     TypeRef::from_ast(type_ref)
                 } else {
                     let self_type = TypeRef::Path(Name::self_type().into());
-                    match self_param.flavor() {
-                        ast::SelfParamFlavor::Owned => self_type,
-                        ast::SelfParamFlavor::Ref => {
+                    match self_param.kind() {
+                        ast::SelfParamKind::Owned => self_type,
+                        ast::SelfParamKind::Ref => {
                             TypeRef::Reference(Box::new(self_type), Mutability::Shared)
                         }
-                        ast::SelfParamFlavor::MutRef => {
+                        ast::SelfParamKind::MutRef => {
                             TypeRef::Reference(Box::new(self_type), Mutability::Mut)
                         }
                     }
diff --git a/crates/ra_hir/src/expr.rs b/crates/ra_hir/src/expr.rs
index 946c9faf2..45012827f 100644
--- a/crates/ra_hir/src/expr.rs
+++ b/crates/ra_hir/src/expr.rs
@@ -6,7 +6,7 @@ use rustc_hash::FxHashMap;
 use ra_arena::{Arena, RawId, impl_arena_id, map::ArenaMap};
 use ra_syntax::{
     SyntaxNodePtr, AstPtr, AstNode,
-    ast::{self, LoopBodyOwner, ArgListOwner, NameOwner, LiteralFlavor, TypeAscriptionOwner}
+    ast::{self, LoopBodyOwner, ArgListOwner, NameOwner, LiteralKind, TypeAscriptionOwner}
 };
 
 use crate::{
@@ -516,8 +516,8 @@ impl ExprCollector {
                     let else_branch = e
                         .else_branch()
                         .map(|b| match b {
-                            ast::ElseBranchFlavor::Block(it) => self.collect_block(it),
-                            ast::ElseBranchFlavor::IfExpr(elif) => {
+                            ast::ElseBranch::Block(it) => self.collect_block(it),
+                            ast::ElseBranch::IfExpr(elif) => {
                                 let expr: &ast::Expr = ast::Expr::cast(elif.syntax()).unwrap();
                                 self.collect_expr(expr)
                             }
@@ -533,8 +533,8 @@ impl ExprCollector {
                     let condition = self.collect_expr_opt(e.condition().and_then(|c| c.expr()));
                     let then_branch = self.collect_block_opt(e.then_branch());
                     let else_branch = e.else_branch().map(|b| match b {
-                        ast::ElseBranchFlavor::Block(it) => self.collect_block(it),
-                        ast::ElseBranchFlavor::IfExpr(elif) => {
+                        ast::ElseBranch::Block(it) => self.collect_block(it),
+                        ast::ElseBranch::IfExpr(elif) => {
                             let expr: &ast::Expr = ast::Expr::cast(elif.syntax()).unwrap();
                             self.collect_expr(expr)
                         }
@@ -726,8 +726,8 @@ impl ExprCollector {
                 self.alloc_expr(Expr::Array { exprs }, syntax_ptr)
             }
             ast::ExprKind::Literal(e) => {
-                let lit = match e.flavor() {
-                    LiteralFlavor::IntNumber { suffix } => {
+                let lit = match e.kind() {
+                    LiteralKind::IntNumber { suffix } => {
                         let known_name = suffix
                             .and_then(|it| IntTy::from_suffix(&it).map(UncertainIntTy::Known));
 
@@ -736,7 +736,7 @@ impl ExprCollector {
                             known_name.unwrap_or(UncertainIntTy::Unknown),
                         )
                     }
-                    LiteralFlavor::FloatNumber { suffix } => {
+                    LiteralKind::FloatNumber { suffix } => {
                         let known_name = suffix
                             .and_then(|it| FloatTy::from_suffix(&it).map(UncertainFloatTy::Known));
 
@@ -745,13 +745,13 @@ impl ExprCollector {
                             known_name.unwrap_or(UncertainFloatTy::Unknown),
                         )
                     }
-                    LiteralFlavor::ByteString => Literal::ByteString(Default::default()),
-                    LiteralFlavor::String => Literal::String(Default::default()),
-                    LiteralFlavor::Byte => {
+                    LiteralKind::ByteString => Literal::ByteString(Default::default()),
+                    LiteralKind::String => Literal::String(Default::default()),
+                    LiteralKind::Byte => {
                         Literal::Int(Default::default(), UncertainIntTy::Known(IntTy::u8()))
                     }
-                    LiteralFlavor::Bool => Literal::Bool(Default::default()),
-                    LiteralFlavor::Char => Literal::Char(Default::default()),
+                    LiteralKind::Bool => Literal::Bool(Default::default()),
+                    LiteralKind::Char => Literal::Char(Default::default()),
                 };
                 self.alloc_expr(Expr::Literal(lit), syntax_ptr)
             }
diff --git a/crates/ra_syntax/src/ast.rs b/crates/ra_syntax/src/ast.rs
index beef2c6e2..9f5c41b0c 100644
--- a/crates/ra_syntax/src/ast.rs
+++ b/crates/ra_syntax/src/ast.rs
@@ -1,22 +1,24 @@
 //! Abstract Syntax Tree, layered on top of untyped `SyntaxNode`s
+
 mod generated;
 mod traits;
 mod tokens;
+mod extensions;
+mod expr_extensions;
 
 use std::marker::PhantomData;
 
-use itertools::Itertools;
-
 use crate::{
-    syntax_node::{SyntaxNode, SyntaxNodeChildren, TreeArc, RaTypes, SyntaxToken, SyntaxElement},
+    syntax_node::{SyntaxNode, SyntaxNodeChildren, TreeArc, RaTypes, SyntaxToken},
     SmolStr,
-    SyntaxKind::*,
 };
 
 pub use self::{
     generated::*,
     traits::*,
     tokens::*,
+    extensions::{PathSegmentKind, StructKind, SelfParamKind},
+    expr_extensions::{ElseBranch, PrefixOp, BinOp, LiteralKind},
 };
 
 /// The main trait to go from untyped `SyntaxNode`  to a typed ast. The
@@ -32,6 +34,18 @@ pub trait AstNode:
     fn syntax(&self) -> &SyntaxNode;
 }
 
+/// Like `AstNode`, but wraps tokens rather than interior nodes.
+pub trait AstToken<'a> {
+    fn cast(token: SyntaxToken<'a>) -> Option<Self>
+    where
+        Self: Sized;
+    fn syntax(&self) -> SyntaxToken<'a>;
+    fn text(&self) -> &'a SmolStr {
+        self.syntax().text()
+    }
+}
+
+/// An iterator over `SyntaxNode` children of a particular AST type.
 #[derive(Debug)]
 pub struct AstChildren<'a, N> {
     inner: SyntaxNodeChildren<'a>,
@@ -51,215 +65,6 @@ impl<'a, N: AstNode + 'a> Iterator for AstChildren<'a, N> {
     }
 }
 
-pub trait AstToken<'a> {
-    fn cast(token: SyntaxToken<'a>) -> Option<Self>
-    where
-        Self: Sized;
-    fn syntax(&self) -> SyntaxToken<'a>;
-    fn text(&self) -> &'a SmolStr {
-        self.syntax().text()
-    }
-}
-
-impl Attr {
-    pub fn is_inner(&self) -> bool {
-        let tt = match self.value() {
-            None => return false,
-            Some(tt) => tt,
-        };
-
-        let prev = match tt.syntax().prev_sibling() {
-            None => return false,
-            Some(prev) => prev,
-        };
-
-        prev.kind() == EXCL
-    }
-
-    pub fn as_atom(&self) -> Option<SmolStr> {
-        let tt = self.value()?;
-        let (_bra, attr, _ket) = tt.syntax().children_with_tokens().collect_tuple()?;
-        if attr.kind() == IDENT {
-            Some(attr.as_token()?.text().clone())
-        } else {
-            None
-        }
-    }
-
-    pub fn as_call(&self) -> Option<(SmolStr, &TokenTree)> {
-        let tt = self.value()?;
-        let (_bra, attr, args, _ket) = tt.syntax().children_with_tokens().collect_tuple()?;
-        let args = TokenTree::cast(args.as_node()?)?;
-        if attr.kind() == IDENT {
-            Some((attr.as_token()?.text().clone(), args))
-        } else {
-            None
-        }
-    }
-
-    pub fn as_named(&self) -> Option<SmolStr> {
-        let tt = self.value()?;
-        let attr = tt.syntax().children_with_tokens().nth(1)?;
-        if attr.kind() == IDENT {
-            Some(attr.as_token()?.text().clone())
-        } else {
-            None
-        }
-    }
-}
-
-impl Name {
-    pub fn text(&self) -> &SmolStr {
-        let ident = self.syntax().first_child_or_token().unwrap().as_token().unwrap();
-        ident.text()
-    }
-}
-
-impl NameRef {
-    pub fn text(&self) -> &SmolStr {
-        let ident = self.syntax().first_child_or_token().unwrap().as_token().unwrap();
-        ident.text()
-    }
-}
-
-impl ImplBlock {
-    pub fn target_type(&self) -> Option<&TypeRef> {
-        match self.target() {
-            (Some(t), None) | (_, Some(t)) => Some(t),
-            _ => None,
-        }
-    }
-
-    pub fn target_trait(&self) -> Option<&TypeRef> {
-        match self.target() {
-            (Some(t), Some(_)) => Some(t),
-            _ => None,
-        }
-    }
-
-    fn target(&self) -> (Option<&TypeRef>, Option<&TypeRef>) {
-        let mut types = children(self);
-        let first = types.next();
-        let second = types.next();
-        (first, second)
-    }
-}
-
-impl Module {
-    pub fn has_semi(&self) -> bool {
-        match self.syntax().last_child_or_token() {
-            None => false,
-            Some(node) => node.kind() == SEMI,
-        }
-    }
-}
-
-impl LetStmt {
-    pub fn has_semi(&self) -> bool {
-        match self.syntax().last_child_or_token() {
-            None => false,
-            Some(node) => node.kind() == SEMI,
-        }
-    }
-}
-
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub enum ElseBranchFlavor<'a> {
-    Block(&'a Block),
-    IfExpr(&'a IfExpr),
-}
-
-impl IfExpr {
-    pub fn then_branch(&self) -> Option<&Block> {
-        self.blocks().nth(0)
-    }
-    pub fn else_branch(&self) -> Option<ElseBranchFlavor> {
-        let res = match self.blocks().nth(1) {
-            Some(block) => ElseBranchFlavor::Block(block),
-            None => {
-                let elif: &IfExpr = child_opt(self)?;
-                ElseBranchFlavor::IfExpr(elif)
-            }
-        };
-        Some(res)
-    }
-
-    fn blocks(&self) -> AstChildren<Block> {
-        children(self)
-    }
-}
-
-impl ExprStmt {
-    pub fn has_semi(&self) -> bool {
-        match self.syntax().last_child_or_token() {
-            None => false,
-            Some(node) => node.kind() == SEMI,
-        }
-    }
-}
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum PathSegmentKind<'a> {
-    Name(&'a NameRef),
-    SelfKw,
-    SuperKw,
-    CrateKw,
-}
-
-impl PathSegment {
-    pub fn parent_path(&self) -> &Path {
-        self.syntax().parent().and_then(Path::cast).expect("segments are always nested in paths")
-    }
-
-    pub fn kind(&self) -> Option<PathSegmentKind> {
-        let res = if let Some(name_ref) = self.name_ref() {
-            PathSegmentKind::Name(name_ref)
-        } else {
-            match self.syntax().first_child_or_token()?.kind() {
-                SELF_KW => PathSegmentKind::SelfKw,
-                SUPER_KW => PathSegmentKind::SuperKw,
-                CRATE_KW => PathSegmentKind::CrateKw,
-                _ => return None,
-            }
-        };
-        Some(res)
-    }
-
-    pub fn has_colon_colon(&self) -> bool {
-        match self.syntax.first_child_or_token().map(|s| s.kind()) {
-            Some(COLONCOLON) => true,
-            _ => false,
-        }
-    }
-}
-
-impl Path {
-    pub fn parent_path(&self) -> Option<&Path> {
-        self.syntax().parent().and_then(Path::cast)
-    }
-}
-
-impl UseTree {
-    pub fn has_star(&self) -> bool {
-        self.syntax().children_with_tokens().any(|it| it.kind() == STAR)
-    }
-}
-
-impl UseTreeList {
-    pub fn parent_use_tree(&self) -> &UseTree {
-        self.syntax()
-            .parent()
-            .and_then(UseTree::cast)
-            .expect("UseTreeLists are always nested in UseTrees")
-    }
-}
-
-impl RefPat {
-    pub fn is_mut(&self) -> bool {
-        self.syntax().children_with_tokens().any(|n| n.kind() == MUT_KW)
-    }
-}
-
 fn child_opt<P: AstNode, C: AstNode>(parent: &P) -> Option<&C> {
     children(parent).next()
 }
@@ -268,342 +73,6 @@ fn children<P: AstNode, C: AstNode>(parent: &P) -> AstChildren<C> {
     AstChildren::new(parent.syntax())
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub enum StructFlavor<'a> {
-    Tuple(&'a PosFieldDefList),
-    Named(&'a NamedFieldDefList),
-    Unit,
-}
-
-impl StructFlavor<'_> {
-    fn from_node<N: AstNode>(node: &N) -> StructFlavor {
-        if let Some(nfdl) = child_opt::<_, NamedFieldDefList>(node) {
-            StructFlavor::Named(nfdl)
-        } else if let Some(pfl) = child_opt::<_, PosFieldDefList>(node) {
-            StructFlavor::Tuple(pfl)
-        } else {
-            StructFlavor::Unit
-        }
-    }
-}
-
-impl StructDef {
-    pub fn flavor(&self) -> StructFlavor {
-        StructFlavor::from_node(self)
-    }
-}
-
-impl EnumVariant {
-    pub fn parent_enum(&self) -> &EnumDef {
-        self.syntax()
-            .parent()
-            .and_then(|it| it.parent())
-            .and_then(EnumDef::cast)
-            .expect("EnumVariants are always nested in Enums")
-    }
-    pub fn flavor(&self) -> StructFlavor {
-        StructFlavor::from_node(self)
-    }
-}
-
-impl PointerType {
-    pub fn is_mut(&self) -> bool {
-        self.syntax().children_with_tokens().any(|n| n.kind() == MUT_KW)
-    }
-}
-
-impl ReferenceType {
-    pub fn is_mut(&self) -> bool {
-        self.syntax().children_with_tokens().any(|n| n.kind() == MUT_KW)
-    }
-}
-
-impl RefExpr {
-    pub fn is_mut(&self) -> bool {
-        self.syntax().children_with_tokens().any(|n| n.kind() == MUT_KW)
-    }
-}
-
-#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
-pub enum PrefixOp {
-    /// The `*` operator for dereferencing
-    Deref,
-    /// The `!` operator for logical inversion
-    Not,
-    /// The `-` operator for negation
-    Neg,
-}
-
-impl PrefixExpr {
-    pub fn op_kind(&self) -> Option<PrefixOp> {
-        match self.op_token()?.kind() {
-            STAR => Some(PrefixOp::Deref),
-            EXCL => Some(PrefixOp::Not),
-            MINUS => Some(PrefixOp::Neg),
-            _ => None,
-        }
-    }
-
-    pub fn op_token(&self) -> Option<SyntaxToken> {
-        self.syntax().first_child_or_token()?.as_token()
-    }
-}
-
-#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
-pub enum BinOp {
-    /// The `||` operator for boolean OR
-    BooleanOr,
-    /// The `&&` operator for boolean AND
-    BooleanAnd,
-    /// The `==` operator for equality testing
-    EqualityTest,
-    /// The `!=` operator for equality testing
-    NegatedEqualityTest,
-    /// The `<=` operator for lesser-equal testing
-    LesserEqualTest,
-    /// The `>=` operator for greater-equal testing
-    GreaterEqualTest,
-    /// The `<` operator for comparison
-    LesserTest,
-    /// The `>` operator for comparison
-    GreaterTest,
-    /// The `+` operator for addition
-    Addition,
-    /// The `*` operator for multiplication
-    Multiplication,
-    /// The `-` operator for subtraction
-    Subtraction,
-    /// The `/` operator for division
-    Division,
-    /// The `%` operator for remainder after division
-    Remainder,
-    /// The `<<` operator for left shift
-    LeftShift,
-    /// The `>>` operator for right shift
-    RightShift,
-    /// The `^` operator for bitwise XOR
-    BitwiseXor,
-    /// The `|` operator for bitwise OR
-    BitwiseOr,
-    /// The `&` operator for bitwise AND
-    BitwiseAnd,
-    /// The `..` operator for right-open ranges
-    RangeRightOpen,
-    /// The `..=` operator for right-closed ranges
-    RangeRightClosed,
-    /// The `=` operator for assignment
-    Assignment,
-    /// The `+=` operator for assignment after addition
-    AddAssign,
-    /// The `/=` operator for assignment after division
-    DivAssign,
-    /// The `*=` operator for assignment after multiplication
-    MulAssign,
-    /// The `%=` operator for assignment after remainders
-    RemAssign,
-    /// The `>>=` operator for assignment after shifting right
-    ShrAssign,
-    /// The `<<=` operator for assignment after shifting left
-    ShlAssign,
-    /// The `-=` operator for assignment after subtraction
-    SubAssign,
-    /// The `|=` operator for assignment after bitwise OR
-    BitOrAssign,
-    /// The `&=` operator for assignment after bitwise AND
-    BitAndAssign,
-    /// The `^=` operator for assignment after bitwise XOR
-    BitXorAssign,
-}
-
-impl BinExpr {
-    fn op_details(&self) -> Option<(SyntaxToken, BinOp)> {
-        self.syntax().children_with_tokens().filter_map(|it| it.as_token()).find_map(|c| {
-            match c.kind() {
-                PIPEPIPE => Some((c, BinOp::BooleanOr)),
-                AMPAMP => Some((c, BinOp::BooleanAnd)),
-                EQEQ => Some((c, BinOp::EqualityTest)),
-                NEQ => Some((c, BinOp::NegatedEqualityTest)),
-                LTEQ => Some((c, BinOp::LesserEqualTest)),
-                GTEQ => Some((c, BinOp::GreaterEqualTest)),
-                L_ANGLE => Some((c, BinOp::LesserTest)),
-                R_ANGLE => Some((c, BinOp::GreaterTest)),
-                PLUS => Some((c, BinOp::Addition)),
-                STAR => Some((c, BinOp::Multiplication)),
-                MINUS => Some((c, BinOp::Subtraction)),
-                SLASH => Some((c, BinOp::Division)),
-                PERCENT => Some((c, BinOp::Remainder)),
-                SHL => Some((c, BinOp::LeftShift)),
-                SHR => Some((c, BinOp::RightShift)),
-                CARET => Some((c, BinOp::BitwiseXor)),
-                PIPE => Some((c, BinOp::BitwiseOr)),
-                AMP => Some((c, BinOp::BitwiseAnd)),
-                DOTDOT => Some((c, BinOp::RangeRightOpen)),
-                DOTDOTEQ => Some((c, BinOp::RangeRightClosed)),
-                EQ => Some((c, BinOp::Assignment)),
-                PLUSEQ => Some((c, BinOp::AddAssign)),
-                SLASHEQ => Some((c, BinOp::DivAssign)),
-                STAREQ => Some((c, BinOp::MulAssign)),
-                PERCENTEQ => Some((c, BinOp::RemAssign)),
-                SHREQ => Some((c, BinOp::ShrAssign)),
-                SHLEQ => Some((c, BinOp::ShlAssign)),
-                MINUSEQ => Some((c, BinOp::SubAssign)),
-                PIPEEQ => Some((c, BinOp::BitOrAssign)),
-                AMPEQ => Some((c, BinOp::BitAndAssign)),
-                CARETEQ => Some((c, BinOp::BitXorAssign)),
-                _ => None,
-            }
-        })
-    }
-
-    pub fn op_kind(&self) -> Option<BinOp> {
-        self.op_details().map(|t| t.1)
-    }
-
-    pub fn op_token(&self) -> Option<SyntaxToken> {
-        self.op_details().map(|t| t.0)
-    }
-
-    pub fn lhs(&self) -> Option<&Expr> {
-        children(self).nth(0)
-    }
-
-    pub fn rhs(&self) -> Option<&Expr> {
-        children(self).nth(1)
-    }
-
-    pub fn sub_exprs(&self) -> (Option<&Expr>, Option<&Expr>) {
-        let mut children = children(self);
-        let first = children.next();
-        let second = children.next();
-        (first, second)
-    }
-}
-
-#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
-pub enum SelfParamFlavor {
-    /// self
-    Owned,
-    /// &self
-    Ref,
-    /// &mut self
-    MutRef,
-}
-
-impl SelfParam {
-    pub fn self_kw_token(&self) -> SyntaxToken {
-        self.syntax()
-            .children_with_tokens()
-            .filter_map(|it| it.as_token())
-            .find(|it| it.kind() == SELF_KW)
-            .expect("invalid tree: self param must have self")
-    }
-
-    pub fn flavor(&self) -> SelfParamFlavor {
-        let borrowed = self.syntax().children_with_tokens().any(|n| n.kind() == AMP);
-        if borrowed {
-            // check for a `mut` coming after the & -- `mut &self` != `&mut self`
-            if self
-                .syntax()
-                .children_with_tokens()
-                .skip_while(|n| n.kind() != AMP)
-                .any(|n| n.kind() == MUT_KW)
-            {
-                SelfParamFlavor::MutRef
-            } else {
-                SelfParamFlavor::Ref
-            }
-        } else {
-            SelfParamFlavor::Owned
-        }
-    }
-}
-
-#[derive(Clone, Debug, PartialEq, Eq, Hash)]
-pub enum LiteralFlavor {
-    String,
-    ByteString,
-    Char,
-    Byte,
-    IntNumber { suffix: Option<SmolStr> },
-    FloatNumber { suffix: Option<SmolStr> },
-    Bool,
-}
-
-impl Literal {
-    pub fn token(&self) -> SyntaxToken {
-        match self.syntax().first_child_or_token().unwrap() {
-            SyntaxElement::Token(token) => token,
-            _ => unreachable!(),
-        }
-    }
-
-    pub fn flavor(&self) -> LiteralFlavor {
-        match self.token().kind() {
-            INT_NUMBER => {
-                let allowed_suffix_list = [
-                    "isize", "i128", "i64", "i32", "i16", "i8", "usize", "u128", "u64", "u32",
-                    "u16", "u8",
-                ];
-                let text = self.token().text().to_string();
-                let suffix = allowed_suffix_list
-                    .iter()
-                    .find(|&s| text.ends_with(s))
-                    .map(|&suf| SmolStr::new(suf));
-                LiteralFlavor::IntNumber { suffix }
-            }
-            FLOAT_NUMBER => {
-                let allowed_suffix_list = ["f64", "f32"];
-                let text = self.token().text().to_string();
-                let suffix = allowed_suffix_list
-                    .iter()
-                    .find(|&s| text.ends_with(s))
-                    .map(|&suf| SmolStr::new(suf));
-                LiteralFlavor::FloatNumber { suffix: suffix }
-            }
-            STRING | RAW_STRING => LiteralFlavor::String,
-            TRUE_KW | FALSE_KW => LiteralFlavor::Bool,
-            BYTE_STRING | RAW_BYTE_STRING => LiteralFlavor::ByteString,
-            CHAR => LiteralFlavor::Char,
-            BYTE => LiteralFlavor::Byte,
-            _ => unreachable!(),
-        }
-    }
-}
-
-impl NamedField {
-    pub fn parent_struct_lit(&self) -> &StructLit {
-        self.syntax().ancestors().find_map(StructLit::cast).unwrap()
-    }
-}
-
-impl BindPat {
-    pub fn is_mutable(&self) -> bool {
-        self.syntax().children_with_tokens().any(|n| n.kind() == MUT_KW)
-    }
-
-    pub fn is_ref(&self) -> bool {
-        self.syntax().children_with_tokens().any(|n| n.kind() == REF_KW)
-    }
-}
-
-impl LifetimeParam {
-    pub fn lifetime_token(&self) -> Option<SyntaxToken> {
-        self.syntax()
-            .children_with_tokens()
-            .filter_map(|it| it.as_token())
-            .find(|it| it.kind() == LIFETIME)
-    }
-}
-
-impl WherePred {
-    pub fn lifetime_token(&self) -> Option<SyntaxToken> {
-        self.syntax()
-            .children_with_tokens()
-            .filter_map(|it| it.as_token())
-            .find(|it| it.kind() == LIFETIME)
-    }
-}
-
 #[test]
 fn test_doc_comment_none() {
     let file = SourceFile::parse(
diff --git a/crates/ra_syntax/src/ast/expr_extensions.rs b/crates/ra_syntax/src/ast/expr_extensions.rs
new file mode 100644
index 000000000..1d8313810
--- /dev/null
+++ b/crates/ra_syntax/src/ast/expr_extensions.rs
@@ -0,0 +1,252 @@
+//! Various extension methods to ast Expr Nodes, which are hard to code-generate.
+
+use crate::{
+    SyntaxToken, SyntaxElement, SmolStr,
+    ast::{self, AstNode, AstChildren, children, child_opt},
+    SyntaxKind::*
+};
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum ElseBranch<'a> {
+    Block(&'a ast::Block),
+    IfExpr(&'a ast::IfExpr),
+}
+
+impl ast::IfExpr {
+    pub fn then_branch(&self) -> Option<&ast::Block> {
+        self.blocks().nth(0)
+    }
+    pub fn else_branch(&self) -> Option<ElseBranch> {
+        let res = match self.blocks().nth(1) {
+            Some(block) => ElseBranch::Block(block),
+            None => {
+                let elif: &ast::IfExpr = child_opt(self)?;
+                ElseBranch::IfExpr(elif)
+            }
+        };
+        Some(res)
+    }
+
+    fn blocks(&self) -> AstChildren<ast::Block> {
+        children(self)
+    }
+}
+
+impl ast::RefExpr {
+    pub fn is_mut(&self) -> bool {
+        self.syntax().children_with_tokens().any(|n| n.kind() == MUT_KW)
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+pub enum PrefixOp {
+    /// The `*` operator for dereferencing
+    Deref,
+    /// The `!` operator for logical inversion
+    Not,
+    /// The `-` operator for negation
+    Neg,
+}
+
+impl ast::PrefixExpr {
+    pub fn op_kind(&self) -> Option<PrefixOp> {
+        match self.op_token()?.kind() {
+            STAR => Some(PrefixOp::Deref),
+            EXCL => Some(PrefixOp::Not),
+            MINUS => Some(PrefixOp::Neg),
+            _ => None,
+        }
+    }
+
+    pub fn op_token(&self) -> Option<SyntaxToken> {
+        self.syntax().first_child_or_token()?.as_token()
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+pub enum BinOp {
+    /// The `||` operator for boolean OR
+    BooleanOr,
+    /// The `&&` operator for boolean AND
+    BooleanAnd,
+    /// The `==` operator for equality testing
+    EqualityTest,
+    /// The `!=` operator for equality testing
+    NegatedEqualityTest,
+    /// The `<=` operator for lesser-equal testing
+    LesserEqualTest,
+    /// The `>=` operator for greater-equal testing
+    GreaterEqualTest,
+    /// The `<` operator for comparison
+    LesserTest,
+    /// The `>` operator for comparison
+    GreaterTest,
+    /// The `+` operator for addition
+    Addition,
+    /// The `*` operator for multiplication
+    Multiplication,
+    /// The `-` operator for subtraction
+    Subtraction,
+    /// The `/` operator for division
+    Division,
+    /// The `%` operator for remainder after division
+    Remainder,
+    /// The `<<` operator for left shift
+    LeftShift,
+    /// The `>>` operator for right shift
+    RightShift,
+    /// The `^` operator for bitwise XOR
+    BitwiseXor,
+    /// The `|` operator for bitwise OR
+    BitwiseOr,
+    /// The `&` operator for bitwise AND
+    BitwiseAnd,
+    /// The `..` operator for right-open ranges
+    RangeRightOpen,
+    /// The `..=` operator for right-closed ranges
+    RangeRightClosed,
+    /// The `=` operator for assignment
+    Assignment,
+    /// The `+=` operator for assignment after addition
+    AddAssign,
+    /// The `/=` operator for assignment after division
+    DivAssign,
+    /// The `*=` operator for assignment after multiplication
+    MulAssign,
+    /// The `%=` operator for assignment after remainders
+    RemAssign,
+    /// The `>>=` operator for assignment after shifting right
+    ShrAssign,
+    /// The `<<=` operator for assignment after shifting left
+    ShlAssign,
+    /// The `-=` operator for assignment after subtraction
+    SubAssign,
+    /// The `|=` operator for assignment after bitwise OR
+    BitOrAssign,
+    /// The `&=` operator for assignment after bitwise AND
+    BitAndAssign,
+    /// The `^=` operator for assignment after bitwise XOR
+    BitXorAssign,
+}
+
+impl ast::BinExpr {
+    fn op_details(&self) -> Option<(SyntaxToken, BinOp)> {
+        self.syntax().children_with_tokens().filter_map(|it| it.as_token()).find_map(|c| {
+            match c.kind() {
+                PIPEPIPE => Some((c, BinOp::BooleanOr)),
+                AMPAMP => Some((c, BinOp::BooleanAnd)),
+                EQEQ => Some((c, BinOp::EqualityTest)),
+                NEQ => Some((c, BinOp::NegatedEqualityTest)),
+                LTEQ => Some((c, BinOp::LesserEqualTest)),
+                GTEQ => Some((c, BinOp::GreaterEqualTest)),
+                L_ANGLE => Some((c, BinOp::LesserTest)),
+                R_ANGLE => Some((c, BinOp::GreaterTest)),
+                PLUS => Some((c, BinOp::Addition)),
+                STAR => Some((c, BinOp::Multiplication)),
+                MINUS => Some((c, BinOp::Subtraction)),
+                SLASH => Some((c, BinOp::Division)),
+                PERCENT => Some((c, BinOp::Remainder)),
+                SHL => Some((c, BinOp::LeftShift)),
+                SHR => Some((c, BinOp::RightShift)),
+                CARET => Some((c, BinOp::BitwiseXor)),
+                PIPE => Some((c, BinOp::BitwiseOr)),
+                AMP => Some((c, BinOp::BitwiseAnd)),
+                DOTDOT => Some((c, BinOp::RangeRightOpen)),
+                DOTDOTEQ => Some((c, BinOp::RangeRightClosed)),
+                EQ => Some((c, BinOp::Assignment)),
+                PLUSEQ => Some((c, BinOp::AddAssign)),
+                SLASHEQ => Some((c, BinOp::DivAssign)),
+                STAREQ => Some((c, BinOp::MulAssign)),
+                PERCENTEQ => Some((c, BinOp::RemAssign)),
+                SHREQ => Some((c, BinOp::ShrAssign)),
+                SHLEQ => Some((c, BinOp::ShlAssign)),
+                MINUSEQ => Some((c, BinOp::SubAssign)),
+                PIPEEQ => Some((c, BinOp::BitOrAssign)),
+                AMPEQ => Some((c, BinOp::BitAndAssign)),
+                CARETEQ => Some((c, BinOp::BitXorAssign)),
+                _ => None,
+            }
+        })
+    }
+
+    pub fn op_kind(&self) -> Option<BinOp> {
+        self.op_details().map(|t| t.1)
+    }
+
+    pub fn op_token(&self) -> Option<SyntaxToken> {
+        self.op_details().map(|t| t.0)
+    }
+
+    pub fn lhs(&self) -> Option<&ast::Expr> {
+        children(self).nth(0)
+    }
+
+    pub fn rhs(&self) -> Option<&ast::Expr> {
+        children(self).nth(1)
+    }
+
+    pub fn sub_exprs(&self) -> (Option<&ast::Expr>, Option<&ast::Expr>) {
+        let mut children = children(self);
+        let first = children.next();
+        let second = children.next();
+        (first, second)
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum LiteralKind {
+    String,
+    ByteString,
+    Char,
+    Byte,
+    IntNumber { suffix: Option<SmolStr> },
+    FloatNumber { suffix: Option<SmolStr> },
+    Bool,
+}
+
+impl ast::Literal {
+    pub fn token(&self) -> SyntaxToken {
+        match self.syntax().first_child_or_token().unwrap() {
+            SyntaxElement::Token(token) => token,
+            _ => unreachable!(),
+        }
+    }
+
+    pub fn kind(&self) -> LiteralKind {
+        match self.token().kind() {
+            INT_NUMBER => {
+                let allowed_suffix_list = [
+                    "isize", "i128", "i64", "i32", "i16", "i8", "usize", "u128", "u64", "u32",
+                    "u16", "u8",
+                ];
+                let text = self.token().text().to_string();
+                let suffix = allowed_suffix_list
+                    .iter()
+                    .find(|&s| text.ends_with(s))
+                    .map(|&suf| SmolStr::new(suf));
+                LiteralKind::IntNumber { suffix }
+            }
+            FLOAT_NUMBER => {
+                let allowed_suffix_list = ["f64", "f32"];
+                let text = self.token().text().to_string();
+                let suffix = allowed_suffix_list
+                    .iter()
+                    .find(|&s| text.ends_with(s))
+                    .map(|&suf| SmolStr::new(suf));
+                LiteralKind::FloatNumber { suffix: suffix }
+            }
+            STRING | RAW_STRING => LiteralKind::String,
+            TRUE_KW | FALSE_KW => LiteralKind::Bool,
+            BYTE_STRING | RAW_BYTE_STRING => LiteralKind::ByteString,
+            CHAR => LiteralKind::Char,
+            BYTE => LiteralKind::Byte,
+            _ => unreachable!(),
+        }
+    }
+}
+
+impl ast::NamedField {
+    pub fn parent_struct_lit(&self) -> &ast::StructLit {
+        self.syntax().ancestors().find_map(ast::StructLit::cast).unwrap()
+    }
+}
diff --git a/crates/ra_syntax/src/ast/extensions.rs b/crates/ra_syntax/src/ast/extensions.rs
new file mode 100644
index 000000000..aec57c380
--- /dev/null
+++ b/crates/ra_syntax/src/ast/extensions.rs
@@ -0,0 +1,303 @@
+//! Various extension methods to ast Nodes, which are hard to code-generate.
+//! Extensions for various expressions live in a sibling `expr_extensions` module.
+
+use itertools::Itertools;
+
+use crate::{
+    SmolStr, SyntaxToken,
+    ast::{self, AstNode, children, child_opt},
+    SyntaxKind::*,
+};
+
+impl ast::Name {
+    pub fn text(&self) -> &SmolStr {
+        let ident = self.syntax().first_child_or_token().unwrap().as_token().unwrap();
+        ident.text()
+    }
+}
+
+impl ast::NameRef {
+    pub fn text(&self) -> &SmolStr {
+        let ident = self.syntax().first_child_or_token().unwrap().as_token().unwrap();
+        ident.text()
+    }
+}
+
+impl ast::Attr {
+    pub fn is_inner(&self) -> bool {
+        let tt = match self.value() {
+            None => return false,
+            Some(tt) => tt,
+        };
+
+        let prev = match tt.syntax().prev_sibling() {
+            None => return false,
+            Some(prev) => prev,
+        };
+
+        prev.kind() == EXCL
+    }
+
+    pub fn as_atom(&self) -> Option<SmolStr> {
+        let tt = self.value()?;
+        let (_bra, attr, _ket) = tt.syntax().children_with_tokens().collect_tuple()?;
+        if attr.kind() == IDENT {
+            Some(attr.as_token()?.text().clone())
+        } else {
+            None
+        }
+    }
+
+    pub fn as_call(&self) -> Option<(SmolStr, &ast::TokenTree)> {
+        let tt = self.value()?;
+        let (_bra, attr, args, _ket) = tt.syntax().children_with_tokens().collect_tuple()?;
+        let args = ast::TokenTree::cast(args.as_node()?)?;
+        if attr.kind() == IDENT {
+            Some((attr.as_token()?.text().clone(), args))
+        } else {
+            None
+        }
+    }
+
+    pub fn as_named(&self) -> Option<SmolStr> {
+        let tt = self.value()?;
+        let attr = tt.syntax().children_with_tokens().nth(1)?;
+        if attr.kind() == IDENT {
+            Some(attr.as_token()?.text().clone())
+        } else {
+            None
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum PathSegmentKind<'a> {
+    Name(&'a ast::NameRef),
+    SelfKw,
+    SuperKw,
+    CrateKw,
+}
+
+impl ast::PathSegment {
+    pub fn parent_path(&self) -> &ast::Path {
+        self.syntax()
+            .parent()
+            .and_then(ast::Path::cast)
+            .expect("segments are always nested in paths")
+    }
+
+    pub fn kind(&self) -> Option<PathSegmentKind> {
+        let res = if let Some(name_ref) = self.name_ref() {
+            PathSegmentKind::Name(name_ref)
+        } else {
+            match self.syntax().first_child_or_token()?.kind() {
+                SELF_KW => PathSegmentKind::SelfKw,
+                SUPER_KW => PathSegmentKind::SuperKw,
+                CRATE_KW => PathSegmentKind::CrateKw,
+                _ => return None,
+            }
+        };
+        Some(res)
+    }
+
+    pub fn has_colon_colon(&self) -> bool {
+        match self.syntax.first_child_or_token().map(|s| s.kind()) {
+            Some(COLONCOLON) => true,
+            _ => false,
+        }
+    }
+}
+
+impl ast::Path {
+    pub fn parent_path(&self) -> Option<&ast::Path> {
+        self.syntax().parent().and_then(ast::Path::cast)
+    }
+}
+
+impl ast::Module {
+    pub fn has_semi(&self) -> bool {
+        match self.syntax().last_child_or_token() {
+            None => false,
+            Some(node) => node.kind() == SEMI,
+        }
+    }
+}
+
+impl ast::UseTree {
+    pub fn has_star(&self) -> bool {
+        self.syntax().children_with_tokens().any(|it| it.kind() == STAR)
+    }
+}
+
+impl ast::UseTreeList {
+    pub fn parent_use_tree(&self) -> &ast::UseTree {
+        self.syntax()
+            .parent()
+            .and_then(ast::UseTree::cast)
+            .expect("UseTreeLists are always nested in UseTrees")
+    }
+}
+
+impl ast::ImplBlock {
+    pub fn target_type(&self) -> Option<&ast::TypeRef> {
+        match self.target() {
+            (Some(t), None) | (_, Some(t)) => Some(t),
+            _ => None,
+        }
+    }
+
+    pub fn target_trait(&self) -> Option<&ast::TypeRef> {
+        match self.target() {
+            (Some(t), Some(_)) => Some(t),
+            _ => None,
+        }
+    }
+
+    fn target(&self) -> (Option<&ast::TypeRef>, Option<&ast::TypeRef>) {
+        let mut types = children(self);
+        let first = types.next();
+        let second = types.next();
+        (first, second)
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum StructKind<'a> {
+    Tuple(&'a ast::PosFieldDefList),
+    Named(&'a ast::NamedFieldDefList),
+    Unit,
+}
+
+impl StructKind<'_> {
+    fn from_node<N: AstNode>(node: &N) -> StructKind {
+        if let Some(nfdl) = child_opt::<_, ast::NamedFieldDefList>(node) {
+            StructKind::Named(nfdl)
+        } else if let Some(pfl) = child_opt::<_, ast::PosFieldDefList>(node) {
+            StructKind::Tuple(pfl)
+        } else {
+            StructKind::Unit
+        }
+    }
+}
+
+impl ast::StructDef {
+    pub fn kind(&self) -> StructKind {
+        StructKind::from_node(self)
+    }
+}
+
+impl ast::EnumVariant {
+    pub fn parent_enum(&self) -> &ast::EnumDef {
+        self.syntax()
+            .parent()
+            .and_then(|it| it.parent())
+            .and_then(ast::EnumDef::cast)
+            .expect("EnumVariants are always nested in Enums")
+    }
+    pub fn kind(&self) -> StructKind {
+        StructKind::from_node(self)
+    }
+}
+
+impl ast::LetStmt {
+    pub fn has_semi(&self) -> bool {
+        match self.syntax().last_child_or_token() {
+            None => false,
+            Some(node) => node.kind() == SEMI,
+        }
+    }
+}
+
+impl ast::ExprStmt {
+    pub fn has_semi(&self) -> bool {
+        match self.syntax().last_child_or_token() {
+            None => false,
+            Some(node) => node.kind() == SEMI,
+        }
+    }
+}
+
+impl ast::RefPat {
+    pub fn is_mut(&self) -> bool {
+        self.syntax().children_with_tokens().any(|n| n.kind() == MUT_KW)
+    }
+}
+
+impl ast::BindPat {
+    pub fn is_mutable(&self) -> bool {
+        self.syntax().children_with_tokens().any(|n| n.kind() == MUT_KW)
+    }
+
+    pub fn is_ref(&self) -> bool {
+        self.syntax().children_with_tokens().any(|n| n.kind() == REF_KW)
+    }
+}
+
+impl ast::PointerType {
+    pub fn is_mut(&self) -> bool {
+        self.syntax().children_with_tokens().any(|n| n.kind() == MUT_KW)
+    }
+}
+
+impl ast::ReferenceType {
+    pub fn is_mut(&self) -> bool {
+        self.syntax().children_with_tokens().any(|n| n.kind() == MUT_KW)
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+pub enum SelfParamKind {
+    /// self
+    Owned,
+    /// &self
+    Ref,
+    /// &mut self
+    MutRef,
+}
+
+impl ast::SelfParam {
+    pub fn self_kw_token(&self) -> SyntaxToken {
+        self.syntax()
+            .children_with_tokens()
+            .filter_map(|it| it.as_token())
+            .find(|it| it.kind() == SELF_KW)
+            .expect("invalid tree: self param must have self")
+    }
+
+    pub fn kind(&self) -> SelfParamKind {
+        let borrowed = self.syntax().children_with_tokens().any(|n| n.kind() == AMP);
+        if borrowed {
+            // check for a `mut` coming after the & -- `mut &self` != `&mut self`
+            if self
+                .syntax()
+                .children_with_tokens()
+                .skip_while(|n| n.kind() != AMP)
+                .any(|n| n.kind() == MUT_KW)
+            {
+                SelfParamKind::MutRef
+            } else {
+                SelfParamKind::Ref
+            }
+        } else {
+            SelfParamKind::Owned
+        }
+    }
+}
+
+impl ast::LifetimeParam {
+    pub fn lifetime_token(&self) -> Option<SyntaxToken> {
+        self.syntax()
+            .children_with_tokens()
+            .filter_map(|it| it.as_token())
+            .find(|it| it.kind() == LIFETIME)
+    }
+}
+
+impl ast::WherePred {
+    pub fn lifetime_token(&self) -> Option<SyntaxToken> {
+        self.syntax()
+            .children_with_tokens()
+            .filter_map(|it| it.as_token())
+            .find(|it| it.kind() == LIFETIME)
+    }
+}
diff --git a/crates/ra_syntax/src/ast/tokens.rs b/crates/ra_syntax/src/ast/tokens.rs
index 7c30ff15c..da7d507bf 100644
--- a/crates/ra_syntax/src/ast/tokens.rs
+++ b/crates/ra_syntax/src/ast/tokens.rs
@@ -1,3 +1,5 @@
+//! There are many AstNodes, but only a few tokens, so we hand-write them here.
+
 use crate::{
     SyntaxToken,
     SyntaxKind::{COMMENT, WHITESPACE},
diff --git a/crates/ra_syntax/src/ast/traits.rs b/crates/ra_syntax/src/ast/traits.rs
index 98aa22085..aaf07d731 100644
--- a/crates/ra_syntax/src/ast/traits.rs
+++ b/crates/ra_syntax/src/ast/traits.rs
@@ -1,3 +1,7 @@
+//! Various traits that are implemented by ast nodes.
+//!
+//! The implementations are usually trivial, and live in generated.rs
+
 use itertools::Itertools;
 
 use crate::{