50 files changed, 843 insertions, 286 deletions

diff --git a/crates/assists/src/handlers/extract_assignment.rs b/crates/assists/src/handlers/pull_assignment_up.rs
index ae99598c0..560d93e10 100644
--- a/crates/assists/src/handlers/extract_assignment.rs
+++ b/crates/assists/src/handlers/pull_assignment_up.rs
@@ -9,9 +9,9 @@ use crate::{
     AssistId, AssistKind,
 };
 
-// Assist: extract_assignment
+// Assist: pull_assignment_up
 //
-// Extracts variable assigment to outside an if or match statement.
+// Extracts variable assignment to outside an if or match statement.
 //
 // ```
 // fn main() {
@@ -36,7 +36,7 @@ use crate::{
 //     };
 // }
 // ```
-pub(crate) fn extract_assigment(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+pub(crate) fn pull_assignment_up(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     let assign_expr = ctx.find_node_at_offset::<ast::BinExpr>()?;
     let name_expr = if assign_expr.op_kind()? == ast::BinOp::Assignment {
         assign_expr.lhs()?
@@ -61,8 +61,8 @@ pub(crate) fn extract_assigment(acc: &mut Assists, ctx: &AssistContext) -> Optio
     let expr_stmt = make::expr_stmt(new_stmt);
 
     acc.add(
-        AssistId("extract_assignment", AssistKind::RefactorExtract),
-        "Extract assignment",
+        AssistId("pull_assignment_up", AssistKind::RefactorExtract),
+        "Pull assignment up",
         old_stmt.syntax().text_range(),
         move |edit| {
             edit.replace(old_stmt.syntax().text_range(), format!("{} = {};", name_expr, expr_stmt));
@@ -104,7 +104,7 @@ fn exprify_if(
             ast::ElseBranch::Block(exprify_block(block, sema, name)?)
         }
         ast::ElseBranch::IfExpr(expr) => {
-            mark::hit!(test_extract_assigment_chained_if);
+            mark::hit!(test_pull_assignment_up_chained_if);
             ast::ElseBranch::IfExpr(ast::IfExpr::cast(
                 exprify_if(&expr, sema, name)?.syntax().to_owned(),
             )?)
@@ -144,7 +144,7 @@ fn is_equivalent(
 ) -> bool {
     match (expr0, expr1) {
         (ast::Expr::FieldExpr(field_expr0), ast::Expr::FieldExpr(field_expr1)) => {
-            mark::hit!(test_extract_assignment_field_assignment);
+            mark::hit!(test_pull_assignment_up_field_assignment);
             sema.resolve_field(field_expr0) == sema.resolve_field(field_expr1)
         }
         (ast::Expr::PathExpr(path0), ast::Expr::PathExpr(path1)) => {
@@ -167,9 +167,9 @@ mod tests {
     use crate::tests::{check_assist, check_assist_not_applicable};
 
     #[test]
-    fn test_extract_assignment_if() {
+    fn test_pull_assignment_up_if() {
         check_assist(
-            extract_assigment,
+            pull_assignment_up,
             r#"
 fn foo() {
     let mut a = 1;
@@ -194,9 +194,9 @@ fn foo() {
     }
 
     #[test]
-    fn test_extract_assignment_match() {
+    fn test_pull_assignment_up_match() {
         check_assist(
-            extract_assigment,
+            pull_assignment_up,
             r#"
 fn foo() {
     let mut a = 1;
@@ -233,9 +233,9 @@ fn foo() {
     }
 
     #[test]
-    fn test_extract_assignment_not_last_not_applicable() {
+    fn test_pull_assignment_up_not_last_not_applicable() {
         check_assist_not_applicable(
-            extract_assigment,
+            pull_assignment_up,
             r#"
 fn foo() {
     let mut a = 1;
@@ -251,10 +251,10 @@ fn foo() {
     }
 
     #[test]
-    fn test_extract_assignment_chained_if() {
-        mark::check!(test_extract_assigment_chained_if);
+    fn test_pull_assignment_up_chained_if() {
+        mark::check!(test_pull_assignment_up_chained_if);
         check_assist(
-            extract_assigment,
+            pull_assignment_up,
             r#"
 fn foo() {
     let mut a = 1;
@@ -283,9 +283,9 @@ fn foo() {
     }
 
     #[test]
-    fn test_extract_assigment_retains_stmts() {
+    fn test_pull_assignment_up_retains_stmts() {
         check_assist(
-            extract_assigment,
+            pull_assignment_up,
             r#"
 fn foo() {
     let mut a = 1;
@@ -314,9 +314,9 @@ fn foo() {
     }
 
     #[test]
-    fn extract_assignment_let_stmt_not_applicable() {
+    fn pull_assignment_up_let_stmt_not_applicable() {
         check_assist_not_applicable(
-            extract_assigment,
+            pull_assignment_up,
             r#"
 fn foo() {
     let mut a = 1;
@@ -331,9 +331,9 @@ fn foo() {
     }
 
     #[test]
-    fn extract_assignment_if_missing_assigment_not_applicable() {
+    fn pull_assignment_up_if_missing_assigment_not_applicable() {
         check_assist_not_applicable(
-            extract_assigment,
+            pull_assignment_up,
             r#"
 fn foo() {
     let mut a = 1;
@@ -346,9 +346,9 @@ fn foo() {
     }
 
     #[test]
-    fn extract_assignment_match_missing_assigment_not_applicable() {
+    fn pull_assignment_up_match_missing_assigment_not_applicable() {
         check_assist_not_applicable(
-            extract_assigment,
+            pull_assignment_up,
             r#"
 fn foo() {
     let mut a = 1;
@@ -367,10 +367,10 @@ fn foo() {
     }
 
     #[test]
-    fn test_extract_assignment_field_assignment() {
-        mark::check!(test_extract_assignment_field_assignment);
+    fn test_pull_assignment_up_field_assignment() {
+        mark::check!(test_pull_assignment_up_field_assignment);
         check_assist(
-            extract_assigment,
+            pull_assignment_up,
             r#"
 struct A(usize);
 
diff --git a/crates/assists/src/lib.rs b/crates/assists/src/lib.rs
index 212464f85..01baa65fe 100644
--- a/crates/assists/src/lib.rs
+++ b/crates/assists/src/lib.rs
@@ -116,7 +116,6 @@ mod handlers {
     mod convert_integer_literal;
     mod early_return;
     mod expand_glob_import;
-    mod extract_assignment;
     mod extract_module_to_file;
     mod extract_struct_from_enum_variant;
     mod extract_variable;
@@ -125,8 +124,8 @@ mod handlers {
     mod flip_binexpr;
     mod flip_comma;
     mod flip_trait_bound;
-    mod generate_derive;
     mod generate_default_from_enum_variant;
+    mod generate_derive;
     mod generate_from_impl_for_enum;
     mod generate_function;
     mod generate_impl;
@@ -139,6 +138,7 @@ mod handlers {
     mod merge_match_arms;
     mod move_bounds;
     mod move_guard;
+    mod pull_assignment_up;
     mod qualify_path;
     mod raw_string;
     mod remove_dbg;
@@ -168,7 +168,6 @@ mod handlers {
             convert_integer_literal::convert_integer_literal,
             early_return::convert_to_guarded_return,
             expand_glob_import::expand_glob_import,
-            extract_assignment::extract_assigment,
             extract_module_to_file::extract_module_to_file,
             extract_struct_from_enum_variant::extract_struct_from_enum_variant,
             extract_variable::extract_variable,
@@ -177,8 +176,8 @@ mod handlers {
             flip_binexpr::flip_binexpr,
             flip_comma::flip_comma,
             flip_trait_bound::flip_trait_bound,
-            generate_derive::generate_derive,
             generate_default_from_enum_variant::generate_default_from_enum_variant,
+            generate_derive::generate_derive,
             generate_from_impl_for_enum::generate_from_impl_for_enum,
             generate_function::generate_function,
             generate_impl::generate_impl,
@@ -192,6 +191,7 @@ mod handlers {
             move_bounds::move_bounds_to_where_clause,
             move_guard::move_arm_cond_to_match_guard,
             move_guard::move_guard_to_arm_body,
+            pull_assignment_up::pull_assignment_up,
             qualify_path::qualify_path,
             raw_string::add_hash,
             raw_string::make_usual_string,
diff --git a/crates/assists/src/tests/generated.rs b/crates/assists/src/tests/generated.rs
index b91a816e8..85e3c6742 100644
--- a/crates/assists/src/tests/generated.rs
+++ b/crates/assists/src/tests/generated.rs
@@ -238,35 +238,6 @@ fn qux(bar: Bar, baz: Baz) {}
 }
 
 #[test]
-fn doctest_extract_assignment() {
-    check_doc_test(
-        "extract_assignment",
-        r#####"
-fn main() {
-    let mut foo = 6;
-
-    if true {
-        <|>foo = 5;
-    } else {
-        foo = 4;
-    }
-}
-"#####,
-        r#####"
-fn main() {
-    let mut foo = 6;
-
-    foo = if true {
-        5
-    } else {
-        4
-    };
-}
-"#####,
-    )
-}
-
-#[test]
 fn doctest_extract_module_to_file() {
     check_doc_test(
         "extract_module_to_file",
@@ -767,6 +738,35 @@ fn handle(action: Action) {
 }
 
 #[test]
+fn doctest_pull_assignment_up() {
+    check_doc_test(
+        "pull_assignment_up",
+        r#####"
+fn main() {
+    let mut foo = 6;
+
+    if true {
+        <|>foo = 5;
+    } else {
+        foo = 4;
+    }
+}
+"#####,
+        r#####"
+fn main() {
+    let mut foo = 6;
+
+    foo = if true {
+        5
+    } else {
+        4
+    };
+}
+"#####,
+    )
+}
+
+#[test]
 fn doctest_qualify_path() {
     check_doc_test(
         "qualify_path",
diff --git a/crates/hir/src/code_model.rs b/crates/hir/src/code_model.rs
index 62eccf475..1a4aa78fb 100644
--- a/crates/hir/src/code_model.rs
+++ b/crates/hir/src/code_model.rs
@@ -5,9 +5,7 @@ use arrayvec::ArrayVec;
 use base_db::{CrateDisplayName, CrateId, Edition, FileId};
 use either::Either;
 use hir_def::{
-    adt::ReprKind,
-    adt::StructKind,
-    adt::VariantData,
+    adt::{ReprKind, StructKind, VariantData},
     builtin_type::BuiltinType,
     expr::{BindingAnnotation, LabelId, Pat, PatId},
     import_map,
@@ -31,7 +29,7 @@ use hir_expand::{
 };
 use hir_ty::{
     autoderef,
-    display::{HirDisplayError, HirFormatter},
+    display::{write_bounds_like_dyn_trait, HirDisplayError, HirFormatter},
     method_resolution,
     traits::{FnTrait, Solution, SolutionVariables},
     ApplicationTy, BoundVar, CallableDefId, Canonical, DebruijnIndex, FnSig, GenericPredicate,
@@ -745,6 +743,18 @@ impl Function {
         db.function_data(self.id).name.clone()
     }
 
+    /// Get this function's return type
+    pub fn ret_type(self, db: &dyn HirDatabase) -> Type {
+        let resolver = self.id.resolver(db.upcast());
+        let ret_type = &db.function_data(self.id).ret_type;
+        let ctx = hir_ty::TyLoweringContext::new(db, &resolver);
+        let environment = TraitEnvironment::lower(db, &resolver);
+        Type {
+            krate: self.id.lookup(db.upcast()).container.module(db.upcast()).krate,
+            ty: InEnvironment { value: Ty::from_hir_ext(&ctx, ret_type).0, environment },
+        }
+    }
+
     pub fn self_param(self, db: &dyn HirDatabase) -> Option<SelfParam> {
         if !db.function_data(self.id).has_self_param {
             return None;
@@ -1278,6 +1288,18 @@ impl TypeParam {
         }
     }
 
+    pub fn trait_bounds(self, db: &dyn HirDatabase) -> Vec<Trait> {
+        db.generic_predicates_for_param(self.id)
+            .into_iter()
+            .filter_map(|pred| match &pred.value {
+                hir_ty::GenericPredicate::Implemented(trait_ref) => {
+                    Some(Trait::from(trait_ref.trait_))
+                }
+                _ => None,
+            })
+            .collect()
+    }
+
     pub fn default(self, db: &dyn HirDatabase) -> Option<Type> {
         let params = db.generic_defaults(self.id.parent);
         let local_idx = hir_ty::param_idx(db, self.id)?;
@@ -1293,6 +1315,20 @@ impl TypeParam {
     }
 }
 
+impl HirDisplay for TypeParam {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
+        write!(f, "{}", self.name(f.db))?;
+        let bounds = f.db.generic_predicates_for_param(self.id);
+        let substs = Substs::type_params(f.db, self.id.parent);
+        let predicates = bounds.iter().cloned().map(|b| b.subst(&substs)).collect::<Vec<_>>();
+        if !(predicates.is_empty() || f.omit_verbose_types()) {
+            write!(f, ": ")?;
+            write_bounds_like_dyn_trait(&predicates, f)?;
+        }
+        Ok(())
+    }
+}
+
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub struct LifetimeParam {
     pub(crate) id: LifetimeParamId,
@@ -1331,6 +1367,12 @@ impl ConstParam {
     pub fn parent(self, _db: &dyn HirDatabase) -> GenericDef {
         self.id.parent.into()
     }
+
+    pub fn ty(self, db: &dyn HirDatabase) -> Type {
+        let def = self.id.parent;
+        let krate = def.module(db.upcast()).krate;
+        Type::new(db, krate, def, db.const_param_ty(self.id))
+    }
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
diff --git a/crates/hir_expand/src/proc_macro.rs b/crates/hir_expand/src/proc_macro.rs
index 7c77f6ce0..1923daca5 100644
--- a/crates/hir_expand/src/proc_macro.rs
+++ b/crates/hir_expand/src/proc_macro.rs
@@ -58,7 +58,7 @@ impl ProcMacroExpander {
 }
 
 fn eat_punct(cursor: &mut Cursor, c: char) -> bool {
-    if let Some(tt::TokenTree::Leaf(tt::Leaf::Punct(punct))) = cursor.token_tree() {
+    if let Some(tt::buffer::TokenTreeRef::Leaf(tt::Leaf::Punct(punct), _)) = cursor.token_tree() {
         if punct.char == c {
             *cursor = cursor.bump();
             return true;
@@ -68,7 +68,7 @@ fn eat_punct(cursor: &mut Cursor, c: char) -> bool {
 }
 
 fn eat_subtree(cursor: &mut Cursor, kind: tt::DelimiterKind) -> bool {
-    if let Some(tt::TokenTree::Subtree(subtree)) = cursor.token_tree() {
+    if let Some(tt::buffer::TokenTreeRef::Subtree(subtree, _)) = cursor.token_tree() {
         if Some(kind) == subtree.delimiter_kind() {
             *cursor = cursor.bump_subtree();
             return true;
@@ -78,7 +78,7 @@ fn eat_subtree(cursor: &mut Cursor, kind: tt::DelimiterKind) -> bool {
 }
 
 fn eat_ident(cursor: &mut Cursor, t: &str) -> bool {
-    if let Some(tt::TokenTree::Leaf(tt::Leaf::Ident(ident))) = cursor.token_tree() {
+    if let Some(tt::buffer::TokenTreeRef::Leaf(tt::Leaf::Ident(ident), _)) = cursor.token_tree() {
         if t == ident.text.as_str() {
             *cursor = cursor.bump();
             return true;
@@ -88,7 +88,7 @@ fn eat_ident(cursor: &mut Cursor, t: &str) -> bool {
 }
 
 fn remove_derive_attrs(tt: &tt::Subtree) -> Option<tt::Subtree> {
-    let buffer = TokenBuffer::new(&tt.token_trees);
+    let buffer = TokenBuffer::from_tokens(&tt.token_trees);
     let mut p = buffer.begin();
     let mut result = tt::Subtree::default();
 
@@ -106,7 +106,7 @@ fn remove_derive_attrs(tt: &tt::Subtree) -> Option<tt::Subtree> {
             }
         }
 
-        result.token_trees.push(curr.token_tree()?.clone());
+        result.token_trees.push(curr.token_tree()?.cloned());
         p = curr.bump();
     }
 
diff --git a/crates/hir_ty/Cargo.toml b/crates/hir_ty/Cargo.toml
index 3d1778590..b0a453961 100644
--- a/crates/hir_ty/Cargo.toml
+++ b/crates/hir_ty/Cargo.toml
@@ -17,9 +17,9 @@ ena = "0.14.0"
 log = "0.4.8"
 rustc-hash = "1.1.0"
 scoped-tls = "1"
-chalk-solve = { version = "0.45", default-features = false }
-chalk-ir = "0.45"
-chalk-recursive = "0.45"
+chalk-solve = { version = "0.47", default-features = false }
+chalk-ir = "0.47"
+chalk-recursive = "0.47"
 
 stdx = { path = "../stdx", version = "0.0.0" }
 hir_def = { path = "../hir_def", version = "0.0.0" }
diff --git a/crates/hir_ty/src/display.rs b/crates/hir_ty/src/display.rs
index 0e827a29e..a54225c18 100644
--- a/crates/hir_ty/src/display.rs
+++ b/crates/hir_ty/src/display.rs
@@ -595,7 +595,7 @@ impl HirDisplay for FnSig {
     }
 }
 
-fn write_bounds_like_dyn_trait(
+pub fn write_bounds_like_dyn_trait(
     predicates: &[GenericPredicate],
     f: &mut HirFormatter,
 ) -> Result<(), HirDisplayError> {
diff --git a/crates/ide/src/display/short_label.rs b/crates/ide/src/display/short_label.rs
index ea49d9f97..990f740b8 100644
--- a/crates/ide/src/display/short_label.rs
+++ b/crates/ide/src/display/short_label.rs
@@ -87,6 +87,17 @@ impl ShortLabel for ast::Variant {
     }
 }
 
+impl ShortLabel for ast::ConstParam {
+    fn short_label(&self) -> Option<String> {
+        let mut buf = "const ".to_owned();
+        buf.push_str(self.name()?.text().as_str());
+        if let Some(type_ref) = self.ty() {
+            format_to!(buf, ": {}", type_ref.syntax());
+        }
+        Some(buf)
+    }
+}
+
 fn short_label_from_ty<T>(node: &T, ty: Option<ast::Type>, prefix: &str) -> Option<String>
 where
     T: NameOwner + VisibilityOwner,
diff --git a/crates/ide/src/hover.rs b/crates/ide/src/hover.rs
index 2737c900f..f2ad95cb6 100644
--- a/crates/ide/src/hover.rs
+++ b/crates/ide/src/hover.rs
@@ -70,7 +70,7 @@ impl HoverConfig {
 #[derive(Debug, Clone)]
 pub enum HoverAction {
     Runnable(Runnable),
-    Implementaion(FilePosition),
+    Implementation(FilePosition),
     GoToType(Vec<HoverGotoTypeData>),
 }
 
@@ -116,12 +116,13 @@ pub(crate) fn hover(
     };
     if let Some(definition) = definition {
         if let Some(markup) = hover_for_definition(db, definition) {
+            let markup = markup.as_str();
             let markup = if !markdown {
-                remove_markdown(&markup.as_str())
+                remove_markdown(markup)
             } else if links_in_hover {
-                rewrite_links(db, &markup.as_str(), &definition)
+                rewrite_links(db, markup, &definition)
             } else {
-                remove_links(&markup.as_str())
+                remove_links(markup)
             };
             res.markup = Markup::from(markup);
             if let Some(action) = show_implementations_action(db, definition) {
@@ -175,22 +176,24 @@ pub(crate) fn hover(
 
 fn show_implementations_action(db: &RootDatabase, def: Definition) -> Option<HoverAction> {
     fn to_action(nav_target: NavigationTarget) -> HoverAction {
-        HoverAction::Implementaion(FilePosition {
+        HoverAction::Implementation(FilePosition {
             file_id: nav_target.file_id,
             offset: nav_target.focus_or_full_range().start(),
         })
     }
 
-    match def {
-        Definition::ModuleDef(it) => match it {
-            ModuleDef::Adt(Adt::Struct(it)) => Some(to_action(it.try_to_nav(db)?)),
-            ModuleDef::Adt(Adt::Union(it)) => Some(to_action(it.try_to_nav(db)?)),
-            ModuleDef::Adt(Adt::Enum(it)) => Some(to_action(it.try_to_nav(db)?)),
-            ModuleDef::Trait(it) => Some(to_action(it.try_to_nav(db)?)),
-            _ => None,
-        },
+    let adt = match def {
+        Definition::ModuleDef(ModuleDef::Trait(it)) => return it.try_to_nav(db).map(to_action),
+        Definition::ModuleDef(ModuleDef::Adt(it)) => Some(it),
+        Definition::SelfType(it) => it.target_ty(db).as_adt(),
         _ => None,
+    }?;
+    match adt {
+        Adt::Struct(it) => it.try_to_nav(db),
+        Adt::Union(it) => it.try_to_nav(db),
+        Adt::Enum(it) => it.try_to_nav(db),
     }
+    .map(to_action)
 }
 
 fn runnable_action(
@@ -225,45 +228,46 @@ fn runnable_action(
 }
 
 fn goto_type_action(db: &RootDatabase, def: Definition) -> Option<HoverAction> {
-    match def {
-        Definition::Local(it) => {
-            let mut targets: Vec<ModuleDef> = Vec::new();
-            let mut push_new_def = |item: ModuleDef| {
-                if !targets.contains(&item) {
-                    targets.push(item);
-                }
-            };
-
-            it.ty(db).walk(db, |t| {
-                if let Some(adt) = t.as_adt() {
-                    push_new_def(adt.into());
-                } else if let Some(trait_) = t.as_dyn_trait() {
-                    push_new_def(trait_.into());
-                } else if let Some(traits) = t.as_impl_traits(db) {
-                    traits.into_iter().for_each(|it| push_new_def(it.into()));
-                } else if let Some(trait_) = t.as_associated_type_parent_trait(db) {
-                    push_new_def(trait_.into());
-                }
-            });
-
-            let targets = targets
-                .into_iter()
-                .filter_map(|it| {
-                    Some(HoverGotoTypeData {
-                        mod_path: render_path(
-                            db,
-                            it.module(db)?,
-                            it.name(db).map(|name| name.to_string()),
-                        ),
-                        nav: it.try_to_nav(db)?,
-                    })
-                })
-                .collect();
-
-            Some(HoverAction::GoToType(targets))
+    let mut targets: Vec<ModuleDef> = Vec::new();
+    let mut push_new_def = |item: ModuleDef| {
+        if !targets.contains(&item) {
+            targets.push(item);
         }
-        _ => None,
+    };
+
+    if let Definition::TypeParam(it) = def {
+        it.trait_bounds(db).into_iter().for_each(|it| push_new_def(it.into()));
+    } else {
+        let ty = match def {
+            Definition::Local(it) => it.ty(db),
+            Definition::ConstParam(it) => it.ty(db),
+            _ => return None,
+        };
+
+        ty.walk(db, |t| {
+            if let Some(adt) = t.as_adt() {
+                push_new_def(adt.into());
+            } else if let Some(trait_) = t.as_dyn_trait() {
+                push_new_def(trait_.into());
+            } else if let Some(traits) = t.as_impl_traits(db) {
+                traits.into_iter().for_each(|it| push_new_def(it.into()));
+            } else if let Some(trait_) = t.as_associated_type_parent_trait(db) {
+                push_new_def(trait_.into());
+            }
+        });
     }
+
+    let targets = targets
+        .into_iter()
+        .filter_map(|it| {
+            Some(HoverGotoTypeData {
+                mod_path: render_path(db, it.module(db)?, it.name(db).map(|name| name.to_string())),
+                nav: it.try_to_nav(db)?,
+            })
+        })
+        .collect();
+
+    Some(HoverAction::GoToType(targets))
 }
 
 fn hover_markup(
@@ -370,10 +374,8 @@ fn hover_for_definition(db: &RootDatabase, def: Definition) -> Option<Markup> {
         }
         Definition::Label(it) => Some(Markup::fenced_block(&it.name(db))),
         Definition::LifetimeParam(it) => Some(Markup::fenced_block(&it.name(db))),
-        Definition::TypeParam(_) | Definition::ConstParam(_) => {
-            // FIXME: Hover for generic param
-            None
-        }
+        Definition::TypeParam(type_param) => Some(Markup::fenced_block(&type_param.display(db))),
+        Definition::ConstParam(it) => from_def_source(db, it, None),
     };
 
     fn from_def_source<A, D>(db: &RootDatabase, def: D, mod_path: Option<String>) -> Option<Markup>
@@ -1393,7 +1395,7 @@ fn bar() { fo<|>o(); }
             r"unsafe trait foo<|>() {}",
             expect![[r#"
                 [
-                    Implementaion(
+                    Implementation(
                         FilePosition {
                             file_id: FileId(
                                 0,
@@ -2105,7 +2107,7 @@ fn foo() { let bar = Bar; bar.fo<|>o(); }
             r#"trait foo<|>() {}"#,
             expect![[r#"
                 [
-                    Implementaion(
+                    Implementation(
                         FilePosition {
                             file_id: FileId(
                                 0,
@@ -2124,7 +2126,7 @@ fn foo() { let bar = Bar; bar.fo<|>o(); }
             r"struct foo<|>() {}",
             expect![[r#"
                 [
-                    Implementaion(
+                    Implementation(
                         FilePosition {
                             file_id: FileId(
                                 0,
@@ -2143,7 +2145,7 @@ fn foo() { let bar = Bar; bar.fo<|>o(); }
             r#"union foo<|>() {}"#,
             expect![[r#"
                 [
-                    Implementaion(
+                    Implementation(
                         FilePosition {
                             file_id: FileId(
                                 0,
@@ -2162,7 +2164,7 @@ fn foo() { let bar = Bar; bar.fo<|>o(); }
             r"enum foo<|>() { A, B }",
             expect![[r#"
                 [
-                    Implementaion(
+                    Implementation(
                         FilePosition {
                             file_id: FileId(
                                 0,
@@ -2176,6 +2178,25 @@ fn foo() { let bar = Bar; bar.fo<|>o(); }
     }
 
     #[test]
+    fn test_hover_self_has_impl_action() {
+        check_actions(
+            r#"struct foo where Self<|>:;"#,
+            expect![[r#"
+                [
+                    Implementation(
+                        FilePosition {
+                            file_id: FileId(
+                                0,
+                            ),
+                            offset: 7,
+                        },
+                    ),
+                ]
+            "#]],
+        );
+    }
+
+    #[test]
     fn test_hover_test_has_action() {
         check_actions(
             r#"
@@ -3064,6 +3085,71 @@ fn main() { let s<|>t = test().get(); }
     }
 
     #[test]
+    fn test_hover_const_param_has_goto_type_action() {
+        check_actions(
+            r#"
+struct Bar;
+struct Foo<const BAR: Bar>;
+
+impl<const BAR: Bar> Foo<BAR<|>> {}
+"#,
+            expect![[r#"
+                [
+                    GoToType(
+                        [
+                            HoverGotoTypeData {
+                                mod_path: "test::Bar",
+                                nav: NavigationTarget {
+                                    file_id: FileId(
+                                        0,
+                                    ),
+                                    full_range: 0..11,
+                                    focus_range: 7..10,
+                                    name: "Bar",
+                                    kind: Struct,
+                                    description: "struct Bar",
+                                },
+                            },
+                        ],
+                    ),
+                ]
+            "#]],
+        );
+    }
+
+    #[test]
+    fn test_hover_type_param_has_goto_type_action() {
+        check_actions(
+            r#"
+trait Foo {}
+
+fn foo<T: Foo>(t: T<|>){}
+"#,
+            expect![[r#"
+                [
+                    GoToType(
+                        [
+                            HoverGotoTypeData {
+                                mod_path: "test::Foo",
+                                nav: NavigationTarget {
+                                    file_id: FileId(
+                                        0,
+                                    ),
+                                    full_range: 0..12,
+                                    focus_range: 6..9,
+                                    name: "Foo",
+                                    kind: Trait,
+                                    description: "trait Foo",
+                                },
+                            },
+                        ],
+                    ),
+                ]
+            "#]],
+        );
+    }
+
+    #[test]
     fn hover_displays_normalized_crate_names() {
         check(
             r#"
@@ -3257,4 +3343,68 @@ fn foo() {
             "#]],
         );
     }
+
+    #[test]
+    fn hover_type_param() {
+        check(
+            r#"
+struct Foo<T>(T);
+trait Copy {}
+trait Clone {}
+trait Sized {}
+impl<T: Copy + Clone> Foo<T<|>> where T: Sized {}
+"#,
+            expect![[r#"
+                *T*
+
+                ```rust
+                T: Copy + Clone + Sized
+                ```
+            "#]],
+        );
+        check(
+            r#"
+struct Foo<T>(T);
+impl<T> Foo<T<|>> {}
+"#,
+            expect![[r#"
+                *T*
+
+                ```rust
+                T
+                ```
+                "#]],
+        );
+        // lifetimes aren't being substituted yet
+        check(
+            r#"
+struct Foo<T>(T);
+impl<T: 'static> Foo<T<|>> {}
+"#,
+            expect![[r#"
+                *T*
+
+                ```rust
+                T: {error}
+                ```
+                "#]],
+        );
+    }
+
+    #[test]
+    fn hover_const_param() {
+        check(
+            r#"
+struct Foo<const LEN: usize>;
+impl<const LEN: usize> Foo<LEN<|>> {}
+"#,
+            expect![[r#"
+                *LEN*
+
+                ```rust
+                const LEN: usize
+                ```
+            "#]],
+        );
+    }
 }
diff --git a/crates/mbe/src/mbe_expander/matcher.rs b/crates/mbe/src/mbe_expander/matcher.rs
index ab5f87c48..fdc8844ce 100644
--- a/crates/mbe/src/mbe_expander/matcher.rs
+++ b/crates/mbe/src/mbe_expander/matcher.rs
@@ -309,7 +309,7 @@ impl<'a> TtIter<'a> {
             }
         }
 
-        let buffer = TokenBuffer::new(&self.inner.as_slice());
+        let buffer = TokenBuffer::from_tokens(&self.inner.as_slice());
         let mut src = SubtreeTokenSource::new(&buffer);
         let mut sink = OffsetTokenSink { cursor: buffer.begin(), error: false };
 
@@ -336,11 +336,11 @@ impl<'a> TtIter<'a> {
             err = Some(err!("no tokens consumed"));
         }
         let res = match res.len() {
-            1 => Some(res[0].clone()),
+            1 => Some(res[0].cloned()),
             0 => None,
             _ => Some(tt::TokenTree::Subtree(tt::Subtree {
                 delimiter: None,
-                token_trees: res.into_iter().cloned().collect(),
+                token_trees: res.into_iter().map(|it| it.cloned()).collect(),
             })),
         };
         ExpandResult { value: res, err }
diff --git a/crates/mbe/src/subtree_source.rs b/crates/mbe/src/subtree_source.rs
index d10d4b70e..d7433bd35 100644
--- a/crates/mbe/src/subtree_source.rs
+++ b/crates/mbe/src/subtree_source.rs
@@ -1,129 +1,104 @@
 //! FIXME: write short doc here
 
 use parser::{Token, TokenSource};
-use std::cell::{Cell, Ref, RefCell};
 use syntax::{lex_single_syntax_kind, SmolStr, SyntaxKind, SyntaxKind::*, T};
-use tt::buffer::{Cursor, TokenBuffer};
+use tt::buffer::TokenBuffer;
 
 #[derive(Debug, Clone, Eq, PartialEq)]
 struct TtToken {
-    kind: SyntaxKind,
-    is_joint_to_next: bool,
+    tt: Token,
     text: SmolStr,
 }
 
-pub(crate) struct SubtreeTokenSource<'a> {
-    cached_cursor: Cell<Cursor<'a>>,
-    cached: RefCell<Vec<Option<TtToken>>>,
+pub(crate) struct SubtreeTokenSource {
+    cached: Vec<TtToken>,
     curr: (Token, usize),
 }
 
-impl<'a> SubtreeTokenSource<'a> {
+impl<'a> SubtreeTokenSource {
     // Helper function used in test
     #[cfg(test)]
     pub(crate) fn text(&self) -> SmolStr {
-        match *self.get(self.curr.1) {
+        match self.cached.get(self.curr.1) {
             Some(ref tt) => tt.text.clone(),
             _ => SmolStr::new(""),
         }
     }
 }
 
-impl<'a> SubtreeTokenSource<'a> {
-    pub(crate) fn new(buffer: &'a TokenBuffer) -> SubtreeTokenSource<'a> {
-        let cursor = buffer.begin();
+impl<'a> SubtreeTokenSource {
+    pub(crate) fn new(buffer: &TokenBuffer) -> SubtreeTokenSource {
+        let mut current = buffer.begin();
+        let mut cached = Vec::with_capacity(100);
 
-        let mut res = SubtreeTokenSource {
-            curr: (Token { kind: EOF, is_jointed_to_next: false }, 0),
-            cached_cursor: Cell::new(cursor),
-            cached: RefCell::new(Vec::with_capacity(10)),
-        };
-        res.curr = (res.mk_token(0), 0);
-        res
-    }
+        while !current.eof() {
+            let cursor = current;
+            let tt = cursor.token_tree();
 
-    fn mk_token(&self, pos: usize) -> Token {
-        match *self.get(pos) {
-            Some(ref tt) => Token { kind: tt.kind, is_jointed_to_next: tt.is_joint_to_next },
-            None => Token { kind: EOF, is_jointed_to_next: false },
-        }
-    }
-
-    fn get(&self, pos: usize) -> Ref<Option<TtToken>> {
-        fn is_lifetime(c: Cursor) -> Option<(Cursor, SmolStr)> {
-            let tkn = c.token_tree();
-
-            if let Some(tt::TokenTree::Leaf(tt::Leaf::Punct(punct))) = tkn {
+            // Check if it is lifetime
+            if let Some(tt::buffer::TokenTreeRef::Leaf(tt::Leaf::Punct(punct), _)) = tt {
                 if punct.char == '\'' {
-                    let next = c.bump();
-                    if let Some(tt::TokenTree::Leaf(tt::Leaf::Ident(ident))) = next.token_tree() {
-                        let res_cursor = next.bump();
-                        let text = SmolStr::new("'".to_string() + &ident.to_string());
-
-                        return Some((res_cursor, text));
+                    let next = cursor.bump();
+                    if let Some(tt::buffer::TokenTreeRef::Leaf(tt::Leaf::Ident(ident), _)) =
+                        next.token_tree()
+                    {
+                        let text = SmolStr::new("'".to_string() + &ident.text);
+                        cached.push(TtToken {
+                            tt: Token { kind: LIFETIME_IDENT, is_jointed_to_next: false },
+                            text,
+                        });
+                        current = next.bump();
+                        continue;
                     } else {
                         panic!("Next token must be ident : {:#?}", next.token_tree());
                     }
                 }
             }
 
-            None
-        }
-
-        if pos < self.cached.borrow().len() {
-            return Ref::map(self.cached.borrow(), |c| &c[pos]);
-        }
-
-        {
-            let mut cached = self.cached.borrow_mut();
-            while pos >= cached.len() {
-                let cursor = self.cached_cursor.get();
-                if cursor.eof() {
-                    cached.push(None);
-                    continue;
+            current = match tt {
+                Some(tt::buffer::TokenTreeRef::Leaf(leaf, _)) => {
+                    cached.push(convert_leaf(&leaf));
+                    cursor.bump()
                 }
-
-                if let Some((curr, text)) = is_lifetime(cursor) {
-                    cached.push(Some(TtToken {
-                        kind: LIFETIME_IDENT,
-                        is_joint_to_next: false,
-                        text,
-                    }));
-                    self.cached_cursor.set(curr);
-                    continue;
+                Some(tt::buffer::TokenTreeRef::Subtree(subtree, _)) => {
+                    cached.push(convert_delim(subtree.delimiter_kind(), false));
+                    cursor.subtree().unwrap()
                 }
-
-                match cursor.token_tree() {
-                    Some(tt::TokenTree::Leaf(leaf)) => {
-                        cached.push(Some(convert_leaf(&leaf)));
-                        self.cached_cursor.set(cursor.bump());
-                    }
-                    Some(tt::TokenTree::Subtree(subtree)) => {
-                        self.cached_cursor.set(cursor.subtree().unwrap());
-                        cached.push(Some(convert_delim(subtree.delimiter_kind(), false)));
-                    }
-                    None => {
-                        if let Some(subtree) = cursor.end() {
-                            cached.push(Some(convert_delim(subtree.delimiter_kind(), true)));
-                            self.cached_cursor.set(cursor.bump());
-                        }
+                None => {
+                    if let Some(subtree) = cursor.end() {
+                        cached.push(convert_delim(subtree.delimiter_kind(), true));
+                        cursor.bump()
+                    } else {
+                        continue;
                     }
                 }
-            }
+            };
         }
 
-        Ref::map(self.cached.borrow(), |c| &c[pos])
+        let mut res = SubtreeTokenSource {
+            curr: (Token { kind: EOF, is_jointed_to_next: false }, 0),
+            cached,
+        };
+        res.curr = (res.token(0), 0);
+        res
+    }
+
+    fn token(&self, pos: usize) -> Token {
+        match self.cached.get(pos) {
+            Some(it) => it.tt,
+            None => Token { kind: EOF, is_jointed_to_next: false },
+        }
     }
 }
 
-impl<'a> TokenSource for SubtreeTokenSource<'a> {
+impl<'a> TokenSource for SubtreeTokenSource {
     fn current(&self) -> Token {
         self.curr.0
     }
 
     /// Lookahead n token
     fn lookahead_nth(&self, n: usize) -> Token {
-        self.mk_token(self.curr.1 + n)
+        self.token(self.curr.1 + n)
     }
 
     /// bump cursor to next token
@@ -131,13 +106,12 @@ impl<'a> TokenSource for SubtreeTokenSource<'a> {
         if self.current().kind == EOF {
             return;
         }
-
-        self.curr = (self.mk_token(self.curr.1 + 1), self.curr.1 + 1);
+        self.curr = (self.token(self.curr.1 + 1), self.curr.1 + 1);
     }
 
     /// Is the current token a specified keyword?
     fn is_keyword(&self, kw: &str) -> bool {
-        match *self.get(self.curr.1) {
+        match self.cached.get(self.curr.1) {
             Some(ref t) => t.text == *kw,
             _ => false,
         }
@@ -155,7 +129,7 @@ fn convert_delim(d: Option<tt::DelimiterKind>, closing: bool) -> TtToken {
     let idx = closing as usize;
     let kind = kinds[idx];
     let text = if !texts.is_empty() { &texts[idx..texts.len() - (1 - idx)] } else { "" };
-    TtToken { kind, is_joint_to_next: false, text: SmolStr::new(text) }
+    TtToken { tt: Token { kind, is_jointed_to_next: false }, text: SmolStr::new(text) }
 }
 
 fn convert_literal(l: &tt::Literal) -> TtToken {
@@ -169,7 +143,7 @@ fn convert_literal(l: &tt::Literal) -> TtToken {
         })
         .unwrap_or_else(|| panic!("Fail to convert given literal {:#?}", &l));
 
-    TtToken { kind, is_joint_to_next: false, text: l.text.clone() }
+    TtToken { tt: Token { kind, is_jointed_to_next: false }, text: l.text.clone() }
 }
 
 fn convert_ident(ident: &tt::Ident) -> TtToken {
@@ -180,7 +154,7 @@ fn convert_ident(ident: &tt::Ident) -> TtToken {
         _ => SyntaxKind::from_keyword(ident.text.as_str()).unwrap_or(IDENT),
     };
 
-    TtToken { kind, is_joint_to_next: false, text: ident.text.clone() }
+    TtToken { tt: Token { kind, is_jointed_to_next: false }, text: ident.text.clone() }
 }
 
 fn convert_punct(p: tt::Punct) -> TtToken {
@@ -194,7 +168,7 @@ fn convert_punct(p: tt::Punct) -> TtToken {
         let s: &str = p.char.encode_utf8(&mut buf);
         SmolStr::new(s)
     };
-    TtToken { kind, is_joint_to_next: p.spacing == tt::Spacing::Joint, text }
+    TtToken { tt: Token { kind, is_jointed_to_next: p.spacing == tt::Spacing::Joint }, text }
 }
 
 fn convert_leaf(leaf: &tt::Leaf) -> TtToken {
@@ -208,6 +182,7 @@ fn convert_leaf(leaf: &tt::Leaf) -> TtToken {
 #[cfg(test)]
 mod tests {
     use super::{convert_literal, TtToken};
+    use parser::Token;
     use syntax::{SmolStr, SyntaxKind};
 
     #[test]
@@ -218,8 +193,7 @@ mod tests {
                 text: SmolStr::new("-42.0")
             }),
             TtToken {
-                kind: SyntaxKind::FLOAT_NUMBER,
-                is_joint_to_next: false,
+                tt: Token { kind: SyntaxKind::FLOAT_NUMBER, is_jointed_to_next: false },
                 text: SmolStr::new("-42.0")
             }
         );
diff --git a/crates/mbe/src/syntax_bridge.rs b/crates/mbe/src/syntax_bridge.rs
index 265c0d63d..671036e1c 100644
--- a/crates/mbe/src/syntax_bridge.rs
+++ b/crates/mbe/src/syntax_bridge.rs
@@ -70,15 +70,12 @@ pub fn token_tree_to_syntax_node(
     tt: &tt::Subtree,
     fragment_kind: FragmentKind,
 ) -> Result<(Parse<SyntaxNode>, TokenMap), ExpandError> {
-    let tmp;
-    let tokens = match tt {
-        tt::Subtree { delimiter: None, token_trees } => token_trees.as_slice(),
-        _ => {
-            tmp = [tt.clone().into()];
-            &tmp[..]
+    let buffer = match tt {
+        tt::Subtree { delimiter: None, token_trees } => {
+            TokenBuffer::from_tokens(token_trees.as_slice())
         }
+        _ => TokenBuffer::from_subtree(tt),
     };
-    let buffer = TokenBuffer::new(&tokens);
     let mut token_source = SubtreeTokenSource::new(&buffer);
     let mut tree_sink = TtTreeSink::new(buffer.begin());
     parser::parse_fragment(&mut token_source, &mut tree_sink, fragment_kind);
@@ -414,7 +411,7 @@ trait TokenConvertor {
     fn id_alloc(&mut self) -> &mut TokenIdAlloc;
 }
 
-impl<'a> SrcToken for (RawToken, &'a str) {
+impl<'a> SrcToken for (&'a RawToken, &'a str) {
     fn kind(&self) -> SyntaxKind {
         self.0.kind
     }
@@ -431,7 +428,7 @@ impl<'a> SrcToken for (RawToken, &'a str) {
 impl RawConvertor<'_> {}
 
 impl<'a> TokenConvertor for RawConvertor<'a> {
-    type Token = (RawToken, &'a str);
+    type Token = (&'a RawToken, &'a str);
 
     fn convert_doc_comment(&self, token: &Self::Token) -> Option<Vec<tt::TokenTree>> {
         convert_doc_comment(&doc_comment(token.1))
@@ -442,11 +439,11 @@ impl<'a> TokenConvertor for RawConvertor<'a> {
         let range = TextRange::at(self.offset, token.len);
         self.offset += token.len;
 
-        Some(((*token, &self.text[range]), range))
+        Some(((token, &self.text[range]), range))
     }
 
     fn peek(&self) -> Option<Self::Token> {
-        let token = self.inner.as_slice().get(0).cloned();
+        let token = self.inner.as_slice().get(0);
 
         token.map(|it| {
             let range = TextRange::at(self.offset, it.len);
@@ -601,17 +598,16 @@ impl<'a> TtTreeSink<'a> {
     }
 }
 
-fn delim_to_str(d: Option<tt::DelimiterKind>, closing: bool) -> SmolStr {
+fn delim_to_str(d: Option<tt::DelimiterKind>, closing: bool) -> &'static str {
     let texts = match d {
         Some(tt::DelimiterKind::Parenthesis) => "()",
         Some(tt::DelimiterKind::Brace) => "{}",
         Some(tt::DelimiterKind::Bracket) => "[]",
-        None => return "".into(),
+        None => return "",
     };
 
     let idx = closing as usize;
-    let text = &texts[idx..texts.len() - (1 - idx)];
-    text.into()
+    &texts[idx..texts.len() - (1 - idx)]
 }
 
 impl<'a> TreeSink for TtTreeSink<'a> {
@@ -626,29 +622,32 @@ impl<'a> TreeSink for TtTreeSink<'a> {
 
         let mut last = self.cursor;
         for _ in 0..n_tokens {
+            let tmp_str: SmolStr;
             if self.cursor.eof() {
                 break;
             }
             last = self.cursor;
-            let text: SmolStr = match self.cursor.token_tree() {
-                Some(tt::TokenTree::Leaf(leaf)) => {
+            let text: &str = match self.cursor.token_tree() {
+                Some(tt::buffer::TokenTreeRef::Leaf(leaf, _)) => {
                     // Mark the range if needed
                     let (text, id) = match leaf {
-                        tt::Leaf::Ident(ident) => (ident.text.clone(), ident.id),
+                        tt::Leaf::Ident(ident) => (&ident.text, ident.id),
                         tt::Leaf::Punct(punct) => {
                             assert!(punct.char.is_ascii());
                             let char = &(punct.char as u8);
-                            let text = std::str::from_utf8(std::slice::from_ref(char)).unwrap();
-                            (SmolStr::new_inline(text), punct.id)
+                            tmp_str = SmolStr::new_inline(
+                                std::str::from_utf8(std::slice::from_ref(char)).unwrap(),
+                            );
+                            (&tmp_str, punct.id)
                         }
-                        tt::Leaf::Literal(lit) => (lit.text.clone(), lit.id),
+                        tt::Leaf::Literal(lit) => (&lit.text, lit.id),
                     };
                     let range = TextRange::at(self.text_pos, TextSize::of(text.as_str()));
                     self.token_map.insert(id, range);
                     self.cursor = self.cursor.bump();
                     text
                 }
-                Some(tt::TokenTree::Subtree(subtree)) => {
+                Some(tt::buffer::TokenTreeRef::Subtree(subtree, _)) => {
                     self.cursor = self.cursor.subtree().unwrap();
                     if let Some(id) = subtree.delimiter.map(|it| it.id) {
                         self.open_delims.insert(id, self.text_pos);
@@ -672,7 +671,7 @@ impl<'a> TreeSink for TtTreeSink<'a> {
                 }
             };
             self.buf += &text;
-            self.text_pos += TextSize::of(text.as_str());
+            self.text_pos += TextSize::of(text);
         }
 
         let text = SmolStr::new(self.buf.as_str());
@@ -682,8 +681,8 @@ impl<'a> TreeSink for TtTreeSink<'a> {
         // Add whitespace between adjoint puncts
         let next = last.bump();
         if let (
-            Some(tt::TokenTree::Leaf(tt::Leaf::Punct(curr))),
-            Some(tt::TokenTree::Leaf(tt::Leaf::Punct(_))),
+            Some(tt::buffer::TokenTreeRef::Leaf(tt::Leaf::Punct(curr), _)),
+            Some(tt::buffer::TokenTreeRef::Leaf(tt::Leaf::Punct(_), _)),
         ) = (last.token_tree(), next.token_tree())
         {
             // Note: We always assume the semi-colon would be the last token in
@@ -742,7 +741,7 @@ mod tests {
         )
         .expand_tt("literals!(foo);");
         let tts = &[expansion.into()];
-        let buffer = tt::buffer::TokenBuffer::new(tts);
+        let buffer = tt::buffer::TokenBuffer::from_tokens(tts);
         let mut tt_src = SubtreeTokenSource::new(&buffer);
         let mut tokens = vec![];
         while tt_src.current().kind != EOF {
diff --git a/crates/parser/src/grammar.rs b/crates/parser/src/grammar.rs
index 63cc90027..bb9ffea8b 100644
--- a/crates/parser/src/grammar.rs
+++ b/crates/parser/src/grammar.rs
@@ -66,6 +66,10 @@ pub(crate) mod fragments {
         expressions::stmt(p, expressions::StmtWithSemi::No)
     }
 
+    pub(crate) fn stmt_optional_semi(p: &mut Parser) {
+        expressions::stmt(p, expressions::StmtWithSemi::Optional)
+    }
+
     pub(crate) fn opt_visibility(p: &mut Parser) {
         let _ = super::opt_visibility(p);
     }
diff --git a/crates/parser/src/lib.rs b/crates/parser/src/lib.rs
index 811e740f9..9dfe63028 100644
--- a/crates/parser/src/lib.rs
+++ b/crates/parser/src/lib.rs
@@ -88,6 +88,7 @@ pub enum FragmentKind {
     Path,
     Expr,
     Statement,
+    StatementOptionalSemi,
     Type,
     Pattern,
     Item,
@@ -118,6 +119,7 @@ pub fn parse_fragment(
         FragmentKind::Visibility => grammar::fragments::opt_visibility,
         FragmentKind::MetaItem => grammar::fragments::meta_item,
         FragmentKind::Statement => grammar::fragments::stmt,
+        FragmentKind::StatementOptionalSemi => grammar::fragments::stmt_optional_semi,
         FragmentKind::Items => grammar::fragments::macro_items,
         FragmentKind::Statements => grammar::fragments::macro_stmts,
         FragmentKind::Attr => grammar::fragments::attr,
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index 685a9fdf0..a5b1d90b1 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -777,9 +777,8 @@ fn manual(fields: &[(&'static str, &'static str, &[&str], &str)]) -> String {
     fields
         .iter()
         .map(|(field, _ty, doc, default)| {
-            let name = field.replace("_", ".");
-            let name = format!("rust-analyzer.{} (default: `{}`)", name, default);
-            format!("{}::\n{}\n", name, doc.join(" "))
+            let name = format!("rust-analyzer.{}", field.replace("_", "."));
+            format!("[[{}]]{} (default: `{}`)::\n{}\n", name, name, default, doc.join(" "))
         })
         .collect::<String>()
 }
diff --git a/crates/rust-analyzer/src/handlers.rs b/crates/rust-analyzer/src/handlers.rs
index dd486070b..c21ca044a 100644
--- a/crates/rust-analyzer/src/handlers.rs
+++ b/crates/rust-analyzer/src/handlers.rs
@@ -1648,7 +1648,7 @@ fn prepare_hover_actions(
     actions
         .iter()
         .filter_map(|it| match it {
-            HoverAction::Implementaion(position) => show_impl_command_link(snap, position),
+            HoverAction::Implementation(position) => show_impl_command_link(snap, position),
             HoverAction::Runnable(r) => runnable_action_links(snap, file_id, r.clone()),
             HoverAction::GoToType(targets) => goto_type_action_links(snap, targets),
         })
diff --git a/crates/ssr/src/parsing.rs b/crates/ssr/src/parsing.rs
index f3b084baf..3d5e4feb7 100644
--- a/crates/ssr/src/parsing.rs
+++ b/crates/ssr/src/parsing.rs
@@ -73,11 +73,18 @@ impl ParsedRule {
             placeholders_by_stand_in: pattern.placeholders_by_stand_in(),
             rules: Vec::new(),
         };
-        builder.try_add(ast::Expr::parse(&raw_pattern), raw_template.map(ast::Expr::parse));
+
+        let raw_template_stmt = raw_template.map(ast::Stmt::parse);
+        if let raw_template_expr @ Some(Ok(_)) = raw_template.map(ast::Expr::parse) {
+            builder.try_add(ast::Expr::parse(&raw_pattern), raw_template_expr);
+        } else {
+            builder.try_add(ast::Expr::parse(&raw_pattern), raw_template_stmt.clone());
+        }
         builder.try_add(ast::Type::parse(&raw_pattern), raw_template.map(ast::Type::parse));
         builder.try_add(ast::Item::parse(&raw_pattern), raw_template.map(ast::Item::parse));
         builder.try_add(ast::Path::parse(&raw_pattern), raw_template.map(ast::Path::parse));
         builder.try_add(ast::Pat::parse(&raw_pattern), raw_template.map(ast::Pat::parse));
+        builder.try_add(ast::Stmt::parse(&raw_pattern), raw_template_stmt);
         builder.build()
     }
 }
@@ -88,7 +95,11 @@ struct RuleBuilder {
 }
 
 impl RuleBuilder {
-    fn try_add<T: AstNode>(&mut self, pattern: Result<T, ()>, template: Option<Result<T, ()>>) {
+    fn try_add<T: AstNode, T2: AstNode>(
+        &mut self,
+        pattern: Result<T, ()>,
+        template: Option<Result<T2, ()>>,
+    ) {
         match (pattern, template) {
             (Ok(pattern), Some(Ok(template))) => self.rules.push(ParsedRule {
                 placeholders_by_stand_in: self.placeholders_by_stand_in.clone(),
diff --git a/crates/ssr/src/tests.rs b/crates/ssr/src/tests.rs
index 63131f6ca..db9cb8ca1 100644
--- a/crates/ssr/src/tests.rs
+++ b/crates/ssr/src/tests.rs
@@ -160,6 +160,97 @@ fn assert_match_failure_reason(pattern: &str, code: &str, snippet: &str, expecte
 }
 
 #[test]
+fn ssr_let_stmt_in_macro_match() {
+    assert_matches(
+        "let a = 0",
+        r#"
+            macro_rules! m1 { ($a:stmt) => {$a}; }
+            fn f() {m1!{ let a = 0 };}"#,
+        // FIXME: Whitespace is not part of the matched block
+        &["leta=0"],
+    );
+}
+
+#[test]
+fn ssr_let_stmt_in_fn_match() {
+    assert_matches("let $a = 10;", "fn main() { let x = 10; x }", &["let x = 10;"]);
+    assert_matches("let $a = $b;", "fn main() { let x = 10; x }", &["let x = 10;"]);
+}
+
+#[test]
+fn ssr_block_expr_match() {
+    assert_matches("{ let $a = $b; }", "fn main() { let x = 10; }", &["{ let x = 10; }"]);
+    assert_matches("{ let $a = $b; $c }", "fn main() { let x = 10; x }", &["{ let x = 10; x }"]);
+}
+
+#[test]
+fn ssr_let_stmt_replace() {
+    // Pattern and template with trailing semicolon
+    assert_ssr_transform(
+        "let $a = $b; ==>> let $a = 11;",
+        "fn main() { let x = 10; x }",
+        expect![["fn main() { let x = 11; x }"]],
+    );
+}
+
+#[test]
+fn ssr_let_stmt_replace_expr() {
+    // Trailing semicolon should be dropped from the new expression
+    assert_ssr_transform(
+        "let $a = $b; ==>> $b",
+        "fn main() { let x = 10; }",
+        expect![["fn main() { 10 }"]],
+    );
+}
+
+#[test]
+fn ssr_blockexpr_replace_stmt_with_stmt() {
+    assert_ssr_transform(
+        "if $a() {$b;} ==>> $b;",
+        "{
+    if foo() {
+        bar();
+    }
+    Ok(())
+}",
+        expect![[r#"{
+    bar();
+    Ok(())
+}"#]],
+    );
+}
+
+#[test]
+fn ssr_blockexpr_match_trailing_expr() {
+    assert_matches(
+        "if $a() {$b;}",
+        "{
+    if foo() {
+        bar();
+    }
+}",
+        &["if foo() {
+        bar();
+    }"],
+    );
+}
+
+#[test]
+fn ssr_blockexpr_replace_trailing_expr_with_stmt() {
+    assert_ssr_transform(
+        "if $a() {$b;} ==>> $b;",
+        "{
+    if foo() {
+        bar();
+    }
+}",
+        expect![["{
+    bar();
+}"]],
+    );
+}
+
+#[test]
 fn ssr_function_to_method() {
     assert_ssr_transform(
         "my_function($a, $b) ==>> ($a).my_method($b)",
diff --git a/crates/syntax/Cargo.toml b/crates/syntax/Cargo.toml
index 181077944..cfeaed9e6 100644
--- a/crates/syntax/Cargo.toml
+++ b/crates/syntax/Cargo.toml
@@ -13,7 +13,7 @@ doctest = false
 [dependencies]
 itertools = "0.10.0"
 rowan = "0.10.0"
-rustc_lexer = { version = "695.0.0", package = "rustc-ap-rustc_lexer" }
+rustc_lexer = { version = "697.0.0", package = "rustc-ap-rustc_lexer" }
 rustc-hash = "1.1.0"
 arrayvec = "0.5.1"
 once_cell = "1.3.1"
diff --git a/crates/syntax/src/lib.rs b/crates/syntax/src/lib.rs
index 4d272f367..da151e328 100644
--- a/crates/syntax/src/lib.rs
+++ b/crates/syntax/src/lib.rs
@@ -212,6 +212,13 @@ impl ast::Attr {
     }
 }
 
+impl ast::Stmt {
+    /// Returns `text`, parsed as statement, but only if it has no errors.
+    pub fn parse(text: &str) -> Result<Self, ()> {
+        parsing::parse_text_fragment(text, parser::FragmentKind::StatementOptionalSemi)
+    }
+}
+
 /// Matches a `SyntaxNode` against an `ast` type.
 ///
 /// # Example:
diff --git a/crates/syntax/src/tests.rs b/crates/syntax/src/tests.rs
index 8c217dfe0..9d3433c9d 100644
--- a/crates/syntax/src/tests.rs
+++ b/crates/syntax/src/tests.rs
@@ -103,6 +103,15 @@ fn type_parser_tests() {
 }
 
 #[test]
+fn stmt_parser_tests() {
+    fragment_parser_dir_test(
+        &["parser/fragments/stmt/ok"],
+        &["parser/fragments/stmt/err"],
+        crate::ast::Stmt::parse,
+    );
+}
+
+#[test]
 fn parser_fuzz_tests() {
     for (_, text) in collect_rust_files(&test_data_dir(), &["parser/fuzz-failures"]) {
         fuzz::check_parser(&text)
diff --git a/crates/syntax/test_data/parser/fragments/stmt/err/0000_attr.rast b/crates/syntax/test_data/parser/fragments/stmt/err/0000_attr.rast
new file mode 100644
index 000000000..5df7507e2
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/err/0000_attr.rast
@@ -0,0 +1 @@
+ERROR
diff --git a/crates/syntax/test_data/parser/fragments/stmt/err/0000_attr.rs b/crates/syntax/test_data/parser/fragments/stmt/err/0000_attr.rs
new file mode 100644
index 000000000..988df0705
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/err/0000_attr.rs
@@ -0,0 +1 @@
+#[foo]
diff --git a/crates/syntax/test_data/parser/fragments/stmt/err/0000_multiple_stmts.rast b/crates/syntax/test_data/parser/fragments/stmt/err/0000_multiple_stmts.rast
new file mode 100644
index 000000000..5df7507e2
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/err/0000_multiple_stmts.rast
@@ -0,0 +1 @@
+ERROR
diff --git a/crates/syntax/test_data/parser/fragments/stmt/err/0000_multiple_stmts.rs b/crates/syntax/test_data/parser/fragments/stmt/err/0000_multiple_stmts.rs
new file mode 100644
index 000000000..7e3b2fd49
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/err/0000_multiple_stmts.rs
@@ -0,0 +1 @@
+a(); b(); c()
diff --git a/crates/syntax/test_data/parser/fragments/stmt/err/0000_open_parenthesis.rast b/crates/syntax/test_data/parser/fragments/stmt/err/0000_open_parenthesis.rast
new file mode 100644
index 000000000..5df7507e2
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/err/0000_open_parenthesis.rast
@@ -0,0 +1 @@
+ERROR
diff --git a/crates/syntax/test_data/parser/fragments/stmt/err/0000_open_parenthesis.rs b/crates/syntax/test_data/parser/fragments/stmt/err/0000_open_parenthesis.rs
new file mode 100644
index 000000000..2d06f3766
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/err/0000_open_parenthesis.rs
@@ -0,0 +1 @@
+(
diff --git a/crates/syntax/test_data/parser/fragments/stmt/err/0000_semicolon.rast b/crates/syntax/test_data/parser/fragments/stmt/err/0000_semicolon.rast
new file mode 100644
index 000000000..5df7507e2
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/err/0000_semicolon.rast
@@ -0,0 +1 @@
+ERROR
diff --git a/crates/syntax/test_data/parser/fragments/stmt/err/0000_semicolon.rs b/crates/syntax/test_data/parser/fragments/stmt/err/0000_semicolon.rs
new file mode 100644
index 000000000..092bc2b04
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/err/0000_semicolon.rs
@@ -0,0 +1 @@
+;
diff --git a/crates/syntax/test_data/parser/fragments/stmt/err/0000_unterminated_expr.rast b/crates/syntax/test_data/parser/fragments/stmt/err/0000_unterminated_expr.rast
new file mode 100644
index 000000000..5df7507e2
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/err/0000_unterminated_expr.rast
@@ -0,0 +1 @@
+ERROR
diff --git a/crates/syntax/test_data/parser/fragments/stmt/err/0000_unterminated_expr.rs b/crates/syntax/test_data/parser/fragments/stmt/err/0000_unterminated_expr.rs
new file mode 100644
index 000000000..ca49acb07
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/err/0000_unterminated_expr.rs
@@ -0,0 +1 @@
+1 +
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_expr.rast b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_expr.rast
new file mode 100644
index 000000000..274fdf16d
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_expr.rast
@@ -0,0 +1,9 @@
+[email protected]
+  [email protected]
+    [email protected]
+      [email protected] "1"
+    [email protected] " "
+    [email protected] "+"
+    [email protected] " "
+    [email protected]
+      [email protected] "1"
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_expr.rs b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_expr.rs
new file mode 100644
index 000000000..8d2f0971e
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_expr.rs
@@ -0,0 +1 @@
+1 + 1
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_expr_block.rast b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_expr_block.rast
new file mode 100644
index 000000000..6c946091f
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_expr_block.rast
@@ -0,0 +1,69 @@
+[email protected]
+  [email protected]
+    [email protected] "{"
+    [email protected] "\n    "
+    [email protected]
+      [email protected] "let"
+      [email protected] " "
+      [email protected]
+        [email protected]
+          [email protected] "x"
+      [email protected] " "
+      [email protected] "="
+      [email protected] " "
+      [email protected]
+        [email protected]
+          [email protected]
+            [email protected]
+              [email protected]
+                [email protected] "foo"
+        [email protected]
+          [email protected] "("
+          [email protected] ")"
+      [email protected] ";"
+    [email protected] "\n    "
+    [email protected]
+      [email protected] "let"
+      [email protected] " "
+      [email protected]
+        [email protected]
+          [email protected] "y"
+      [email protected] " "
+      [email protected] "="
+      [email protected] " "
+      [email protected]
+        [email protected]
+          [email protected]
+            [email protected]
+              [email protected]
+                [email protected] "bar"
+        [email protected]
+          [email protected] "("
+          [email protected] ")"
+      [email protected] ";"
+    [email protected] "\n    "
+    [email protected]
+      [email protected]
+        [email protected]
+          [email protected]
+            [email protected]
+              [email protected] "Ok"
+      [email protected]
+        [email protected] "("
+        [email protected]
+          [email protected]
+            [email protected]
+              [email protected]
+                [email protected]
+                  [email protected] "x"
+          [email protected] " "
+          [email protected] "+"
+          [email protected] " "
+          [email protected]
+            [email protected]
+              [email protected]
+                [email protected]
+                  [email protected] "y"
+        [email protected] ")"
+    [email protected] "\n"
+    [email protected] "}"
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_expr_block.rs b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_expr_block.rs
new file mode 100644
index 000000000..ffa5c1e66
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_expr_block.rs
@@ -0,0 +1,5 @@
+{
+    let x = foo();
+    let y = bar();
+    Ok(x + y)
+}
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_fn_call.rast b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_fn_call.rast
new file mode 100644
index 000000000..8c186da93
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_fn_call.rast
@@ -0,0 +1,11 @@
+[email protected]
+  [email protected]
+    [email protected]
+      [email protected]
+        [email protected]
+          [email protected]
+            [email protected] "foo"
+    [email protected]
+      [email protected] "("
+      [email protected] ")"
+  [email protected] ";"
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_fn_call.rs b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_fn_call.rs
new file mode 100644
index 000000000..a280f9a5c
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_fn_call.rs
@@ -0,0 +1 @@
+foo();
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_let_stmt.rast b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_let_stmt.rast
new file mode 100644
index 000000000..8ab38da21
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_let_stmt.rast
@@ -0,0 +1,12 @@
+[email protected]
+  [email protected] "let"
+  [email protected] " "
+  [email protected]
+    [email protected]
+      [email protected] "x"
+  [email protected] " "
+  [email protected] "="
+  [email protected] " "
+  [email protected]
+    [email protected] "10"
+  [email protected] ";"
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_let_stmt.rs b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_let_stmt.rs
new file mode 100644
index 000000000..de8a7f1fc
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_let_stmt.rs
@@ -0,0 +1 @@
+let x = 10;
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_macro_let_stmt.rast b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_macro_let_stmt.rast
new file mode 100644
index 000000000..81d6df29a
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_macro_let_stmt.rast
@@ -0,0 +1,21 @@
+[email protected]
+  [email protected]
+    [email protected]
+      [email protected]
+        [email protected]
+          [email protected] "m1"
+    [email protected] "!"
+    [email protected]
+      [email protected] "{"
+      [email protected] " "
+      [email protected] "let"
+      [email protected] " "
+      [email protected] "a"
+      [email protected] " "
+      [email protected] "="
+      [email protected] " "
+      [email protected] "0"
+      [email protected] ";"
+      [email protected] " "
+      [email protected] "}"
+  [email protected] ";"
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_macro_let_stmt.rs b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_macro_let_stmt.rs
new file mode 100644
index 000000000..075f30159
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_macro_let_stmt.rs
@@ -0,0 +1 @@
+m1!{ let a = 0; };
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_macro_unterminated_let_stmt.rast b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_macro_unterminated_let_stmt.rast
new file mode 100644
index 000000000..81d6df29a
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_macro_unterminated_let_stmt.rast
@@ -0,0 +1,21 @@
+[email protected]
+  [email protected]
+    [email protected]
+      [email protected]
+        [email protected]
+          [email protected] "m1"
+    [email protected] "!"
+    [email protected]
+      [email protected] "{"
+      [email protected] " "
+      [email protected] "let"
+      [email protected] " "
+      [email protected] "a"
+      [email protected] " "
+      [email protected] "="
+      [email protected] " "
+      [email protected] "0"
+      [email protected] ";"
+      [email protected] " "
+      [email protected] "}"
+  [email protected] ";"
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_macro_unterminated_let_stmt.rs b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_macro_unterminated_let_stmt.rs
new file mode 100644
index 000000000..075f30159
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_macro_unterminated_let_stmt.rs
@@ -0,0 +1 @@
+m1!{ let a = 0; };
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_struct_item.rast b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_struct_item.rast
new file mode 100644
index 000000000..64c5d2969
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_struct_item.rast
@@ -0,0 +1,22 @@
+[email protected]
+  [email protected] "struct"
+  [email protected] " "
+  [email protected]
+    [email protected] "Foo"
+  [email protected] " "
+  [email protected]
+    [email protected] "{"
+    [email protected] "\n    "
+    [email protected]
+      [email protected]
+        [email protected] "bar"
+      [email protected] ":"
+      [email protected] " "
+      [email protected]
+        [email protected]
+          [email protected]
+            [email protected]
+              [email protected] "u32"
+    [email protected] ","
+    [email protected] "\n"
+    [email protected] "}"
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_struct_item.rs b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_struct_item.rs
new file mode 100644
index 000000000..e5473e3ac
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_struct_item.rs
@@ -0,0 +1,3 @@
+struct Foo {
+    bar: u32,
+}
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_unterminated_fn_call.rast b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_unterminated_fn_call.rast
new file mode 100644
index 000000000..9089906bc
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_unterminated_fn_call.rast
@@ -0,0 +1,10 @@
+[email protected]
+  [email protected]
+    [email protected]
+      [email protected]
+        [email protected]
+          [email protected]
+            [email protected] "foo"
+    [email protected]
+      [email protected] "("
+      [email protected] ")"
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_unterminated_fn_call.rs b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_unterminated_fn_call.rs
new file mode 100644
index 000000000..eb28ef440
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_unterminated_fn_call.rs
@@ -0,0 +1 @@
+foo()
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_unterminated_let_stmt.rast b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_unterminated_let_stmt.rast
new file mode 100644
index 000000000..37663671f
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_unterminated_let_stmt.rast
@@ -0,0 +1,11 @@
+[email protected]
+  [email protected] "let"
+  [email protected] " "
+  [email protected]
+    [email protected]
+      [email protected] "x"
+  [email protected] " "
+  [email protected] "="
+  [email protected] " "
+  [email protected]
+    [email protected] "10"
diff --git a/crates/syntax/test_data/parser/fragments/stmt/ok/0000_unterminated_let_stmt.rs b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_unterminated_let_stmt.rs
new file mode 100644
index 000000000..78364b2a9
--- /dev/null
+++ b/crates/syntax/test_data/parser/fragments/stmt/ok/0000_unterminated_let_stmt.rs
@@ -0,0 +1 @@
+let x = 10
diff --git a/crates/tt/src/buffer.rs b/crates/tt/src/buffer.rs
index 02c771f70..3606c887d 100644
--- a/crates/tt/src/buffer.rs
+++ b/crates/tt/src/buffer.rs
@@ -1,6 +1,6 @@
 //! FIXME: write short doc here
 
-use crate::{Subtree, TokenTree};
+use crate::{Leaf, Subtree, TokenTree};
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 struct EntryId(usize);
@@ -13,7 +13,7 @@ struct EntryPtr(EntryId, usize);
 #[derive(Debug)]
 enum Entry<'t> {
     // Mimicking types from proc-macro.
-    Subtree(&'t TokenTree, EntryId),
+    Subtree(Option<&'t TokenTree>, &'t Subtree, EntryId),
     Leaf(&'t TokenTree),
     // End entries contain a pointer to the entry from the containing
     // token tree, or None if this is the outermost level.
@@ -27,37 +27,64 @@ pub struct TokenBuffer<'t> {
     buffers: Vec<Box<[Entry<'t>]>>,
 }
 
-impl<'t> TokenBuffer<'t> {
-    pub fn new(tokens: &'t [TokenTree]) -> TokenBuffer<'t> {
-        let mut buffers = vec![];
-
-        let idx = TokenBuffer::new_inner(tokens, &mut buffers, None);
-        assert_eq!(idx, 0);
-
-        TokenBuffer { buffers }
-    }
+trait TokenList<'a> {
+    fn entries(&self) -> (Vec<(usize, (&'a Subtree, Option<&'a TokenTree>))>, Vec<Entry<'a>>);
+}
 
-    fn new_inner(
-        tokens: &'t [TokenTree],
-        buffers: &mut Vec<Box<[Entry<'t>]>>,
-        next: Option<EntryPtr>,
-    ) -> usize {
+impl<'a> TokenList<'a> for &'a [TokenTree] {
+    fn entries(&self) -> (Vec<(usize, (&'a Subtree, Option<&'a TokenTree>))>, Vec<Entry<'a>>) {
         // Must contain everything in tokens and then the Entry::End
-        let start_capacity = tokens.len() + 1;
+        let start_capacity = self.len() + 1;
         let mut entries = Vec::with_capacity(start_capacity);
         let mut children = vec![];
-
-        for (idx, tt) in tokens.iter().enumerate() {
+        for (idx, tt) in self.iter().enumerate() {
             match tt {
                 TokenTree::Leaf(_) => {
                     entries.push(Entry::Leaf(tt));
                 }
                 TokenTree::Subtree(subtree) => {
                     entries.push(Entry::End(None));
-                    children.push((idx, (subtree, tt)));
+                    children.push((idx, (subtree, Some(tt))));
                 }
             }
         }
+        (children, entries)
+    }
+}
+
+impl<'a> TokenList<'a> for &'a Subtree {
+    fn entries(&self) -> (Vec<(usize, (&'a Subtree, Option<&'a TokenTree>))>, Vec<Entry<'a>>) {
+        // Must contain everything in tokens and then the Entry::End
+        let mut entries = vec![];
+        let mut children = vec![];
+        entries.push(Entry::End(None));
+        children.push((0usize, (*self, None)));
+        (children, entries)
+    }
+}
+
+impl<'t> TokenBuffer<'t> {
+    pub fn from_tokens(tokens: &'t [TokenTree]) -> TokenBuffer<'t> {
+        Self::new(tokens)
+    }
+
+    pub fn from_subtree(subtree: &'t Subtree) -> TokenBuffer<'t> {
+        Self::new(subtree)
+    }
+
+    fn new<T: TokenList<'t>>(tokens: T) -> TokenBuffer<'t> {
+        let mut buffers = vec![];
+        let idx = TokenBuffer::new_inner(tokens, &mut buffers, None);
+        assert_eq!(idx, 0);
+        TokenBuffer { buffers }
+    }
+
+    fn new_inner<T: TokenList<'t>>(
+        tokens: T,
+        buffers: &mut Vec<Box<[Entry<'t>]>>,
+        next: Option<EntryPtr>,
+    ) -> usize {
+        let (children, mut entries) = tokens.entries();
 
         entries.push(Entry::End(next));
         let res = buffers.len();
@@ -65,11 +92,11 @@ impl<'t> TokenBuffer<'t> {
 
         for (child_idx, (subtree, tt)) in children {
             let idx = TokenBuffer::new_inner(
-                &subtree.token_trees,
+                subtree.token_trees.as_slice(),
                 buffers,
                 Some(EntryPtr(EntryId(res), child_idx + 1)),
             );
-            buffers[res].as_mut()[child_idx] = Entry::Subtree(tt, EntryId(idx));
+            buffers[res].as_mut()[child_idx] = Entry::Subtree(tt, subtree, EntryId(idx));
         }
 
         res
@@ -87,6 +114,24 @@ impl<'t> TokenBuffer<'t> {
     }
 }
 
+#[derive(Debug)]
+pub enum TokenTreeRef<'a> {
+    Subtree(&'a Subtree, Option<&'a TokenTree>),
+    Leaf(&'a Leaf, &'a TokenTree),
+}
+
+impl<'a> TokenTreeRef<'a> {
+    pub fn cloned(&self) -> TokenTree {
+        match &self {
+            TokenTreeRef::Subtree(subtree, tt) => match tt {
+                Some(it) => (*it).clone(),
+                None => (*subtree).clone().into(),
+            },
+            TokenTreeRef::Leaf(_, tt) => (*tt).clone(),
+        }
+    }
+}
+
 /// A safe version of `Cursor` from `syn` crate https://github.com/dtolnay/syn/blob/6533607f91686545cb034d2838beea338d9d0742/src/buffer.rs#L125
 #[derive(Copy, Clone, Debug)]
 pub struct Cursor<'a> {
@@ -114,12 +159,11 @@ impl<'a> Cursor<'a> {
         match self.entry() {
             Some(Entry::End(Some(ptr))) => {
                 let idx = ptr.1;
-                if let Some(Entry::Subtree(TokenTree::Subtree(subtree), _)) =
+                if let Some(Entry::Subtree(_, subtree, _)) =
                     self.buffer.entry(&EntryPtr(ptr.0, idx - 1))
                 {
                     return Some(subtree);
                 }
-
                 None
             }
             _ => None,
@@ -134,7 +178,7 @@ impl<'a> Cursor<'a> {
     /// a cursor into that subtree
     pub fn subtree(self) -> Option<Cursor<'a>> {
         match self.entry() {
-            Some(Entry::Subtree(_, entry_id)) => {
+            Some(Entry::Subtree(_, _, entry_id)) => {
                 Some(Cursor::create(self.buffer, EntryPtr(*entry_id, 0)))
             }
             _ => None,
@@ -142,10 +186,13 @@ impl<'a> Cursor<'a> {
     }
 
     /// If the cursor is pointing at a `TokenTree`, returns it
-    pub fn token_tree(self) -> Option<&'a TokenTree> {
+    pub fn token_tree(self) -> Option<TokenTreeRef<'a>> {
         match self.entry() {
-            Some(Entry::Leaf(tt)) => Some(tt),
-            Some(Entry::Subtree(tt, _)) => Some(tt),
+            Some(Entry::Leaf(tt)) => match tt {
+                TokenTree::Leaf(leaf) => Some(TokenTreeRef::Leaf(leaf, *tt)),
+                TokenTree::Subtree(subtree) => Some(TokenTreeRef::Subtree(subtree, Some(tt))),
+            },
+            Some(Entry::Subtree(tt, subtree, _)) => Some(TokenTreeRef::Subtree(subtree, *tt)),
             Some(Entry::End(_)) => None,
             None => None,
         }
@@ -172,7 +219,7 @@ impl<'a> Cursor<'a> {
     /// a cursor into that subtree
     pub fn bump_subtree(self) -> Cursor<'a> {
         match self.entry() {
-            Some(Entry::Subtree(_, _)) => self.subtree().unwrap(),
+            Some(Entry::Subtree(_, _, _)) => self.subtree().unwrap(),
             _ => self.bump(),
         }
     }