3 files changed, 185 insertions, 23 deletions

diff --git a/crates/syntax/src/ast/edit_in_place.rs b/crates/syntax/src/ast/edit_in_place.rs
index 529bd0eb1..04f97f368 100644
--- a/crates/syntax/src/ast/edit_in_place.rs
+++ b/crates/syntax/src/ast/edit_in_place.rs
@@ -14,10 +14,29 @@ use crate::{
 use super::NameOwner;
 
 pub trait GenericParamsOwnerEdit: ast::GenericParamsOwner + AstNodeEdit {
+    fn get_or_create_generic_param_list(&self) -> ast::GenericParamList;
     fn get_or_create_where_clause(&self) -> ast::WhereClause;
 }
 
 impl GenericParamsOwnerEdit for ast::Fn {
+    fn get_or_create_generic_param_list(&self) -> ast::GenericParamList {
+        match self.generic_param_list() {
+            Some(it) => it,
+            None => {
+                let position = if let Some(name) = self.name() {
+                    Position::after(name.syntax)
+                } else if let Some(fn_token) = self.fn_token() {
+                    Position::after(fn_token)
+                } else if let Some(param_list) = self.param_list() {
+                    Position::before(param_list.syntax)
+                } else {
+                    Position::last_child_of(self.syntax())
+                };
+                create_generic_param_list(position)
+            }
+        }
+    }
+
     fn get_or_create_where_clause(&self) -> WhereClause {
         if self.where_clause().is_none() {
             let position = if let Some(ty) = self.ret_type() {
@@ -34,6 +53,20 @@ impl GenericParamsOwnerEdit for ast::Fn {
 }
 
 impl GenericParamsOwnerEdit for ast::Impl {
+    fn get_or_create_generic_param_list(&self) -> ast::GenericParamList {
+        match self.generic_param_list() {
+            Some(it) => it,
+            None => {
+                let position = if let Some(imp_token) = self.impl_token() {
+                    Position::after(imp_token)
+                } else {
+                    Position::last_child_of(self.syntax())
+                };
+                create_generic_param_list(position)
+            }
+        }
+    }
+
     fn get_or_create_where_clause(&self) -> WhereClause {
         if self.where_clause().is_none() {
             let position = if let Some(items) = self.assoc_item_list() {
@@ -48,6 +81,22 @@ impl GenericParamsOwnerEdit for ast::Impl {
 }
 
 impl GenericParamsOwnerEdit for ast::Trait {
+    fn get_or_create_generic_param_list(&self) -> ast::GenericParamList {
+        match self.generic_param_list() {
+            Some(it) => it,
+            None => {
+                let position = if let Some(name) = self.name() {
+                    Position::after(name.syntax)
+                } else if let Some(trait_token) = self.trait_token() {
+                    Position::after(trait_token)
+                } else {
+                    Position::last_child_of(self.syntax())
+                };
+                create_generic_param_list(position)
+            }
+        }
+    }
+
     fn get_or_create_where_clause(&self) -> WhereClause {
         if self.where_clause().is_none() {
             let position = if let Some(items) = self.assoc_item_list() {
@@ -62,6 +111,22 @@ impl GenericParamsOwnerEdit for ast::Trait {
 }
 
 impl GenericParamsOwnerEdit for ast::Struct {
+    fn get_or_create_generic_param_list(&self) -> ast::GenericParamList {
+        match self.generic_param_list() {
+            Some(it) => it,
+            None => {
+                let position = if let Some(name) = self.name() {
+                    Position::after(name.syntax)
+                } else if let Some(struct_token) = self.struct_token() {
+                    Position::after(struct_token)
+                } else {
+                    Position::last_child_of(self.syntax())
+                };
+                create_generic_param_list(position)
+            }
+        }
+    }
+
     fn get_or_create_where_clause(&self) -> WhereClause {
         if self.where_clause().is_none() {
             let tfl = self.field_list().and_then(|fl| match fl {
@@ -84,6 +149,22 @@ impl GenericParamsOwnerEdit for ast::Struct {
 }
 
 impl GenericParamsOwnerEdit for ast::Enum {
+    fn get_or_create_generic_param_list(&self) -> ast::GenericParamList {
+        match self.generic_param_list() {
+            Some(it) => it,
+            None => {
+                let position = if let Some(name) = self.name() {
+                    Position::after(name.syntax)
+                } else if let Some(enum_token) = self.enum_token() {
+                    Position::after(enum_token)
+                } else {
+                    Position::last_child_of(self.syntax())
+                };
+                create_generic_param_list(position)
+            }
+        }
+    }
+
     fn get_or_create_where_clause(&self) -> WhereClause {
         if self.where_clause().is_none() {
             let position = if let Some(gpl) = self.generic_param_list() {
@@ -104,6 +185,37 @@ fn create_where_clause(position: Position) {
     ted::insert(position, where_clause.syntax());
 }
 
+fn create_generic_param_list(position: Position) -> ast::GenericParamList {
+    let gpl = make::generic_param_list(empty()).clone_for_update();
+    ted::insert_raw(position, gpl.syntax());
+    gpl
+}
+
+impl ast::GenericParamList {
+    pub fn add_generic_param(&self, generic_param: ast::GenericParam) {
+        match self.generic_params().last() {
+            Some(last_param) => {
+                let mut elems = Vec::new();
+                if !last_param
+                    .syntax()
+                    .siblings_with_tokens(Direction::Next)
+                    .any(|it| it.kind() == T![,])
+                {
+                    elems.push(make::token(T![,]).into());
+                    elems.push(make::tokens::single_space().into());
+                };
+                elems.push(generic_param.syntax().clone().into());
+                let after_last_param = Position::after(last_param.syntax());
+                ted::insert_all(after_last_param, elems);
+            }
+            None => {
+                let after_l_angle = Position::after(self.l_angle_token().unwrap());
+                ted::insert(after_l_angle, generic_param.syntax())
+            }
+        }
+    }
+}
+
 impl ast::WhereClause {
     pub fn add_predicate(&self, predicate: ast::WherePred) {
         if let Some(pred) = self.predicates().last() {
@@ -164,3 +276,44 @@ impl ast::Use {
         ted::remove(self.syntax())
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::fmt;
+
+    use crate::SourceFile;
+
+    use super::*;
+
+    fn ast_mut_from_text<N: AstNode>(text: &str) -> N {
+        let parse = SourceFile::parse(text);
+        parse.tree().syntax().descendants().find_map(N::cast).unwrap().clone_for_update()
+    }
+
+    #[test]
+    fn test_create_generic_param_list() {
+        fn check_create_gpl<N: GenericParamsOwnerEdit + fmt::Display>(before: &str, after: &str) {
+            let gpl_owner = ast_mut_from_text::<N>(before);
+            gpl_owner.get_or_create_generic_param_list();
+            assert_eq!(gpl_owner.to_string(), after);
+        }
+
+        check_create_gpl::<ast::Fn>("fn foo", "fn foo<>");
+        check_create_gpl::<ast::Fn>("fn foo() {}", "fn foo<>() {}");
+
+        check_create_gpl::<ast::Impl>("impl", "impl<>");
+        check_create_gpl::<ast::Impl>("impl Struct {}", "impl<> Struct {}");
+        check_create_gpl::<ast::Impl>("impl Trait for Struct {}", "impl<> Trait for Struct {}");
+
+        check_create_gpl::<ast::Trait>("trait Trait<>", "trait Trait<>");
+        check_create_gpl::<ast::Trait>("trait Trait<> {}", "trait Trait<> {}");
+
+        check_create_gpl::<ast::Struct>("struct A", "struct A<>");
+        check_create_gpl::<ast::Struct>("struct A;", "struct A<>;");
+        check_create_gpl::<ast::Struct>("struct A();", "struct A<>();");
+        check_create_gpl::<ast::Struct>("struct A {}", "struct A<> {}");
+
+        check_create_gpl::<ast::Enum>("enum E", "enum E<>");
+        check_create_gpl::<ast::Enum>("enum E {", "enum E<> {");
+    }
+}
diff --git a/crates/syntax/src/ted.rs b/crates/syntax/src/ted.rs
index 177d4ff67..450f2e447 100644
--- a/crates/syntax/src/ted.rs
+++ b/crates/syntax/src/ted.rs
@@ -165,6 +165,13 @@ fn ws_between(left: &SyntaxElement, right: &SyntaxElement) -> Option<SyntaxToken
     if right.kind() == T![;] || right.kind() == T![,] {
         return None;
     }
+    if left.kind() == T![<] || right.kind() == T![>] {
+        return None;
+    }
+    if left.kind() == T![&] && right.kind() == SyntaxKind::LIFETIME {
+        return None;
+    }
+
     if right.kind() == SyntaxKind::USE {
         let indent = IndentLevel::from_element(left);
         return Some(make::tokens::whitespace(&format!("\n{}", indent)));
diff --git a/crates/syntax/test_data/parser/inline/ok/0117_macro_call_type.rast b/crates/syntax/test_data/parser/inline/ok/0117_macro_call_type.rast
index 3016a6574..1ff3f7656 100644
--- a/crates/syntax/test_data/parser/inline/ok/0117_macro_call_type.rast
+++ b/crates/syntax/test_data/parser/inline/ok/0117_macro_call_type.rast
@@ -7,15 +7,16 @@ [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]
+      [email protected]
+        [email protected]
+          [email protected]
+            [email protected]
+              [email protected] "foo"
+        [email protected] "!"
+        [email protected]
+          [email protected] "("
+          [email protected] ")"
     [email protected] ";"
   [email protected] "\n"
   [email protected]
@@ -26,19 +27,20 @@ [email protected]
     [email protected] " "
     [email protected] "="
     [email protected] " "
-    [email protected]
-      [email protected]
-        [email protected]
-          [email protected]
-            [email protected]
-              [email protected] "crate"
-        [email protected] "::"
-        [email protected]
-          [email protected]
-            [email protected] "foo"
-      [email protected] "!"
-      [email protected]
-        [email protected] "("
-        [email protected] ")"
+    [email protected]
+      [email protected]
+        [email protected]
+          [email protected]
+            [email protected]
+              [email protected]
+                [email protected] "crate"
+          [email protected] "::"
+          [email protected]
+            [email protected]
+              [email protected] "foo"
+        [email protected] "!"
+        [email protected]
+          [email protected] "("
+          [email protected] ")"
     [email protected] ";"
   [email protected] "\n"