22 files changed, 297 insertions, 91 deletions

diff --git a/crates/ra_assists/src/assist_ctx.rs b/crates/ra_assists/src/assist_ctx.rs
index c3e653299..2fe7c3de3 100644
--- a/crates/ra_assists/src/assist_ctx.rs
+++ b/crates/ra_assists/src/assist_ctx.rs
@@ -5,12 +5,12 @@ use ra_fmt::{leading_indent, reindent};
 use ra_ide_db::RootDatabase;
 use ra_syntax::{
     algo::{self, find_covering_element, find_node_at_offset},
-    AstNode, SourceFile, SyntaxElement, SyntaxKind, SyntaxNode, SyntaxToken, TextRange, TextUnit,
+    AstNode, SourceFile, SyntaxElement, SyntaxKind, SyntaxNode, SyntaxToken, TextRange, TextSize,
     TokenAtOffset,
 };
 use ra_text_edit::TextEditBuilder;
 
-use crate::{AssistAction, AssistId, AssistLabel, GroupLabel, ResolvedAssist};
+use crate::{AssistAction, AssistFile, AssistId, AssistLabel, GroupLabel, ResolvedAssist};
 use algo::SyntaxRewriter;
 
 #[derive(Clone, Debug)]
@@ -178,8 +178,9 @@ impl<'a> AssistGroup<'a> {
 #[derive(Default)]
 pub(crate) struct ActionBuilder {
     edit: TextEditBuilder,
-    cursor_position: Option<TextUnit>,
+    cursor_position: Option<TextSize>,
     target: Option<TextRange>,
+    file: AssistFile,
 }
 
 impl ActionBuilder {
@@ -210,12 +211,12 @@ impl ActionBuilder {
     }
 
     /// Append specified `text` at the given `offset`
-    pub(crate) fn insert(&mut self, offset: TextUnit, text: impl Into<String>) {
+    pub(crate) fn insert(&mut self, offset: TextSize, text: impl Into<String>) {
         self.edit.insert(offset, text.into())
     }
 
     /// Specify desired position of the cursor after the assist is applied.
-    pub(crate) fn set_cursor(&mut self, offset: TextUnit) {
+    pub(crate) fn set_cursor(&mut self, offset: TextSize) {
         self.cursor_position = Some(offset)
     }
 
@@ -241,11 +242,16 @@ impl ActionBuilder {
         algo::diff(&node, &new).into_text_edit(&mut self.edit)
     }
 
+    pub(crate) fn set_file(&mut self, assist_file: AssistFile) {
+        self.file = assist_file
+    }
+
     fn build(self) -> AssistAction {
         AssistAction {
             edit: self.edit.finish(),
             cursor_position: self.cursor_position,
             target: self.target,
+            file: self.file,
         }
     }
 }
diff --git a/crates/ra_assists/src/doc_tests/generated.rs b/crates/ra_assists/src/doc_tests/generated.rs
index b39e60870..e4fa9ee36 100644
--- a/crates/ra_assists/src/doc_tests/generated.rs
+++ b/crates/ra_assists/src/doc_tests/generated.rs
@@ -66,7 +66,7 @@ fn doctest_add_function() {
 struct Baz;
 fn baz() -> Baz { Baz }
 fn foo() {
-     bar<|>("", baz());
+    bar<|>("", baz());
 }
 
 "#####,
@@ -74,7 +74,7 @@ fn foo() {
 struct Baz;
 fn baz() -> Baz { Baz }
 fn foo() {
-     bar("", baz());
+    bar("", baz());
 }
 
 fn bar(arg: &str, baz: Baz) {
diff --git a/crates/ra_assists/src/handlers/add_custom_impl.rs b/crates/ra_assists/src/handlers/add_custom_impl.rs
index 15f9b216b..4ea26a550 100644
--- a/crates/ra_assists/src/handlers/add_custom_impl.rs
+++ b/crates/ra_assists/src/handlers/add_custom_impl.rs
@@ -2,7 +2,7 @@ use ra_syntax::{
     ast::{self, AstNode},
     Direction, SmolStr,
     SyntaxKind::{IDENT, WHITESPACE},
-    TextRange, TextUnit,
+    TextRange, TextSize,
 };
 use stdx::SepBy;
 
@@ -60,7 +60,6 @@ pub(crate) fn add_custom_impl(ctx: AssistCtx) -> Option<Assist> {
             .collect::<Vec<SmolStr>>();
         let has_more_derives = !new_attr_input.is_empty();
         let new_attr_input = new_attr_input.iter().sep_by(", ").surround_with("(", ")").to_string();
-        let new_attr_input_len = new_attr_input.len();
 
         let mut buf = String::new();
         buf.push_str("\n\nimpl ");
@@ -70,8 +69,9 @@ pub(crate) fn add_custom_impl(ctx: AssistCtx) -> Option<Assist> {
         buf.push_str(" {\n");
 
         let cursor_delta = if has_more_derives {
+            let delta = input.syntax().text_range().len() - TextSize::of(&new_attr_input);
             edit.replace(input.syntax().text_range(), new_attr_input);
-            input.syntax().text_range().len() - TextUnit::from_usize(new_attr_input_len)
+            delta
         } else {
             let attr_range = attr.syntax().text_range();
             edit.delete(attr_range);
@@ -81,13 +81,13 @@ pub(crate) fn add_custom_impl(ctx: AssistCtx) -> Option<Assist> {
                 .next_sibling_or_token()
                 .filter(|t| t.kind() == WHITESPACE)
                 .map(|t| t.text_range())
-                .unwrap_or_else(|| TextRange::from_to(TextUnit::from(0), TextUnit::from(0)));
+                .unwrap_or_else(|| TextRange::new(TextSize::from(0), TextSize::from(0)));
             edit.delete(line_break_range);
 
             attr_range.len() + line_break_range.len()
         };
 
-        edit.set_cursor(start_offset + TextUnit::of_str(&buf) - cursor_delta);
+        edit.set_cursor(start_offset + TextSize::of(&buf) - cursor_delta);
         buf.push_str("\n}");
         edit.insert(start_offset, buf);
     })
diff --git a/crates/ra_assists/src/handlers/add_derive.rs b/crates/ra_assists/src/handlers/add_derive.rs
index b0d1a0a80..6254eb7c4 100644
--- a/crates/ra_assists/src/handlers/add_derive.rs
+++ b/crates/ra_assists/src/handlers/add_derive.rs
@@ -1,7 +1,7 @@
 use ra_syntax::{
     ast::{self, AstNode, AttrsOwner},
     SyntaxKind::{COMMENT, WHITESPACE},
-    TextUnit,
+    TextSize,
 };
 
 use crate::{Assist, AssistCtx, AssistId};
@@ -37,9 +37,9 @@ pub(crate) fn add_derive(ctx: AssistCtx) -> Option<Assist> {
         let offset = match derive_attr {
             None => {
                 edit.insert(node_start, "#[derive()]\n");
-                node_start + TextUnit::of_str("#[derive(")
+                node_start + TextSize::of("#[derive(")
             }
-            Some(tt) => tt.syntax().text_range().end() - TextUnit::of_char(')'),
+            Some(tt) => tt.syntax().text_range().end() - TextSize::of(')'),
         };
         edit.target(nominal.syntax().text_range());
         edit.set_cursor(offset)
@@ -47,7 +47,7 @@ pub(crate) fn add_derive(ctx: AssistCtx) -> Option<Assist> {
 }
 
 // Insert `derive` after doc comments.
-fn derive_insertion_offset(nominal: &ast::NominalDef) -> Option<TextUnit> {
+fn derive_insertion_offset(nominal: &ast::NominalDef) -> Option<TextSize> {
     let non_ws_child = nominal
         .syntax()
         .children_with_tokens()
diff --git a/crates/ra_assists/src/handlers/add_explicit_type.rs b/crates/ra_assists/src/handlers/add_explicit_type.rs
index 6c56d93d8..bc313782b 100644
--- a/crates/ra_assists/src/handlers/add_explicit_type.rs
+++ b/crates/ra_assists/src/handlers/add_explicit_type.rs
@@ -37,8 +37,8 @@ pub(crate) fn add_explicit_type(ctx: AssistCtx) -> Option<Assist> {
     let stmt_range = stmt.syntax().text_range();
     let eq_range = stmt.eq_token()?.text_range();
     // Assist should only be applicable if cursor is between 'let' and '='
-    let let_range = TextRange::from_to(stmt_range.start(), eq_range.start());
-    let cursor_in_range = ctx.frange.range.is_subrange(&let_range);
+    let let_range = TextRange::new(stmt_range.start(), eq_range.start());
+    let cursor_in_range = let_range.contains_range(ctx.frange.range);
     if !cursor_in_range {
         return None;
     }
diff --git a/crates/ra_assists/src/handlers/add_from_impl_for_enum.rs b/crates/ra_assists/src/handlers/add_from_impl_for_enum.rs
index 0621487e8..03806724a 100644
--- a/crates/ra_assists/src/handlers/add_from_impl_for_enum.rs
+++ b/crates/ra_assists/src/handlers/add_from_impl_for_enum.rs
@@ -1,6 +1,6 @@
 use ra_syntax::{
     ast::{self, AstNode, NameOwner},
-    TextUnit,
+    TextSize,
 };
 use stdx::format_to;
 
@@ -65,7 +65,7 @@ impl From<{0}> for {1} {{
                 variant_name
             );
             edit.insert(start_offset, buf);
-            edit.set_cursor(start_offset + TextUnit::of_str("\n\n"));
+            edit.set_cursor(start_offset + TextSize::of("\n\n"));
         },
     )
 }
diff --git a/crates/ra_assists/src/handlers/add_function.rs b/crates/ra_assists/src/handlers/add_function.rs
index ad4ab66ed..6c7456579 100644
--- a/crates/ra_assists/src/handlers/add_function.rs
+++ b/crates/ra_assists/src/handlers/add_function.rs
@@ -1,10 +1,10 @@
 use ra_syntax::{
     ast::{self, AstNode},
-    SyntaxKind, SyntaxNode, TextUnit,
+    SyntaxKind, SyntaxNode, TextSize,
 };
 
-use crate::{Assist, AssistCtx, AssistId};
-use ast::{edit::IndentLevel, ArgListOwner, CallExpr, Expr};
+use crate::{Assist, AssistCtx, AssistFile, AssistId};
+use ast::{edit::IndentLevel, ArgListOwner, ModuleItemOwner};
 use hir::HirDisplay;
 use rustc_hash::{FxHashMap, FxHashSet};
 
@@ -16,7 +16,7 @@ use rustc_hash::{FxHashMap, FxHashSet};
 // struct Baz;
 // fn baz() -> Baz { Baz }
 // fn foo() {
-//      bar<|>("", baz());
+//     bar<|>("", baz());
 // }
 //
 // ```
@@ -25,7 +25,7 @@ use rustc_hash::{FxHashMap, FxHashSet};
 // struct Baz;
 // fn baz() -> Baz { Baz }
 // fn foo() {
-//      bar("", baz());
+//     bar("", baz());
 // }
 //
 // fn bar(arg: &str, baz: Baz) {
@@ -38,21 +38,30 @@ pub(crate) fn add_function(ctx: AssistCtx) -> Option<Assist> {
     let call = path_expr.syntax().parent().and_then(ast::CallExpr::cast)?;
     let path = path_expr.path()?;
 
-    if path.qualifier().is_some() {
-        return None;
-    }
-
     if ctx.sema.resolve_path(&path).is_some() {
         // The function call already resolves, no need to add a function
         return None;
     }
 
-    let function_builder = FunctionBuilder::from_call(&ctx, &call)?;
+    let target_module = if let Some(qualifier) = path.qualifier() {
+        if let Some(hir::PathResolution::Def(hir::ModuleDef::Module(module))) =
+            ctx.sema.resolve_path(&qualifier)
+        {
+            Some(module.definition_source(ctx.sema.db))
+        } else {
+            return None;
+        }
+    } else {
+        None
+    };
+
+    let function_builder = FunctionBuilder::from_call(&ctx, &call, &path, target_module)?;
 
     ctx.add_assist(AssistId("add_function"), "Add function", |edit| {
         edit.target(call.syntax().text_range());
 
         if let Some(function_template) = function_builder.render() {
+            edit.set_file(function_template.file);
             edit.set_cursor(function_template.cursor_offset);
             edit.insert(function_template.insert_offset, function_template.fn_def.to_string());
         }
@@ -60,32 +69,70 @@ pub(crate) fn add_function(ctx: AssistCtx) -> Option<Assist> {
 }
 
 struct FunctionTemplate {
-    insert_offset: TextUnit,
-    cursor_offset: TextUnit,
+    insert_offset: TextSize,
+    cursor_offset: TextSize,
     fn_def: ast::SourceFile,
+    file: AssistFile,
 }
 
 struct FunctionBuilder {
-    append_fn_at: SyntaxNode,
+    target: GeneratedFunctionTarget,
     fn_name: ast::Name,
     type_params: Option<ast::TypeParamList>,
     params: ast::ParamList,
+    file: AssistFile,
+    needs_pub: bool,
 }
 
 impl FunctionBuilder {
-    fn from_call(ctx: &AssistCtx, call: &ast::CallExpr) -> Option<Self> {
-        let append_fn_at = next_space_for_fn(&call)?;
-        let fn_name = fn_name(&call)?;
+    /// Prepares a generated function that matches `call` in `generate_in`
+    /// (or as close to `call` as possible, if `generate_in` is `None`)
+    fn from_call(
+        ctx: &AssistCtx,
+        call: &ast::CallExpr,
+        path: &ast::Path,
+        target_module: Option<hir::InFile<hir::ModuleSource>>,
+    ) -> Option<Self> {
+        let needs_pub = target_module.is_some();
+        let mut file = AssistFile::default();
+        let target = if let Some(target_module) = target_module {
+            let (in_file, target) = next_space_for_fn_in_module(ctx.sema.db, target_module)?;
+            file = in_file;
+            target
+        } else {
+            next_space_for_fn_after_call_site(&call)?
+        };
+        let fn_name = fn_name(&path)?;
         let (type_params, params) = fn_args(ctx, &call)?;
-        Some(Self { append_fn_at, fn_name, type_params, params })
+        Some(Self { target, fn_name, type_params, params, file, needs_pub })
     }
+
     fn render(self) -> Option<FunctionTemplate> {
         let placeholder_expr = ast::make::expr_todo();
         let fn_body = ast::make::block_expr(vec![], Some(placeholder_expr));
-        let fn_def = ast::make::fn_def(self.fn_name, self.type_params, self.params, fn_body);
-        let fn_def = ast::make::add_newlines(2, fn_def);
-        let fn_def = IndentLevel::from_node(&self.append_fn_at).increase_indent(fn_def);
-        let insert_offset = self.append_fn_at.text_range().end();
+        let mut fn_def = ast::make::fn_def(self.fn_name, self.type_params, self.params, fn_body);
+        if self.needs_pub {
+            fn_def = ast::make::add_pub_crate_modifier(fn_def);
+        }
+
+        let (fn_def, insert_offset) = match self.target {
+            GeneratedFunctionTarget::BehindItem(it) => {
+                let with_leading_blank_line = ast::make::add_leading_newlines(2, fn_def);
+                let indented = IndentLevel::from_node(&it).increase_indent(with_leading_blank_line);
+                (indented, it.text_range().end())
+            }
+            GeneratedFunctionTarget::InEmptyItemList(it) => {
+                let indent_once = IndentLevel(1);
+                let indent = IndentLevel::from_node(it.syntax());
+
+                let fn_def = ast::make::add_leading_newlines(1, fn_def);
+                let fn_def = indent_once.increase_indent(fn_def);
+                let fn_def = ast::make::add_trailing_newlines(1, fn_def);
+                let fn_def = indent.increase_indent(fn_def);
+                (fn_def, it.syntax().text_range().start() + TextSize::of('{'))
+            }
+        };
+
         let cursor_offset_from_fn_start = fn_def
             .syntax()
             .descendants()
@@ -94,19 +141,24 @@ impl FunctionBuilder {
             .text_range()
             .start();
         let cursor_offset = insert_offset + cursor_offset_from_fn_start;
-        Some(FunctionTemplate { insert_offset, cursor_offset, fn_def })
+        Some(FunctionTemplate { insert_offset, cursor_offset, fn_def, file: self.file })
     }
 }
 
-fn fn_name(call: &CallExpr) -> Option<ast::Name> {
-    let name = call.expr()?.syntax().to_string();
+enum GeneratedFunctionTarget {
+    BehindItem(SyntaxNode),
+    InEmptyItemList(ast::ItemList),
+}
+
+fn fn_name(call: &ast::Path) -> Option<ast::Name> {
+    let name = call.segment()?.syntax().to_string();
     Some(ast::make::name(&name))
 }
 
 /// Computes the type variables and arguments required for the generated function
 fn fn_args(
     ctx: &AssistCtx,
-    call: &CallExpr,
+    call: &ast::CallExpr,
 ) -> Option<(Option<ast::TypeParamList>, ast::ParamList)> {
     let mut arg_names = Vec::new();
     let mut arg_types = Vec::new();
@@ -158,9 +210,9 @@ fn deduplicate_arg_names(arg_names: &mut Vec<String>) {
     }
 }
 
-fn fn_arg_name(fn_arg: &Expr) -> Option<String> {
+fn fn_arg_name(fn_arg: &ast::Expr) -> Option<String> {
     match fn_arg {
-        Expr::CastExpr(cast_expr) => fn_arg_name(&cast_expr.expr()?),
+        ast::Expr::CastExpr(cast_expr) => fn_arg_name(&cast_expr.expr()?),
         _ => Some(
             fn_arg
                 .syntax()
@@ -172,7 +224,7 @@ fn fn_arg_name(fn_arg: &Expr) -> Option<String> {
     }
 }
 
-fn fn_arg_type(ctx: &AssistCtx, fn_arg: &Expr) -> Option<String> {
+fn fn_arg_type(ctx: &AssistCtx, fn_arg: &ast::Expr) -> Option<String> {
     let ty = ctx.sema.type_of_expr(fn_arg)?;
     if ty.is_unknown() {
         return None;
@@ -184,7 +236,7 @@ fn fn_arg_type(ctx: &AssistCtx, fn_arg: &Expr) -> Option<String> {
 /// directly after the current block
 /// We want to write the generated function directly after
 /// fns, impls or macro calls, but inside mods
-fn next_space_for_fn(expr: &CallExpr) -> Option<SyntaxNode> {
+fn next_space_for_fn_after_call_site(expr: &ast::CallExpr) -> Option<GeneratedFunctionTarget> {
     let mut ancestors = expr.syntax().ancestors().peekable();
     let mut last_ancestor: Option<SyntaxNode> = None;
     while let Some(next_ancestor) = ancestors.next() {
@@ -201,7 +253,32 @@ fn next_space_for_fn(expr: &CallExpr) -> Option<SyntaxNode> {
         }
         last_ancestor = Some(next_ancestor);
     }
-    last_ancestor
+    last_ancestor.map(GeneratedFunctionTarget::BehindItem)
+}
+
+fn next_space_for_fn_in_module(
+    db: &dyn hir::db::AstDatabase,
+    module: hir::InFile<hir::ModuleSource>,
+) -> Option<(AssistFile, GeneratedFunctionTarget)> {
+    let file = module.file_id.original_file(db);
+    let assist_file = AssistFile::TargetFile(file);
+    let assist_item = match module.value {
+        hir::ModuleSource::SourceFile(it) => {
+            if let Some(last_item) = it.items().last() {
+                GeneratedFunctionTarget::BehindItem(last_item.syntax().clone())
+            } else {
+                GeneratedFunctionTarget::BehindItem(it.syntax().clone())
+            }
+        }
+        hir::ModuleSource::Module(it) => {
+            if let Some(last_item) = it.item_list().and_then(|it| it.items().last()) {
+                GeneratedFunctionTarget::BehindItem(last_item.syntax().clone())
+            } else {
+                GeneratedFunctionTarget::InEmptyItemList(it.item_list()?)
+            }
+        }
+    };
+    Some((assist_file, assist_item))
 }
 
 #[cfg(test)]
@@ -714,6 +791,111 @@ fn bar(baz_1: Baz, baz_2: Baz, arg_1: &str, arg_2: &str) {
     }
 
     #[test]
+    fn add_function_in_module() {
+        check_assist(
+            add_function,
+            r"
+mod bar {}
+
+fn foo() {
+    bar::my_fn<|>()
+}
+",
+            r"
+mod bar {
+    pub(crate) fn my_fn() {
+        <|>todo!()
+    }
+}
+
+fn foo() {
+    bar::my_fn()
+}
+",
+        )
+    }
+
+    #[test]
+    fn add_function_in_module_containing_other_items() {
+        check_assist(
+            add_function,
+            r"
+mod bar {
+    fn something_else() {}
+}
+
+fn foo() {
+    bar::my_fn<|>()
+}
+",
+            r"
+mod bar {
+    fn something_else() {}
+
+    pub(crate) fn my_fn() {
+        <|>todo!()
+    }
+}
+
+fn foo() {
+    bar::my_fn()
+}
+",
+        )
+    }
+
+    #[test]
+    fn add_function_in_nested_module() {
+        check_assist(
+            add_function,
+            r"
+mod bar {
+    mod baz {}
+}
+
+fn foo() {
+    bar::baz::my_fn<|>()
+}
+",
+            r"
+mod bar {
+    mod baz {
+        pub(crate) fn my_fn() {
+            <|>todo!()
+        }
+    }
+}
+
+fn foo() {
+    bar::baz::my_fn()
+}
+",
+        )
+    }
+
+    #[test]
+    fn add_function_in_another_file() {
+        check_assist(
+            add_function,
+            r"
+//- /main.rs
+mod foo;
+
+fn main() {
+    foo::bar<|>()
+}
+//- /foo.rs
+",
+            r"
+
+
+pub(crate) fn bar() {
+    <|>todo!()
+}",
+        )
+    }
+
+    #[test]
     fn add_function_not_applicable_if_function_already_exists() {
         check_assist_not_applicable(
             add_function,
diff --git a/crates/ra_assists/src/handlers/add_impl.rs b/crates/ra_assists/src/handlers/add_impl.rs
index 6622eadb2..d26f8b93d 100644
--- a/crates/ra_assists/src/handlers/add_impl.rs
+++ b/crates/ra_assists/src/handlers/add_impl.rs
@@ -1,6 +1,6 @@
 use ra_syntax::{
     ast::{self, AstNode, NameOwner, TypeParamsOwner},
-    TextUnit,
+    TextSize,
 };
 use stdx::{format_to, SepBy};
 
@@ -51,7 +51,7 @@ pub(crate) fn add_impl(ctx: AssistCtx) -> Option<Assist> {
             format_to!(buf, "<{}>", generic_params)
         }
         buf.push_str(" {\n");
-        edit.set_cursor(start_offset + TextUnit::of_str(&buf));
+        edit.set_cursor(start_offset + TextSize::of(&buf));
         buf.push_str("\n}");
         edit.insert(start_offset, buf);
     })
diff --git a/crates/ra_assists/src/handlers/add_new.rs b/crates/ra_assists/src/handlers/add_new.rs
index 240b19fa3..0f9174a29 100644
--- a/crates/ra_assists/src/handlers/add_new.rs
+++ b/crates/ra_assists/src/handlers/add_new.rs
@@ -3,7 +3,7 @@ use ra_syntax::{
     ast::{
         self, AstNode, NameOwner, StructKind, TypeAscriptionOwner, TypeParamsOwner, VisibilityOwner,
     },
-    TextUnit, T,
+    TextSize, T,
 };
 use stdx::{format_to, SepBy};
 
@@ -77,16 +77,16 @@ pub(crate) fn add_new(ctx: AssistCtx) -> Option<Assist> {
                     .text_range()
                     .end();
 
-                Some((start, TextUnit::from_usize(1)))
+                Some((start, TextSize::of("\n")))
             })
             .unwrap_or_else(|| {
                 buf = generate_impl_text(&strukt, &buf);
                 let start = strukt.syntax().text_range().end();
 
-                (start, TextUnit::from_usize(3))
+                (start, TextSize::of("\n}\n"))
             });
 
-        edit.set_cursor(start_offset + TextUnit::of_str(&buf) - end_offset);
+        edit.set_cursor(start_offset + TextSize::of(&buf) - end_offset);
         edit.insert(start_offset, buf);
     })
 }
diff --git a/crates/ra_assists/src/handlers/apply_demorgan.rs b/crates/ra_assists/src/handlers/apply_demorgan.rs
index 239807e24..260b9e073 100644
--- a/crates/ra_assists/src/handlers/apply_demorgan.rs
+++ b/crates/ra_assists/src/handlers/apply_demorgan.rs
@@ -26,7 +26,7 @@ pub(crate) fn apply_demorgan(ctx: AssistCtx) -> Option<Assist> {
     let op = expr.op_kind()?;
     let op_range = expr.op_token()?.text_range();
     let opposite_op = opposite_logic_op(op)?;
-    let cursor_in_range = ctx.frange.range.is_subrange(&op_range);
+    let cursor_in_range = op_range.contains_range(ctx.frange.range);
     if !cursor_in_range {
         return None;
     }
diff --git a/crates/ra_assists/src/handlers/change_visibility.rs b/crates/ra_assists/src/handlers/change_visibility.rs
index cd6d1ee6c..44f6a1dae 100644
--- a/crates/ra_assists/src/handlers/change_visibility.rs
+++ b/crates/ra_assists/src/handlers/change_visibility.rs
@@ -5,7 +5,7 @@ use ra_syntax::{
         ATTR, COMMENT, CONST_DEF, ENUM_DEF, FN_DEF, MODULE, STRUCT_DEF, TRAIT_DEF, VISIBILITY,
         WHITESPACE,
     },
-    SyntaxNode, TextUnit, T,
+    SyntaxNode, TextSize, T,
 };
 
 use crate::{Assist, AssistCtx, AssistId};
@@ -67,7 +67,7 @@ fn add_vis(ctx: AssistCtx) -> Option<Assist> {
     })
 }
 
-fn vis_offset(node: &SyntaxNode) -> TextUnit {
+fn vis_offset(node: &SyntaxNode) -> TextSize {
     node.children_with_tokens()
         .skip_while(|it| match it.kind() {
             WHITESPACE | COMMENT | ATTR => true,
diff --git a/crates/ra_assists/src/handlers/flip_binexpr.rs b/crates/ra_assists/src/handlers/flip_binexpr.rs
index bfcc09e90..8030efb35 100644
--- a/crates/ra_assists/src/handlers/flip_binexpr.rs
+++ b/crates/ra_assists/src/handlers/flip_binexpr.rs
@@ -23,7 +23,7 @@ pub(crate) fn flip_binexpr(ctx: AssistCtx) -> Option<Assist> {
     let rhs = expr.rhs()?.syntax().clone();
     let op_range = expr.op_token()?.text_range();
     // The assist should be applied only if the cursor is on the operator
-    let cursor_in_range = ctx.frange.range.is_subrange(&op_range);
+    let cursor_in_range = op_range.contains_range(ctx.frange.range);
     if !cursor_in_range {
         return None;
     }
diff --git a/crates/ra_assists/src/handlers/inline_local_variable.rs b/crates/ra_assists/src/handlers/inline_local_variable.rs
index c4fb425b0..f5702f6e0 100644
--- a/crates/ra_assists/src/handlers/inline_local_variable.rs
+++ b/crates/ra_assists/src/handlers/inline_local_variable.rs
@@ -52,7 +52,7 @@ pub(crate) fn inline_local_variable(ctx: AssistCtx) -> Option<Assist> {
         .next_sibling_or_token()
         .and_then(|it| ast::Whitespace::cast(it.as_token()?.clone()))
     {
-        TextRange::from_to(
+        TextRange::new(
             let_stmt.syntax().text_range().start(),
             whitespace.syntax().text_range().end(),
         )
diff --git a/crates/ra_assists/src/handlers/introduce_variable.rs b/crates/ra_assists/src/handlers/introduce_variable.rs
index 8c09e6bcd..eda9ac296 100644
--- a/crates/ra_assists/src/handlers/introduce_variable.rs
+++ b/crates/ra_assists/src/handlers/introduce_variable.rs
@@ -4,7 +4,7 @@ use ra_syntax::{
         BLOCK_EXPR, BREAK_EXPR, COMMENT, LAMBDA_EXPR, LOOP_EXPR, MATCH_ARM, PATH_EXPR, RETURN_EXPR,
         WHITESPACE,
     },
-    SyntaxNode, TextUnit,
+    SyntaxNode, TextSize,
 };
 use stdx::format_to;
 use test_utils::tested_by;
@@ -47,10 +47,10 @@ pub(crate) fn introduce_variable(ctx: AssistCtx) -> Option<Assist> {
 
         let cursor_offset = if wrap_in_block {
             buf.push_str("{ let var_name = ");
-            TextUnit::of_str("{ let ")
+            TextSize::of("{ let ")
         } else {
             buf.push_str("let var_name = ");
-            TextUnit::of_str("let ")
+            TextSize::of("let ")
         };
         format_to!(buf, "{}", expr.syntax());
         let full_stmt = ast::ExprStmt::cast(anchor_stmt.clone());
diff --git a/crates/ra_assists/src/handlers/invert_if.rs b/crates/ra_assists/src/handlers/invert_if.rs
index 4c5716868..682e08512 100644
--- a/crates/ra_assists/src/handlers/invert_if.rs
+++ b/crates/ra_assists/src/handlers/invert_if.rs
@@ -28,7 +28,7 @@ pub(crate) fn invert_if(ctx: AssistCtx) -> Option<Assist> {
     let if_keyword = ctx.find_token_at_offset(T![if])?;
     let expr = ast::IfExpr::cast(if_keyword.parent())?;
     let if_range = if_keyword.text_range();
-    let cursor_in_range = ctx.frange.range.is_subrange(&if_range);
+    let cursor_in_range = if_range.contains_range(ctx.frange.range);
     if !cursor_in_range {
         return None;
     }
diff --git a/crates/ra_assists/src/handlers/merge_match_arms.rs b/crates/ra_assists/src/handlers/merge_match_arms.rs
index eb967ab92..5a77d3dbc 100644
--- a/crates/ra_assists/src/handlers/merge_match_arms.rs
+++ b/crates/ra_assists/src/handlers/merge_match_arms.rs
@@ -3,7 +3,7 @@ use std::iter::successors;
 use ra_syntax::{
     algo::neighbor,
     ast::{self, AstNode},
-    Direction, TextUnit,
+    Direction, TextSize,
 };
 
 use crate::{Assist, AssistCtx, AssistId, TextRange};
@@ -42,8 +42,8 @@ pub(crate) fn merge_match_arms(ctx: AssistCtx) -> Option<Assist> {
     let current_text_range = current_arm.syntax().text_range();
 
     enum CursorPos {
-        InExpr(TextUnit),
-        InPat(TextUnit),
+        InExpr(TextSize),
+        InPat(TextSize),
     }
     let cursor_pos = ctx.frange.range.start();
     let cursor_pos = if current_expr.syntax().text_range().contains(cursor_pos) {
@@ -89,10 +89,10 @@ pub(crate) fn merge_match_arms(ctx: AssistCtx) -> Option<Assist> {
 
         edit.target(current_text_range);
         edit.set_cursor(match cursor_pos {
-            CursorPos::InExpr(back_offset) => start + TextUnit::from_usize(arm.len()) - back_offset,
+            CursorPos::InExpr(back_offset) => start + TextSize::of(&arm) - back_offset,
             CursorPos::InPat(offset) => offset,
         });
-        edit.replace(TextRange::from_to(start, end), arm);
+        edit.replace(TextRange::new(start, end), arm);
     })
 }
 
diff --git a/crates/ra_assists/src/handlers/move_guard.rs b/crates/ra_assists/src/handlers/move_guard.rs
index 1cc498638..d5ccdd91c 100644
--- a/crates/ra_assists/src/handlers/move_guard.rs
+++ b/crates/ra_assists/src/handlers/move_guard.rs
@@ -1,7 +1,7 @@
 use ra_syntax::{
     ast,
     ast::{AstNode, AstToken, IfExpr, MatchArm},
-    TextUnit,
+    TextSize,
 };
 
 use crate::{Assist, AssistCtx, AssistId};
@@ -49,16 +49,16 @@ pub(crate) fn move_guard_to_arm_body(ctx: AssistCtx) -> Option<Assist> {
                     edit.delete(ele);
                     ele.len()
                 } else {
-                    TextUnit::from(0)
+                    TextSize::from(0)
                 }
             }
-            _ => TextUnit::from(0),
+            _ => TextSize::from(0),
         };
 
         edit.delete(guard.syntax().text_range());
         edit.replace_node_and_indent(arm_expr.syntax(), buf);
         edit.set_cursor(
-            arm_expr.syntax().text_range().start() + TextUnit::from(3) - offseting_amount,
+            arm_expr.syntax().text_range().start() + TextSize::from(3) - offseting_amount,
         );
     })
 }
@@ -123,7 +123,7 @@ pub(crate) fn move_arm_cond_to_match_guard(ctx: AssistCtx) -> Option<Assist> {
             }
 
             edit.insert(match_pat.syntax().text_range().end(), buf);
-            edit.set_cursor(match_pat.syntax().text_range().end() + TextUnit::from(1));
+            edit.set_cursor(match_pat.syntax().text_range().end() + TextSize::from(1));
         },
     )
 }
diff --git a/crates/ra_assists/src/handlers/raw_string.rs b/crates/ra_assists/src/handlers/raw_string.rs
index 7e4b83f13..567400b9c 100644
--- a/crates/ra_assists/src/handlers/raw_string.rs
+++ b/crates/ra_assists/src/handlers/raw_string.rs
@@ -2,7 +2,7 @@ use ra_syntax::{
     ast::{self, HasStringValue},
     AstToken,
     SyntaxKind::{RAW_STRING, STRING},
-    TextUnit,
+    TextSize,
 };
 
 use crate::{Assist, AssistCtx, AssistId};
@@ -81,7 +81,7 @@ pub(crate) fn add_hash(ctx: AssistCtx) -> Option<Assist> {
     let token = ctx.find_token_at_offset(RAW_STRING)?;
     ctx.add_assist(AssistId("add_hash"), "Add # to raw string", |edit| {
         edit.target(token.text_range());
-        edit.insert(token.text_range().start() + TextUnit::of_char('r'), "#");
+        edit.insert(token.text_range().start() + TextSize::of('r'), "#");
         edit.insert(token.text_range().end(), "#");
     })
 }
diff --git a/crates/ra_assists/src/handlers/remove_dbg.rs b/crates/ra_assists/src/handlers/remove_dbg.rs
index 5085649b4..4e5eb4350 100644
--- a/crates/ra_assists/src/handlers/remove_dbg.rs
+++ b/crates/ra_assists/src/handlers/remove_dbg.rs
@@ -1,6 +1,6 @@
 use ra_syntax::{
     ast::{self, AstNode},
-    TextUnit, T,
+    TextSize, T,
 };
 
 use crate::{Assist, AssistCtx, AssistId};
@@ -38,9 +38,9 @@ pub(crate) fn remove_dbg(ctx: AssistCtx) -> Option<Assist> {
         let offset_start = file_range
             .start()
             .checked_sub(macro_range.start())
-            .unwrap_or_else(|| TextUnit::from(0));
+            .unwrap_or_else(|| TextSize::from(0));
 
-        let dbg_size = TextUnit::of_str("dbg!(");
+        let dbg_size = TextSize::of("dbg!(");
 
         if offset_start > dbg_size {
             file_range.start() - dbg_size
@@ -53,7 +53,7 @@ pub(crate) fn remove_dbg(ctx: AssistCtx) -> Option<Assist> {
         let macro_args = macro_call.token_tree()?.syntax().clone();
 
         let text = macro_args.text();
-        let without_parens = TextUnit::of_char('(')..text.len() - TextUnit::of_char(')');
+        let without_parens = TextSize::of('(')..text.len() - TextSize::of(')');
         text.slice(without_parens).to_string()
     };
 
diff --git a/crates/ra_assists/src/handlers/remove_mut.rs b/crates/ra_assists/src/handlers/remove_mut.rs
index 6884830eb..e598023b2 100644
--- a/crates/ra_assists/src/handlers/remove_mut.rs
+++ b/crates/ra_assists/src/handlers/remove_mut.rs
@@ -27,6 +27,6 @@ pub(crate) fn remove_mut(ctx: AssistCtx) -> Option<Assist> {
 
     ctx.add_assist(AssistId("remove_mut"), "Remove `mut` keyword", |edit| {
         edit.set_cursor(delete_from);
-        edit.delete(TextRange::from_to(delete_from, delete_to));
+        edit.delete(TextRange::new(delete_from, delete_to));
     })
 }
diff --git a/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs b/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs
index 94f5d6c50..2f02df303 100644
--- a/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs
+++ b/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs
@@ -43,7 +43,7 @@ pub(crate) fn replace_qualified_name_with_use(ctx: AssistCtx) -> Option<Assist>
             if let Some(last) = path.segment() {
                 // Here we are assuming the assist will provide a correct use statement
                 // so we can delete the path qualifier
-                edit.delete(TextRange::from_to(
+                edit.delete(TextRange::new(
                     path.syntax().text_range().start(),
                     last.syntax().text_range().start(),
                 ));
diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index a00136da1..64bd87afb 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -17,9 +17,9 @@ mod doc_tests;
 pub mod utils;
 pub mod ast_transform;
 
-use ra_db::FileRange;
+use ra_db::{FileId, FileRange};
 use ra_ide_db::RootDatabase;
-use ra_syntax::{TextRange, TextUnit};
+use ra_syntax::{TextRange, TextSize};
 use ra_text_edit::TextEdit;
 
 pub(crate) use crate::assist_ctx::{Assist, AssistCtx, AssistHandler};
@@ -51,9 +51,10 @@ impl AssistLabel {
 #[derive(Debug, Clone)]
 pub struct AssistAction {
     pub edit: TextEdit,
-    pub cursor_position: Option<TextUnit>,
+    pub cursor_position: Option<TextSize>,
     // FIXME: This belongs to `AssistLabel`
     pub target: Option<TextRange>,
+    pub file: AssistFile,
 }
 
 #[derive(Debug, Clone)]
@@ -63,6 +64,18 @@ pub struct ResolvedAssist {
     pub action: AssistAction,
 }
 
+#[derive(Debug, Clone, Copy)]
+pub enum AssistFile {
+    CurrentFile,
+    TargetFile(FileId),
+}
+
+impl Default for AssistFile {
+    fn default() -> Self {
+        Self::CurrentFile
+    }
+}
+
 /// Return all the assists applicable at the given position.
 ///
 /// Assists are returned in the "unresolved" state, that is only labels are
@@ -91,7 +104,7 @@ pub fn resolved_assists(db: &RootDatabase, range: FileRange) -> Vec<ResolvedAssi
         .flat_map(|it| it.0)
         .map(|it| it.into_resolved().unwrap())
         .collect::<Vec<_>>();
-    a.sort_by_key(|it| it.action.target.map_or(TextUnit::from(!0u32), |it| it.len()));
+    a.sort_by_key(|it| it.action.target.map_or(TextSize::from(!0u32), |it| it.len()));
     a
 }
 
@@ -184,7 +197,7 @@ mod helpers {
     use ra_ide_db::{symbol_index::SymbolsDatabase, RootDatabase};
     use test_utils::{add_cursor, assert_eq_text, extract_range_or_offset, RangeOrOffset};
 
-    use crate::{AssistCtx, AssistHandler};
+    use crate::{AssistCtx, AssistFile, AssistHandler};
     use hir::Semantics;
 
     pub(crate) fn with_single_file(text: &str) -> (RootDatabase, FileId) {
@@ -246,7 +259,13 @@ mod helpers {
             (Some(assist), ExpectedResult::After(after)) => {
                 let action = assist.0[0].action.clone().unwrap();
 
-                let mut actual = action.edit.apply(&text_without_caret);
+                let assisted_file_text = if let AssistFile::TargetFile(file_id) = action.file {
+                    db.file_text(file_id).as_ref().to_owned()
+                } else {
+                    text_without_caret
+                };
+
+                let mut actual = action.edit.apply(&assisted_file_text);
                 match action.cursor_position {
                     None => {
                         if let RangeOrOffset::Offset(before_cursor_pos) = range_or_offset {
@@ -289,8 +308,7 @@ mod tests {
         let before = "struct Foo { <|>bar: u32 }";
         let (before_cursor_pos, before) = extract_offset(before);
         let (db, file_id) = helpers::with_single_file(&before);
-        let frange =
-            FileRange { file_id, range: TextRange::offset_len(before_cursor_pos, 0.into()) };
+        let frange = FileRange { file_id, range: TextRange::empty(before_cursor_pos) };
         let assists = resolved_assists(&db, frange);
         let mut assists = assists.iter();