8 files changed, 274 insertions, 15 deletions

diff --git a/crates/assists/src/assist_context.rs b/crates/assists/src/assist_context.rs
index 69499ea32..80cf9aba1 100644
--- a/crates/assists/src/assist_context.rs
+++ b/crates/assists/src/assist_context.rs
@@ -4,10 +4,10 @@ use std::mem;
 
 use algo::find_covering_element;
 use hir::Semantics;
-use ide_db::base_db::{FileId, FileRange};
+use ide_db::base_db::{AnchoredPathBuf, FileId, FileRange};
 use ide_db::{
     label::Label,
-    source_change::{SourceChange, SourceFileEdit},
+    source_change::{FileSystemEdit, SourceChange, SourceFileEdit},
     RootDatabase,
 };
 use syntax::{
@@ -209,6 +209,7 @@ pub(crate) struct AssistBuilder {
     file_id: FileId,
     is_snippet: bool,
     source_file_edits: Vec<SourceFileEdit>,
+    file_system_edits: Vec<FileSystemEdit>,
 }
 
 impl AssistBuilder {
@@ -218,6 +219,7 @@ impl AssistBuilder {
             file_id,
             is_snippet: false,
             source_file_edits: Vec::default(),
+            file_system_edits: Vec::default(),
         }
     }
 
@@ -282,12 +284,17 @@ impl AssistBuilder {
             algo::diff(&node, &new).into_text_edit(&mut self.edit);
         }
     }
+    pub(crate) fn create_file(&mut self, dst: AnchoredPathBuf, content: impl Into<String>) {
+        let file_system_edit =
+            FileSystemEdit::CreateFile { dst: dst.clone(), initial_contents: content.into() };
+        self.file_system_edits.push(file_system_edit);
+    }
 
     fn finish(mut self) -> SourceChange {
         self.commit();
         SourceChange {
             source_file_edits: mem::take(&mut self.source_file_edits),
-            file_system_edits: Default::default(),
+            file_system_edits: mem::take(&mut self.file_system_edits),
             is_snippet: self.is_snippet,
         }
     }
diff --git a/crates/assists/src/handlers/extract_module_to_file.rs b/crates/assists/src/handlers/extract_module_to_file.rs
new file mode 100644
index 000000000..3e67fdca2
--- /dev/null
+++ b/crates/assists/src/handlers/extract_module_to_file.rs
@@ -0,0 +1,133 @@
+use ast::edit::IndentLevel;
+use ide_db::base_db::AnchoredPathBuf;
+use syntax::{
+    ast::{self, edit::AstNodeEdit, NameOwner},
+    AstNode,
+};
+
+use crate::{AssistContext, AssistId, AssistKind, Assists};
+
+// Assist: extract_module_to_file
+//
+// This assist extract module to file.
+//
+// ```
+// mod foo {<|>
+//     fn t() {}
+// }
+// ```
+// ->
+// ```
+// mod foo;
+// ```
+pub(crate) fn extract_module_to_file(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let module_ast = ctx.find_node_at_offset::<ast::Module>()?;
+    let module_name = module_ast.name()?;
+
+    let module_def = ctx.sema.to_def(&module_ast)?;
+    let parent_module = module_def.parent(ctx.db())?;
+
+    let module_items = module_ast.item_list()?;
+    let target = module_ast.syntax().text_range();
+    let anchor_file_id = ctx.frange.file_id;
+
+    acc.add(
+        AssistId("extract_module_to_file", AssistKind::RefactorExtract),
+        "Extract module to file",
+        target,
+        |builder| {
+            let path = {
+                let dir = match parent_module.name(ctx.db()) {
+                    Some(name) if !parent_module.is_mod_rs(ctx.db()) => format!("{}/", name),
+                    _ => String::new(),
+                };
+                format!("./{}{}.rs", dir, module_name)
+            };
+            let contents = {
+                let items = module_items.dedent(IndentLevel(1)).to_string();
+                let mut items =
+                    items.trim_start_matches('{').trim_end_matches('}').trim().to_string();
+                if !items.is_empty() {
+                    items.push('\n');
+                }
+                items
+            };
+
+            builder.replace(target, format!("mod {};", module_name));
+
+            let dst = AnchoredPathBuf { anchor: anchor_file_id, path };
+            builder.create_file(dst, contents);
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::check_assist;
+
+    use super::*;
+
+    #[test]
+    fn extract_from_root() {
+        check_assist(
+            extract_module_to_file,
+            r#"
+mod tests {<|>
+    #[test] fn t() {}
+}
+"#,
+            r#"
+//- /main.rs
+mod tests;
+//- /tests.rs
+#[test] fn t() {}
+"#,
+        );
+    }
+
+    #[test]
+    fn extract_from_submodule() {
+        check_assist(
+            extract_module_to_file,
+            r#"
+//- /main.rs
+mod submodule;
+//- /submodule.rs
+mod inner<|> {
+    fn f() {}
+}
+fn g() {}
+"#,
+            r#"
+//- /submodule.rs
+mod inner;
+fn g() {}
+//- /submodule/inner.rs
+fn f() {}
+"#,
+        );
+    }
+
+    #[test]
+    fn extract_from_mod_rs() {
+        check_assist(
+            extract_module_to_file,
+            r#"
+//- /main.rs
+mod submodule;
+//- /submodule/mod.rs
+mod inner<|> {
+    fn f() {}
+}
+fn g() {}
+"#,
+            r#"
+//- /submodule/mod.rs
+mod inner;
+fn g() {}
+//- /submodule/inner.rs
+fn f() {}
+"#,
+        );
+    }
+}
diff --git a/crates/assists/src/handlers/invert_if.rs b/crates/assists/src/handlers/invert_if.rs
index 91e2f5c8c..f9c33b3f7 100644
--- a/crates/assists/src/handlers/invert_if.rs
+++ b/crates/assists/src/handlers/invert_if.rs
@@ -78,6 +78,15 @@ mod tests {
     }
 
     #[test]
+    fn invert_if_remove_not_parentheses() {
+        check_assist(
+            invert_if,
+            "fn f() { i<|>f !(x == 3 || x == 4 || x == 5) { 3 * 2 } else { 1 } }",
+            "fn f() { if x == 3 || x == 4 || x == 5 { 1 } else { 3 * 2 } }",
+        )
+    }
+
+    #[test]
     fn invert_if_remove_inequality() {
         check_assist(
             invert_if,
diff --git a/crates/assists/src/handlers/remove_unused_param.rs b/crates/assists/src/handlers/remove_unused_param.rs
index 1ff5e92b0..f72dd49ed 100644
--- a/crates/assists/src/handlers/remove_unused_param.rs
+++ b/crates/assists/src/handlers/remove_unused_param.rs
@@ -2,9 +2,10 @@ use ide_db::{defs::Definition, search::Reference};
 use syntax::{
     algo::find_node_at_range,
     ast::{self, ArgListOwner},
-    AstNode, SyntaxNode, TextRange, T,
+    AstNode, SyntaxKind, SyntaxNode, TextRange, T,
 };
 use test_utils::mark;
+use SyntaxKind::WHITESPACE;
 
 use crate::{
     assist_context::AssistBuilder, utils::next_prev, AssistContext, AssistId, AssistKind, Assists,
@@ -56,7 +57,7 @@ pub(crate) fn remove_unused_param(acc: &mut Assists, ctx: &AssistContext) -> Opt
         "Remove unused parameter",
         param.syntax().text_range(),
         |builder| {
-            builder.delete(range_with_coma(param.syntax()));
+            builder.delete(range_to_remove(param.syntax()));
             for usage in fn_def.usages(&ctx.sema).all() {
                 process_usage(ctx, builder, usage, param_position);
             }
@@ -80,19 +81,34 @@ fn process_usage(
     let arg = call_expr.arg_list()?.args().nth(arg_to_remove)?;
 
     builder.edit_file(usage.file_range.file_id);
-    builder.delete(range_with_coma(arg.syntax()));
+    builder.delete(range_to_remove(arg.syntax()));
 
     Some(())
 }
 
-fn range_with_coma(node: &SyntaxNode) -> TextRange {
-    let up_to = next_prev().find_map(|dir| {
+fn range_to_remove(node: &SyntaxNode) -> TextRange {
+    let up_to_comma = next_prev().find_map(|dir| {
         node.siblings_with_tokens(dir)
             .filter_map(|it| it.into_token())
             .find(|it| it.kind() == T![,])
+            .map(|it| (dir, it))
     });
-    let up_to = up_to.map_or(node.text_range(), |it| it.text_range());
-    node.text_range().cover(up_to)
+    if let Some((dir, token)) = up_to_comma {
+        if node.next_sibling().is_some() {
+            let up_to_space = token
+                .siblings_with_tokens(dir)
+                .skip(1)
+                .take_while(|it| it.kind() == WHITESPACE)
+                .last()
+                .and_then(|it| it.into_token());
+            return node
+                .text_range()
+                .cover(up_to_space.map_or(token.text_range(), |it| it.text_range()));
+        }
+        node.text_range().cover(token.text_range())
+    } else {
+        node.text_range()
+    }
 }
 
 #[cfg(test)]
@@ -119,6 +135,57 @@ fn b() { foo(9, ) }
     }
 
     #[test]
+    fn remove_unused_first_param() {
+        check_assist(
+            remove_unused_param,
+            r#"
+fn foo(<|>x: i32, y: i32) { y; }
+fn a() { foo(1, 2) }
+fn b() { foo(1, 2,) }
+"#,
+            r#"
+fn foo(y: i32) { y; }
+fn a() { foo(2) }
+fn b() { foo(2,) }
+"#,
+        );
+    }
+
+    #[test]
+    fn remove_unused_single_param() {
+        check_assist(
+            remove_unused_param,
+            r#"
+fn foo(<|>x: i32) { 0; }
+fn a() { foo(1) }
+fn b() { foo(1, ) }
+"#,
+            r#"
+fn foo() { 0; }
+fn a() { foo() }
+fn b() { foo( ) }
+"#,
+        );
+    }
+
+    #[test]
+    fn remove_unused_surrounded_by_parms() {
+        check_assist(
+            remove_unused_param,
+            r#"
+fn foo(x: i32, <|>y: i32, z: i32) { x; }
+fn a() { foo(1, 2, 3) }
+fn b() { foo(1, 2, 3,) }
+"#,
+            r#"
+fn foo(x: i32, z: i32) { x; }
+fn a() { foo(1, 3) }
+fn b() { foo(1, 3,) }
+"#,
+        );
+    }
+
+    #[test]
     fn remove_unused_qualified_call() {
         check_assist(
             remove_unused_param,
diff --git a/crates/assists/src/lib.rs b/crates/assists/src/lib.rs
index 6e736ccb3..6b89b2d04 100644
--- a/crates/assists/src/lib.rs
+++ b/crates/assists/src/lib.rs
@@ -129,6 +129,7 @@ mod handlers {
     mod convert_integer_literal;
     mod early_return;
     mod expand_glob_import;
+    mod extract_module_to_file;
     mod extract_struct_from_enum_variant;
     mod extract_variable;
     mod fill_match_arms;
@@ -179,6 +180,7 @@ mod handlers {
             convert_integer_literal::convert_integer_literal,
             early_return::convert_to_guarded_return,
             expand_glob_import::expand_glob_import,
+            extract_module_to_file::extract_module_to_file,
             extract_struct_from_enum_variant::extract_struct_from_enum_variant,
             extract_variable::extract_variable,
             fill_match_arms::fill_match_arms,
diff --git a/crates/assists/src/tests.rs b/crates/assists/src/tests.rs
index 709a34d03..b41f4874a 100644
--- a/crates/assists/src/tests.rs
+++ b/crates/assists/src/tests.rs
@@ -2,6 +2,7 @@ mod generated;
 
 use hir::Semantics;
 use ide_db::base_db::{fixture::WithFixture, FileId, FileRange, SourceDatabaseExt};
+use ide_db::source_change::FileSystemEdit;
 use ide_db::RootDatabase;
 use syntax::TextRange;
 use test_utils::{assert_eq_text, extract_offset, extract_range};
@@ -47,7 +48,7 @@ fn check_doc_test(assist_id: &str, before: &str, after: &str) {
     let before = db.file_text(file_id).to_string();
     let frange = FileRange { file_id, range: selection.into() };
 
-    let mut assist = Assist::resolved(&db, &AssistConfig::default(), frange)
+    let assist = Assist::resolved(&db, &AssistConfig::default(), frange)
         .into_iter()
         .find(|assist| assist.assist.id.0 == assist_id)
         .unwrap_or_else(|| {
@@ -63,9 +64,12 @@ fn check_doc_test(assist_id: &str, before: &str, after: &str) {
         });
 
     let actual = {
-        let change = assist.source_change.source_file_edits.pop().unwrap();
         let mut actual = before;
-        change.edit.apply(&mut actual);
+        for source_file_edit in assist.source_change.source_file_edits {
+            if source_file_edit.file_id == file_id {
+                source_file_edit.edit.apply(&mut actual)
+            }
+        }
         actual
     };
     assert_eq_text!(&after, &actual);
@@ -99,7 +103,8 @@ fn check(handler: Handler, before: &str, expected: ExpectedResult, assist_label:
         (Some(assist), ExpectedResult::After(after)) => {
             let mut source_change = assist.source_change;
             assert!(!source_change.source_file_edits.is_empty());
-            let skip_header = source_change.source_file_edits.len() == 1;
+            let skip_header = source_change.source_file_edits.len() == 1
+                && source_change.file_system_edits.len() == 0;
             source_change.source_file_edits.sort_by_key(|it| it.file_id);
 
             let mut buf = String::new();
@@ -115,6 +120,21 @@ fn check(handler: Handler, before: &str, expected: ExpectedResult, assist_label:
                 buf.push_str(&text);
             }
 
+            for file_system_edit in source_change.file_system_edits.clone() {
+                match file_system_edit {
+                    FileSystemEdit::CreateFile { dst, initial_contents } => {
+                        let sr = db.file_source_root(dst.anchor);
+                        let sr = db.source_root(sr);
+                        let mut base = sr.path_for_file(&dst.anchor).unwrap().clone();
+                        base.pop();
+                        let created_file_path = format!("{}{}", base.to_string(), &dst.path[1..]);
+                        format_to!(buf, "//- {}\n", created_file_path);
+                        buf.push_str(&initial_contents);
+                    }
+                    _ => (),
+                }
+            }
+
             assert_eq_text!(after, &buf);
         }
         (Some(assist), ExpectedResult::Target(target)) => {
diff --git a/crates/assists/src/tests/generated.rs b/crates/assists/src/tests/generated.rs
index cc7c4a343..e9093ec53 100644
--- a/crates/assists/src/tests/generated.rs
+++ b/crates/assists/src/tests/generated.rs
@@ -236,6 +236,21 @@ fn qux(bar: Bar, baz: Baz) {}
 }
 
 #[test]
+fn doctest_extract_module_to_file() {
+    check_doc_test(
+        "extract_module_to_file",
+        r#####"
+mod foo {<|>
+    fn t() {}
+}
+"#####,
+        r#####"
+mod foo;
+"#####,
+    )
+}
+
+#[test]
 fn doctest_extract_struct_from_enum_variant() {
     check_doc_test(
         "extract_struct_from_enum_variant",
diff --git a/crates/assists/src/utils.rs b/crates/assists/src/utils.rs
index f2cacf7c8..d41084b59 100644
--- a/crates/assists/src/utils.rs
+++ b/crates/assists/src/utils.rs
@@ -232,7 +232,13 @@ fn invert_special_case(expr: &ast::Expr) -> Option<ast::Expr> {
             };
             Some(make::expr_method_call(receiver, method, arg_list))
         }
-        ast::Expr::PrefixExpr(pe) if pe.op_kind()? == ast::PrefixOp::Not => pe.expr(),
+        ast::Expr::PrefixExpr(pe) if pe.op_kind()? == ast::PrefixOp::Not => {
+            if let ast::Expr::ParenExpr(parexpr) = pe.expr()? {
+                parexpr.expr()
+            } else {
+                pe.expr()
+            }
+        }
         // FIXME:
         // ast::Expr::Literal(true | false )
         _ => None,