16 files changed, 704 insertions, 74 deletions

diff --git a/crates/ide_assists/src/assist_context.rs b/crates/ide_assists/src/assist_context.rs
index 1482d37f8..8714e4978 100644
--- a/crates/ide_assists/src/assist_context.rs
+++ b/crates/ide_assists/src/assist_context.rs
@@ -13,7 +13,7 @@ use ide_db::{
     RootDatabase,
 };
 use syntax::{
-    algo::{self, find_node_at_offset, SyntaxRewriter},
+    algo::{self, find_node_at_offset, find_node_at_range, SyntaxRewriter},
     AstNode, AstToken, SourceFile, SyntaxElement, SyntaxKind, SyntaxNode, SyntaxNodePtr,
     SyntaxToken, TextRange, TextSize, TokenAtOffset,
 };
@@ -89,6 +89,9 @@ impl<'a> AssistContext<'a> {
     pub(crate) fn find_node_at_offset<N: AstNode>(&self) -> Option<N> {
         find_node_at_offset(self.source_file.syntax(), self.offset())
     }
+    pub(crate) fn find_node_at_range<N: AstNode>(&self) -> Option<N> {
+        find_node_at_range(self.source_file.syntax(), self.frange.range)
+    }
     pub(crate) fn find_node_at_offset_with_descend<N: AstNode>(&self) -> Option<N> {
         self.sema.find_node_at_offset_with_descend(self.source_file.syntax(), self.offset())
     }
diff --git a/crates/ide_assists/src/handlers/auto_import.rs b/crates/ide_assists/src/handlers/auto_import.rs
index 7019039b9..5ccd7f7a2 100644
--- a/crates/ide_assists/src/handlers/auto_import.rs
+++ b/crates/ide_assists/src/handlers/auto_import.rs
@@ -61,6 +61,8 @@ use crate::{AssistContext, AssistId, AssistKind, Assists, GroupLabel};
 // - `plain`: This setting does not impose any restrictions in imports.
 //
 // In `VS Code` the configuration for this is `rust-analyzer.assist.importPrefix`.
+//
+// image::https://user-images.githubusercontent.com/48062697/113020673-b85be580-917a-11eb-9022-59585f35d4f8.gif[]
 
 // Assist: auto_import
 //
diff --git a/crates/ide_assists/src/handlers/convert_into_to_from.rs b/crates/ide_assists/src/handlers/convert_into_to_from.rs
new file mode 100644
index 000000000..199e1ad5c
--- /dev/null
+++ b/crates/ide_assists/src/handlers/convert_into_to_from.rs
@@ -0,0 +1,355 @@
+use ide_db::{
+    helpers::{mod_path_to_ast, FamousDefs},
+    traits::resolve_target_trait,
+};
+use syntax::ast::{self, AstNode, NameOwner};
+
+use crate::{AssistContext, AssistId, AssistKind, Assists};
+
+// Assist: convert_into_to_from
+//
+// Converts an Into impl to an equivalent From impl.
+//
+// ```
+// # //- /lib.rs crate:core
+// # pub mod convert { pub trait Into<T> { pub fn into(self) -> T; } }
+// # //- /lib.rs crate:main deps:core
+// # use core::convert::Into;
+// impl $0Into<Thing> for usize {
+//     fn into(self) -> Thing {
+//         Thing {
+//             b: self.to_string(),
+//             a: self
+//         }
+//     }
+// }
+// ```
+// ->
+// ```
+// # use core::convert::Into;
+// impl From<usize> for Thing {
+//     fn from(val: usize) -> Self {
+//         Thing {
+//             b: val.to_string(),
+//             a: val
+//         }
+//     }
+// }
+// ```
+pub(crate) fn convert_into_to_from(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let impl_ = ctx.find_node_at_offset::<ast::Impl>()?;
+    let src_type = impl_.self_ty()?;
+    let ast_trait = impl_.trait_()?;
+
+    let module = ctx.sema.scope(impl_.syntax()).module()?;
+
+    let trait_ = resolve_target_trait(&ctx.sema, &impl_)?;
+    if trait_ != FamousDefs(&ctx.sema, Some(module.krate())).core_convert_Into()? {
+        return None;
+    }
+
+    let src_type_path = {
+        let src_type_path = src_type.syntax().descendants().find_map(ast::Path::cast)?;
+        let src_type_def = match ctx.sema.resolve_path(&src_type_path) {
+            Some(hir::PathResolution::Def(module_def)) => module_def,
+            _ => return None,
+        };
+
+        mod_path_to_ast(&module.find_use_path(ctx.db(), src_type_def)?)
+    };
+
+    let dest_type = match &ast_trait {
+        ast::Type::PathType(path) => {
+            path.path()?.segment()?.generic_arg_list()?.generic_args().next()?
+        }
+        _ => return None,
+    };
+
+    let into_fn = impl_.assoc_item_list()?.assoc_items().find_map(|item| {
+        if let ast::AssocItem::Fn(f) = item {
+            if f.name()?.text() == "into" {
+                return Some(f);
+            }
+        };
+        None
+    })?;
+
+    let into_fn_name = into_fn.name()?;
+    let into_fn_params = into_fn.param_list()?;
+    let into_fn_return = into_fn.ret_type()?;
+
+    let selfs = into_fn
+        .body()?
+        .syntax()
+        .descendants()
+        .filter_map(ast::NameRef::cast)
+        .filter(|name| name.text() == "self" || name.text() == "Self");
+
+    acc.add(
+        AssistId("convert_into_to_from", AssistKind::RefactorRewrite),
+        "Convert Into to From",
+        impl_.syntax().text_range(),
+        |builder| {
+            builder.replace(src_type.syntax().text_range(), dest_type.to_string());
+            builder.replace(ast_trait.syntax().text_range(), format!("From<{}>", src_type));
+            builder.replace(into_fn_return.syntax().text_range(), "-> Self");
+            builder.replace(
+                into_fn_params.syntax().text_range(),
+                format!("(val: {})", src_type.to_string()),
+            );
+            builder.replace(into_fn_name.syntax().text_range(), "from");
+
+            for s in selfs {
+                match s.text().as_ref() {
+                    "self" => builder.replace(s.syntax().text_range(), "val"),
+                    "Self" => builder.replace(s.syntax().text_range(), src_type_path.to_string()),
+                    _ => {}
+                }
+            }
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use crate::tests::check_assist;
+
+    #[test]
+    fn convert_into_to_from_converts_a_struct() {
+        check_convert_into_to_from(
+            r#"
+struct Thing {
+    a: String,
+    b: usize
+}
+
+impl $0core::convert::Into<Thing> for usize {
+    fn into(self) -> Thing {
+        Thing {
+            b: self.to_string(),
+            a: self
+        }
+    }
+}
+"#,
+            r#"
+struct Thing {
+    a: String,
+    b: usize
+}
+
+impl From<usize> for Thing {
+    fn from(val: usize) -> Self {
+        Thing {
+            b: val.to_string(),
+            a: val
+        }
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn convert_into_to_from_converts_enums() {
+        check_convert_into_to_from(
+            r#"
+enum Thing {
+    Foo(String),
+    Bar(String)
+}
+
+impl $0core::convert::Into<String> for Thing {
+    fn into(self) -> String {
+        match self {
+            Self::Foo(s) => s,
+            Self::Bar(s) => s
+        }
+    }
+}
+"#,
+            r#"
+enum Thing {
+    Foo(String),
+    Bar(String)
+}
+
+impl From<Thing> for String {
+    fn from(val: Thing) -> Self {
+        match val {
+            Thing::Foo(s) => s,
+            Thing::Bar(s) => s
+        }
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn convert_into_to_from_on_enum_with_lifetimes() {
+        check_convert_into_to_from(
+            r#"
+enum Thing<'a> {
+    Foo(&'a str),
+    Bar(&'a str)
+}
+
+impl<'a> $0core::convert::Into<&'a str> for Thing<'a> {
+    fn into(self) -> &'a str {
+        match self {
+            Self::Foo(s) => s,
+            Self::Bar(s) => s
+        }
+    }
+}
+"#,
+            r#"
+enum Thing<'a> {
+    Foo(&'a str),
+    Bar(&'a str)
+}
+
+impl<'a> From<Thing<'a>> for &'a str {
+    fn from(val: Thing<'a>) -> Self {
+        match val {
+            Thing::Foo(s) => s,
+            Thing::Bar(s) => s
+        }
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn convert_into_to_from_works_on_references() {
+        check_convert_into_to_from(
+            r#"
+struct Thing(String);
+
+impl $0core::convert::Into<String> for &Thing {
+    fn into(self) -> Thing {
+        self.0.clone()
+    }
+}
+"#,
+            r#"
+struct Thing(String);
+
+impl From<&Thing> for String {
+    fn from(val: &Thing) -> Self {
+        val.0.clone()
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn convert_into_to_from_works_on_qualified_structs() {
+        check_convert_into_to_from(
+            r#"
+mod things {
+    pub struct Thing(String);
+    pub struct BetterThing(String);
+}
+
+impl $0core::convert::Into<things::BetterThing> for &things::Thing {
+    fn into(self) -> Thing {
+        things::BetterThing(self.0.clone())
+    }
+}
+"#,
+            r#"
+mod things {
+    pub struct Thing(String);
+    pub struct BetterThing(String);
+}
+
+impl From<&things::Thing> for things::BetterThing {
+    fn from(val: &things::Thing) -> Self {
+        things::BetterThing(val.0.clone())
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn convert_into_to_from_works_on_qualified_enums() {
+        check_convert_into_to_from(
+            r#"
+mod things {
+    pub enum Thing {
+        A(String)
+    }
+    pub struct BetterThing {
+        B(String)
+    }
+}
+
+impl $0core::convert::Into<things::BetterThing> for &things::Thing {
+    fn into(self) -> Thing {
+        match self {
+            Self::A(s) => things::BetterThing::B(s)
+        }
+    }
+}
+"#,
+            r#"
+mod things {
+    pub enum Thing {
+        A(String)
+    }
+    pub struct BetterThing {
+        B(String)
+    }
+}
+
+impl From<&things::Thing> for things::BetterThing {
+    fn from(val: &things::Thing) -> Self {
+        match val {
+            things::Thing::A(s) => things::BetterThing::B(s)
+        }
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn convert_into_to_from_not_applicable_on_any_trait_named_into() {
+        check_assist_not_applicable(
+            r#"
+pub trait Into<T> {{
+    pub fn into(self) -> T;
+}}
+
+struct Thing {
+    a: String,
+}
+
+impl $0Into<Thing> for String {
+    fn into(self) -> Thing {
+        Thing {
+            a: self
+        }
+    }
+}
+"#,
+        );
+    }
+
+    fn check_convert_into_to_from(before: &str, after: &str) {
+        let before = &format!("//- /main.rs crate:main deps:core{}{}", before, FamousDefs::FIXTURE);
+        check_assist(convert_into_to_from, before, after);
+    }
+
+    fn check_assist_not_applicable(before: &str) {
+        let before = &format!("//- /main.rs crate:main deps:core{}{}", before, FamousDefs::FIXTURE);
+        crate::tests::check_assist_not_applicable(convert_into_to_from, before);
+    }
+}
diff --git a/crates/ide_assists/src/handlers/extract_struct_from_enum_variant.rs b/crates/ide_assists/src/handlers/extract_struct_from_enum_variant.rs
index 596c536a7..a8d6355bd 100644
--- a/crates/ide_assists/src/handlers/extract_struct_from_enum_variant.rs
+++ b/crates/ide_assists/src/handlers/extract_struct_from_enum_variant.rs
@@ -195,7 +195,7 @@ fn extract_struct_def(
 
 fn update_variant(rewriter: &mut SyntaxRewriter, variant: &ast::Variant) -> Option<()> {
     let name = variant.name()?;
-    let tuple_field = make::tuple_field(None, make::ty(name.text()));
+    let tuple_field = make::tuple_field(None, make::ty(&name.text()));
     let replacement = make::variant(
         name,
         Some(ast::FieldList::TupleFieldList(make::tuple_field_list(iter::once(tuple_field)))),
diff --git a/crates/ide_assists/src/handlers/extract_type_alias.rs b/crates/ide_assists/src/handlers/extract_type_alias.rs
new file mode 100644
index 000000000..442a209b9
--- /dev/null
+++ b/crates/ide_assists/src/handlers/extract_type_alias.rs
@@ -0,0 +1,149 @@
+use syntax::ast::{self, AstNode};
+
+use crate::{AssistContext, AssistId, AssistKind, Assists};
+
+// Assist: extract_type_alias
+//
+// Extracts the selected type as a type alias.
+//
+// ```
+// struct S {
+//     field: $0(u8, u8, u8)$0,
+// }
+// ```
+// ->
+// ```
+// type $0Type = (u8, u8, u8);
+//
+// struct S {
+//     field: Type,
+// }
+// ```
+pub(crate) fn extract_type_alias(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    if ctx.frange.range.is_empty() {
+        return None;
+    }
+
+    let node = ctx.find_node_at_range::<ast::Type>()?;
+    let insert = ctx.find_node_at_offset::<ast::Item>()?.syntax().text_range().start();
+    let target = node.syntax().text_range();
+
+    acc.add(
+        AssistId("extract_type_alias", AssistKind::RefactorExtract),
+        "Extract type as type alias",
+        target,
+        |builder| {
+            builder.edit_file(ctx.frange.file_id);
+            builder.replace(target, "Type");
+            match ctx.config.snippet_cap {
+                Some(cap) => {
+                    builder.insert_snippet(cap, insert, format!("type $0Type = {};\n\n", node));
+                }
+                None => {
+                    builder.insert(insert, format!("type Type = {};\n\n", node));
+                }
+            }
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_not_applicable};
+
+    use super::*;
+
+    #[test]
+    fn test_not_applicable_without_selection() {
+        check_assist_not_applicable(
+            extract_type_alias,
+            r"
+struct S {
+    field: $0(u8, u8, u8),
+}
+            ",
+        );
+    }
+
+    #[test]
+    fn test_simple_types() {
+        check_assist(
+            extract_type_alias,
+            r"
+struct S {
+    field: $0u8$0,
+}
+            ",
+            r#"
+type $0Type = u8;
+
+struct S {
+    field: Type,
+}
+            "#,
+        );
+    }
+
+    #[test]
+    fn test_generic_type_arg() {
+        check_assist(
+            extract_type_alias,
+            r"
+fn generic<T>() {}
+
+fn f() {
+    generic::<$0()$0>();
+}
+            ",
+            r#"
+fn generic<T>() {}
+
+type $0Type = ();
+
+fn f() {
+    generic::<Type>();
+}
+            "#,
+        );
+    }
+
+    #[test]
+    fn test_inner_type_arg() {
+        check_assist(
+            extract_type_alias,
+            r"
+struct Vec<T> {}
+struct S {
+    v: Vec<Vec<$0Vec<u8>$0>>,
+}
+            ",
+            r#"
+struct Vec<T> {}
+type $0Type = Vec<u8>;
+
+struct S {
+    v: Vec<Vec<Type>>,
+}
+            "#,
+        );
+    }
+
+    #[test]
+    fn test_extract_inner_type() {
+        check_assist(
+            extract_type_alias,
+            r"
+struct S {
+    field: ($0u8$0,),
+}
+            ",
+            r#"
+type $0Type = u8;
+
+struct S {
+    field: (Type,),
+}
+            "#,
+        );
+    }
+}
diff --git a/crates/ide_assists/src/handlers/extract_variable.rs b/crates/ide_assists/src/handlers/extract_variable.rs
index 7a32483dc..136b9a55b 100644
--- a/crates/ide_assists/src/handlers/extract_variable.rs
+++ b/crates/ide_assists/src/handlers/extract_variable.rs
@@ -2,7 +2,8 @@ use stdx::format_to;
 use syntax::{
     ast::{self, AstNode},
     SyntaxKind::{
-        BLOCK_EXPR, BREAK_EXPR, CLOSURE_EXPR, COMMENT, LOOP_EXPR, MATCH_ARM, PATH_EXPR, RETURN_EXPR,
+        BLOCK_EXPR, BREAK_EXPR, CLOSURE_EXPR, COMMENT, LOOP_EXPR, MATCH_ARM, MATCH_GUARD,
+        PATH_EXPR, RETURN_EXPR,
     },
     SyntaxNode,
 };
@@ -147,9 +148,18 @@ impl Anchor {
             }
 
             if let Some(parent) = node.parent() {
-                if parent.kind() == MATCH_ARM || parent.kind() == CLOSURE_EXPR {
+                if parent.kind() == CLOSURE_EXPR {
+                    cov_mark::hit!(test_extract_var_in_closure_no_block);
                     return Some(Anchor::WrapInBlock(node));
                 }
+                if parent.kind() == MATCH_ARM {
+                    if node.kind() == MATCH_GUARD {
+                        cov_mark::hit!(test_extract_var_in_match_guard);
+                    } else {
+                        cov_mark::hit!(test_extract_var_in_match_arm_no_block);
+                        return Some(Anchor::WrapInBlock(node));
+                    }
+                }
             }
 
             if let Some(stmt) = ast::Stmt::cast(node.clone()) {
@@ -280,9 +290,10 @@ fn foo() {
 
     #[test]
     fn test_extract_var_in_match_arm_no_block() {
+        cov_mark::check!(test_extract_var_in_match_arm_no_block);
         check_assist(
             extract_variable,
-            "
+            r#"
 fn main() {
     let x = true;
     let tuple = match x {
@@ -290,8 +301,8 @@ fn main() {
         _ => (0, false)
     };
 }
-",
-            "
+"#,
+            r#"
 fn main() {
     let x = true;
     let tuple = match x {
@@ -299,7 +310,7 @@ fn main() {
         _ => (0, false)
     };
 }
-",
+"#,
         );
     }
 
@@ -307,7 +318,7 @@ fn main() {
     fn test_extract_var_in_match_arm_with_block() {
         check_assist(
             extract_variable,
-            "
+            r#"
 fn main() {
     let x = true;
     let tuple = match x {
@@ -318,8 +329,8 @@ fn main() {
         _ => (0, false)
     };
 }
-",
-            "
+"#,
+            r#"
 fn main() {
     let x = true;
     let tuple = match x {
@@ -331,24 +342,50 @@ fn main() {
         _ => (0, false)
     };
 }
-",
+"#,
+        );
+    }
+
+    #[test]
+    fn test_extract_var_in_match_guard() {
+        cov_mark::check!(test_extract_var_in_match_guard);
+        check_assist(
+            extract_variable,
+            r#"
+fn main() {
+    match () {
+        () if $010 > 0$0 => 1
+        _ => 2
+    };
+}
+"#,
+            r#"
+fn main() {
+    let $0var_name = 10 > 0;
+    match () {
+        () if var_name => 1
+        _ => 2
+    };
+}
+"#,
         );
     }
 
     #[test]
     fn test_extract_var_in_closure_no_block() {
+        cov_mark::check!(test_extract_var_in_closure_no_block);
         check_assist(
             extract_variable,
-            "
+            r#"
 fn main() {
     let lambda = |x: u32| $0x * 2$0;
 }
-",
-            "
+"#,
+            r#"
 fn main() {
     let lambda = |x: u32| { let $0var_name = x * 2; var_name };
 }
-",
+"#,
         );
     }
 
@@ -356,16 +393,16 @@ fn main() {
     fn test_extract_var_in_closure_with_block() {
         check_assist(
             extract_variable,
-            "
+            r#"
 fn main() {
     let lambda = |x: u32| { $0x * 2$0 };
 }
-",
-            "
+"#,
+            r#"
 fn main() {
     let lambda = |x: u32| { let $0var_name = x * 2; var_name };
 }
-",
+"#,
         );
     }
 
diff --git a/crates/ide_assists/src/handlers/generate_default_from_new.rs b/crates/ide_assists/src/handlers/generate_default_from_new.rs
index 81c54ba3e..dc14552d6 100644
--- a/crates/ide_assists/src/handlers/generate_default_from_new.rs
+++ b/crates/ide_assists/src/handlers/generate_default_from_new.rs
@@ -92,7 +92,7 @@ fn is_default_implemented(ctx: &AssistContext, impl_: &Impl) -> bool {
         None => return false,
     };
 
-    let ty = impl_def.target_ty(db);
+    let ty = impl_def.self_ty(db);
     let krate = impl_def.module(db).krate();
     let default = FamousDefs(&ctx.sema, Some(krate)).core_default_Default();
     let default_trait = match default {
diff --git a/crates/ide_assists/src/handlers/generate_enum_is_method.rs b/crates/ide_assists/src/handlers/generate_enum_is_method.rs
index 7e181a480..a9f71a703 100644
--- a/crates/ide_assists/src/handlers/generate_enum_is_method.rs
+++ b/crates/ide_assists/src/handlers/generate_enum_is_method.rs
@@ -44,7 +44,7 @@ pub(crate) fn generate_enum_is_method(acc: &mut Assists, ctx: &AssistContext) ->
     };
 
     let enum_lowercase_name = to_lower_snake_case(&parent_enum.name()?.to_string());
-    let fn_name = format!("is_{}", &to_lower_snake_case(variant_name.text()));
+    let fn_name = format!("is_{}", &to_lower_snake_case(&variant_name.text()));
 
     // Return early if we've found an existing new fn
     let impl_def = find_struct_impl(&ctx, &parent_enum, &fn_name)?;
diff --git a/crates/ide_assists/src/handlers/generate_enum_projection_method.rs b/crates/ide_assists/src/handlers/generate_enum_projection_method.rs
index 871bcab50..e2f572ba3 100644
--- a/crates/ide_assists/src/handlers/generate_enum_projection_method.rs
+++ b/crates/ide_assists/src/handlers/generate_enum_projection_method.rs
@@ -132,7 +132,8 @@ fn generate_enum_projection_method(
         ast::StructKind::Unit => return None,
     };
 
-    let fn_name = format!("{}_{}", props.fn_name_prefix, &to_lower_snake_case(variant_name.text()));
+    let fn_name =
+        format!("{}_{}", props.fn_name_prefix, &to_lower_snake_case(&variant_name.text()));
 
     // Return early if we've found an existing new fn
     let impl_def = find_struct_impl(&ctx, &parent_enum, &fn_name)?;
diff --git a/crates/ide_assists/src/handlers/generate_impl.rs b/crates/ide_assists/src/handlers/generate_impl.rs
index a8e3c4fc2..fd2e250bc 100644
--- a/crates/ide_assists/src/handlers/generate_impl.rs
+++ b/crates/ide_assists/src/handlers/generate_impl.rs
@@ -72,6 +72,17 @@ mod tests {
         check_assist(
             generate_impl,
             r#"
+            struct MyOwnArray<T, const S: usize> {}$0"#,
+            r#"
+            struct MyOwnArray<T, const S: usize> {}
+
+            impl<T, const S: usize> MyOwnArray<T, S> {
+                $0
+            }"#,
+        );
+        check_assist(
+            generate_impl,
+            r#"
             #[cfg(feature = "foo")]
             struct Foo<'a, T: Foo<'a>> {$0}"#,
             r#"
@@ -114,11 +125,11 @@ mod tests {
         check_assist(
             generate_impl,
             r#"
-            struct Defaulted<'a, 'b: 'a, T: Debug + Clone + 'a + 'b = String> {}$0"#,
+            struct Defaulted<'a, 'b: 'a, T: Debug + Clone + 'a + 'b = String, const S: usize> {}$0"#,
             r#"
-            struct Defaulted<'a, 'b: 'a, T: Debug + Clone + 'a + 'b = String> {}
+            struct Defaulted<'a, 'b: 'a, T: Debug + Clone + 'a + 'b = String, const S: usize> {}
 
-            impl<'a, 'b: 'a, T: Debug + Clone + 'a + 'b> Defaulted<'a, 'b, T> {
+            impl<'a, 'b: 'a, T: Debug + Clone + 'a + 'b, const S: usize> Defaulted<'a, 'b, T, S> {
                 $0
             }"#,
         );
diff --git a/crates/ide_assists/src/handlers/generate_is_empty_from_len.rs b/crates/ide_assists/src/handlers/generate_is_empty_from_len.rs
index b8834d283..910010a04 100644
--- a/crates/ide_assists/src/handlers/generate_is_empty_from_len.rs
+++ b/crates/ide_assists/src/handlers/generate_is_empty_from_len.rs
@@ -91,7 +91,7 @@ fn get_impl_method(
 
     let scope = ctx.sema.scope(impl_.syntax());
     let krate = impl_def.module(db).krate();
-    let ty = impl_def.target_ty(db);
+    let ty = impl_def.self_ty(db);
     let traits_in_scope = scope.traits_in_scope();
     ty.iterate_method_candidates(db, krate, &traits_in_scope, Some(fn_name), |_, func| Some(func))
 }
diff --git a/crates/ide_assists/src/handlers/reorder_fields.rs b/crates/ide_assists/src/handlers/reorder_fields.rs
index 383ca6c47..1a95135ca 100644
--- a/crates/ide_assists/src/handlers/reorder_fields.rs
+++ b/crates/ide_assists/src/handlers/reorder_fields.rs
@@ -1,6 +1,8 @@
+use either::Either;
+use itertools::Itertools;
 use rustc_hash::FxHashMap;
 
-use syntax::{algo, ast, match_ast, AstNode, SyntaxKind::*, SyntaxNode};
+use syntax::{ast, ted, AstNode};
 
 use crate::{AssistContext, AssistId, AssistKind, Assists};
 
@@ -22,60 +24,70 @@ use crate::{AssistContext, AssistId, AssistKind, Assists};
 pub(crate) fn reorder_fields(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     let record = ctx
         .find_node_at_offset::<ast::RecordExpr>()
-        .map(|it| it.syntax().clone())
-        .or_else(|| ctx.find_node_at_offset::<ast::RecordPat>().map(|it| it.syntax().clone()))?;
-
-    let path = record.children().find_map(ast::Path::cast)?;
+        .map(Either::Left)
+        .or_else(|| ctx.find_node_at_offset::<ast::RecordPat>().map(Either::Right))?;
 
+    let path = record.as_ref().either(|it| it.path(), |it| it.path())?;
     let ranks = compute_fields_ranks(&path, &ctx)?;
+    let get_rank_of_field =
+        |of: Option<_>| *ranks.get(&of.unwrap_or_default()).unwrap_or(&usize::MAX);
 
-    let fields: Vec<SyntaxNode> = {
-        let field_kind = match record.kind() {
-            RECORD_EXPR => RECORD_EXPR_FIELD,
-            RECORD_PAT => RECORD_PAT_FIELD,
-            _ => {
-                stdx::never!();
-                return None;
-            }
-        };
-        record.children().flat_map(|n| n.children()).filter(|n| n.kind() == field_kind).collect()
+    let field_list = match &record {
+        Either::Left(it) => Either::Left(it.record_expr_field_list()?),
+        Either::Right(it) => Either::Right(it.record_pat_field_list()?),
     };
-
-    let sorted_fields = {
-        let mut fields = fields.clone();
-        fields.sort_by_key(|node| *ranks.get(&get_field_name(node)).unwrap_or(&usize::max_value()));
-        fields
+    let fields = match field_list {
+        Either::Left(it) => Either::Left((
+            it.fields()
+                .sorted_unstable_by_key(|field| {
+                    get_rank_of_field(field.field_name().map(|it| it.to_string()))
+                })
+                .collect::<Vec<_>>(),
+            it,
+        )),
+        Either::Right(it) => Either::Right((
+            it.fields()
+                .sorted_unstable_by_key(|field| {
+                    get_rank_of_field(field.field_name().map(|it| it.to_string()))
+                })
+                .collect::<Vec<_>>(),
+            it,
+        )),
     };
 
-    if sorted_fields == fields {
+    let is_sorted = fields.as_ref().either(
+        |(sorted, field_list)| field_list.fields().zip(sorted).all(|(a, b)| a == *b),
+        |(sorted, field_list)| field_list.fields().zip(sorted).all(|(a, b)| a == *b),
+    );
+    if is_sorted {
         cov_mark::hit!(reorder_sorted_fields);
         return None;
     }
-
-    let target = record.text_range();
+    let target = record.as_ref().either(AstNode::syntax, AstNode::syntax).text_range();
     acc.add(
         AssistId("reorder_fields", AssistKind::RefactorRewrite),
         "Reorder record fields",
         target,
-        |edit| {
-            let mut rewriter = algo::SyntaxRewriter::default();
-            for (old, new) in fields.iter().zip(&sorted_fields) {
-                rewriter.replace(old, new);
+        |builder| match fields {
+            Either::Left((sorted, field_list)) => {
+                replace(builder.make_ast_mut(field_list).fields(), sorted)
+            }
+            Either::Right((sorted, field_list)) => {
+                replace(builder.make_ast_mut(field_list).fields(), sorted)
             }
-            edit.rewrite(rewriter);
         },
     )
 }
 
-fn get_field_name(node: &SyntaxNode) -> String {
-    let res = match_ast! {
-        match node {
-            ast::RecordExprField(field) => field.field_name().map(|it| it.to_string()),
-            ast::RecordPatField(field) => field.field_name().map(|it| it.to_string()),
-            _ => None,
-        }
-    };
-    res.unwrap_or_default()
+fn replace<T: AstNode + PartialEq>(
+    fields: impl Iterator<Item = T>,
+    sorted_fields: impl IntoIterator<Item = T>,
+) {
+    fields.zip(sorted_fields).filter(|(field, sorted)| field != sorted).for_each(
+        |(field, sorted_field)| {
+            ted::replace(field.syntax(), sorted_field.syntax().clone_for_update());
+        },
+    );
 }
 
 fn compute_fields_ranks(path: &ast::Path, ctx: &AssistContext) -> Option<FxHashMap<String, usize>> {
@@ -86,7 +98,7 @@ fn compute_fields_ranks(path: &ast::Path, ctx: &AssistContext) -> Option<FxHashM
 
     let res = strukt
         .fields(ctx.db())
-        .iter()
+        .into_iter()
         .enumerate()
         .map(|(idx, field)| (field.name(ctx.db()).to_string(), idx))
         .collect();
@@ -137,7 +149,6 @@ const test: Foo = Foo { foo: 1, bar: 0 };
 "#,
         )
     }
-
     #[test]
     fn reorder_struct_pattern() {
         check_assist(
diff --git a/crates/ide_assists/src/handlers/replace_derive_with_manual_impl.rs b/crates/ide_assists/src/handlers/replace_derive_with_manual_impl.rs
index 4f0ef52ca..f872d20c8 100644
--- a/crates/ide_assists/src/handlers/replace_derive_with_manual_impl.rs
+++ b/crates/ide_assists/src/handlers/replace_derive_with_manual_impl.rs
@@ -165,7 +165,7 @@ fn impl_def_from_trait(
     }
     let impl_def = make::impl_trait(
         trait_path.clone(),
-        make::path_unqualified(make::path_segment(make::name_ref(annotated_name.text()))),
+        make::path_unqualified(make::path_segment(make::name_ref(&annotated_name.text()))),
     );
     let (impl_def, first_assoc_item) =
         add_trait_assoc_items_to_impl(sema, trait_items, trait_, impl_def, target_scope);
@@ -178,12 +178,13 @@ fn update_attribute(
     trait_name: &ast::NameRef,
     attr: &ast::Attr,
 ) {
+    let trait_name = trait_name.text();
     let new_attr_input = input
         .syntax()
         .descendants_with_tokens()
         .filter(|t| t.kind() == IDENT)
         .filter_map(|t| t.into_token().map(|t| t.text().to_string()))
-        .filter(|t| t != trait_name.text())
+        .filter(|t| t != &trait_name)
         .collect::<Vec<_>>();
     let has_more_derives = !new_attr_input.is_empty();
 
diff --git a/crates/ide_assists/src/lib.rs b/crates/ide_assists/src/lib.rs
index 8c068a6c0..3e2c82dac 100644
--- a/crates/ide_assists/src/lib.rs
+++ b/crates/ide_assists/src/lib.rs
@@ -117,10 +117,12 @@ mod handlers {
     mod convert_integer_literal;
     mod convert_comment_block;
     mod convert_iter_for_each_to_for;
+    mod convert_into_to_from;
     mod early_return;
     mod expand_glob_import;
     mod extract_function;
     mod extract_struct_from_enum_variant;
+    mod extract_type_alias;
     mod extract_variable;
     mod fill_match_arms;
     mod fix_visibility;
@@ -184,9 +186,11 @@ mod handlers {
             convert_integer_literal::convert_integer_literal,
             convert_comment_block::convert_comment_block,
             convert_iter_for_each_to_for::convert_iter_for_each_to_for,
+            convert_into_to_from::convert_into_to_from,
             early_return::convert_to_guarded_return,
             expand_glob_import::expand_glob_import,
             extract_struct_from_enum_variant::extract_struct_from_enum_variant,
+            extract_type_alias::extract_type_alias,
             fill_match_arms::fill_match_arms,
             fix_visibility::fix_visibility,
             flip_binexpr::flip_binexpr,
diff --git a/crates/ide_assists/src/tests/generated.rs b/crates/ide_assists/src/tests/generated.rs
index 736027ff0..27a22ca10 100644
--- a/crates/ide_assists/src/tests/generated.rs
+++ b/crates/ide_assists/src/tests/generated.rs
@@ -206,6 +206,38 @@ const _: i32 = 0b1010;
 }
 
 #[test]
+fn doctest_convert_into_to_from() {
+    check_doc_test(
+        "convert_into_to_from",
+        r#####"
+//- /lib.rs crate:core
+pub mod convert { pub trait Into<T> { pub fn into(self) -> T; } }
+//- /lib.rs crate:main deps:core
+use core::convert::Into;
+impl $0Into<Thing> for usize {
+    fn into(self) -> Thing {
+        Thing {
+            b: self.to_string(),
+            a: self
+        }
+    }
+}
+"#####,
+        r#####"
+use core::convert::Into;
+impl From<usize> for Thing {
+    fn from(val: usize) -> Self {
+        Thing {
+            b: val.to_string(),
+            a: val
+        }
+    }
+}
+"#####,
+    )
+}
+
+#[test]
 fn doctest_convert_iter_for_each_to_for() {
     check_doc_test(
         "convert_iter_for_each_to_for",
@@ -329,6 +361,25 @@ enum A { One(One) }
 }
 
 #[test]
+fn doctest_extract_type_alias() {
+    check_doc_test(
+        "extract_type_alias",
+        r#####"
+struct S {
+    field: $0(u8, u8, u8)$0,
+}
+"#####,
+        r#####"
+type $0Type = (u8, u8, u8);
+
+struct S {
+    field: Type,
+}
+"#####,
+    )
+}
+
+#[test]
 fn doctest_extract_variable() {
     check_doc_test(
         "extract_variable",
diff --git a/crates/ide_assists/src/utils.rs b/crates/ide_assists/src/utils.rs
index 62f959082..d67524937 100644
--- a/crates/ide_assists/src/utils.rs
+++ b/crates/ide_assists/src/utils.rs
@@ -246,7 +246,7 @@ fn invert_special_case(sema: &Semantics<RootDatabase>, expr: &ast::Expr) -> Opti
             let method = mce.name_ref()?;
             let arg_list = mce.arg_list()?;
 
-            let method = match method.text() {
+            let method = match method.text().as_str() {
                 "is_some" => "is_none",
                 "is_none" => "is_some",
                 "is_ok" => "is_err",
@@ -338,11 +338,11 @@ pub(crate) fn find_struct_impl(
         // (we currently use the wrong type parameter)
         // also we wouldn't want to use e.g. `impl S<u32>`
 
-        let same_ty = match blk.target_ty(db).as_adt() {
+        let same_ty = match blk.self_ty(db).as_adt() {
             Some(def) => def == struct_def,
             None => false,
         };
-        let not_trait_impl = blk.target_trait(db).is_none();
+        let not_trait_impl = blk.trait_(db).is_none();
 
         if !(same_ty && not_trait_impl) {
             None
@@ -434,7 +434,8 @@ fn generate_impl_text_inner(adt: &ast::Adt, trait_text: Option<&str>, code: &str
             }
             buf
         });
-        let generics = lifetimes.chain(type_params).format(", ");
+        let const_params = generic_params.const_params().map(|t| t.syntax().to_string());
+        let generics = lifetimes.chain(type_params).chain(const_params).format(", ");
         format_to!(buf, "<{}>", generics);
     }
     buf.push(' ');
@@ -442,7 +443,7 @@ fn generate_impl_text_inner(adt: &ast::Adt, trait_text: Option<&str>, code: &str
         buf.push_str(trait_text);
         buf.push_str(" for ");
     }
-    buf.push_str(adt.name().unwrap().text());
+    buf.push_str(&adt.name().unwrap().text());
     if let Some(generic_params) = generic_params {
         let lifetime_params = generic_params
             .lifetime_params()
@@ -452,7 +453,11 @@ fn generate_impl_text_inner(adt: &ast::Adt, trait_text: Option<&str>, code: &str
             .type_params()
             .filter_map(|it| it.name())
             .map(|it| SmolStr::from(it.text()));
-        format_to!(buf, "<{}>", lifetime_params.chain(type_params).format(", "))
+        let const_params = generic_params
+            .const_params()
+            .filter_map(|it| it.name())
+            .map(|it| SmolStr::from(it.text()));
+        format_to!(buf, "<{}>", lifetime_params.chain(type_params).chain(const_params).format(", "))
     }
 
     match adt.where_clause() {