4 files changed, 612 insertions, 4 deletions

diff --git a/crates/ide_db/src/assists.rs b/crates/ide_db/src/assists.rs
new file mode 100644
index 000000000..7881d8369
--- /dev/null
+++ b/crates/ide_db/src/assists.rs
@@ -0,0 +1,136 @@
+//! This module defines the `Assist` data structure. The actual assist live in
+//! the `ide_assists` downstream crate. We want to define the data structures in
+//! this low-level crate though, because `ide_diagnostics` also need them
+//! (fixits for diagnostics and assists are the same thing under the hood). We
+//! want to compile `ide_assists` and `ide_diagnostics` in parallel though, so
+//! we pull the common definitions upstream, to this crate.
+
+use std::str::FromStr;
+
+use syntax::TextRange;
+
+use crate::{label::Label, source_change::SourceChange};
+
+#[derive(Debug, Clone)]
+pub struct Assist {
+    pub id: AssistId,
+    /// Short description of the assist, as shown in the UI.
+    pub label: Label,
+    pub group: Option<GroupLabel>,
+    /// Target ranges are used to sort assists: the smaller the target range,
+    /// the more specific assist is, and so it should be sorted first.
+    pub target: TextRange,
+    /// Computing source change sometimes is much more costly then computing the
+    /// other fields. Additionally, the actual change is not required to show
+    /// the lightbulb UI, it only is needed when the user tries to apply an
+    /// assist. So, we compute it lazily: the API allow requesting assists with
+    /// or without source change. We could (and in fact, used to) distinguish
+    /// between resolved and unresolved assists at the type level, but this is
+    /// cumbersome, especially if you want to embed an assist into another data
+    /// structure, such as a diagnostic.
+    pub source_change: Option<SourceChange>,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum AssistKind {
+    // FIXME: does the None variant make sense? Probably not.
+    None,
+
+    QuickFix,
+    Generate,
+    Refactor,
+    RefactorExtract,
+    RefactorInline,
+    RefactorRewrite,
+}
+
+impl AssistKind {
+    pub fn contains(self, other: AssistKind) -> bool {
+        if self == other {
+            return true;
+        }
+
+        match self {
+            AssistKind::None | AssistKind::Generate => true,
+            AssistKind::Refactor => match other {
+                AssistKind::RefactorExtract
+                | AssistKind::RefactorInline
+                | AssistKind::RefactorRewrite => true,
+                _ => false,
+            },
+            _ => false,
+        }
+    }
+
+    pub fn name(&self) -> &str {
+        match self {
+            AssistKind::None => "None",
+            AssistKind::QuickFix => "QuickFix",
+            AssistKind::Generate => "Generate",
+            AssistKind::Refactor => "Refactor",
+            AssistKind::RefactorExtract => "RefactorExtract",
+            AssistKind::RefactorInline => "RefactorInline",
+            AssistKind::RefactorRewrite => "RefactorRewrite",
+        }
+    }
+}
+
+impl FromStr for AssistKind {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "None" => Ok(AssistKind::None),
+            "QuickFix" => Ok(AssistKind::QuickFix),
+            "Generate" => Ok(AssistKind::Generate),
+            "Refactor" => Ok(AssistKind::Refactor),
+            "RefactorExtract" => Ok(AssistKind::RefactorExtract),
+            "RefactorInline" => Ok(AssistKind::RefactorInline),
+            "RefactorRewrite" => Ok(AssistKind::RefactorRewrite),
+            unknown => Err(format!("Unknown AssistKind: '{}'", unknown)),
+        }
+    }
+}
+
+/// Unique identifier of the assist, should not be shown to the user
+/// directly.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct AssistId(pub &'static str, pub AssistKind);
+
+/// A way to control how many asssist to resolve during the assist resolution.
+/// When an assist is resolved, its edits are calculated that might be costly to always do by default.
+#[derive(Debug)]
+pub enum AssistResolveStrategy {
+    /// No assists should be resolved.
+    None,
+    /// All assists should be resolved.
+    All,
+    /// Only a certain assist should be resolved.
+    Single(SingleResolve),
+}
+
+/// Hold the [`AssistId`] data of a certain assist to resolve.
+/// The original id object cannot be used due to a `'static` lifetime
+/// and the requirement to construct this struct dynamically during the resolve handling.
+#[derive(Debug)]
+pub struct SingleResolve {
+    /// The id of the assist.
+    pub assist_id: String,
+    // The kind of the assist.
+    pub assist_kind: AssistKind,
+}
+
+impl AssistResolveStrategy {
+    pub fn should_resolve(&self, id: &AssistId) -> bool {
+        match self {
+            AssistResolveStrategy::None => false,
+            AssistResolveStrategy::All => true,
+            AssistResolveStrategy::Single(single_resolve) => {
+                single_resolve.assist_id == id.0 && single_resolve.assist_kind == id.1
+            }
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct GroupLabel(pub String);
diff --git a/crates/ide_db/src/helpers/insert_use/tests.rs b/crates/ide_db/src/helpers/insert_use/tests.rs
index 70b11bf81..5a88ec742 100644
--- a/crates/ide_db/src/helpers/insert_use/tests.rs
+++ b/crates/ide_db/src/helpers/insert_use/tests.rs
@@ -511,13 +511,14 @@ use std::io;
 }
 
 #[test]
-#[ignore] // FIXME: Support this
 fn split_out_merge() {
+    // FIXME: This is suboptimal, we want to get `use std::fmt::{self, Result}`
+    // instead.
     check_module(
         "std::fmt::Result",
         r"use std::{fmt, io};",
-        r"use std::fmt::{self, Result};
-use std::io;",
+        r"use std::fmt::Result;
+use std::{fmt, io};",
     )
 }
 
diff --git a/crates/ide_db/src/lib.rs b/crates/ide_db/src/lib.rs
index 105607dca..7bbd08d6f 100644
--- a/crates/ide_db/src/lib.rs
+++ b/crates/ide_db/src/lib.rs
@@ -3,11 +3,11 @@
 //! It is mainly a `HirDatabase` for semantic analysis, plus a `SymbolsDatabase`, for fuzzy search.
 
 mod apply_change;
+pub mod assists;
 pub mod label;
 pub mod line_index;
 pub mod symbol_index;
 pub mod defs;
-pub mod search;
 pub mod items_locator;
 pub mod source_change;
 pub mod ty_filter;
@@ -15,6 +15,9 @@ pub mod traits;
 pub mod call_info;
 pub mod helpers;
 
+pub mod search;
+pub mod rename;
+
 use std::{fmt, sync::Arc};
 
 use base_db::{
diff --git a/crates/ide_db/src/rename.rs b/crates/ide_db/src/rename.rs
new file mode 100644
index 000000000..643e67781
--- /dev/null
+++ b/crates/ide_db/src/rename.rs
@@ -0,0 +1,468 @@
+//! Rename infrastructure for rust-analyzer. It is used primarily for the
+//! literal "rename" in the ide (look for tests there), but it is also available
+//! as a general-purpose service. For example, it is used by the fix for the
+//! "incorrect case" diagnostic.
+//!
+//! It leverages the [`crate::search`] functionality to find what needs to be
+//! renamed. The actual renames are tricky -- field shorthands need special
+//! attention, and, when renaming modules, you also want to rename files on the
+//! file system.
+//!
+//! Another can of worms are macros:
+//!
+//! ```
+//! macro_rules! m { () => { fn f() {} } }
+//! m!();
+//! fn main() {
+//!     f() // <- rename me
+//! }
+//! ```
+//!
+//! The correct behavior in such cases is probably to show a dialog to the user.
+//! Our current behavior is ¯\_(ツ)_/¯.
+use std::fmt;
+
+use base_db::{AnchoredPathBuf, FileId, FileRange};
+use either::Either;
+use hir::{AsAssocItem, FieldSource, HasSource, InFile, ModuleSource, Semantics};
+use stdx::never;
+use syntax::{
+    ast::{self, NameOwner},
+    lex_single_syntax_kind, AstNode, SyntaxKind, TextRange, T,
+};
+use text_edit::TextEdit;
+
+use crate::{
+    defs::Definition,
+    search::FileReference,
+    source_change::{FileSystemEdit, SourceChange},
+    RootDatabase,
+};
+
+pub type Result<T, E = RenameError> = std::result::Result<T, E>;
+
+#[derive(Debug)]
+pub struct RenameError(pub String);
+
+impl fmt::Display for RenameError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(&self.0, f)
+    }
+}
+
+#[macro_export]
+macro_rules! _format_err {
+    ($fmt:expr) => { RenameError(format!($fmt)) };
+    ($fmt:expr, $($arg:tt)+) => { RenameError(format!($fmt, $($arg)+)) }
+}
+pub use _format_err as format_err;
+
+#[macro_export]
+macro_rules! _bail {
+    ($($tokens:tt)*) => { return Err(format_err!($($tokens)*)) }
+}
+pub use _bail as bail;
+
+impl Definition {
+    pub fn rename(&self, sema: &Semantics<RootDatabase>, new_name: &str) -> Result<SourceChange> {
+        match *self {
+            Definition::ModuleDef(hir::ModuleDef::Module(module)) => {
+                rename_mod(sema, module, new_name)
+            }
+            Definition::ModuleDef(hir::ModuleDef::BuiltinType(_)) => {
+                bail!("Cannot rename builtin type")
+            }
+            Definition::SelfType(_) => bail!("Cannot rename `Self`"),
+            def => rename_reference(sema, def, new_name),
+        }
+    }
+
+    /// Textual range of the identifier which will change when renaming this
+    /// `Definition`. Note that some definitions, like buitin types, can't be
+    /// renamed.
+    pub fn range_for_rename(self, sema: &Semantics<RootDatabase>) -> Option<FileRange> {
+        // FIXME: the `original_file_range` calls here are wrong -- they never fail,
+        // and _fall back_ to the entirety of the macro call. Such fall back is
+        // incorrect for renames. The safe behavior would be to return an error for
+        // such cases. The correct behavior would be to return an auxiliary list of
+        // "can't rename these occurrences in macros" items, and then show some kind
+        // of a dialog to the user. See:
+        cov_mark::hit!(macros_are_broken_lol);
+
+        let res = match self {
+            Definition::Macro(mac) => {
+                let src = mac.source(sema.db)?;
+                let name = match &src.value {
+                    Either::Left(it) => it.name()?,
+                    Either::Right(it) => it.name()?,
+                };
+                src.with_value(name.syntax()).original_file_range(sema.db)
+            }
+            Definition::Field(field) => {
+                let src = field.source(sema.db)?;
+
+                match &src.value {
+                    FieldSource::Named(record_field) => {
+                        let name = record_field.name()?;
+                        src.with_value(name.syntax()).original_file_range(sema.db)
+                    }
+                    FieldSource::Pos(_) => {
+                        return None;
+                    }
+                }
+            }
+            Definition::ModuleDef(module_def) => match module_def {
+                hir::ModuleDef::Module(module) => {
+                    let src = module.declaration_source(sema.db)?;
+                    let name = src.value.name()?;
+                    src.with_value(name.syntax()).original_file_range(sema.db)
+                }
+                hir::ModuleDef::Function(it) => name_range(it, sema)?,
+                hir::ModuleDef::Adt(adt) => match adt {
+                    hir::Adt::Struct(it) => name_range(it, sema)?,
+                    hir::Adt::Union(it) => name_range(it, sema)?,
+                    hir::Adt::Enum(it) => name_range(it, sema)?,
+                },
+                hir::ModuleDef::Variant(it) => name_range(it, sema)?,
+                hir::ModuleDef::Const(it) => name_range(it, sema)?,
+                hir::ModuleDef::Static(it) => name_range(it, sema)?,
+                hir::ModuleDef::Trait(it) => name_range(it, sema)?,
+                hir::ModuleDef::TypeAlias(it) => name_range(it, sema)?,
+                hir::ModuleDef::BuiltinType(_) => return None,
+            },
+            Definition::SelfType(_) => return None,
+            Definition::Local(local) => {
+                let src = local.source(sema.db);
+                let name = match &src.value {
+                    Either::Left(bind_pat) => bind_pat.name()?,
+                    Either::Right(_) => return None,
+                };
+                src.with_value(name.syntax()).original_file_range(sema.db)
+            }
+            Definition::GenericParam(generic_param) => match generic_param {
+                hir::GenericParam::TypeParam(type_param) => {
+                    let src = type_param.source(sema.db)?;
+                    let name = match &src.value {
+                        Either::Left(type_param) => type_param.name()?,
+                        Either::Right(_trait) => return None,
+                    };
+                    src.with_value(name.syntax()).original_file_range(sema.db)
+                }
+                hir::GenericParam::LifetimeParam(lifetime_param) => {
+                    let src = lifetime_param.source(sema.db)?;
+                    let lifetime = src.value.lifetime()?;
+                    src.with_value(lifetime.syntax()).original_file_range(sema.db)
+                }
+                hir::GenericParam::ConstParam(it) => name_range(it, sema)?,
+            },
+            Definition::Label(label) => {
+                let src = label.source(sema.db);
+                let lifetime = src.value.lifetime()?;
+                src.with_value(lifetime.syntax()).original_file_range(sema.db)
+            }
+        };
+        return Some(res);
+
+        fn name_range<D>(def: D, sema: &Semantics<RootDatabase>) -> Option<FileRange>
+        where
+            D: HasSource,
+            D::Ast: ast::NameOwner,
+        {
+            let src = def.source(sema.db)?;
+            let name = src.value.name()?;
+            let res = src.with_value(name.syntax()).original_file_range(sema.db);
+            Some(res)
+        }
+    }
+}
+
+fn rename_mod(
+    sema: &Semantics<RootDatabase>,
+    module: hir::Module,
+    new_name: &str,
+) -> Result<SourceChange> {
+    if IdentifierKind::classify(new_name)? != IdentifierKind::Ident {
+        bail!("Invalid name `{0}`: cannot rename module to {0}", new_name);
+    }
+
+    let mut source_change = SourceChange::default();
+
+    let InFile { file_id, value: def_source } = module.definition_source(sema.db);
+    let file_id = file_id.original_file(sema.db);
+    if let ModuleSource::SourceFile(..) = def_source {
+        // mod is defined in path/to/dir/mod.rs
+        let path = if module.is_mod_rs(sema.db) {
+            format!("../{}/mod.rs", new_name)
+        } else {
+            format!("{}.rs", new_name)
+        };
+        let dst = AnchoredPathBuf { anchor: file_id, path };
+        let move_file = FileSystemEdit::MoveFile { src: file_id, dst };
+        source_change.push_file_system_edit(move_file);
+    }
+
+    if let Some(InFile { file_id, value: decl_source }) = module.declaration_source(sema.db) {
+        let file_id = file_id.original_file(sema.db);
+        match decl_source.name() {
+            Some(name) => source_change.insert_source_edit(
+                file_id,
+                TextEdit::replace(name.syntax().text_range(), new_name.to_string()),
+            ),
+            _ => never!("Module source node is missing a name"),
+        }
+    }
+    let def = Definition::ModuleDef(hir::ModuleDef::Module(module));
+    let usages = def.usages(sema).all();
+    let ref_edits = usages.iter().map(|(&file_id, references)| {
+        (file_id, source_edit_from_references(references, def, new_name))
+    });
+    source_change.extend(ref_edits);
+
+    Ok(source_change)
+}
+
+fn rename_reference(
+    sema: &Semantics<RootDatabase>,
+    mut def: Definition,
+    new_name: &str,
+) -> Result<SourceChange> {
+    let ident_kind = IdentifierKind::classify(new_name)?;
+
+    if matches!(
+        def, // is target a lifetime?
+        Definition::GenericParam(hir::GenericParam::LifetimeParam(_)) | Definition::Label(_)
+    ) {
+        match ident_kind {
+            IdentifierKind::Ident | IdentifierKind::Underscore => {
+                cov_mark::hit!(rename_not_a_lifetime_ident_ref);
+                bail!("Invalid name `{}`: not a lifetime identifier", new_name);
+            }
+            IdentifierKind::Lifetime => cov_mark::hit!(rename_lifetime),
+        }
+    } else {
+        match (ident_kind, def) {
+            (IdentifierKind::Lifetime, _) => {
+                cov_mark::hit!(rename_not_an_ident_ref);
+                bail!("Invalid name `{}`: not an identifier", new_name);
+            }
+            (IdentifierKind::Ident, _) => cov_mark::hit!(rename_non_local),
+            (IdentifierKind::Underscore, _) => (),
+        }
+    }
+
+    def = match def {
+        // HACK: resolve trait impl items to the item def of the trait definition
+        // so that we properly resolve all trait item references
+        Definition::ModuleDef(mod_def) => mod_def
+            .as_assoc_item(sema.db)
+            .and_then(|it| it.containing_trait_impl(sema.db))
+            .and_then(|it| {
+                it.items(sema.db).into_iter().find_map(|it| match (it, mod_def) {
+                    (hir::AssocItem::Function(trait_func), hir::ModuleDef::Function(func))
+                        if trait_func.name(sema.db) == func.name(sema.db) =>
+                    {
+                        Some(Definition::ModuleDef(hir::ModuleDef::Function(trait_func)))
+                    }
+                    (hir::AssocItem::Const(trait_konst), hir::ModuleDef::Const(konst))
+                        if trait_konst.name(sema.db) == konst.name(sema.db) =>
+                    {
+                        Some(Definition::ModuleDef(hir::ModuleDef::Const(trait_konst)))
+                    }
+                    (
+                        hir::AssocItem::TypeAlias(trait_type_alias),
+                        hir::ModuleDef::TypeAlias(type_alias),
+                    ) if trait_type_alias.name(sema.db) == type_alias.name(sema.db) => {
+                        Some(Definition::ModuleDef(hir::ModuleDef::TypeAlias(trait_type_alias)))
+                    }
+                    _ => None,
+                })
+            })
+            .unwrap_or(def),
+        _ => def,
+    };
+    let usages = def.usages(sema).all();
+
+    if !usages.is_empty() && ident_kind == IdentifierKind::Underscore {
+        cov_mark::hit!(rename_underscore_multiple);
+        bail!("Cannot rename reference to `_` as it is being referenced multiple times");
+    }
+    let mut source_change = SourceChange::default();
+    source_change.extend(usages.iter().map(|(&file_id, references)| {
+        (file_id, source_edit_from_references(references, def, new_name))
+    }));
+
+    let (file_id, edit) = source_edit_from_def(sema, def, new_name)?;
+    source_change.insert_source_edit(file_id, edit);
+    Ok(source_change)
+}
+
+pub fn source_edit_from_references(
+    references: &[FileReference],
+    def: Definition,
+    new_name: &str,
+) -> TextEdit {
+    let mut edit = TextEdit::builder();
+    for reference in references {
+        let (range, replacement) = match &reference.name {
+            // if the ranges differ then the node is inside a macro call, we can't really attempt
+            // to make special rewrites like shorthand syntax and such, so just rename the node in
+            // the macro input
+            ast::NameLike::NameRef(name_ref)
+                if name_ref.syntax().text_range() == reference.range =>
+            {
+                source_edit_from_name_ref(name_ref, new_name, def)
+            }
+            ast::NameLike::Name(name) if name.syntax().text_range() == reference.range => {
+                source_edit_from_name(name, new_name)
+            }
+            _ => None,
+        }
+        .unwrap_or_else(|| (reference.range, new_name.to_string()));
+        edit.replace(range, replacement);
+    }
+    edit.finish()
+}
+
+fn source_edit_from_name(name: &ast::Name, new_name: &str) -> Option<(TextRange, String)> {
+    if let Some(_) = ast::RecordPatField::for_field_name(name) {
+        if let Some(ident_pat) = name.syntax().parent().and_then(ast::IdentPat::cast) {
+            return Some((
+                TextRange::empty(ident_pat.syntax().text_range().start()),
+                [new_name, ": "].concat(),
+            ));
+        }
+    }
+    None
+}
+
+fn source_edit_from_name_ref(
+    name_ref: &ast::NameRef,
+    new_name: &str,
+    def: Definition,
+) -> Option<(TextRange, String)> {
+    if let Some(record_field) = ast::RecordExprField::for_name_ref(name_ref) {
+        let rcf_name_ref = record_field.name_ref();
+        let rcf_expr = record_field.expr();
+        match (rcf_name_ref, rcf_expr.and_then(|it| it.name_ref())) {
+            // field: init-expr, check if we can use a field init shorthand
+            (Some(field_name), Some(init)) => {
+                if field_name == *name_ref {
+                    if init.text() == new_name {
+                        cov_mark::hit!(test_rename_field_put_init_shorthand);
+                        // same names, we can use a shorthand here instead.
+                        // we do not want to erase attributes hence this range start
+                        let s = field_name.syntax().text_range().start();
+                        let e = record_field.syntax().text_range().end();
+                        return Some((TextRange::new(s, e), new_name.to_owned()));
+                    }
+                } else if init == *name_ref {
+                    if field_name.text() == new_name {
+                        cov_mark::hit!(test_rename_local_put_init_shorthand);
+                        // same names, we can use a shorthand here instead.
+                        // we do not want to erase attributes hence this range start
+                        let s = field_name.syntax().text_range().start();
+                        let e = record_field.syntax().text_range().end();
+                        return Some((TextRange::new(s, e), new_name.to_owned()));
+                    }
+                }
+                None
+            }
+            // init shorthand
+            // FIXME: instead of splitting the shorthand, recursively trigger a rename of the
+            // other name https://github.com/rust-analyzer/rust-analyzer/issues/6547
+            (None, Some(_)) if matches!(def, Definition::Field(_)) => {
+                cov_mark::hit!(test_rename_field_in_field_shorthand);
+                let s = name_ref.syntax().text_range().start();
+                Some((TextRange::empty(s), format!("{}: ", new_name)))
+            }
+            (None, Some(_)) if matches!(def, Definition::Local(_)) => {
+                cov_mark::hit!(test_rename_local_in_field_shorthand);
+                let s = name_ref.syntax().text_range().end();
+                Some((TextRange::empty(s), format!(": {}", new_name)))
+            }
+            _ => None,
+        }
+    } else if let Some(record_field) = ast::RecordPatField::for_field_name_ref(name_ref) {
+        let rcf_name_ref = record_field.name_ref();
+        let rcf_pat = record_field.pat();
+        match (rcf_name_ref, rcf_pat) {
+            // field: rename
+            (Some(field_name), Some(ast::Pat::IdentPat(pat))) if field_name == *name_ref => {
+                // field name is being renamed
+                if pat.name().map_or(false, |it| it.text() == new_name) {
+                    cov_mark::hit!(test_rename_field_put_init_shorthand_pat);
+                    // same names, we can use a shorthand here instead/
+                    // we do not want to erase attributes hence this range start
+                    let s = field_name.syntax().text_range().start();
+                    let e = record_field.syntax().text_range().end();
+                    Some((TextRange::new(s, e), pat.to_string()))
+                } else {
+                    None
+                }
+            }
+            _ => None,
+        }
+    } else {
+        None
+    }
+}
+
+fn source_edit_from_def(
+    sema: &Semantics<RootDatabase>,
+    def: Definition,
+    new_name: &str,
+) -> Result<(FileId, TextEdit)> {
+    let frange = def
+        .range_for_rename(sema)
+        .ok_or_else(|| format_err!("No identifier available to rename"))?;
+
+    let mut replacement_text = String::new();
+    let mut repl_range = frange.range;
+    if let Definition::Local(local) = def {
+        if let Either::Left(pat) = local.source(sema.db).value {
+            if matches!(
+                pat.syntax().parent().and_then(ast::RecordPatField::cast),
+                Some(pat_field) if pat_field.name_ref().is_none()
+            ) {
+                replacement_text.push_str(": ");
+                replacement_text.push_str(new_name);
+                repl_range = TextRange::new(
+                    pat.syntax().text_range().end(),
+                    pat.syntax().text_range().end(),
+                );
+            }
+        }
+    }
+    if replacement_text.is_empty() {
+        replacement_text.push_str(new_name);
+    }
+    let edit = TextEdit::replace(repl_range, replacement_text);
+    Ok((frange.file_id, edit))
+}
+
+#[derive(Copy, Clone, Debug, PartialEq)]
+pub enum IdentifierKind {
+    Ident,
+    Lifetime,
+    Underscore,
+}
+
+impl IdentifierKind {
+    pub fn classify(new_name: &str) -> Result<IdentifierKind> {
+        match lex_single_syntax_kind(new_name) {
+            Some(res) => match res {
+                (SyntaxKind::IDENT, _) => Ok(IdentifierKind::Ident),
+                (T![_], _) => Ok(IdentifierKind::Underscore),
+                (SyntaxKind::LIFETIME_IDENT, _) if new_name != "'static" && new_name != "'_" => {
+                    Ok(IdentifierKind::Lifetime)
+                }
+                (SyntaxKind::LIFETIME_IDENT, _) => {
+                    bail!("Invalid name `{}`: not a lifetime identifier", new_name)
+                }
+                (_, Some(syntax_error)) => bail!("Invalid name `{}`: {}", new_name, syntax_error),
+                (_, None) => bail!("Invalid name `{}`: not an identifier", new_name),
+            },
+            None => bail!("Invalid name `{}`: not an identifier", new_name),
+        }
+    }
+}