fix: avoid generating colliding names in extract_variable

crates/ide-assists/src/handlers/destructure_tuple_binding.rs

@@ -6,7 +6,6 @@ use ide_db::{
     text_edit::TextRange,
 };
 use itertools::Itertools;
-use syntax::SmolStr;
 use syntax::{
     ast::{self, make, AstNode, FieldExpr, HasName, IdentPat},
     ted,
@@ -134,17 +133,8 @@ fn collect_data(ident_pat: IdentPat, ctx: &AssistContext<'_>) -> Option<TupleDat
             .map(|(_, refs)| refs.to_vec())
     });
 
-    let mut name_generator = {
+    let mut name_generator =
-        let mut names = vec![];
+        suggest_name::NameGenerator::new_from_scope_locals(ctx.sema.scope(ident_pat.syntax()));
-        if let Some(scope) = ctx.sema.scope(ident_pat.syntax()) {
-            scope.process_all_names(&mut |name, scope| {
-                if let hir::ScopeDef::Local(_) = scope {
-                    names.push(name.as_str().into())
-                }
-            })
-        }
-        suggest_name::NameGenerator::new_with_names(names.iter().map(|s: &SmolStr| s.as_str()))
-    };
 
     let field_names = field_types
         .into_iter()

crates/ide-assists/src/handlers/extract_variable.rs

@@ -336,10 +336,12 @@ impl ExtractionKind {
             }
         }
 
+        let mut name_generator =
+            suggest_name::NameGenerator::new_from_scope_locals(ctx.sema.scope(to_extract.syntax()));
         let var_name = if let Some(literal_name) = get_literal_name(ctx, to_extract) {
-            literal_name
+            name_generator.suggest_name(&literal_name)
         } else {
-            suggest_name::for_variable(to_extract, &ctx.sema)
+            name_generator.for_variable(to_extract, &ctx.sema)
         };
 
         let var_name = match self {
@@ -352,10 +354,10 @@ impl ExtractionKind {
 }
 
 fn get_literal_name(ctx: &AssistContext<'_>, expr: &ast::Expr) -> Option<String> {
-    let literal = match expr {
+    let ast::Expr::Literal(literal) = expr else {
-        ast::Expr::Literal(literal) => literal,
+        return None;
-        _ => return None,
     };
+
     let inner = match literal.kind() {
         ast::LiteralKind::String(string) => string.value().ok()?.into_owned(),
         ast::LiteralKind::ByteString(byte_string) => {
@@ -2632,4 +2634,33 @@ fn foo() {
             "Extract into static",
         );
     }
+
+    #[test]
+    fn extract_variable_name_conflicts() {
+        check_assist_by_label(
+            extract_variable,
+            r#"
+struct S { x: i32 };
+
+fn main() {
+    let s = 2;
+    let t = $0S { x: 1 }$0;
+    let t2 = t;
+    let x = s;
+}
+"#,
+            r#"
+struct S { x: i32 };
+
+fn main() {
+    let s = 2;
+    let $0s1 = S { x: 1 };
+    let t = s1;
+    let t2 = t;
+    let x = s;
+}
+"#,
+            "Extract into variable",
+        );
+    }
 }

crates/ide-assists/src/handlers/replace_is_method_with_if_let_method.rs

@@ -20,7 +20,7 @@ use crate::{AssistContext, AssistId, AssistKind, Assists};
 // ```
 // fn main() {
 //     let x = Some(1);
-//     if let Some(${0:x}) = x {}
+//     if let Some(${0:x1}) = x {}
 // }
 // ```
 pub(crate) fn replace_is_method_with_if_let_method(
@@ -40,10 +40,13 @@ pub(crate) fn replace_is_method_with_if_let_method(
         "is_some" | "is_ok" => {
             let receiver = call_expr.receiver()?;
 
+            let mut name_generator = suggest_name::NameGenerator::new_from_scope_locals(
+                ctx.sema.scope(if_expr.syntax()),
+            );
             let var_name = if let ast::Expr::PathExpr(path_expr) = receiver.clone() {
-                path_expr.path()?.to_string()
+                name_generator.suggest_name(&path_expr.path()?.to_string())
             } else {
-                suggest_name::for_variable(&receiver, &ctx.sema)
+                name_generator.for_variable(&receiver, &ctx.sema)
             };
 
             let (assist_id, message, text) = if name_ref.text() == "is_some" {
@@ -98,7 +101,7 @@ fn main() {
             r#"
 fn main() {
     let x = Some(1);
-    if let Some(${0:x}) = x {}
+    if let Some(${0:x1}) = x {}
 }
 "#,
         );
@@ -150,7 +153,7 @@ fn main() {
             r#"
 fn main() {
     let x = Ok(1);
-    if let Ok(${0:x}) = x {}
+    if let Ok(${0:x1}) = x {}
 }
 "#,
         );

crates/ide-assists/src/tests/generated.rs

@@ -2885,7 +2885,7 @@ fn main() {
         r#####"
 fn main() {
     let x = Some(1);
-    if let Some(${0:x}) = x {}
+    if let Some(${0:x1}) = x {}
 }
 "#####,
     )

crates/ide-db/src/syntax_helpers/suggest_name.rs

@@ -2,13 +2,13 @@
 
 use std::{collections::hash_map::Entry, str::FromStr};
 
-use hir::Semantics;
+use hir::{Semantics, SemanticsScope};
 use itertools::Itertools;
 use rustc_hash::FxHashMap;
 use stdx::to_lower_snake_case;
 use syntax::{
     ast::{self, HasName},
-    match_ast, AstNode, Edition, SmolStr, SmolStrBuilder,
+    match_ast, AstNode, Edition, SmolStr, SmolStrBuilder, ToSmolStr,
 };
 
 use crate::RootDatabase;
@@ -100,6 +100,19 @@ impl NameGenerator {
         generator
     }
 
+    pub fn new_from_scope_locals(scope: Option<SemanticsScope<'_>>) -> Self {
+        let mut generator = Self::new();
+        if let Some(scope) = scope {
+            scope.process_all_names(&mut |name, scope| {
+                if let hir::ScopeDef::Local(_) = scope {
+                    generator.insert(name.as_str());
+                }
+            });
+        }
+
+        generator
+    }
+
     /// Suggest a name without conflicts. If the name conflicts with existing names,
     /// it will try to resolve the conflict by adding a numeric suffix.
     pub fn suggest_name(&mut self, name: &str) -> SmolStr {
@@ -162,6 +175,59 @@ impl NameGenerator {
         self.suggest_name(&c.to_string())
     }
 
+    /// Suggest name of variable for given expression
+    ///
+    /// In current implementation, the function tries to get the name from
+    /// the following sources:
+    ///
+    /// * if expr is an argument to function/method, use parameter name
+    /// * if expr is a function/method call, use function name
+    /// * expression type name if it exists (E.g. `()`, `fn() -> ()` or `!` do not have names)
+    /// * fallback: `var_name`
+    ///
+    /// It also applies heuristics to filter out less informative names
+    ///
+    /// Currently it sticks to the first name found.
+    pub fn for_variable(
+        &mut self,
+        expr: &ast::Expr,
+        sema: &Semantics<'_, RootDatabase>,
+    ) -> SmolStr {
+        // `from_param` does not benefit from stripping it need the largest
+        // context possible so we check firstmost
+        if let Some(name) = from_param(expr, sema) {
+            return self.suggest_name(&name);
+        }
+
+        let mut next_expr = Some(expr.clone());
+        while let Some(expr) = next_expr {
+            let name = from_call(&expr)
+                .or_else(|| from_type(&expr, sema))
+                .or_else(|| from_field_name(&expr));
+            if let Some(name) = name {
+                return self.suggest_name(&name);
+            }
+
+            match expr {
+                ast::Expr::RefExpr(inner) => next_expr = inner.expr(),
+                ast::Expr::AwaitExpr(inner) => next_expr = inner.expr(),
+                // ast::Expr::BlockExpr(block) => expr = block.tail_expr(),
+                ast::Expr::CastExpr(inner) => next_expr = inner.expr(),
+                ast::Expr::MethodCallExpr(method) if is_useless_method(&method) => {
+                    next_expr = method.receiver();
+                }
+                ast::Expr::ParenExpr(inner) => next_expr = inner.expr(),
+                ast::Expr::TryExpr(inner) => next_expr = inner.expr(),
+                ast::Expr::PrefixExpr(prefix) if prefix.op_kind() == Some(ast::UnaryOp::Deref) => {
+                    next_expr = prefix.expr()
+                }
+                _ => break,
+            }
+        }
+
+        self.suggest_name("var_name")
+    }
+
     /// Insert a name into the pool
     fn insert(&mut self, name: &str) {
         let (prefix, suffix) = Self::split_numeric_suffix(name);
@@ -191,63 +257,8 @@ impl NameGenerator {
     }
 }
 
-/// Suggest name of variable for given expression
+fn normalize(name: &str) -> Option<SmolStr> {
-///
+    let name = to_lower_snake_case(name).to_smolstr();
-/// **NOTE**: it is caller's responsibility to guarantee uniqueness of the name.
-/// I.e. it doesn't look for names in scope.
-///
-/// # Current implementation
-///
-/// In current implementation, the function tries to get the name from
-/// the following sources:
-///
-/// * if expr is an argument to function/method, use parameter name
-/// * if expr is a function/method call, use function name
-/// * expression type name if it exists (E.g. `()`, `fn() -> ()` or `!` do not have names)
-/// * fallback: `var_name`
-///
-/// It also applies heuristics to filter out less informative names
-///
-/// Currently it sticks to the first name found.
-// FIXME: Microoptimize and return a `SmolStr` here.
-pub fn for_variable(expr: &ast::Expr, sema: &Semantics<'_, RootDatabase>) -> String {
-    // `from_param` does not benefit from stripping
-    // it need the largest context possible
-    // so we check firstmost
-    if let Some(name) = from_param(expr, sema) {
-        return name;
-    }
-
-    let mut next_expr = Some(expr.clone());
-    while let Some(expr) = next_expr {
-        let name =
-            from_call(&expr).or_else(|| from_type(&expr, sema)).or_else(|| from_field_name(&expr));
-        if let Some(name) = name {
-            return name;
-        }
-
-        match expr {
-            ast::Expr::RefExpr(inner) => next_expr = inner.expr(),
-            ast::Expr::AwaitExpr(inner) => next_expr = inner.expr(),
-            // ast::Expr::BlockExpr(block) => expr = block.tail_expr(),
-            ast::Expr::CastExpr(inner) => next_expr = inner.expr(),
-            ast::Expr::MethodCallExpr(method) if is_useless_method(&method) => {
-                next_expr = method.receiver();
-            }
-            ast::Expr::ParenExpr(inner) => next_expr = inner.expr(),
-            ast::Expr::TryExpr(inner) => next_expr = inner.expr(),
-            ast::Expr::PrefixExpr(prefix) if prefix.op_kind() == Some(ast::UnaryOp::Deref) => {
-                next_expr = prefix.expr()
-            }
-            _ => break,
-        }
-    }
-
-    "var_name".to_owned()
-}
-
-fn normalize(name: &str) -> Option<String> {
-    let name = to_lower_snake_case(name);
 
     if USELESS_NAMES.contains(&name.as_str()) {
         return None;
@@ -280,11 +291,11 @@ fn is_useless_method(method: &ast::MethodCallExpr) -> bool {
     }
 }
 
-fn from_call(expr: &ast::Expr) -> Option<String> {
+fn from_call(expr: &ast::Expr) -> Option<SmolStr> {
     from_func_call(expr).or_else(|| from_method_call(expr))
 }
 
-fn from_func_call(expr: &ast::Expr) -> Option<String> {
+fn from_func_call(expr: &ast::Expr) -> Option<SmolStr> {
     let call = match expr {
         ast::Expr::CallExpr(call) => call,
         _ => return None,
@@ -297,7 +308,7 @@ fn from_func_call(expr: &ast::Expr) -> Option<String> {
     normalize(ident.text())
 }
 
-fn from_method_call(expr: &ast::Expr) -> Option<String> {
+fn from_method_call(expr: &ast::Expr) -> Option<SmolStr> {
     let method = match expr {
         ast::Expr::MethodCallExpr(call) => call,
         _ => return None,
@@ -319,7 +330,7 @@ fn from_method_call(expr: &ast::Expr) -> Option<String> {
     normalize(name)
 }
 
-fn from_param(expr: &ast::Expr, sema: &Semantics<'_, RootDatabase>) -> Option<String> {
+fn from_param(expr: &ast::Expr, sema: &Semantics<'_, RootDatabase>) -> Option<SmolStr> {
     let arg_list = expr.syntax().parent().and_then(ast::ArgList::cast)?;
     let args_parent = arg_list.syntax().parent()?;
     let func = match_ast! {
@@ -338,7 +349,7 @@ fn from_param(expr: &ast::Expr, sema: &Semantics<'_, RootDatabase>) -> Option<St
     let param = func.params().into_iter().nth(idx)?;
     let pat = sema.source(param)?.value.right()?.pat()?;
     let name = var_name_from_pat(&pat)?;
-    normalize(&name.to_string())
+    normalize(&name.to_smolstr())
 }
 
 fn var_name_from_pat(pat: &ast::Pat) -> Option<ast::Name> {
@@ -350,7 +361,7 @@ fn var_name_from_pat(pat: &ast::Pat) -> Option<ast::Name> {
     }
 }
 
-fn from_type(expr: &ast::Expr, sema: &Semantics<'_, RootDatabase>) -> Option<String> {
+fn from_type(expr: &ast::Expr, sema: &Semantics<'_, RootDatabase>) -> Option<SmolStr> {
     let ty = sema.type_of_expr(expr)?.adjusted();
     let ty = ty.remove_ref().unwrap_or(ty);
     let edition = sema.scope(expr.syntax())?.krate().edition(sema.db);
@@ -358,7 +369,7 @@ fn from_type(expr: &ast::Expr, sema: &Semantics<'_, RootDatabase>) -> Option<Str
     name_of_type(&ty, sema.db, edition)
 }
 
-fn name_of_type(ty: &hir::Type, db: &RootDatabase, edition: Edition) -> Option<String> {
+fn name_of_type(ty: &hir::Type, db: &RootDatabase, edition: Edition) -> Option<SmolStr> {
     let name = if let Some(adt) = ty.as_adt() {
         let name = adt.name(db).display(db, edition).to_string();
 
@@ -393,7 +404,7 @@ fn trait_name(trait_: &hir::Trait, db: &RootDatabase, edition: Edition) -> Optio
     Some(name)
 }
 
-fn from_field_name(expr: &ast::Expr) -> Option<String> {
+fn from_field_name(expr: &ast::Expr) -> Option<SmolStr> {
     let field = match expr {
         ast::Expr::FieldExpr(field) => field,
         _ => return None,
@@ -424,7 +435,7 @@ mod tests {
             frange.range,
             "selection is not an expression(yet contained in one)"
         );
-        let name = for_variable(&expr, &sema);
+        let name = NameGenerator::new().for_variable(&expr, &sema);
         assert_eq!(&name, expected);
     }