biomejs · arendjr · Nov 26, 2025 · Nov 26, 2025
diff --git a/crates/biome_js_type_info/src/format_type_info.rs b/crates/biome_js_type_info/src/format_type_info.rs
@@ -818,7 +818,14 @@ impl Format<FormatTypeContext> for Literal {
             Self::Object(obj) => write!(f, [&obj]),
             Self::RegExp(regex) => write!(
                 f,
-                [token("regex:"), space(), text(regex, TextSize::default())]
+                [
+                    token("regex:"),
+                    space(),
+                    token("/"),
+                    text(&regex.pattern, TextSize::default()),
+                    token("/"),
+                    text(&regex.flags, TextSize::default())
+                ]
             ),
             Self::String(lit) => write!(
                 f,

diff --git a/crates/biome_js_type_info/src/local_inference.rs b/crates/biome_js_type_info/src/local_inference.rs
@@ -22,13 +22,13 @@ use biome_js_syntax::{
     TsReturnTypeAnnotation, TsTypeAliasDeclaration, TsTypeAnnotation, TsTypeArguments, TsTypeList,
     TsTypeParameter, TsTypeParameters, TsTypeofType, inner_string_text, unescape_js_string,
 };
-use biome_rowan::{AstNode, SyntaxResult, Text, TokenText};
+use biome_rowan::{AstNode, SyntaxResult, Text, TextRange, TokenText};
 
 use crate::globals::{
     GLOBAL_GLOBAL_ID, GLOBAL_INSTANCEOF_PROMISE_ID, GLOBAL_NUMBER_ID, GLOBAL_STRING_ID,
     GLOBAL_UNDEFINED_ID,
 };
-use crate::literal::{BooleanLiteral, NumberLiteral, StringLiteral};
+use crate::literal::{BooleanLiteral, NumberLiteral, RegexpLiteral, StringLiteral};
 use crate::{
     AssertsReturnType, CallArgumentType, Class, Constructor, DestructureField, Function,
     FunctionParameter, FunctionParameterBinding, GenericTypeParameter, Interface, Literal, Module,
@@ -614,7 +614,7 @@ impl TypeData {
                 Literal::Number(NumberLiteral::new(text_from_token(expr.value_token())?))
             }
             AnyJsLiteralExpression::JsRegexLiteralExpression(expr) => {
-                Literal::RegExp(text_from_token(expr.value_token())?)
+                Literal::RegExp(split_regex_literal(expr.value_token())?)
             }
             AnyJsLiteralExpression::JsStringLiteralExpression(expr) => Literal::String(
                 StringLiteral::from(Text::from(expr.inner_string_text().ok()?)),
@@ -2536,6 +2536,28 @@ fn return_type_from_annotation(
         .and_then(|ty| ReturnType::from_any_ts_return_type(resolver, scope_id, &ty))
 }
 
+#[inline]
+fn split_regex_literal(token: SyntaxResult<JsSyntaxToken>) -> Option<RegexpLiteral> {
+    let literal = token.ok()?.token_text_trimmed();
+    let open_index: usize = literal.find('/')? + 1;
+    let close_index: usize = literal.rfind('/')?;
+    if open_index == close_index {
+        return None;
+    }
+
+    let literal_len = usize::from(literal.len());
+
+    Some(RegexpLiteral {
+        pattern: literal
+            .clone()
+            .slice(TextRange::try_from((open_index, close_index)).ok()?)
+            .into(),
+        flags: literal
+            .slice(TextRange::try_from((close_index + 1, literal_len)).ok()?)
+            .into(),
+    })
+}
+
 #[inline]
 fn text_from_any_js_name(name: AnyJsName) -> Option<Text> {
     match name {

diff --git a/crates/biome_js_type_info/src/type_data.rs b/crates/biome_js_type_info/src/type_data.rs
@@ -22,6 +22,7 @@ use biome_rowan::Text;
 use crate::{
     ModuleId, Resolvable, ResolvedTypeId, ResolverId, TypeResolver,
     globals::{GLOBAL_NUMBER_ID, GLOBAL_STRING_ID, GLOBAL_UNKNOWN_ID},
+    literal::RegexpLiteral,
     type_data::literal::{BooleanLiteral, NumberLiteral, StringLiteral},
 };
 
@@ -647,7 +648,7 @@ pub enum Literal {
     Boolean(BooleanLiteral),
     Number(NumberLiteral),
     Object(ObjectLiteral),
-    RegExp(Text),
+    RegExp(RegexpLiteral),
     String(StringLiteral),
     Template(Text), // TODO: Custom impl of PartialEq for template literals
 }

diff --git a/crates/biome_js_type_info/src/type_data/literal.rs b/crates/biome_js_type_info/src/type_data/literal.rs
@@ -81,6 +81,35 @@ impl NumberLiteral {
     }
 }
 
+#[derive(Clone, Debug, Default, Eq, Hash, PartialEq, Resolvable)]
+pub struct RegexpLiteral {
+    /// The pattern to match against.
+    ///
+    /// Examples:
+    ///
+    /// ```js
+    /// const regex1 = /hello/;
+    /// //     Pattern: ^^^^^
+    ///
+    /// const regex2 = new RegExp("world", "i");
+    /// //                Pattern: ^^^^^
+    /// ```
+    pub pattern: Text,
+
+    /// The flags carried by the expression.
+    ///
+    /// Examples:
+    ///
+    /// ```js
+    /// const regex1 = /hello/i;
+    /// //              Flag: ^
+    ///
+    /// const regex2 = new RegExp("world", "g");
+    /// //                            Flag: ^
+    /// ```
+    pub flags: Text,
+}
+
 #[derive(Clone, Debug, Default, Eq, Hash, PartialEq, Resolvable)]
 pub struct StringLiteral(Text);
 

diff --git a/crates/biome_js_type_info/tests/local_inference.rs b/crates/biome_js_type_info/tests/local_inference.rs
@@ -45,6 +45,17 @@ fn infer_type_of_regex() {
     assert_type_data_snapshot(CODE, &ty, &resolver, "infer_type_of_regex");
 }
 
+#[test]
+fn infer_type_of_regex_with_flags() {
+    const CODE: &str = r#"/ab+c/gi"#;
+
+    let root = parse_ts(CODE);
+    let expr = get_expression(&root);
+    let mut resolver = GlobalsResolver::default();
+    let ty = TypeData::from_any_js_expression(&mut resolver, ScopeId::GLOBAL, &expr);
+    assert_type_data_snapshot(CODE, &ty, &resolver, "infer_type_of_regex_with_flags");
+}
+
 #[test]
 fn infer_type_of_typeof_expression() {
     const CODE: &str = r#"typeof foo"#;

diff --git a/crates/biome_js_type_info/tests/snapshots/infer_type_of_regex_with_flags.snap b/crates/biome_js_type_info/tests/snapshots/infer_type_of_regex_with_flags.snap
@@ -0,0 +1,16 @@
+---
+source: crates/biome_js_type_info/tests/utils.rs
+expression: content
+---
+## Input
+
+```ts
+/ab+c/gi;
+
+```
+
+## Result
+
+```
+regex: /ab+c/gi
+```