biomejs · arendjr · Nov 19, 2025 · Nov 19, 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
@@ -788,23 +788,50 @@ impl Format<FormatTypeContext> for Interface {
 
 impl Format<FormatTypeContext> for Literal {
     fn fmt(&self, f: &mut Formatter<FormatTypeContext>) -> FormatResult<()> {
-        write!(f, [&format_args![token("value:"), space()]])?;
         match self {
-            Self::BigInt(bigint_text) => write!(f, [text(bigint_text, TextSize::default())]),
+            Self::BigInt(bigint_text) => write!(
+                f,
+                [
+                    token("bigint:"),
+                    space(),
+                    text(bigint_text, TextSize::default())
+                ]
+            ),
             Self::Boolean(lit) => write!(
                 f,
-                [text(
-                    lit.as_bool().to_string().as_str(),
-                    TextSize::default()
-                )]
+                [
+                    token("bool:"),
+                    space(),
+                    text(lit.as_bool().to_string().as_str(), TextSize::default())
+                ]
             ),
             Self::Number(lit) => {
-                write!(f, [text(lit.as_str(), TextSize::default())])
+                write!(
+                    f,
+                    [
+                        token("number:"),
+                        space(),
+                        text(lit.as_str(), TextSize::default())
+                    ]
+                )
             }
             Self::Object(obj) => write!(f, [&obj]),
-            Self::RegExp(regexp_text) => write!(f, [text(regexp_text, TextSize::default())]),
-            Self::String(lit) => write!(f, [text(lit.as_str(), TextSize::default())]),
-            Self::Template(template_text) => write!(f, [text(template_text, TextSize::default())]),
+            Self::RegExp(regex) => write!(
+                f,
+                [token("regex:"), space(), text(regex, TextSize::default())]
+            ),
+            Self::String(lit) => write!(
+                f,
+                [
+                    token("string:"),
+                    space(),
+                    text(lit.as_str(), TextSize::default())
+                ]
+            ),
+            Self::Template(tmpl) => write!(
+                f,
+                [token("string:"), space(), text(tmpl, TextSize::default())]
+            ),
         }
     }
 }

diff --git a/crates/biome_js_type_info/src/globals.rs b/crates/biome_js_type_info/src/globals.rs
@@ -1,6 +1,6 @@
 //! Hardcoded global definitions.
 
-// FIXME: Implement inference from type definitions.
+// FIXME: Implement inference from type definitions: https://github.com/biomejs/biome/issues/5977
 
 use std::{
     borrow::Cow,
@@ -59,22 +59,25 @@ pub const PROMISE_RACE_ID: TypeId = TypeId::new(22);
 pub const PROMISE_REJECT_ID: TypeId = TypeId::new(23);
 pub const PROMISE_RESOLVE_ID: TypeId = TypeId::new(24);
 pub const PROMISE_TRY_ID: TypeId = TypeId::new(25);
-pub const BIGINT_STRING_LITERAL_ID: TypeId = TypeId::new(26);
-pub const BOOLEAN_STRING_LITERAL_ID: TypeId = TypeId::new(27);
-pub const FUNCTION_STRING_LITERAL_ID: TypeId = TypeId::new(28);
-pub const NUMBER_STRING_LITERAL_ID: TypeId = TypeId::new(29);
-pub const OBJECT_STRING_LITERAL_ID: TypeId = TypeId::new(30);
-pub const STRING_STRING_LITERAL_ID: TypeId = TypeId::new(31);
-pub const SYMBOL_STRING_LITERAL_ID: TypeId = TypeId::new(32);
-pub const UNDEFINED_STRING_LITERAL_ID: TypeId = TypeId::new(33);
-pub const TYPEOF_OPERATOR_RETURN_UNION_ID: TypeId = TypeId::new(34);
-pub const T_ID: TypeId = TypeId::new(35);
-pub const U_ID: TypeId = TypeId::new(36);
-pub const CONDITIONAL_CALLBACK_ID: TypeId = TypeId::new(37);
-pub const MAP_CALLBACK_ID: TypeId = TypeId::new(38);
-pub const VOID_CALLBACK_ID: TypeId = TypeId::new(39);
-pub const FETCH_ID: TypeId = TypeId::new(40);
-pub const NUM_PREDEFINED_TYPES: usize = 41; // Must be one more than the highest `TypeId` above.
+pub const INSTANCEOF_REGEXP_ID: TypeId = TypeId::new(26);
+pub const REGEXP_ID: TypeId = TypeId::new(27);
+pub const REGEXP_EXEC_ID: TypeId = TypeId::new(28);
+pub const BIGINT_STRING_LITERAL_ID: TypeId = TypeId::new(29);
+pub const BOOLEAN_STRING_LITERAL_ID: TypeId = TypeId::new(30);
+pub const FUNCTION_STRING_LITERAL_ID: TypeId = TypeId::new(31);
+pub const NUMBER_STRING_LITERAL_ID: TypeId = TypeId::new(32);
+pub const OBJECT_STRING_LITERAL_ID: TypeId = TypeId::new(33);
+pub const STRING_STRING_LITERAL_ID: TypeId = TypeId::new(34);
+pub const SYMBOL_STRING_LITERAL_ID: TypeId = TypeId::new(35);
+pub const UNDEFINED_STRING_LITERAL_ID: TypeId = TypeId::new(36);
+pub const TYPEOF_OPERATOR_RETURN_UNION_ID: TypeId = TypeId::new(37);
+pub const T_ID: TypeId = TypeId::new(38);
+pub const U_ID: TypeId = TypeId::new(39);
+pub const CONDITIONAL_CALLBACK_ID: TypeId = TypeId::new(40);
+pub const MAP_CALLBACK_ID: TypeId = TypeId::new(41);
+pub const VOID_CALLBACK_ID: TypeId = TypeId::new(42);
+pub const FETCH_ID: TypeId = TypeId::new(43);
+pub const NUM_PREDEFINED_TYPES: usize = 44; // Must be one more than the highest `TypeId` above.
 
 pub const GLOBAL_UNKNOWN_ID: ResolvedTypeId = ResolvedTypeId::new(GLOBAL_LEVEL, UNKNOWN_ID);
 pub const GLOBAL_UNDEFINED_ID: ResolvedTypeId = ResolvedTypeId::new(GLOBAL_LEVEL, UNDEFINED_ID);
@@ -83,6 +86,9 @@ pub const GLOBAL_CONDITIONAL_ID: ResolvedTypeId = ResolvedTypeId::new(GLOBAL_LEV
 pub const GLOBAL_NUMBER_ID: ResolvedTypeId = ResolvedTypeId::new(GLOBAL_LEVEL, NUMBER_ID);
 pub const GLOBAL_STRING_ID: ResolvedTypeId = ResolvedTypeId::new(GLOBAL_LEVEL, STRING_ID);
 pub const GLOBAL_ARRAY_ID: ResolvedTypeId = ResolvedTypeId::new(GLOBAL_LEVEL, ARRAY_ID);
+pub const GLOBAL_INSTANCEOF_REGEXP_ID: ResolvedTypeId =
+    ResolvedTypeId::new(GLOBAL_LEVEL, INSTANCEOF_REGEXP_ID);
+pub const GLOBAL_REGEXP_ID: ResolvedTypeId = ResolvedTypeId::new(GLOBAL_LEVEL, REGEXP_ID);
 pub const GLOBAL_GLOBAL_ID /* :smirk: */: ResolvedTypeId = ResolvedTypeId::new(GLOBAL_LEVEL, GLOBAL_ID);
 pub const GLOBAL_INSTANCEOF_PROMISE_ID: ResolvedTypeId =
     ResolvedTypeId::new(GLOBAL_LEVEL, INSTANCEOF_PROMISE_ID);
@@ -140,24 +146,27 @@ pub fn global_type_name(id: TypeId) -> &'static str {
         23 => "Promise.reject",
         24 => "Promise.resolve",
         25 => "Promise.try",
-        26 => "\"bigint\"",
-        27 => "\"boolean\"",
-        28 => "\"function\"",
-        29 => "\"number\"",
-        30 => "\"object\"",
-        31 => "\"string\"",
-        32 => "\"symbol\"",
-        33 => "\"undefined\"",
-        34 => {
+        26 => "instanceof RegExp",
+        27 => "RegExp",
+        28 => "RegExp.exec",
+        29 => "\"bigint\"",
+        30 => "\"boolean\"",
+        31 => "\"function\"",
+        32 => "\"number\"",
+        33 => "\"object\"",
+        34 => "\"string\"",
+        35 => "\"symbol\"",
+        36 => "\"undefined\"",
+        37 => {
             "\"bigint\" | \"boolean\" | \"function\" | \"number\" | \"object\" \
                 | \"string\" | \"symbol\" | \"undefined\""
         }
-        35 => "T",
-        36 => "U",
-        37 => "() => conditional",
-        38 => "<U>(item: T) => U",
-        39 => "() => void",
-        40 => "fetch",
+        38 => "T",
+        39 => "U",
+        40 => "() => conditional",
+        41 => "<U>(item: T) => U",
+        42 => "() => void",
+        43 => "fetch",
         _ => "inferred type",
     }
 }
@@ -215,6 +224,16 @@ impl Default for GlobalsResolver {
             })
         };
 
+        let regexp_method_definition = |id: TypeId| {
+            TypeData::from(Function {
+                is_async: false,
+                type_parameters: Default::default(),
+                name: Some(Text::new_static(global_type_name(id))),
+                parameters: Default::default(),
+                return_type: ReturnType::Type(GLOBAL_INSTANCEOF_REGEXP_ID.into()),
+            })
+        };
+
         let string_literal = |value: &'static str| -> TypeData {
             TypeData::from(Literal::String(Text::new_static(value).into()))
         };
@@ -311,6 +330,15 @@ impl Default for GlobalsResolver {
             promise_method_definition(PROMISE_REJECT_ID),
             promise_method_definition(PROMISE_RESOLVE_ID),
             promise_method_definition(PROMISE_TRY_ID),
+            TypeData::instance_of(TypeReference::from(GLOBAL_REGEXP_ID)),
+            TypeData::Class(Box::new(Class {
+                name: Some(Text::new_static("RegExp")),
+                type_parameters: Box::default(),
+                extends: None,
+                implements: [].into(),
+                members: Box::new([method("exec", REGEXP_EXEC_ID)]),
+            })),
+            regexp_method_definition(REGEXP_EXEC_ID),
             string_literal("bigint"),
             string_literal("boolean"),
             string_literal("function"),
@@ -454,6 +482,8 @@ impl TypeResolver for GlobalsResolver {
             Some(GLOBAL_ARRAY_ID)
         } else if qualifier.is_promise() && !qualifier.has_known_type_parameters() {
             Some(GLOBAL_PROMISE_ID)
+        } else if qualifier.is_regex() && !qualifier.has_known_type_parameters() {
+            Some(GLOBAL_REGEXP_ID)
         } else if !qualifier.type_only
             && let Some(ident) = qualifier.path.identifier()
         {

diff --git a/crates/biome_js_type_info/src/type_data.rs b/crates/biome_js_type_info/src/type_data.rs
@@ -1402,6 +1402,17 @@ impl TypeReferenceQualifier {
         self.path.is_identifier("Promise")
     }
 
+    /// Checks whether this type qualifier references the `RegExp` type.
+    ///
+    /// This method simply checks whether the reference is for a literal
+    /// `RegExp`, without considering whether another symbol named `RegExp` is
+    /// in scope. It can be used _after_ type resolution has failed to find a
+    /// `RegExp` symbol in scope, but should not be used _instead of_ such type
+    /// resolution.
+    pub fn is_regex(&self) -> bool {
+        self.path.is_identifier("RegExp")
+    }
+
     pub fn with_excluded_binding_id(mut self, binding_id: BindingId) -> Self {
         self.excluded_binding_id = Some(binding_id);
         self

diff --git a/crates/biome_js_type_info/tests/local_inference.rs b/crates/biome_js_type_info/tests/local_inference.rs
@@ -34,6 +34,17 @@ fn infer_type_of_object_member_expression() {
     );
 }
 
+#[test]
+fn infer_type_of_regex() {
+    const CODE: &str = r#"/ab+c/"#;
+
+    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");
+}
+
 #[test]
 fn infer_type_of_typeof_expression() {
     const CODE: &str = r#"typeof foo"#;

diff --git a/...biome_js_type_info/tests/snapshots/infer_flattened_type_from_direct_promise_instance.snap b/...biome_js_type_info/tests/snapshots/infer_flattened_type_from_direct_promise_instance.snap
@@ -18,7 +18,7 @@ instanceof Promise
 ## Registered types
 
 ```
-Global TypeId(0) => value: value
+Global TypeId(0) => string: value
 
 Global TypeId(1) => Call unresolved reference "resolve" (scope ID: 0)(Global TypeId(0))
 

diff --git a/...biome_js_type_info/tests/snapshots/infer_flattened_type_from_static_promise_function.snap b/...biome_js_type_info/tests/snapshots/infer_flattened_type_from_static_promise_function.snap
@@ -20,5 +20,5 @@ instanceof Promise
 ```
 Global TypeId(0) => Promise.resolve
 
-Global TypeId(1) => value: value
+Global TypeId(1) => string: value
 ```
diff --git a/crates/biome_js_type_info/tests/snapshots/infer_flattened_type_of_typeof_expression.snap b/crates/biome_js_type_info/tests/snapshots/infer_flattened_type_of_typeof_expression.snap
@@ -20,7 +20,7 @@ typeof foo;
 ## Registered types
 
 ```
-Thin TypeId(0) => value: foo
+Thin TypeId(0) => string: foo
 
-Global TypeId(0) => value: foo
+Global TypeId(0) => string: foo
 ```
diff --git a/.../biome_js_type_info/tests/snapshots/infer_resolved_type_from_direct_promise_instance.snap b/.../biome_js_type_info/tests/snapshots/infer_resolved_type_from_direct_promise_instance.snap
@@ -18,7 +18,7 @@ new Promise
 ## Registered types
 
 ```
-Global TypeId(0) => value: value
+Global TypeId(0) => string: value
 
 Global TypeId(1) => Call unresolved reference "resolve" (scope ID: 0)(Global TypeId(0))
 

diff --git a/.../biome_js_type_info/tests/snapshots/infer_resolved_type_from_static_promise_function.snap b/.../biome_js_type_info/tests/snapshots/infer_resolved_type_from_static_promise_function.snap
@@ -20,5 +20,5 @@ Call Global TypeId(0)(Global TypeId(1))
 ```
 Global TypeId(0) => Promise.resolve
 
-Global TypeId(1) => value: value
+Global TypeId(1) => string: value
 ```
diff --git a/crates/biome_js_type_info/tests/snapshots/infer_type_of_binary_expression_eq.snap b/crates/biome_js_type_info/tests/snapshots/infer_type_of_binary_expression_eq.snap
@@ -12,12 +12,12 @@ const a = 1 === 1;
 ## Result
 
 ```
-a => value: true
+a => bool: true
 
 ```
 
 ## Registered types
 
 ```
-Global TypeId(0) => value: true
+Global TypeId(0) => bool: true
 ```
diff --git a/crates/biome_js_type_info/tests/snapshots/infer_type_of_binary_expression_ne.snap b/crates/biome_js_type_info/tests/snapshots/infer_type_of_binary_expression_ne.snap
@@ -12,12 +12,12 @@ const a = 0 !== 1;
 ## Result
 
 ```
-a => value: true
+a => bool: true
 
 ```
 
 ## Registered types
 
 ```
-Global TypeId(0) => value: true
+Global TypeId(0) => bool: true
 ```
diff --git a/crates/biome_js_type_info/tests/snapshots/infer_type_of_literal.snap b/crates/biome_js_type_info/tests/snapshots/infer_type_of_literal.snap
@@ -12,12 +12,12 @@ const a = 123.45;
 ## Result
 
 ```
-a => value: 123.45
+a => number: 123.45
 
 ```
 
 ## Registered types
 
 ```
-Global TypeId(0) => value: 123.45
+Global TypeId(0) => number: 123.45
 ```
diff --git a/crates/biome_js_type_info/tests/snapshots/infer_type_of_regex.snap b/crates/biome_js_type_info/tests/snapshots/infer_type_of_regex.snap
@@ -0,0 +1,16 @@
+---
+source: crates/biome_js_type_info/tests/utils.rs
+expression: content
+---
+## Input
+
+```ts
+/ab+c/;
+
+```
+
+## Result
+
+```
+regex: /ab+c/
+```
diff --git a/crates/biome_js_type_info/tests/snapshots/test_reference_to_falsy_subset_of.snap b/crates/biome_js_type_info/tests/snapshots/test_reference_to_falsy_subset_of.snap
@@ -24,7 +24,7 @@ Global TypeId(1) => undefined | Global TypeId(0) | number
 
 Global TypeId(2) => undefined | Global TypeId(0) | number
 
-Global TypeId(3) => value: 0
+Global TypeId(3) => number: 0
 
 Global TypeId(4) => undefined | Global TypeId(0) | Global TypeId(3)
 ```
diff --git a/...iome_module_graph/tests/snapshots/test_resolve_export_type_referencing_imported_type.snap b/...iome_module_graph/tests/snapshots/test_resolve_export_type_referencing_imported_type.snap
@@ -50,7 +50,7 @@ Module TypeId(0) => Promise
 
 Module TypeId(1) => Module(0) TypeId(7)
 
-Module TypeId(2) => value: true
+Module TypeId(2) => bool: true
 
 Module TypeId(3) => Object {
   prototype: No prototype
@@ -114,9 +114,9 @@ BindingId(0) => JsBindingData {
 ## Registered types
 
 ```
-Module TypeId(0) => value: true
+Module TypeId(0) => bool: true
 
-Module TypeId(1) => value: false
+Module TypeId(1) => bool: false
 
 Module TypeId(2) => Module(0) TypeId(0) | Module(0) TypeId(1)
 

diff --git a/crates/biome_module_graph/tests/snapshots/test_resolve_export_types.snap b/crates/biome_module_graph/tests/snapshots/test_resolve_export_types.snap
@@ -73,13 +73,13 @@ BindingId(3) => JsBindingData {
 ## Registered types
 
 ```
-Module TypeId(0) => value: 42
+Module TypeId(0) => number: 42
 
 Module TypeId(1) => Module(0) TypeId(0)
 
 Module TypeId(2) => number
 
-Module TypeId(3) => value: Life, The Universe, and Everything
+Module TypeId(3) => string: Life, The Universe, and Everything
 
 Module TypeId(4) => Module(0) TypeId(10)