diff --git a/tests/baselines/reference/intersectionWithUnionConstraint.errors.txt b/tests/baselines/reference/intersectionWithUnionConstraint.errors.txt
new file mode 100644
index 00000000000..8892e412805
--- /dev/null
+++ b/tests/baselines/reference/intersectionWithUnionConstraint.errors.txt
@@ -0,0 +1,71 @@
+tests/cases/conformance/types/intersection/intersectionWithUnionConstraint.ts(7,9): error TS2322: Type 'T & U' is not assignable to type 'string | number'.
+  Type 'string | undefined' is not assignable to type 'string | number'.
+    Type 'undefined' is not assignable to type 'string | number'.
+      Type 'T & U' is not assignable to type 'number'.
+tests/cases/conformance/types/intersection/intersectionWithUnionConstraint.ts(8,9): error TS2322: Type 'T & U' is not assignable to type 'string | null'.
+  Type 'string | undefined' is not assignable to type 'string | null'.
+    Type 'undefined' is not assignable to type 'string | null'.
+      Type 'T & U' is not assignable to type 'string'.
+tests/cases/conformance/types/intersection/intersectionWithUnionConstraint.ts(10,9): error TS2322: Type 'T & U' is not assignable to type 'number | null'.
+  Type 'string | undefined' is not assignable to type 'number | null'.
+    Type 'undefined' is not assignable to type 'number | null'.
+      Type 'T & U' is not assignable to type 'number'.
+tests/cases/conformance/types/intersection/intersectionWithUnionConstraint.ts(11,9): error TS2322: Type 'T & U' is not assignable to type 'number | undefined'.
+  Type 'string | undefined' is not assignable to type 'number | undefined'.
+    Type 'string' is not assignable to type 'number | undefined'.
+      Type 'T & U' is not assignable to type 'number'.
+tests/cases/conformance/types/intersection/intersectionWithUnionConstraint.ts(12,9): error TS2322: Type 'T & U' is not assignable to type 'null | undefined'.
+  Type 'string | undefined' is not assignable to type 'null | undefined'.
+    Type 'string' is not assignable to type 'null | undefined'.
+      Type 'T & U' is not assignable to type 'null'.
+
+
+==== tests/cases/conformance/types/intersection/intersectionWithUnionConstraint.ts (5 errors) ====
+    function f1<T extends string | number, U extends string | number>(x: T & U) {
+        // Combined constraint of 'T & U' is 'string | number'
+        let y: string | number = x;
+    }
+    
+    function f2<T extends string | number | undefined, U extends string | null | undefined>(x: T & U) {
+        let y1: string | number = x;     // Error
+            ~~
+!!! error TS2322: Type 'T & U' is not assignable to type 'string | number'.
+!!! error TS2322:   Type 'string | undefined' is not assignable to type 'string | number'.
+!!! error TS2322:     Type 'undefined' is not assignable to type 'string | number'.
+!!! error TS2322:       Type 'T & U' is not assignable to type 'number'.
+        let y2: string | null = x;       // Error
+            ~~
+!!! error TS2322: Type 'T & U' is not assignable to type 'string | null'.
+!!! error TS2322:   Type 'string | undefined' is not assignable to type 'string | null'.
+!!! error TS2322:     Type 'undefined' is not assignable to type 'string | null'.
+!!! error TS2322:       Type 'T & U' is not assignable to type 'string'.
+        let y3: string | undefined = x;
+        let y4: number | null = x;       // Error
+            ~~
+!!! error TS2322: Type 'T & U' is not assignable to type 'number | null'.
+!!! error TS2322:   Type 'string | undefined' is not assignable to type 'number | null'.
+!!! error TS2322:     Type 'undefined' is not assignable to type 'number | null'.
+!!! error TS2322:       Type 'T & U' is not assignable to type 'number'.
+        let y5: number | undefined = x;  // Error
+            ~~
+!!! error TS2322: Type 'T & U' is not assignable to type 'number | undefined'.
+!!! error TS2322:   Type 'string | undefined' is not assignable to type 'number | undefined'.
+!!! error TS2322:     Type 'string' is not assignable to type 'number | undefined'.
+!!! error TS2322:       Type 'T & U' is not assignable to type 'number'.
+        let y6: null | undefined = x;    // Error
+            ~~
+!!! error TS2322: Type 'T & U' is not assignable to type 'null | undefined'.
+!!! error TS2322:   Type 'string | undefined' is not assignable to type 'null | undefined'.
+!!! error TS2322:     Type 'string' is not assignable to type 'null | undefined'.
+!!! error TS2322:       Type 'T & U' is not assignable to type 'null'.
+    }
+    
+    type T1 = (string | number | undefined) & (string | null | undefined);  // string | undefined
+    
+    // Repro from #23648
+    
+    type Example<T, U> = { [K in keyof T]: K extends keyof U ? UnexpectedError<K> : NoErrorHere<K> }
+    
+    type UnexpectedError<T extends PropertyKey> = T
+    type NoErrorHere<T extends PropertyKey> = T
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/intersectionWithUnionConstraint.js b/tests/baselines/reference/intersectionWithUnionConstraint.js
new file mode 100644
index 00000000000..6069dbda75c
--- /dev/null
+++ b/tests/baselines/reference/intersectionWithUnionConstraint.js
@@ -0,0 +1,39 @@
+//// [intersectionWithUnionConstraint.ts]
+function f1<T extends string | number, U extends string | number>(x: T & U) {
+    // Combined constraint of 'T & U' is 'string | number'
+    let y: string | number = x;
+}
+
+function f2<T extends string | number | undefined, U extends string | null | undefined>(x: T & U) {
+    let y1: string | number = x;     // Error
+    let y2: string | null = x;       // Error
+    let y3: string | undefined = x;
+    let y4: number | null = x;       // Error
+    let y5: number | undefined = x;  // Error
+    let y6: null | undefined = x;    // Error
+}
+
+type T1 = (string | number | undefined) & (string | null | undefined);  // string | undefined
+
+// Repro from #23648
+
+type Example<T, U> = { [K in keyof T]: K extends keyof U ? UnexpectedError<K> : NoErrorHere<K> }
+
+type UnexpectedError<T extends PropertyKey> = T
+type NoErrorHere<T extends PropertyKey> = T
+
+
+//// [intersectionWithUnionConstraint.js]
+"use strict";
+function f1(x) {
+    // Combined constraint of 'T & U' is 'string | number'
+    var y = x;
+}
+function f2(x) {
+    var y1 = x; // Error
+    var y2 = x; // Error
+    var y3 = x;
+    var y4 = x; // Error
+    var y5 = x; // Error
+    var y6 = x; // Error
+}
diff --git a/tests/baselines/reference/intersectionWithUnionConstraint.symbols b/tests/baselines/reference/intersectionWithUnionConstraint.symbols
new file mode 100644
index 00000000000..d7ee1e86a22
--- /dev/null
+++ b/tests/baselines/reference/intersectionWithUnionConstraint.symbols
@@ -0,0 +1,78 @@
+=== tests/cases/conformance/types/intersection/intersectionWithUnionConstraint.ts ===
+function f1<T extends string | number, U extends string | number>(x: T & U) {
+>f1 : Symbol(f1, Decl(intersectionWithUnionConstraint.ts, 0, 0))
+>T : Symbol(T, Decl(intersectionWithUnionConstraint.ts, 0, 12))
+>U : Symbol(U, Decl(intersectionWithUnionConstraint.ts, 0, 38))
+>x : Symbol(x, Decl(intersectionWithUnionConstraint.ts, 0, 66))
+>T : Symbol(T, Decl(intersectionWithUnionConstraint.ts, 0, 12))
+>U : Symbol(U, Decl(intersectionWithUnionConstraint.ts, 0, 38))
+
+    // Combined constraint of 'T & U' is 'string | number'
+    let y: string | number = x;
+>y : Symbol(y, Decl(intersectionWithUnionConstraint.ts, 2, 7))
+>x : Symbol(x, Decl(intersectionWithUnionConstraint.ts, 0, 66))
+}
+
+function f2<T extends string | number | undefined, U extends string | null | undefined>(x: T & U) {
+>f2 : Symbol(f2, Decl(intersectionWithUnionConstraint.ts, 3, 1))
+>T : Symbol(T, Decl(intersectionWithUnionConstraint.ts, 5, 12))
+>U : Symbol(U, Decl(intersectionWithUnionConstraint.ts, 5, 50))
+>x : Symbol(x, Decl(intersectionWithUnionConstraint.ts, 5, 88))
+>T : Symbol(T, Decl(intersectionWithUnionConstraint.ts, 5, 12))
+>U : Symbol(U, Decl(intersectionWithUnionConstraint.ts, 5, 50))
+
+    let y1: string | number = x;     // Error
+>y1 : Symbol(y1, Decl(intersectionWithUnionConstraint.ts, 6, 7))
+>x : Symbol(x, Decl(intersectionWithUnionConstraint.ts, 5, 88))
+
+    let y2: string | null = x;       // Error
+>y2 : Symbol(y2, Decl(intersectionWithUnionConstraint.ts, 7, 7))
+>x : Symbol(x, Decl(intersectionWithUnionConstraint.ts, 5, 88))
+
+    let y3: string | undefined = x;
+>y3 : Symbol(y3, Decl(intersectionWithUnionConstraint.ts, 8, 7))
+>x : Symbol(x, Decl(intersectionWithUnionConstraint.ts, 5, 88))
+
+    let y4: number | null = x;       // Error
+>y4 : Symbol(y4, Decl(intersectionWithUnionConstraint.ts, 9, 7))
+>x : Symbol(x, Decl(intersectionWithUnionConstraint.ts, 5, 88))
+
+    let y5: number | undefined = x;  // Error
+>y5 : Symbol(y5, Decl(intersectionWithUnionConstraint.ts, 10, 7))
+>x : Symbol(x, Decl(intersectionWithUnionConstraint.ts, 5, 88))
+
+    let y6: null | undefined = x;    // Error
+>y6 : Symbol(y6, Decl(intersectionWithUnionConstraint.ts, 11, 7))
+>x : Symbol(x, Decl(intersectionWithUnionConstraint.ts, 5, 88))
+}
+
+type T1 = (string | number | undefined) & (string | null | undefined);  // string | undefined
+>T1 : Symbol(T1, Decl(intersectionWithUnionConstraint.ts, 12, 1))
+
+// Repro from #23648
+
+type Example<T, U> = { [K in keyof T]: K extends keyof U ? UnexpectedError<K> : NoErrorHere<K> }
+>Example : Symbol(Example, Decl(intersectionWithUnionConstraint.ts, 14, 70))
+>T : Symbol(T, Decl(intersectionWithUnionConstraint.ts, 18, 13))
+>U : Symbol(U, Decl(intersectionWithUnionConstraint.ts, 18, 15))
+>K : Symbol(K, Decl(intersectionWithUnionConstraint.ts, 18, 24))
+>T : Symbol(T, Decl(intersectionWithUnionConstraint.ts, 18, 13))
+>K : Symbol(K, Decl(intersectionWithUnionConstraint.ts, 18, 24))
+>U : Symbol(U, Decl(intersectionWithUnionConstraint.ts, 18, 15))
+>UnexpectedError : Symbol(UnexpectedError, Decl(intersectionWithUnionConstraint.ts, 18, 96))
+>K : Symbol(K, Decl(intersectionWithUnionConstraint.ts, 18, 24))
+>NoErrorHere : Symbol(NoErrorHere, Decl(intersectionWithUnionConstraint.ts, 20, 47))
+>K : Symbol(K, Decl(intersectionWithUnionConstraint.ts, 18, 24))
+
+type UnexpectedError<T extends PropertyKey> = T
+>UnexpectedError : Symbol(UnexpectedError, Decl(intersectionWithUnionConstraint.ts, 18, 96))
+>T : Symbol(T, Decl(intersectionWithUnionConstraint.ts, 20, 21))
+>PropertyKey : Symbol(PropertyKey, Decl(lib.d.ts, --, --))
+>T : Symbol(T, Decl(intersectionWithUnionConstraint.ts, 20, 21))
+
+type NoErrorHere<T extends PropertyKey> = T
+>NoErrorHere : Symbol(NoErrorHere, Decl(intersectionWithUnionConstraint.ts, 20, 47))
+>T : Symbol(T, Decl(intersectionWithUnionConstraint.ts, 21, 17))
+>PropertyKey : Symbol(PropertyKey, Decl(lib.d.ts, --, --))
+>T : Symbol(T, Decl(intersectionWithUnionConstraint.ts, 21, 17))
+
diff --git a/tests/baselines/reference/intersectionWithUnionConstraint.types b/tests/baselines/reference/intersectionWithUnionConstraint.types
new file mode 100644
index 00000000000..df5fa0f14d3
--- /dev/null
+++ b/tests/baselines/reference/intersectionWithUnionConstraint.types
@@ -0,0 +1,83 @@
+=== tests/cases/conformance/types/intersection/intersectionWithUnionConstraint.ts ===
+function f1<T extends string | number, U extends string | number>(x: T & U) {
+>f1 : <T extends string | number, U extends string | number>(x: T & U) => void
+>T : T
+>U : U
+>x : T & U
+>T : T
+>U : U
+
+    // Combined constraint of 'T & U' is 'string | number'
+    let y: string | number = x;
+>y : string | number
+>x : T & U
+}
+
+function f2<T extends string | number | undefined, U extends string | null | undefined>(x: T & U) {
+>f2 : <T extends string | number | undefined, U extends string | null | undefined>(x: T & U) => void
+>T : T
+>U : U
+>null : null
+>x : T & U
+>T : T
+>U : U
+
+    let y1: string | number = x;     // Error
+>y1 : string | number
+>x : T & U
+
+    let y2: string | null = x;       // Error
+>y2 : string | null
+>null : null
+>x : T & U
+
+    let y3: string | undefined = x;
+>y3 : string | undefined
+>x : T & U
+
+    let y4: number | null = x;       // Error
+>y4 : number | null
+>null : null
+>x : T & U
+
+    let y5: number | undefined = x;  // Error
+>y5 : number | undefined
+>x : T & U
+
+    let y6: null | undefined = x;    // Error
+>y6 : null | undefined
+>null : null
+>x : T & U
+}
+
+type T1 = (string | number | undefined) & (string | null | undefined);  // string | undefined
+>T1 : string | undefined
+>null : null
+
+// Repro from #23648
+
+type Example<T, U> = { [K in keyof T]: K extends keyof U ? UnexpectedError<K> : NoErrorHere<K> }
+>Example : Example<T, U>
+>T : T
+>U : U
+>K : K
+>T : T
+>K : K
+>U : U
+>UnexpectedError : T
+>K : K
+>NoErrorHere : T
+>K : K
+
+type UnexpectedError<T extends PropertyKey> = T
+>UnexpectedError : T
+>T : T
+>PropertyKey : string | number | symbol
+>T : T
+
+type NoErrorHere<T extends PropertyKey> = T
+>NoErrorHere : T
+>T : T
+>PropertyKey : string | number | symbol
+>T : T
+