diff --git a/tests/baselines/reference/isomorphicMappedTypeInference.js b/tests/baselines/reference/isomorphicMappedTypeInference.js
new file mode 100644
index 0000000000000..0fc646043dcb7
--- /dev/null
+++ b/tests/baselines/reference/isomorphicMappedTypeInference.js
@@ -0,0 +1,222 @@
+//// [isomorphicMappedTypeInference.ts]
+
+type Box<T> = {
+    value: T;
+}
+
+type Boxified<T> = {
+    [P in keyof T]: Box<T[P]>;
+}
+
+function box<T>(x: T): Box<T> {
+    return { value: x };
+}
+
+function unbox<T>(x: Box<T>): T {
+    return x.value;
+}
+
+function boxify<T>(obj: T): Boxified<T> {
+    let result = {} as Boxified<T>;
+    for (let k in obj) {
+        result[k] = box(obj[k]);
+    }
+    return result;
+}
+
+function unboxify<T>(obj: Boxified<T>): T {
+    let result = {} as T;
+    for (let k in obj) {
+        result[k] = unbox(obj[k]);
+    }
+    return result;
+}
+
+function assignBoxified<T>(obj: Boxified<T>, values: T) {
+    for (let k in values) {
+        obj[k].value = values[k];
+    }
+}
+
+function f1() {
+    let v = {
+        a: 42,
+        b: "hello",
+        c: true
+    };
+    let b = boxify(v);
+    let x: number = b.a.value;
+}
+
+function f2() {
+    let b = {
+        a: box(42),
+        b: box("hello"),
+        c: box(true)
+    };
+    let v = unboxify(b);
+    let x: number = v.a;
+}
+
+function f3() {
+    let b = {
+        a: box(42),
+        b: box("hello"),
+        c: box(true)
+    };
+    assignBoxified(b, { c: false });
+}
+
+function f4() {
+    let b = {
+        a: box(42),
+        b: box("hello"),
+        c: box(true)
+    };
+    b = boxify(unboxify(b));
+    b = unboxify(boxify(b));
+}
+
+function makeRecord<T, K extends string>(obj: { [P in K]: T }) {
+    return obj;
+}
+
+function f5(s: string) {
+    let b = makeRecord({
+        a: box(42),
+        b: box("hello"),
+        c: box(true)
+    });
+    let v = unboxify(b);
+    let x: string | number | boolean = v.a;
+}
+
+function makeDictionary<T>(obj: { [x: string]: T }) {
+    return obj;
+}
+
+function f6(s: string) {
+    let b = makeDictionary({
+        a: box(42),
+        b: box("hello"),
+        c: box(true)
+    });
+    let v = unboxify(b);
+    let x: string | number | boolean = v[s];
+}
+
+//// [isomorphicMappedTypeInference.js]
+function box(x) {
+    return { value: x };
+}
+function unbox(x) {
+    return x.value;
+}
+function boxify(obj) {
+    var result = {};
+    for (var k in obj) {
+        result[k] = box(obj[k]);
+    }
+    return result;
+}
+function unboxify(obj) {
+    var result = {};
+    for (var k in obj) {
+        result[k] = unbox(obj[k]);
+    }
+    return result;
+}
+function assignBoxified(obj, values) {
+    for (var k in values) {
+        obj[k].value = values[k];
+    }
+}
+function f1() {
+    var v = {
+        a: 42,
+        b: "hello",
+        c: true
+    };
+    var b = boxify(v);
+    var x = b.a.value;
+}
+function f2() {
+    var b = {
+        a: box(42),
+        b: box("hello"),
+        c: box(true)
+    };
+    var v = unboxify(b);
+    var x = v.a;
+}
+function f3() {
+    var b = {
+        a: box(42),
+        b: box("hello"),
+        c: box(true)
+    };
+    assignBoxified(b, { c: false });
+}
+function f4() {
+    var b = {
+        a: box(42),
+        b: box("hello"),
+        c: box(true)
+    };
+    b = boxify(unboxify(b));
+    b = unboxify(boxify(b));
+}
+function makeRecord(obj) {
+    return obj;
+}
+function f5(s) {
+    var b = makeRecord({
+        a: box(42),
+        b: box("hello"),
+        c: box(true)
+    });
+    var v = unboxify(b);
+    var x = v.a;
+}
+function makeDictionary(obj) {
+    return obj;
+}
+function f6(s) {
+    var b = makeDictionary({
+        a: box(42),
+        b: box("hello"),
+        c: box(true)
+    });
+    var v = unboxify(b);
+    var x = v[s];
+}
+
+
+//// [isomorphicMappedTypeInference.d.ts]
+declare type Box<T> = {
+    value: T;
+};
+declare type Boxified<T> = {
+    [P in keyof T]: Box<T[P]>;
+};
+declare function box<T>(x: T): Box<T>;
+declare function unbox<T>(x: Box<T>): T;
+declare function boxify<T>(obj: T): Boxified<T>;
+declare function unboxify<T>(obj: Boxified<T>): T;
+declare function assignBoxified<T>(obj: Boxified<T>, values: T): void;
+declare function f1(): void;
+declare function f2(): void;
+declare function f3(): void;
+declare function f4(): void;
+declare function makeRecord<T, K extends string>(obj: {
+    [P in K]: T;
+}): {
+    [P in K]: T;
+};
+declare function f5(s: string): void;
+declare function makeDictionary<T>(obj: {
+    [x: string]: T;
+}): {
+    [x: string]: T;
+};
+declare function f6(s: string): void;
diff --git a/tests/baselines/reference/isomorphicMappedTypeInference.symbols b/tests/baselines/reference/isomorphicMappedTypeInference.symbols
new file mode 100644
index 0000000000000..62dcc6316bcf7
--- /dev/null
+++ b/tests/baselines/reference/isomorphicMappedTypeInference.symbols
@@ -0,0 +1,334 @@
+=== tests/cases/conformance/types/mapped/isomorphicMappedTypeInference.ts ===
+
+type Box<T> = {
+>Box : Symbol(Box, Decl(isomorphicMappedTypeInference.ts, 0, 0))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 1, 9))
+
+    value: T;
+>value : Symbol(value, Decl(isomorphicMappedTypeInference.ts, 1, 15))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 1, 9))
+}
+
+type Boxified<T> = {
+>Boxified : Symbol(Boxified, Decl(isomorphicMappedTypeInference.ts, 3, 1))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 5, 14))
+
+    [P in keyof T]: Box<T[P]>;
+>P : Symbol(P, Decl(isomorphicMappedTypeInference.ts, 6, 5))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 5, 14))
+>Box : Symbol(Box, Decl(isomorphicMappedTypeInference.ts, 0, 0))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 5, 14))
+>P : Symbol(P, Decl(isomorphicMappedTypeInference.ts, 6, 5))
+}
+
+function box<T>(x: T): Box<T> {
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 9, 13))
+>x : Symbol(x, Decl(isomorphicMappedTypeInference.ts, 9, 16))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 9, 13))
+>Box : Symbol(Box, Decl(isomorphicMappedTypeInference.ts, 0, 0))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 9, 13))
+
+    return { value: x };
+>value : Symbol(value, Decl(isomorphicMappedTypeInference.ts, 10, 12))
+>x : Symbol(x, Decl(isomorphicMappedTypeInference.ts, 9, 16))
+}
+
+function unbox<T>(x: Box<T>): T {
+>unbox : Symbol(unbox, Decl(isomorphicMappedTypeInference.ts, 11, 1))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 13, 15))
+>x : Symbol(x, Decl(isomorphicMappedTypeInference.ts, 13, 18))
+>Box : Symbol(Box, Decl(isomorphicMappedTypeInference.ts, 0, 0))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 13, 15))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 13, 15))
+
+    return x.value;
+>x.value : Symbol(value, Decl(isomorphicMappedTypeInference.ts, 1, 15))
+>x : Symbol(x, Decl(isomorphicMappedTypeInference.ts, 13, 18))
+>value : Symbol(value, Decl(isomorphicMappedTypeInference.ts, 1, 15))
+}
+
+function boxify<T>(obj: T): Boxified<T> {
+>boxify : Symbol(boxify, Decl(isomorphicMappedTypeInference.ts, 15, 1))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 17, 16))
+>obj : Symbol(obj, Decl(isomorphicMappedTypeInference.ts, 17, 19))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 17, 16))
+>Boxified : Symbol(Boxified, Decl(isomorphicMappedTypeInference.ts, 3, 1))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 17, 16))
+
+    let result = {} as Boxified<T>;
+>result : Symbol(result, Decl(isomorphicMappedTypeInference.ts, 18, 7))
+>Boxified : Symbol(Boxified, Decl(isomorphicMappedTypeInference.ts, 3, 1))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 17, 16))
+
+    for (let k in obj) {
+>k : Symbol(k, Decl(isomorphicMappedTypeInference.ts, 19, 12))
+>obj : Symbol(obj, Decl(isomorphicMappedTypeInference.ts, 17, 19))
+
+        result[k] = box(obj[k]);
+>result : Symbol(result, Decl(isomorphicMappedTypeInference.ts, 18, 7))
+>k : Symbol(k, Decl(isomorphicMappedTypeInference.ts, 19, 12))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+>obj : Symbol(obj, Decl(isomorphicMappedTypeInference.ts, 17, 19))
+>k : Symbol(k, Decl(isomorphicMappedTypeInference.ts, 19, 12))
+    }
+    return result;
+>result : Symbol(result, Decl(isomorphicMappedTypeInference.ts, 18, 7))
+}
+
+function unboxify<T>(obj: Boxified<T>): T {
+>unboxify : Symbol(unboxify, Decl(isomorphicMappedTypeInference.ts, 23, 1))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 25, 18))
+>obj : Symbol(obj, Decl(isomorphicMappedTypeInference.ts, 25, 21))
+>Boxified : Symbol(Boxified, Decl(isomorphicMappedTypeInference.ts, 3, 1))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 25, 18))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 25, 18))
+
+    let result = {} as T;
+>result : Symbol(result, Decl(isomorphicMappedTypeInference.ts, 26, 7))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 25, 18))
+
+    for (let k in obj) {
+>k : Symbol(k, Decl(isomorphicMappedTypeInference.ts, 27, 12))
+>obj : Symbol(obj, Decl(isomorphicMappedTypeInference.ts, 25, 21))
+
+        result[k] = unbox(obj[k]);
+>result : Symbol(result, Decl(isomorphicMappedTypeInference.ts, 26, 7))
+>k : Symbol(k, Decl(isomorphicMappedTypeInference.ts, 27, 12))
+>unbox : Symbol(unbox, Decl(isomorphicMappedTypeInference.ts, 11, 1))
+>obj : Symbol(obj, Decl(isomorphicMappedTypeInference.ts, 25, 21))
+>k : Symbol(k, Decl(isomorphicMappedTypeInference.ts, 27, 12))
+    }
+    return result;
+>result : Symbol(result, Decl(isomorphicMappedTypeInference.ts, 26, 7))
+}
+
+function assignBoxified<T>(obj: Boxified<T>, values: T) {
+>assignBoxified : Symbol(assignBoxified, Decl(isomorphicMappedTypeInference.ts, 31, 1))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 33, 24))
+>obj : Symbol(obj, Decl(isomorphicMappedTypeInference.ts, 33, 27))
+>Boxified : Symbol(Boxified, Decl(isomorphicMappedTypeInference.ts, 3, 1))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 33, 24))
+>values : Symbol(values, Decl(isomorphicMappedTypeInference.ts, 33, 44))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 33, 24))
+
+    for (let k in values) {
+>k : Symbol(k, Decl(isomorphicMappedTypeInference.ts, 34, 12))
+>values : Symbol(values, Decl(isomorphicMappedTypeInference.ts, 33, 44))
+
+        obj[k].value = values[k];
+>obj[k].value : Symbol(value, Decl(isomorphicMappedTypeInference.ts, 1, 15))
+>obj : Symbol(obj, Decl(isomorphicMappedTypeInference.ts, 33, 27))
+>k : Symbol(k, Decl(isomorphicMappedTypeInference.ts, 34, 12))
+>value : Symbol(value, Decl(isomorphicMappedTypeInference.ts, 1, 15))
+>values : Symbol(values, Decl(isomorphicMappedTypeInference.ts, 33, 44))
+>k : Symbol(k, Decl(isomorphicMappedTypeInference.ts, 34, 12))
+    }
+}
+
+function f1() {
+>f1 : Symbol(f1, Decl(isomorphicMappedTypeInference.ts, 37, 1))
+
+    let v = {
+>v : Symbol(v, Decl(isomorphicMappedTypeInference.ts, 40, 7))
+
+        a: 42,
+>a : Symbol(a, Decl(isomorphicMappedTypeInference.ts, 40, 13))
+
+        b: "hello",
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 41, 14))
+
+        c: true
+>c : Symbol(c, Decl(isomorphicMappedTypeInference.ts, 42, 19))
+
+    };
+    let b = boxify(v);
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 45, 7))
+>boxify : Symbol(boxify, Decl(isomorphicMappedTypeInference.ts, 15, 1))
+>v : Symbol(v, Decl(isomorphicMappedTypeInference.ts, 40, 7))
+
+    let x: number = b.a.value;
+>x : Symbol(x, Decl(isomorphicMappedTypeInference.ts, 46, 7))
+>b.a.value : Symbol(value, Decl(isomorphicMappedTypeInference.ts, 1, 15))
+>b.a : Symbol(a)
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 45, 7))
+>a : Symbol(a)
+>value : Symbol(value, Decl(isomorphicMappedTypeInference.ts, 1, 15))
+}
+
+function f2() {
+>f2 : Symbol(f2, Decl(isomorphicMappedTypeInference.ts, 47, 1))
+
+    let b = {
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 50, 7))
+
+        a: box(42),
+>a : Symbol(a, Decl(isomorphicMappedTypeInference.ts, 50, 13))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+
+        b: box("hello"),
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 51, 19))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+
+        c: box(true)
+>c : Symbol(c, Decl(isomorphicMappedTypeInference.ts, 52, 24))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+
+    };
+    let v = unboxify(b);
+>v : Symbol(v, Decl(isomorphicMappedTypeInference.ts, 55, 7))
+>unboxify : Symbol(unboxify, Decl(isomorphicMappedTypeInference.ts, 23, 1))
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 50, 7))
+
+    let x: number = v.a;
+>x : Symbol(x, Decl(isomorphicMappedTypeInference.ts, 56, 7))
+>v.a : Symbol(a, Decl(isomorphicMappedTypeInference.ts, 50, 13))
+>v : Symbol(v, Decl(isomorphicMappedTypeInference.ts, 55, 7))
+>a : Symbol(a, Decl(isomorphicMappedTypeInference.ts, 50, 13))
+}
+
+function f3() {
+>f3 : Symbol(f3, Decl(isomorphicMappedTypeInference.ts, 57, 1))
+
+    let b = {
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 60, 7))
+
+        a: box(42),
+>a : Symbol(a, Decl(isomorphicMappedTypeInference.ts, 60, 13))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+
+        b: box("hello"),
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 61, 19))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+
+        c: box(true)
+>c : Symbol(c, Decl(isomorphicMappedTypeInference.ts, 62, 24))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+
+    };
+    assignBoxified(b, { c: false });
+>assignBoxified : Symbol(assignBoxified, Decl(isomorphicMappedTypeInference.ts, 31, 1))
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 60, 7))
+>c : Symbol(c, Decl(isomorphicMappedTypeInference.ts, 65, 23))
+}
+
+function f4() {
+>f4 : Symbol(f4, Decl(isomorphicMappedTypeInference.ts, 66, 1))
+
+    let b = {
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 69, 7))
+
+        a: box(42),
+>a : Symbol(a, Decl(isomorphicMappedTypeInference.ts, 69, 13))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+
+        b: box("hello"),
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 70, 19))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+
+        c: box(true)
+>c : Symbol(c, Decl(isomorphicMappedTypeInference.ts, 71, 24))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+
+    };
+    b = boxify(unboxify(b));
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 69, 7))
+>boxify : Symbol(boxify, Decl(isomorphicMappedTypeInference.ts, 15, 1))
+>unboxify : Symbol(unboxify, Decl(isomorphicMappedTypeInference.ts, 23, 1))
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 69, 7))
+
+    b = unboxify(boxify(b));
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 69, 7))
+>unboxify : Symbol(unboxify, Decl(isomorphicMappedTypeInference.ts, 23, 1))
+>boxify : Symbol(boxify, Decl(isomorphicMappedTypeInference.ts, 15, 1))
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 69, 7))
+}
+
+function makeRecord<T, K extends string>(obj: { [P in K]: T }) {
+>makeRecord : Symbol(makeRecord, Decl(isomorphicMappedTypeInference.ts, 76, 1))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 78, 20))
+>K : Symbol(K, Decl(isomorphicMappedTypeInference.ts, 78, 22))
+>obj : Symbol(obj, Decl(isomorphicMappedTypeInference.ts, 78, 41))
+>P : Symbol(P, Decl(isomorphicMappedTypeInference.ts, 78, 49))
+>K : Symbol(K, Decl(isomorphicMappedTypeInference.ts, 78, 22))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 78, 20))
+
+    return obj;
+>obj : Symbol(obj, Decl(isomorphicMappedTypeInference.ts, 78, 41))
+}
+
+function f5(s: string) {
+>f5 : Symbol(f5, Decl(isomorphicMappedTypeInference.ts, 80, 1))
+>s : Symbol(s, Decl(isomorphicMappedTypeInference.ts, 82, 12))
+
+    let b = makeRecord({
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 83, 7))
+>makeRecord : Symbol(makeRecord, Decl(isomorphicMappedTypeInference.ts, 76, 1))
+
+        a: box(42),
+>a : Symbol(a, Decl(isomorphicMappedTypeInference.ts, 83, 24))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+
+        b: box("hello"),
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 84, 19))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+
+        c: box(true)
+>c : Symbol(c, Decl(isomorphicMappedTypeInference.ts, 85, 24))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+
+    });
+    let v = unboxify(b);
+>v : Symbol(v, Decl(isomorphicMappedTypeInference.ts, 88, 7))
+>unboxify : Symbol(unboxify, Decl(isomorphicMappedTypeInference.ts, 23, 1))
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 83, 7))
+
+    let x: string | number | boolean = v.a;
+>x : Symbol(x, Decl(isomorphicMappedTypeInference.ts, 89, 7))
+>v.a : Symbol(a)
+>v : Symbol(v, Decl(isomorphicMappedTypeInference.ts, 88, 7))
+>a : Symbol(a)
+}
+
+function makeDictionary<T>(obj: { [x: string]: T }) {
+>makeDictionary : Symbol(makeDictionary, Decl(isomorphicMappedTypeInference.ts, 90, 1))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 92, 24))
+>obj : Symbol(obj, Decl(isomorphicMappedTypeInference.ts, 92, 27))
+>x : Symbol(x, Decl(isomorphicMappedTypeInference.ts, 92, 35))
+>T : Symbol(T, Decl(isomorphicMappedTypeInference.ts, 92, 24))
+
+    return obj;
+>obj : Symbol(obj, Decl(isomorphicMappedTypeInference.ts, 92, 27))
+}
+
+function f6(s: string) {
+>f6 : Symbol(f6, Decl(isomorphicMappedTypeInference.ts, 94, 1))
+>s : Symbol(s, Decl(isomorphicMappedTypeInference.ts, 96, 12))
+
+    let b = makeDictionary({
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 97, 7))
+>makeDictionary : Symbol(makeDictionary, Decl(isomorphicMappedTypeInference.ts, 90, 1))
+
+        a: box(42),
+>a : Symbol(a, Decl(isomorphicMappedTypeInference.ts, 97, 28))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+
+        b: box("hello"),
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 98, 19))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+
+        c: box(true)
+>c : Symbol(c, Decl(isomorphicMappedTypeInference.ts, 99, 24))
+>box : Symbol(box, Decl(isomorphicMappedTypeInference.ts, 7, 1))
+
+    });
+    let v = unboxify(b);
+>v : Symbol(v, Decl(isomorphicMappedTypeInference.ts, 102, 7))
+>unboxify : Symbol(unboxify, Decl(isomorphicMappedTypeInference.ts, 23, 1))
+>b : Symbol(b, Decl(isomorphicMappedTypeInference.ts, 97, 7))
+
+    let x: string | number | boolean = v[s];
+>x : Symbol(x, Decl(isomorphicMappedTypeInference.ts, 103, 7))
+>v : Symbol(v, Decl(isomorphicMappedTypeInference.ts, 102, 7))
+>s : Symbol(s, Decl(isomorphicMappedTypeInference.ts, 96, 12))
+}
diff --git a/tests/baselines/reference/isomorphicMappedTypeInference.types b/tests/baselines/reference/isomorphicMappedTypeInference.types
new file mode 100644
index 0000000000000..00a80639f732c
--- /dev/null
+++ b/tests/baselines/reference/isomorphicMappedTypeInference.types
@@ -0,0 +1,405 @@
+=== tests/cases/conformance/types/mapped/isomorphicMappedTypeInference.ts ===
+
+type Box<T> = {
+>Box : Box<T>
+>T : T
+
+    value: T;
+>value : T
+>T : T
+}
+
+type Boxified<T> = {
+>Boxified : Boxified<T>
+>T : T
+
+    [P in keyof T]: Box<T[P]>;
+>P : P
+>T : T
+>Box : Box<T>
+>T : T
+>P : P
+}
+
+function box<T>(x: T): Box<T> {
+>box : <T>(x: T) => Box<T>
+>T : T
+>x : T
+>T : T
+>Box : Box<T>
+>T : T
+
+    return { value: x };
+>{ value: x } : { value: T; }
+>value : T
+>x : T
+}
+
+function unbox<T>(x: Box<T>): T {
+>unbox : <T>(x: Box<T>) => T
+>T : T
+>x : Box<T>
+>Box : Box<T>
+>T : T
+>T : T
+
+    return x.value;
+>x.value : T
+>x : Box<T>
+>value : T
+}
+
+function boxify<T>(obj: T): Boxified<T> {
+>boxify : <T>(obj: T) => Boxified<T>
+>T : T
+>obj : T
+>T : T
+>Boxified : Boxified<T>
+>T : T
+
+    let result = {} as Boxified<T>;
+>result : Boxified<T>
+>{} as Boxified<T> : Boxified<T>
+>{} : {}
+>Boxified : Boxified<T>
+>T : T
+
+    for (let k in obj) {
+>k : keyof T
+>obj : T
+
+        result[k] = box(obj[k]);
+>result[k] = box(obj[k]) : Box<T[keyof T]>
+>result[k] : Box<T[keyof T]>
+>result : Boxified<T>
+>k : keyof T
+>box(obj[k]) : Box<T[keyof T]>
+>box : <T>(x: T) => Box<T>
+>obj[k] : T[keyof T]
+>obj : T
+>k : keyof T
+    }
+    return result;
+>result : Boxified<T>
+}
+
+function unboxify<T>(obj: Boxified<T>): T {
+>unboxify : <T>(obj: Boxified<T>) => T
+>T : T
+>obj : Boxified<T>
+>Boxified : Boxified<T>
+>T : T
+>T : T
+
+    let result = {} as T;
+>result : T
+>{} as T : T
+>{} : {}
+>T : T
+
+    for (let k in obj) {
+>k : keyof T
+>obj : Boxified<T>
+
+        result[k] = unbox(obj[k]);
+>result[k] = unbox(obj[k]) : T[keyof T]
+>result[k] : T[keyof T]
+>result : T
+>k : keyof T
+>unbox(obj[k]) : T[keyof T]
+>unbox : <T>(x: Box<T>) => T
+>obj[k] : Box<T[keyof T]>
+>obj : Boxified<T>
+>k : keyof T
+    }
+    return result;
+>result : T
+}
+
+function assignBoxified<T>(obj: Boxified<T>, values: T) {
+>assignBoxified : <T>(obj: Boxified<T>, values: T) => void
+>T : T
+>obj : Boxified<T>
+>Boxified : Boxified<T>
+>T : T
+>values : T
+>T : T
+
+    for (let k in values) {
+>k : keyof T
+>values : T
+
+        obj[k].value = values[k];
+>obj[k].value = values[k] : T[keyof T]
+>obj[k].value : T[keyof T]
+>obj[k] : Box<T[keyof T]>
+>obj : Boxified<T>
+>k : keyof T
+>value : T[keyof T]
+>values[k] : T[keyof T]
+>values : T
+>k : keyof T
+    }
+}
+
+function f1() {
+>f1 : () => void
+
+    let v = {
+>v : { a: number; b: string; c: boolean; }
+>{        a: 42,        b: "hello",        c: true    } : { a: number; b: string; c: boolean; }
+
+        a: 42,
+>a : number
+>42 : 42
+
+        b: "hello",
+>b : string
+>"hello" : "hello"
+
+        c: true
+>c : boolean
+>true : true
+
+    };
+    let b = boxify(v);
+>b : Boxified<{ a: number; b: string; c: boolean; }>
+>boxify(v) : Boxified<{ a: number; b: string; c: boolean; }>
+>boxify : <T>(obj: T) => Boxified<T>
+>v : { a: number; b: string; c: boolean; }
+
+    let x: number = b.a.value;
+>x : number
+>b.a.value : number
+>b.a : Box<number>
+>b : Boxified<{ a: number; b: string; c: boolean; }>
+>a : Box<number>
+>value : number
+}
+
+function f2() {
+>f2 : () => void
+
+    let b = {
+>b : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+>{        a: box(42),        b: box("hello"),        c: box(true)    } : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+
+        a: box(42),
+>a : Box<number>
+>box(42) : Box<number>
+>box : <T>(x: T) => Box<T>
+>42 : 42
+
+        b: box("hello"),
+>b : Box<string>
+>box("hello") : Box<string>
+>box : <T>(x: T) => Box<T>
+>"hello" : "hello"
+
+        c: box(true)
+>c : Box<boolean>
+>box(true) : Box<boolean>
+>box : <T>(x: T) => Box<T>
+>true : true
+
+    };
+    let v = unboxify(b);
+>v : { a: number; b: string; c: boolean; }
+>unboxify(b) : { a: number; b: string; c: boolean; }
+>unboxify : <T>(obj: Boxified<T>) => T
+>b : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+
+    let x: number = v.a;
+>x : number
+>v.a : number
+>v : { a: number; b: string; c: boolean; }
+>a : number
+}
+
+function f3() {
+>f3 : () => void
+
+    let b = {
+>b : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+>{        a: box(42),        b: box("hello"),        c: box(true)    } : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+
+        a: box(42),
+>a : Box<number>
+>box(42) : Box<number>
+>box : <T>(x: T) => Box<T>
+>42 : 42
+
+        b: box("hello"),
+>b : Box<string>
+>box("hello") : Box<string>
+>box : <T>(x: T) => Box<T>
+>"hello" : "hello"
+
+        c: box(true)
+>c : Box<boolean>
+>box(true) : Box<boolean>
+>box : <T>(x: T) => Box<T>
+>true : true
+
+    };
+    assignBoxified(b, { c: false });
+>assignBoxified(b, { c: false }) : void
+>assignBoxified : <T>(obj: Boxified<T>, values: T) => void
+>b : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+>{ c: false } : { c: false; }
+>c : boolean
+>false : false
+}
+
+function f4() {
+>f4 : () => void
+
+    let b = {
+>b : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+>{        a: box(42),        b: box("hello"),        c: box(true)    } : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+
+        a: box(42),
+>a : Box<number>
+>box(42) : Box<number>
+>box : <T>(x: T) => Box<T>
+>42 : 42
+
+        b: box("hello"),
+>b : Box<string>
+>box("hello") : Box<string>
+>box : <T>(x: T) => Box<T>
+>"hello" : "hello"
+
+        c: box(true)
+>c : Box<boolean>
+>box(true) : Box<boolean>
+>box : <T>(x: T) => Box<T>
+>true : true
+
+    };
+    b = boxify(unboxify(b));
+>b = boxify(unboxify(b)) : Boxified<{ a: number; b: string; c: boolean; }>
+>b : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+>boxify(unboxify(b)) : Boxified<{ a: number; b: string; c: boolean; }>
+>boxify : <T>(obj: T) => Boxified<T>
+>unboxify(b) : { a: number; b: string; c: boolean; }
+>unboxify : <T>(obj: Boxified<T>) => T
+>b : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+
+    b = unboxify(boxify(b));
+>b = unboxify(boxify(b)) : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+>b : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+>unboxify(boxify(b)) : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+>unboxify : <T>(obj: Boxified<T>) => T
+>boxify(b) : Boxified<{ a: Box<number>; b: Box<string>; c: Box<boolean>; }>
+>boxify : <T>(obj: T) => Boxified<T>
+>b : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+}
+
+function makeRecord<T, K extends string>(obj: { [P in K]: T }) {
+>makeRecord : <T, K extends string>(obj: { [P in K]: T; }) => { [P in K]: T; }
+>T : T
+>K : K
+>obj : { [P in K]: T; }
+>P : P
+>K : K
+>T : T
+
+    return obj;
+>obj : { [P in K]: T; }
+}
+
+function f5(s: string) {
+>f5 : (s: string) => void
+>s : string
+
+    let b = makeRecord({
+>b : { a: Box<number> | Box<string> | Box<boolean>; b: Box<number> | Box<string> | Box<boolean>; c: Box<number> | Box<string> | Box<boolean>; }
+>makeRecord({        a: box(42),        b: box("hello"),        c: box(true)    }) : { a: Box<number> | Box<string> | Box<boolean>; b: Box<number> | Box<string> | Box<boolean>; c: Box<number> | Box<string> | Box<boolean>; }
+>makeRecord : <T, K extends string>(obj: { [P in K]: T; }) => { [P in K]: T; }
+>{        a: box(42),        b: box("hello"),        c: box(true)    } : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+
+        a: box(42),
+>a : Box<number>
+>box(42) : Box<number>
+>box : <T>(x: T) => Box<T>
+>42 : 42
+
+        b: box("hello"),
+>b : Box<string>
+>box("hello") : Box<string>
+>box : <T>(x: T) => Box<T>
+>"hello" : "hello"
+
+        c: box(true)
+>c : Box<boolean>
+>box(true) : Box<boolean>
+>box : <T>(x: T) => Box<T>
+>true : true
+
+    });
+    let v = unboxify(b);
+>v : { a: string | number | boolean; b: string | number | boolean; c: string | number | boolean; }
+>unboxify(b) : { a: string | number | boolean; b: string | number | boolean; c: string | number | boolean; }
+>unboxify : <T>(obj: Boxified<T>) => T
+>b : { a: Box<number> | Box<string> | Box<boolean>; b: Box<number> | Box<string> | Box<boolean>; c: Box<number> | Box<string> | Box<boolean>; }
+
+    let x: string | number | boolean = v.a;
+>x : string | number | boolean
+>v.a : string | number | boolean
+>v : { a: string | number | boolean; b: string | number | boolean; c: string | number | boolean; }
+>a : string | number | boolean
+}
+
+function makeDictionary<T>(obj: { [x: string]: T }) {
+>makeDictionary : <T>(obj: { [x: string]: T; }) => { [x: string]: T; }
+>T : T
+>obj : { [x: string]: T; }
+>x : string
+>T : T
+
+    return obj;
+>obj : { [x: string]: T; }
+}
+
+function f6(s: string) {
+>f6 : (s: string) => void
+>s : string
+
+    let b = makeDictionary({
+>b : { [x: string]: Box<number> | Box<string> | Box<boolean>; }
+>makeDictionary({        a: box(42),        b: box("hello"),        c: box(true)    }) : { [x: string]: Box<number> | Box<string> | Box<boolean>; }
+>makeDictionary : <T>(obj: { [x: string]: T; }) => { [x: string]: T; }
+>{        a: box(42),        b: box("hello"),        c: box(true)    } : { a: Box<number>; b: Box<string>; c: Box<boolean>; }
+
+        a: box(42),
+>a : Box<number>
+>box(42) : Box<number>
+>box : <T>(x: T) => Box<T>
+>42 : 42
+
+        b: box("hello"),
+>b : Box<string>
+>box("hello") : Box<string>
+>box : <T>(x: T) => Box<T>
+>"hello" : "hello"
+
+        c: box(true)
+>c : Box<boolean>
+>box(true) : Box<boolean>
+>box : <T>(x: T) => Box<T>
+>true : true
+
+    });
+    let v = unboxify(b);
+>v : { [x: string]: string | number | boolean; }
+>unboxify(b) : { [x: string]: string | number | boolean; }
+>unboxify : <T>(obj: Boxified<T>) => T
+>b : { [x: string]: Box<number> | Box<string> | Box<boolean>; }
+
+    let x: string | number | boolean = v[s];
+>x : string | number | boolean
+>v[s] : string | number | boolean
+>v : { [x: string]: string | number | boolean; }
+>s : string
+}
diff --git a/tests/cases/conformance/types/mapped/isomorphicMappedTypeInference.ts b/tests/cases/conformance/types/mapped/isomorphicMappedTypeInference.ts
new file mode 100644
index 0000000000000..19a0c4889a50f
--- /dev/null
+++ b/tests/cases/conformance/types/mapped/isomorphicMappedTypeInference.ts
@@ -0,0 +1,107 @@
+// @noimplicitany: true
+// @declaration: true
+
+type Box<T> = {
+    value: T;
+}
+
+type Boxified<T> = {
+    [P in keyof T]: Box<T[P]>;
+}
+
+function box<T>(x: T): Box<T> {
+    return { value: x };
+}
+
+function unbox<T>(x: Box<T>): T {
+    return x.value;
+}
+
+function boxify<T>(obj: T): Boxified<T> {
+    let result = {} as Boxified<T>;
+    for (let k in obj) {
+        result[k] = box(obj[k]);
+    }
+    return result;
+}
+
+function unboxify<T>(obj: Boxified<T>): T {
+    let result = {} as T;
+    for (let k in obj) {
+        result[k] = unbox(obj[k]);
+    }
+    return result;
+}
+
+function assignBoxified<T>(obj: Boxified<T>, values: T) {
+    for (let k in values) {
+        obj[k].value = values[k];
+    }
+}
+
+function f1() {
+    let v = {
+        a: 42,
+        b: "hello",
+        c: true
+    };
+    let b = boxify(v);
+    let x: number = b.a.value;
+}
+
+function f2() {
+    let b = {
+        a: box(42),
+        b: box("hello"),
+        c: box(true)
+    };
+    let v = unboxify(b);
+    let x: number = v.a;
+}
+
+function f3() {
+    let b = {
+        a: box(42),
+        b: box("hello"),
+        c: box(true)
+    };
+    assignBoxified(b, { c: false });
+}
+
+function f4() {
+    let b = {
+        a: box(42),
+        b: box("hello"),
+        c: box(true)
+    };
+    b = boxify(unboxify(b));
+    b = unboxify(boxify(b));
+}
+
+function makeRecord<T, K extends string>(obj: { [P in K]: T }) {
+    return obj;
+}
+
+function f5(s: string) {
+    let b = makeRecord({
+        a: box(42),
+        b: box("hello"),
+        c: box(true)
+    });
+    let v = unboxify(b);
+    let x: string | number | boolean = v.a;
+}
+
+function makeDictionary<T>(obj: { [x: string]: T }) {
+    return obj;
+}
+
+function f6(s: string) {
+    let b = makeDictionary({
+        a: box(42),
+        b: box("hello"),
+        c: box(true)
+    });
+    let v = unboxify(b);
+    let x: string | number | boolean = v[s];
+}
\ No newline at end of file