diff --git a/tests/baselines/reference/reverseMappedPartiallyInferableTypes.errors.txt b/tests/baselines/reference/reverseMappedPartiallyInferableTypes.errors.txt
new file mode 100644
index 0000000000000..63ea9a9f2797f
--- /dev/null
+++ b/tests/baselines/reference/reverseMappedPartiallyInferableTypes.errors.txt
@@ -0,0 +1,101 @@
+tests/cases/compiler/reverseMappedPartiallyInferableTypes.ts(91,20): error TS2571: Object is of type 'unknown'.
+
+
+==== tests/cases/compiler/reverseMappedPartiallyInferableTypes.ts (1 errors) ====
+    // Repro from #30505
+    
+    export type Prop<T> = { (): T }
+    export type PropType<T> = Prop<T>;
+    export type PropDefaultValue<T> = T;
+    
+    
+    export type PropValidatorFunction<T> = (value: T) => boolean;
+    export type PropValidator<T> = PropOptions<T>;
+    
+    
+    export type PropOptions<T> = {
+        type: PropType<T>;
+    
+        value?: PropDefaultValue<T>,
+        required?: boolean;
+        validator?: PropValidatorFunction<T>;
+    }
+    
+    export type RecordPropsDefinition<T> = {
+        [K in keyof T]: PropValidator<T[K]>
+    }
+    export type PropsDefinition<T> = RecordPropsDefinition<T>;
+    
+    
+    declare function extend<T>({ props }: { props: PropsDefinition<T> }):  PropsDefinition<T>;
+    
+    interface MyType {
+        valid: boolean;
+    }
+    
+    const r = extend({
+        props: {
+            notResolved: {
+                type: Object as PropType<MyType>,
+                validator: x => {
+                    return x.valid;
+                }
+            },
+            explicit: {
+                type: Object as PropType<MyType>,
+                validator: (x: MyType) => {
+                    return x.valid;
+                }
+            }
+        }
+    })
+    
+    r.explicit
+    r.notResolved
+    r.explicit.required
+    r.notResolved.required
+    
+    // Modified repro from #30505
+    
+    type Box<T> = {
+        contents?: T;
+        contains?(content: T): boolean;
+    };
+    
+    type Mapped<T> = {
+        [K in keyof T]: Box<T[K]>;
+    }
+    
+    declare function id<T>(arg: Mapped<T>): Mapped<T>;
+    
+    // All properties have inferable types
+    
+    const obj1 = id({
+        foo: {
+            contents: ""
+        }
+    });
+    
+    // Some properties have inferable types
+    
+    const obj2 = id({
+        foo: {
+            contents: "",
+            contains(k) {
+                return k.length > 0;
+            }
+        }
+    });
+    
+    // No properties have inferable types
+    
+    const obj3 = id({
+        foo: {
+            contains(k) {
+                return k.length > 0;
+                       ~
+!!! error TS2571: Object is of type 'unknown'.
+            }
+        }
+    });
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/reverseMappedPartiallyInferableTypes.js b/tests/baselines/reference/reverseMappedPartiallyInferableTypes.js
new file mode 100644
index 0000000000000..e5a9c2a57ae46
--- /dev/null
+++ b/tests/baselines/reference/reverseMappedPartiallyInferableTypes.js
@@ -0,0 +1,144 @@
+//// [reverseMappedPartiallyInferableTypes.ts]
+// Repro from #30505
+
+export type Prop<T> = { (): T }
+export type PropType<T> = Prop<T>;
+export type PropDefaultValue<T> = T;
+
+
+export type PropValidatorFunction<T> = (value: T) => boolean;
+export type PropValidator<T> = PropOptions<T>;
+
+
+export type PropOptions<T> = {
+    type: PropType<T>;
+
+    value?: PropDefaultValue<T>,
+    required?: boolean;
+    validator?: PropValidatorFunction<T>;
+}
+
+export type RecordPropsDefinition<T> = {
+    [K in keyof T]: PropValidator<T[K]>
+}
+export type PropsDefinition<T> = RecordPropsDefinition<T>;
+
+
+declare function extend<T>({ props }: { props: PropsDefinition<T> }):  PropsDefinition<T>;
+
+interface MyType {
+    valid: boolean;
+}
+
+const r = extend({
+    props: {
+        notResolved: {
+            type: Object as PropType<MyType>,
+            validator: x => {
+                return x.valid;
+            }
+        },
+        explicit: {
+            type: Object as PropType<MyType>,
+            validator: (x: MyType) => {
+                return x.valid;
+            }
+        }
+    }
+})
+
+r.explicit
+r.notResolved
+r.explicit.required
+r.notResolved.required
+
+// Modified repro from #30505
+
+type Box<T> = {
+    contents?: T;
+    contains?(content: T): boolean;
+};
+
+type Mapped<T> = {
+    [K in keyof T]: Box<T[K]>;
+}
+
+declare function id<T>(arg: Mapped<T>): Mapped<T>;
+
+// All properties have inferable types
+
+const obj1 = id({
+    foo: {
+        contents: ""
+    }
+});
+
+// Some properties have inferable types
+
+const obj2 = id({
+    foo: {
+        contents: "",
+        contains(k) {
+            return k.length > 0;
+        }
+    }
+});
+
+// No properties have inferable types
+
+const obj3 = id({
+    foo: {
+        contains(k) {
+            return k.length > 0;
+        }
+    }
+});
+
+
+//// [reverseMappedPartiallyInferableTypes.js]
+"use strict";
+// Repro from #30505
+exports.__esModule = true;
+var r = extend({
+    props: {
+        notResolved: {
+            type: Object,
+            validator: function (x) {
+                return x.valid;
+            }
+        },
+        explicit: {
+            type: Object,
+            validator: function (x) {
+                return x.valid;
+            }
+        }
+    }
+});
+r.explicit;
+r.notResolved;
+r.explicit.required;
+r.notResolved.required;
+// All properties have inferable types
+var obj1 = id({
+    foo: {
+        contents: ""
+    }
+});
+// Some properties have inferable types
+var obj2 = id({
+    foo: {
+        contents: "",
+        contains: function (k) {
+            return k.length > 0;
+        }
+    }
+});
+// No properties have inferable types
+var obj3 = id({
+    foo: {
+        contains: function (k) {
+            return k.length > 0;
+        }
+    }
+});
diff --git a/tests/baselines/reference/reverseMappedPartiallyInferableTypes.symbols b/tests/baselines/reference/reverseMappedPartiallyInferableTypes.symbols
new file mode 100644
index 0000000000000..ac264a37e9ebc
--- /dev/null
+++ b/tests/baselines/reference/reverseMappedPartiallyInferableTypes.symbols
@@ -0,0 +1,259 @@
+=== tests/cases/compiler/reverseMappedPartiallyInferableTypes.ts ===
+// Repro from #30505
+
+export type Prop<T> = { (): T }
+>Prop : Symbol(Prop, Decl(reverseMappedPartiallyInferableTypes.ts, 0, 0))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 2, 17))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 2, 17))
+
+export type PropType<T> = Prop<T>;
+>PropType : Symbol(PropType, Decl(reverseMappedPartiallyInferableTypes.ts, 2, 31))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 3, 21))
+>Prop : Symbol(Prop, Decl(reverseMappedPartiallyInferableTypes.ts, 0, 0))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 3, 21))
+
+export type PropDefaultValue<T> = T;
+>PropDefaultValue : Symbol(PropDefaultValue, Decl(reverseMappedPartiallyInferableTypes.ts, 3, 34))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 4, 29))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 4, 29))
+
+
+export type PropValidatorFunction<T> = (value: T) => boolean;
+>PropValidatorFunction : Symbol(PropValidatorFunction, Decl(reverseMappedPartiallyInferableTypes.ts, 4, 36))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 7, 34))
+>value : Symbol(value, Decl(reverseMappedPartiallyInferableTypes.ts, 7, 40))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 7, 34))
+
+export type PropValidator<T> = PropOptions<T>;
+>PropValidator : Symbol(PropValidator, Decl(reverseMappedPartiallyInferableTypes.ts, 7, 61))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 8, 26))
+>PropOptions : Symbol(PropOptions, Decl(reverseMappedPartiallyInferableTypes.ts, 8, 46))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 8, 26))
+
+
+export type PropOptions<T> = {
+>PropOptions : Symbol(PropOptions, Decl(reverseMappedPartiallyInferableTypes.ts, 8, 46))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 11, 24))
+
+    type: PropType<T>;
+>type : Symbol(type, Decl(reverseMappedPartiallyInferableTypes.ts, 11, 30))
+>PropType : Symbol(PropType, Decl(reverseMappedPartiallyInferableTypes.ts, 2, 31))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 11, 24))
+
+    value?: PropDefaultValue<T>,
+>value : Symbol(value, Decl(reverseMappedPartiallyInferableTypes.ts, 12, 22))
+>PropDefaultValue : Symbol(PropDefaultValue, Decl(reverseMappedPartiallyInferableTypes.ts, 3, 34))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 11, 24))
+
+    required?: boolean;
+>required : Symbol(required, Decl(reverseMappedPartiallyInferableTypes.ts, 14, 32))
+
+    validator?: PropValidatorFunction<T>;
+>validator : Symbol(validator, Decl(reverseMappedPartiallyInferableTypes.ts, 15, 23))
+>PropValidatorFunction : Symbol(PropValidatorFunction, Decl(reverseMappedPartiallyInferableTypes.ts, 4, 36))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 11, 24))
+}
+
+export type RecordPropsDefinition<T> = {
+>RecordPropsDefinition : Symbol(RecordPropsDefinition, Decl(reverseMappedPartiallyInferableTypes.ts, 17, 1))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 19, 34))
+
+    [K in keyof T]: PropValidator<T[K]>
+>K : Symbol(K, Decl(reverseMappedPartiallyInferableTypes.ts, 20, 5))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 19, 34))
+>PropValidator : Symbol(PropValidator, Decl(reverseMappedPartiallyInferableTypes.ts, 7, 61))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 19, 34))
+>K : Symbol(K, Decl(reverseMappedPartiallyInferableTypes.ts, 20, 5))
+}
+export type PropsDefinition<T> = RecordPropsDefinition<T>;
+>PropsDefinition : Symbol(PropsDefinition, Decl(reverseMappedPartiallyInferableTypes.ts, 21, 1))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 22, 28))
+>RecordPropsDefinition : Symbol(RecordPropsDefinition, Decl(reverseMappedPartiallyInferableTypes.ts, 17, 1))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 22, 28))
+
+
+declare function extend<T>({ props }: { props: PropsDefinition<T> }):  PropsDefinition<T>;
+>extend : Symbol(extend, Decl(reverseMappedPartiallyInferableTypes.ts, 22, 58))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 25, 24))
+>props : Symbol(props, Decl(reverseMappedPartiallyInferableTypes.ts, 25, 28))
+>props : Symbol(props, Decl(reverseMappedPartiallyInferableTypes.ts, 25, 39))
+>PropsDefinition : Symbol(PropsDefinition, Decl(reverseMappedPartiallyInferableTypes.ts, 21, 1))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 25, 24))
+>PropsDefinition : Symbol(PropsDefinition, Decl(reverseMappedPartiallyInferableTypes.ts, 21, 1))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 25, 24))
+
+interface MyType {
+>MyType : Symbol(MyType, Decl(reverseMappedPartiallyInferableTypes.ts, 25, 90))
+
+    valid: boolean;
+>valid : Symbol(MyType.valid, Decl(reverseMappedPartiallyInferableTypes.ts, 27, 18))
+}
+
+const r = extend({
+>r : Symbol(r, Decl(reverseMappedPartiallyInferableTypes.ts, 31, 5))
+>extend : Symbol(extend, Decl(reverseMappedPartiallyInferableTypes.ts, 22, 58))
+
+    props: {
+>props : Symbol(props, Decl(reverseMappedPartiallyInferableTypes.ts, 31, 18))
+
+        notResolved: {
+>notResolved : Symbol(notResolved, Decl(reverseMappedPartiallyInferableTypes.ts, 32, 12))
+
+            type: Object as PropType<MyType>,
+>type : Symbol(type, Decl(reverseMappedPartiallyInferableTypes.ts, 33, 22))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>PropType : Symbol(PropType, Decl(reverseMappedPartiallyInferableTypes.ts, 2, 31))
+>MyType : Symbol(MyType, Decl(reverseMappedPartiallyInferableTypes.ts, 25, 90))
+
+            validator: x => {
+>validator : Symbol(validator, Decl(reverseMappedPartiallyInferableTypes.ts, 34, 45))
+>x : Symbol(x, Decl(reverseMappedPartiallyInferableTypes.ts, 35, 22))
+
+                return x.valid;
+>x.valid : Symbol(MyType.valid, Decl(reverseMappedPartiallyInferableTypes.ts, 27, 18))
+>x : Symbol(x, Decl(reverseMappedPartiallyInferableTypes.ts, 35, 22))
+>valid : Symbol(MyType.valid, Decl(reverseMappedPartiallyInferableTypes.ts, 27, 18))
+            }
+        },
+        explicit: {
+>explicit : Symbol(explicit, Decl(reverseMappedPartiallyInferableTypes.ts, 38, 10))
+
+            type: Object as PropType<MyType>,
+>type : Symbol(type, Decl(reverseMappedPartiallyInferableTypes.ts, 39, 19))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>PropType : Symbol(PropType, Decl(reverseMappedPartiallyInferableTypes.ts, 2, 31))
+>MyType : Symbol(MyType, Decl(reverseMappedPartiallyInferableTypes.ts, 25, 90))
+
+            validator: (x: MyType) => {
+>validator : Symbol(validator, Decl(reverseMappedPartiallyInferableTypes.ts, 40, 45))
+>x : Symbol(x, Decl(reverseMappedPartiallyInferableTypes.ts, 41, 24))
+>MyType : Symbol(MyType, Decl(reverseMappedPartiallyInferableTypes.ts, 25, 90))
+
+                return x.valid;
+>x.valid : Symbol(MyType.valid, Decl(reverseMappedPartiallyInferableTypes.ts, 27, 18))
+>x : Symbol(x, Decl(reverseMappedPartiallyInferableTypes.ts, 41, 24))
+>valid : Symbol(MyType.valid, Decl(reverseMappedPartiallyInferableTypes.ts, 27, 18))
+            }
+        }
+    }
+})
+
+r.explicit
+>r.explicit : Symbol(explicit, Decl(reverseMappedPartiallyInferableTypes.ts, 38, 10))
+>r : Symbol(r, Decl(reverseMappedPartiallyInferableTypes.ts, 31, 5))
+>explicit : Symbol(explicit, Decl(reverseMappedPartiallyInferableTypes.ts, 38, 10))
+
+r.notResolved
+>r.notResolved : Symbol(notResolved, Decl(reverseMappedPartiallyInferableTypes.ts, 32, 12))
+>r : Symbol(r, Decl(reverseMappedPartiallyInferableTypes.ts, 31, 5))
+>notResolved : Symbol(notResolved, Decl(reverseMappedPartiallyInferableTypes.ts, 32, 12))
+
+r.explicit.required
+>r.explicit.required : Symbol(required, Decl(reverseMappedPartiallyInferableTypes.ts, 14, 32))
+>r.explicit : Symbol(explicit, Decl(reverseMappedPartiallyInferableTypes.ts, 38, 10))
+>r : Symbol(r, Decl(reverseMappedPartiallyInferableTypes.ts, 31, 5))
+>explicit : Symbol(explicit, Decl(reverseMappedPartiallyInferableTypes.ts, 38, 10))
+>required : Symbol(required, Decl(reverseMappedPartiallyInferableTypes.ts, 14, 32))
+
+r.notResolved.required
+>r.notResolved.required : Symbol(required, Decl(reverseMappedPartiallyInferableTypes.ts, 14, 32))
+>r.notResolved : Symbol(notResolved, Decl(reverseMappedPartiallyInferableTypes.ts, 32, 12))
+>r : Symbol(r, Decl(reverseMappedPartiallyInferableTypes.ts, 31, 5))
+>notResolved : Symbol(notResolved, Decl(reverseMappedPartiallyInferableTypes.ts, 32, 12))
+>required : Symbol(required, Decl(reverseMappedPartiallyInferableTypes.ts, 14, 32))
+
+// Modified repro from #30505
+
+type Box<T> = {
+>Box : Symbol(Box, Decl(reverseMappedPartiallyInferableTypes.ts, 51, 22))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 55, 9))
+
+    contents?: T;
+>contents : Symbol(contents, Decl(reverseMappedPartiallyInferableTypes.ts, 55, 15))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 55, 9))
+
+    contains?(content: T): boolean;
+>contains : Symbol(contains, Decl(reverseMappedPartiallyInferableTypes.ts, 56, 17))
+>content : Symbol(content, Decl(reverseMappedPartiallyInferableTypes.ts, 57, 14))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 55, 9))
+
+};
+
+type Mapped<T> = {
+>Mapped : Symbol(Mapped, Decl(reverseMappedPartiallyInferableTypes.ts, 58, 2))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 60, 12))
+
+    [K in keyof T]: Box<T[K]>;
+>K : Symbol(K, Decl(reverseMappedPartiallyInferableTypes.ts, 61, 5))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 60, 12))
+>Box : Symbol(Box, Decl(reverseMappedPartiallyInferableTypes.ts, 51, 22))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 60, 12))
+>K : Symbol(K, Decl(reverseMappedPartiallyInferableTypes.ts, 61, 5))
+}
+
+declare function id<T>(arg: Mapped<T>): Mapped<T>;
+>id : Symbol(id, Decl(reverseMappedPartiallyInferableTypes.ts, 62, 1))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 64, 20))
+>arg : Symbol(arg, Decl(reverseMappedPartiallyInferableTypes.ts, 64, 23))
+>Mapped : Symbol(Mapped, Decl(reverseMappedPartiallyInferableTypes.ts, 58, 2))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 64, 20))
+>Mapped : Symbol(Mapped, Decl(reverseMappedPartiallyInferableTypes.ts, 58, 2))
+>T : Symbol(T, Decl(reverseMappedPartiallyInferableTypes.ts, 64, 20))
+
+// All properties have inferable types
+
+const obj1 = id({
+>obj1 : Symbol(obj1, Decl(reverseMappedPartiallyInferableTypes.ts, 68, 5))
+>id : Symbol(id, Decl(reverseMappedPartiallyInferableTypes.ts, 62, 1))
+
+    foo: {
+>foo : Symbol(foo, Decl(reverseMappedPartiallyInferableTypes.ts, 68, 17))
+
+        contents: ""
+>contents : Symbol(contents, Decl(reverseMappedPartiallyInferableTypes.ts, 69, 10))
+    }
+});
+
+// Some properties have inferable types
+
+const obj2 = id({
+>obj2 : Symbol(obj2, Decl(reverseMappedPartiallyInferableTypes.ts, 76, 5))
+>id : Symbol(id, Decl(reverseMappedPartiallyInferableTypes.ts, 62, 1))
+
+    foo: {
+>foo : Symbol(foo, Decl(reverseMappedPartiallyInferableTypes.ts, 76, 17))
+
+        contents: "",
+>contents : Symbol(contents, Decl(reverseMappedPartiallyInferableTypes.ts, 77, 10))
+
+        contains(k) {
+>contains : Symbol(contains, Decl(reverseMappedPartiallyInferableTypes.ts, 78, 21))
+>k : Symbol(k, Decl(reverseMappedPartiallyInferableTypes.ts, 79, 17))
+
+            return k.length > 0;
+>k.length : Symbol(String.length, Decl(lib.es5.d.ts, --, --))
+>k : Symbol(k, Decl(reverseMappedPartiallyInferableTypes.ts, 79, 17))
+>length : Symbol(String.length, Decl(lib.es5.d.ts, --, --))
+        }
+    }
+});
+
+// No properties have inferable types
+
+const obj3 = id({
+>obj3 : Symbol(obj3, Decl(reverseMappedPartiallyInferableTypes.ts, 87, 5))
+>id : Symbol(id, Decl(reverseMappedPartiallyInferableTypes.ts, 62, 1))
+
+    foo: {
+>foo : Symbol(foo, Decl(reverseMappedPartiallyInferableTypes.ts, 87, 17))
+
+        contains(k) {
+>contains : Symbol(contains, Decl(reverseMappedPartiallyInferableTypes.ts, 88, 10))
+>k : Symbol(k, Decl(reverseMappedPartiallyInferableTypes.ts, 89, 17))
+
+            return k.length > 0;
+>k : Symbol(k, Decl(reverseMappedPartiallyInferableTypes.ts, 89, 17))
+        }
+    }
+});
+
diff --git a/tests/baselines/reference/reverseMappedPartiallyInferableTypes.types b/tests/baselines/reference/reverseMappedPartiallyInferableTypes.types
new file mode 100644
index 0000000000000..49cd5cf8962ce
--- /dev/null
+++ b/tests/baselines/reference/reverseMappedPartiallyInferableTypes.types
@@ -0,0 +1,231 @@
+=== tests/cases/compiler/reverseMappedPartiallyInferableTypes.ts ===
+// Repro from #30505
+
+export type Prop<T> = { (): T }
+>Prop : Prop<T>
+
+export type PropType<T> = Prop<T>;
+>PropType : Prop<T>
+
+export type PropDefaultValue<T> = T;
+>PropDefaultValue : T
+
+
+export type PropValidatorFunction<T> = (value: T) => boolean;
+>PropValidatorFunction : PropValidatorFunction<T>
+>value : T
+
+export type PropValidator<T> = PropOptions<T>;
+>PropValidator : PropOptions<T>
+
+
+export type PropOptions<T> = {
+>PropOptions : PropOptions<T>
+
+    type: PropType<T>;
+>type : Prop<T>
+
+    value?: PropDefaultValue<T>,
+>value : T | undefined
+
+    required?: boolean;
+>required : boolean | undefined
+
+    validator?: PropValidatorFunction<T>;
+>validator : PropValidatorFunction<T> | undefined
+}
+
+export type RecordPropsDefinition<T> = {
+>RecordPropsDefinition : RecordPropsDefinition<T>
+
+    [K in keyof T]: PropValidator<T[K]>
+}
+export type PropsDefinition<T> = RecordPropsDefinition<T>;
+>PropsDefinition : RecordPropsDefinition<T>
+
+
+declare function extend<T>({ props }: { props: PropsDefinition<T> }):  PropsDefinition<T>;
+>extend : <T>({ props }: { props: RecordPropsDefinition<T>; }) => RecordPropsDefinition<T>
+>props : RecordPropsDefinition<T>
+>props : RecordPropsDefinition<T>
+
+interface MyType {
+    valid: boolean;
+>valid : boolean
+}
+
+const r = extend({
+>r : RecordPropsDefinition<{ notResolved: MyType; explicit: MyType; }>
+>extend({    props: {        notResolved: {            type: Object as PropType<MyType>,            validator: x => {                return x.valid;            }        },        explicit: {            type: Object as PropType<MyType>,            validator: (x: MyType) => {                return x.valid;            }        }    }}) : RecordPropsDefinition<{ notResolved: MyType; explicit: MyType; }>
+>extend : <T>({ props }: { props: RecordPropsDefinition<T>; }) => RecordPropsDefinition<T>
+>{    props: {        notResolved: {            type: Object as PropType<MyType>,            validator: x => {                return x.valid;            }        },        explicit: {            type: Object as PropType<MyType>,            validator: (x: MyType) => {                return x.valid;            }        }    }} : { props: { notResolved: { type: Prop<MyType>; validator: (x: MyType) => boolean; }; explicit: { type: Prop<MyType>; validator: (x: MyType) => boolean; }; }; }
+
+    props: {
+>props : { notResolved: { type: Prop<MyType>; validator: (x: MyType) => boolean; }; explicit: { type: Prop<MyType>; validator: (x: MyType) => boolean; }; }
+>{        notResolved: {            type: Object as PropType<MyType>,            validator: x => {                return x.valid;            }        },        explicit: {            type: Object as PropType<MyType>,            validator: (x: MyType) => {                return x.valid;            }        }    } : { notResolved: { type: Prop<MyType>; validator: (x: MyType) => boolean; }; explicit: { type: Prop<MyType>; validator: (x: MyType) => boolean; }; }
+
+        notResolved: {
+>notResolved : { type: Prop<MyType>; validator: (x: MyType) => boolean; }
+>{            type: Object as PropType<MyType>,            validator: x => {                return x.valid;            }        } : { type: Prop<MyType>; validator: (x: MyType) => boolean; }
+
+            type: Object as PropType<MyType>,
+>type : Prop<MyType>
+>Object as PropType<MyType> : Prop<MyType>
+>Object : ObjectConstructor
+
+            validator: x => {
+>validator : (x: MyType) => boolean
+>x => {                return x.valid;            } : (x: MyType) => boolean
+>x : MyType
+
+                return x.valid;
+>x.valid : boolean
+>x : MyType
+>valid : boolean
+            }
+        },
+        explicit: {
+>explicit : { type: Prop<MyType>; validator: (x: MyType) => boolean; }
+>{            type: Object as PropType<MyType>,            validator: (x: MyType) => {                return x.valid;            }        } : { type: Prop<MyType>; validator: (x: MyType) => boolean; }
+
+            type: Object as PropType<MyType>,
+>type : Prop<MyType>
+>Object as PropType<MyType> : Prop<MyType>
+>Object : ObjectConstructor
+
+            validator: (x: MyType) => {
+>validator : (x: MyType) => boolean
+>(x: MyType) => {                return x.valid;            } : (x: MyType) => boolean
+>x : MyType
+
+                return x.valid;
+>x.valid : boolean
+>x : MyType
+>valid : boolean
+            }
+        }
+    }
+})
+
+r.explicit
+>r.explicit : PropOptions<MyType>
+>r : RecordPropsDefinition<{ notResolved: MyType; explicit: MyType; }>
+>explicit : PropOptions<MyType>
+
+r.notResolved
+>r.notResolved : PropOptions<MyType>
+>r : RecordPropsDefinition<{ notResolved: MyType; explicit: MyType; }>
+>notResolved : PropOptions<MyType>
+
+r.explicit.required
+>r.explicit.required : boolean | undefined
+>r.explicit : PropOptions<MyType>
+>r : RecordPropsDefinition<{ notResolved: MyType; explicit: MyType; }>
+>explicit : PropOptions<MyType>
+>required : boolean | undefined
+
+r.notResolved.required
+>r.notResolved.required : boolean | undefined
+>r.notResolved : PropOptions<MyType>
+>r : RecordPropsDefinition<{ notResolved: MyType; explicit: MyType; }>
+>notResolved : PropOptions<MyType>
+>required : boolean | undefined
+
+// Modified repro from #30505
+
+type Box<T> = {
+>Box : Box<T>
+
+    contents?: T;
+>contents : T | undefined
+
+    contains?(content: T): boolean;
+>contains : ((content: T) => boolean) | undefined
+>content : T
+
+};
+
+type Mapped<T> = {
+>Mapped : Mapped<T>
+
+    [K in keyof T]: Box<T[K]>;
+}
+
+declare function id<T>(arg: Mapped<T>): Mapped<T>;
+>id : <T>(arg: Mapped<T>) => Mapped<T>
+>arg : Mapped<T>
+
+// All properties have inferable types
+
+const obj1 = id({
+>obj1 : Mapped<{ foo: string; }>
+>id({    foo: {        contents: ""    }}) : Mapped<{ foo: string; }>
+>id : <T>(arg: Mapped<T>) => Mapped<T>
+>{    foo: {        contents: ""    }} : { foo: { contents: string; }; }
+
+    foo: {
+>foo : { contents: string; }
+>{        contents: ""    } : { contents: string; }
+
+        contents: ""
+>contents : string
+>"" : ""
+    }
+});
+
+// Some properties have inferable types
+
+const obj2 = id({
+>obj2 : Mapped<{ foo: string; }>
+>id({    foo: {        contents: "",        contains(k) {            return k.length > 0;        }    }}) : Mapped<{ foo: string; }>
+>id : <T>(arg: Mapped<T>) => Mapped<T>
+>{    foo: {        contents: "",        contains(k) {            return k.length > 0;        }    }} : { foo: { contents: string; contains(k: string): boolean; }; }
+
+    foo: {
+>foo : { contents: string; contains(k: string): boolean; }
+>{        contents: "",        contains(k) {            return k.length > 0;        }    } : { contents: string; contains(k: string): boolean; }
+
+        contents: "",
+>contents : string
+>"" : ""
+
+        contains(k) {
+>contains : (k: string) => boolean
+>k : string
+
+            return k.length > 0;
+>k.length > 0 : boolean
+>k.length : number
+>k : string
+>length : number
+>0 : 0
+        }
+    }
+});
+
+// No properties have inferable types
+
+const obj3 = id({
+>obj3 : Mapped<unknown>
+>id({    foo: {        contains(k) {            return k.length > 0;        }    }}) : Mapped<unknown>
+>id : <T>(arg: Mapped<T>) => Mapped<T>
+>{    foo: {        contains(k) {            return k.length > 0;        }    }} : { foo: { contains(k: unknown): boolean; }; }
+
+    foo: {
+>foo : { contains(k: unknown): boolean; }
+>{        contains(k) {            return k.length > 0;        }    } : { contains(k: unknown): boolean; }
+
+        contains(k) {
+>contains : (k: unknown) => boolean
+>k : unknown
+
+            return k.length > 0;
+>k.length > 0 : boolean
+>k.length : any
+>k : unknown
+>length : any
+>0 : 0
+        }
+    }
+});
+