diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 5525ff30ddab7..cc4c8476de6f5 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -14921,10 +14921,19 @@ namespace ts {
             return type;
         }
 
+        // We consider a type to be partially inferable if it isn't marked non-inferable or if it is
+        // an object literal type with at least one property of an inferable type. For example, an object
+        // literal { a: 123, b: x => true } is marked non-inferable because it contains a context sensitive
+        // arrow function, but is considered partially inferable because property 'a' has an inferable type.
+        function isPartiallyInferableType(type: Type): boolean {
+            return !(getObjectFlags(type) & ObjectFlags.NonInferrableType) ||
+                isObjectLiteralType(type) && some(getPropertiesOfType(type), prop => isPartiallyInferableType(getTypeOfSymbol(prop)));
+        }
+
         function createReverseMappedType(source: Type, target: MappedType, constraint: IndexType) {
-            // If any property contains context sensitive functions that have been skipped, the source type
-            // is incomplete and we can't infer a meaningful input type.
-            if (getObjectFlags(source) & ObjectFlags.NonInferrableType || getPropertiesOfType(source).length === 0 && !getIndexInfoOfType(source, IndexKind.String)) {
+            // We consider a source type reverse mappable if it has a string index signature or if
+            // it has one or more properties and is of a partially inferable type.
+            if (!(getIndexInfoOfType(source, IndexKind.String) || getPropertiesOfType(source).length !== 0 && isPartiallyInferableType(source))) {
                 return undefined;
             }
             // For arrays and tuples we infer new arrays and tuples where the reverse mapping has been
@@ -15309,7 +15318,11 @@ namespace ts {
                         const inferredType = inferTypeForHomomorphicMappedType(source, target, <IndexType>constraintType);
                         if (inferredType) {
                             const savePriority = priority;
-                            priority |= InferencePriority.HomomorphicMappedType;
+                            // We assign a lower priority to inferences made from types containing non-inferrable
+                            // types because we may only have a partial result (i.e. we may have failed to make
+                            // reverse inferences for some properties).
+                            priority |= getObjectFlags(source) & ObjectFlags.NonInferrableType ?
+                                InferencePriority.PartialHomomorphicMappedType : InferencePriority.HomomorphicMappedType;
                             inferFromTypes(inferredType, inference.typeParameter);
                             priority = savePriority;
                         }
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 53b3d82bc2763..e33d0f447859d 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -4424,15 +4424,16 @@ namespace ts {
     export type TypeMapper = (t: TypeParameter) => Type;
 
     export const enum InferencePriority {
-        NakedTypeVariable           = 1 << 0,  // Naked type variable in union or intersection type
-        HomomorphicMappedType       = 1 << 1,  // Reverse inference for homomorphic mapped type
-        MappedTypeConstraint        = 1 << 2,  // Reverse inference for mapped type
-        ReturnType                  = 1 << 3,  // Inference made from return type of generic function
-        LiteralKeyof                = 1 << 4,  // Inference made from a string literal to a keyof T
-        NoConstraints               = 1 << 5,  // Don't infer from constraints of instantiable types
-        AlwaysStrict                = 1 << 6,  // Always use strict rules for contravariant inferences
-
-        PriorityImpliesCombination  = ReturnType | MappedTypeConstraint | LiteralKeyof,  // These priorities imply that the resulting type should be a combination of all candidates
+        NakedTypeVariable            = 1 << 0,  // Naked type variable in union or intersection type
+        HomomorphicMappedType        = 1 << 1,  // Reverse inference for homomorphic mapped type
+        PartialHomomorphicMappedType = 1 << 2,  // Partial reverse inference for homomorphic mapped type
+        MappedTypeConstraint         = 1 << 3,  // Reverse inference for mapped type
+        ReturnType                   = 1 << 4,  // Inference made from return type of generic function
+        LiteralKeyof                 = 1 << 5,  // Inference made from a string literal to a keyof T
+        NoConstraints                = 1 << 6,  // Don't infer from constraints of instantiable types
+        AlwaysStrict                 = 1 << 7,  // Always use strict rules for contravariant inferences
+
+        PriorityImpliesCombination = ReturnType | MappedTypeConstraint | LiteralKeyof,  // These priorities imply that the resulting type should be a combination of all candidates
     }
 
     /* @internal */
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
index ae473420de5ba..4bdfa84ca494d 100644
--- a/tests/baselines/reference/api/tsserverlibrary.d.ts
+++ b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -2418,12 +2418,13 @@ declare namespace ts {
     enum InferencePriority {
         NakedTypeVariable = 1,
         HomomorphicMappedType = 2,
-        MappedTypeConstraint = 4,
-        ReturnType = 8,
-        LiteralKeyof = 16,
-        NoConstraints = 32,
-        AlwaysStrict = 64,
-        PriorityImpliesCombination = 28
+        PartialHomomorphicMappedType = 4,
+        MappedTypeConstraint = 8,
+        ReturnType = 16,
+        LiteralKeyof = 32,
+        NoConstraints = 64,
+        AlwaysStrict = 128,
+        PriorityImpliesCombination = 56
     }
     /** @deprecated Use FileExtensionInfo instead. */
     type JsFileExtensionInfo = FileExtensionInfo;
diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
index 038a953d08188..7f0e63cfc030b 100644
--- a/tests/baselines/reference/api/typescript.d.ts
+++ b/tests/baselines/reference/api/typescript.d.ts
@@ -2418,12 +2418,13 @@ declare namespace ts {
     enum InferencePriority {
         NakedTypeVariable = 1,
         HomomorphicMappedType = 2,
-        MappedTypeConstraint = 4,
-        ReturnType = 8,
-        LiteralKeyof = 16,
-        NoConstraints = 32,
-        AlwaysStrict = 64,
-        PriorityImpliesCombination = 28
+        PartialHomomorphicMappedType = 4,
+        MappedTypeConstraint = 8,
+        ReturnType = 16,
+        LiteralKeyof = 32,
+        NoConstraints = 64,
+        AlwaysStrict = 128,
+        PriorityImpliesCombination = 56
     }
     /** @deprecated Use FileExtensionInfo instead. */
     type JsFileExtensionInfo = FileExtensionInfo;
diff --git a/tests/baselines/reference/mappedTypeInferenceErrors.errors.txt b/tests/baselines/reference/mappedTypeInferenceErrors.errors.txt
index f83f01f77bf60..0c5e835db96d4 100644
--- a/tests/baselines/reference/mappedTypeInferenceErrors.errors.txt
+++ b/tests/baselines/reference/mappedTypeInferenceErrors.errors.txt
@@ -20,7 +20,7 @@ tests/cases/conformance/types/mapped/mappedTypeInferenceErrors.ts(16,9): error T
             baz: 42
             ~~~
 !!! error TS2322: Type 'number' is not assignable to type '() => unknown'.
-!!! related TS6500 tests/cases/conformance/types/mapped/mappedTypeInferenceErrors.ts:16:9: The expected type comes from property 'baz' which is declared here on type 'ComputedOf<{ bar: number; baz: unknown; }>'
+!!! related TS6500 tests/cases/conformance/types/mapped/mappedTypeInferenceErrors.ts:16:9: The expected type comes from property 'baz' which is declared here on type 'ComputedOf<{ bar: unknown; baz: unknown; }>'
         }
     });
     
\ No newline at end of file
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
+        }
+    }
+});
+
diff --git a/tests/cases/compiler/reverseMappedPartiallyInferableTypes.ts b/tests/cases/compiler/reverseMappedPartiallyInferableTypes.ts
new file mode 100644
index 0000000000000..799ff641c5a43
--- /dev/null
+++ b/tests/cases/compiler/reverseMappedPartiallyInferableTypes.ts
@@ -0,0 +1,96 @@
+// @strict: true
+
+// 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;
+        }
+    }
+});