From 37d539d92c114ebe50e0d74ae0e4b6c7b170c5d6 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Tue, 3 Mar 2020 12:19:14 -0800
Subject: [PATCH 1/6] Treat intersections of only objects as a single object in
 relations

---
 src/compiler/checker.ts | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 18d32322297f0..bb3083144fe3b 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -15363,7 +15363,9 @@ namespace ts {
                         //
                         //    - For a primitive type or type parameter (such as 'number = A & B') there is no point in
                         //          breaking the intersection apart.
-                        result = someTypeRelatedToType(<IntersectionType>source, target, /*reportErrors*/ false, IntersectionState.Source);
+                        if (!isNonGenericObjectType(target) || !every((<IntersectionType>source).types, isNonGenericObjectType)) {
+                            result = someTypeRelatedToType(<IntersectionType>source, target, /*reportErrors*/ false, IntersectionState.Source);
+                        }
                     }
                     if (!result && (source.flags & TypeFlags.StructuredOrInstantiable || target.flags & TypeFlags.StructuredOrInstantiable)) {
                         if (result = recursiveTypeRelatedTo(source, target, reportErrors, intersectionState)) {

From 583ca838db4b887e9b1365c371ea8e4c897c57f5 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Tue, 3 Mar 2020 14:08:24 -0800
Subject: [PATCH 2/6] Exclude intersections containing non-inferrable types

---
 src/compiler/checker.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index bb3083144fe3b..fe5d10949e7ff 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -15363,7 +15363,7 @@ namespace ts {
                         //
                         //    - For a primitive type or type parameter (such as 'number = A & B') there is no point in
                         //          breaking the intersection apart.
-                        if (!isNonGenericObjectType(target) || !every((<IntersectionType>source).types, isNonGenericObjectType)) {
+                        if (!isNonGenericObjectType(target) || !every((<IntersectionType>source).types, t => isNonGenericObjectType(t) && !(getObjectFlags(t) & ObjectFlags.NonInferrableType))) {
                             result = someTypeRelatedToType(<IntersectionType>source, target, /*reportErrors*/ false, IntersectionState.Source);
                         }
                     }

From 1e114d2c5466c71067cb755ae8eb9d936e8b9add Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Tue, 3 Mar 2020 14:09:05 -0800
Subject: [PATCH 3/6] Accept new baselines

---
 ...ormalizedIntersectionTooComplex.errors.txt |   6 +-
 .../propTypeValidatorInference.errors.txt     | 118 ++++++++++++++++++
 2 files changed, 121 insertions(+), 3 deletions(-)
 create mode 100644 tests/baselines/reference/propTypeValidatorInference.errors.txt

diff --git a/tests/baselines/reference/normalizedIntersectionTooComplex.errors.txt b/tests/baselines/reference/normalizedIntersectionTooComplex.errors.txt
index 64e7d7f00c510..4e214eff50715 100644
--- a/tests/baselines/reference/normalizedIntersectionTooComplex.errors.txt
+++ b/tests/baselines/reference/normalizedIntersectionTooComplex.errors.txt
@@ -1,5 +1,5 @@
+tests/cases/compiler/normalizedIntersectionTooComplex.ts(36,14): error TS2590: Expression produces a union type that is too complex to represent.
 tests/cases/compiler/normalizedIntersectionTooComplex.ts(36,40): error TS7006: Parameter 'x' implicitly has an 'any' type.
-tests/cases/compiler/normalizedIntersectionTooComplex.ts(36,40): error TS2590: Expression produces a union type that is too complex to represent.
 
 
 ==== tests/cases/compiler/normalizedIntersectionTooComplex.ts (2 errors) ====
@@ -39,8 +39,8 @@ tests/cases/compiler/normalizedIntersectionTooComplex.ts(36,40): error TS2590: E
     declare var all: keyof Big;
     const ctor = getCtor(all);
     const comp = ctor({ common: "ok", ref: x => console.log(x) });
+                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2590: Expression produces a union type that is too complex to represent.
                                            ~
 !!! error TS7006: Parameter 'x' implicitly has an 'any' type.
-                                           ~~~~~~~~~~~~~~~~~~~
-!!! error TS2590: Expression produces a union type that is too complex to represent.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/propTypeValidatorInference.errors.txt b/tests/baselines/reference/propTypeValidatorInference.errors.txt
new file mode 100644
index 0000000000000..277ac5ce532ea
--- /dev/null
+++ b/tests/baselines/reference/propTypeValidatorInference.errors.txt
@@ -0,0 +1,118 @@
+tests/cases/compiler/file.ts(35,5): error TS2322: Type 'Validator<InferProps<{ foo: Validator<string>; bar: Requireable<boolean>; baz: Requireable<any>; }>>' is not assignable to type 'Validator<{ foo: string; bar?: boolean | undefined; baz?: any; }>'.
+  Type 'InferProps<{ foo: Validator<string>; bar: Requireable<boolean>; baz: Requireable<any>; }>' is not assignable to type '{ foo: string; bar?: boolean | undefined; baz?: any; }'.
+    Types of property 'bar' are incompatible.
+      Type 'boolean | null | undefined' is not assignable to type 'boolean | undefined'.
+        Type 'null' is not assignable to type 'boolean | undefined'.
+tests/cases/compiler/file.ts(36,5): error TS2322: Type 'Validator<string | boolean | InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>>' is not assignable to type 'Validator<string | boolean | { foo?: string | undefined; bar: number; }>'.
+  Type 'string | boolean | InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>' is not assignable to type 'string | boolean | { foo?: string | undefined; bar: number; }'.
+    Type 'InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>' is not assignable to type 'string | boolean | { foo?: string | undefined; bar: number; }'.
+      Type 'InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>' is not assignable to type '{ foo?: string | undefined; bar: number; }'.
+        Types of property 'foo' are incompatible.
+          Type 'string | null | undefined' is not assignable to type 'string | undefined'.
+            Type 'null' is not assignable to type 'string | undefined'.
+
+
+==== tests/cases/compiler/node_modules/prop-types/index.d.ts (0 errors) ====
+    export const nominalTypeHack: unique symbol;
+    
+    export type IsOptional<T> = undefined | null extends T ? true : undefined extends T ? true : null extends T ? true : false;
+    
+    export type RequiredKeys<V> = { [K in keyof V]-?: Exclude<V[K], undefined> extends Validator<infer T> ? IsOptional<T> extends true ? never : K : never }[keyof V];
+    export type OptionalKeys<V> = Exclude<keyof V, RequiredKeys<V>>;
+    export type InferPropsInner<V> = { [K in keyof V]-?: InferType<V[K]>; };
+    
+    export interface Validator<T> {
+        (props: object, propName: string, componentName: string, location: string, propFullName: string): Error | null;
+        [nominalTypeHack]?: T;
+    }
+    
+    export interface Requireable<T> extends Validator<T | undefined | null> {
+        isRequired: Validator<NonNullable<T>>;
+    }
+    
+    export type ValidationMap<T> = { [K in keyof T]?: Validator<T[K]> };
+    
+    export type InferType<V> = V extends Validator<infer T> ? T : any;
+    export type InferProps<V> =
+        & InferPropsInner<Pick<V, RequiredKeys<V>>>
+        & Partial<InferPropsInner<Pick<V, OptionalKeys<V>>>>;
+    
+    export const any: Requireable<any>;
+    export const array: Requireable<any[]>;
+    export const bool: Requireable<boolean>;
+    export const string: Requireable<string>;
+    export const number: Requireable<number>;
+    export function shape<P extends ValidationMap<any>>(type: P): Requireable<InferProps<P>>;
+    export function oneOfType<T extends Validator<any>>(types: T[]): Requireable<NonNullable<InferType<T>>>;
+    
+    
+==== tests/cases/compiler/file.ts (2 errors) ====
+    import * as PropTypes from "prop-types";
+    interface Props {
+        any?: any;
+        array: string[];
+        bool: boolean;
+        shape: {
+            foo: string;
+            bar?: boolean;
+            baz?: any
+        };
+        oneOfType: string | boolean | {
+            foo?: string;
+            bar: number;
+        };
+    }
+    
+    type PropTypesMap = PropTypes.ValidationMap<Props>;
+    
+    const innerProps = {
+        foo: PropTypes.string.isRequired,
+        bar: PropTypes.bool,
+        baz: PropTypes.any
+    };
+    
+    const arrayOfTypes = [PropTypes.string, PropTypes.bool, PropTypes.shape({
+        foo: PropTypes.string,
+        bar: PropTypes.number.isRequired
+    })];
+    
+    // TS checking
+    const propTypes: PropTypesMap = {
+        any: PropTypes.any,
+        array: PropTypes.array.isRequired,
+        bool: PropTypes.bool.isRequired,
+        shape: PropTypes.shape(innerProps).isRequired,
+        ~~~~~
+!!! error TS2322: Type 'Validator<InferProps<{ foo: Validator<string>; bar: Requireable<boolean>; baz: Requireable<any>; }>>' is not assignable to type 'Validator<{ foo: string; bar?: boolean | undefined; baz?: any; }>'.
+!!! error TS2322:   Type 'InferProps<{ foo: Validator<string>; bar: Requireable<boolean>; baz: Requireable<any>; }>' is not assignable to type '{ foo: string; bar?: boolean | undefined; baz?: any; }'.
+!!! error TS2322:     Types of property 'bar' are incompatible.
+!!! error TS2322:       Type 'boolean | null | undefined' is not assignable to type 'boolean | undefined'.
+!!! error TS2322:         Type 'null' is not assignable to type 'boolean | undefined'.
+!!! related TS6500 tests/cases/compiler/file.ts:6:5: The expected type comes from property 'shape' which is declared here on type 'ValidationMap<Props>'
+        oneOfType: PropTypes.oneOfType(arrayOfTypes).isRequired,
+        ~~~~~~~~~
+!!! error TS2322: Type 'Validator<string | boolean | InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>>' is not assignable to type 'Validator<string | boolean | { foo?: string | undefined; bar: number; }>'.
+!!! error TS2322:   Type 'string | boolean | InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>' is not assignable to type 'string | boolean | { foo?: string | undefined; bar: number; }'.
+!!! error TS2322:     Type 'InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>' is not assignable to type 'string | boolean | { foo?: string | undefined; bar: number; }'.
+!!! error TS2322:       Type 'InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>' is not assignable to type '{ foo?: string | undefined; bar: number; }'.
+!!! error TS2322:         Types of property 'foo' are incompatible.
+!!! error TS2322:           Type 'string | null | undefined' is not assignable to type 'string | undefined'.
+!!! error TS2322:             Type 'null' is not assignable to type 'string | undefined'.
+!!! related TS6500 tests/cases/compiler/file.ts:11:5: The expected type comes from property 'oneOfType' which is declared here on type 'ValidationMap<Props>'
+    };
+    
+    // JS checking
+    const propTypesWithoutAnnotation = {
+        any: PropTypes.any,
+        array: PropTypes.array.isRequired,
+        bool: PropTypes.bool.isRequired,
+        shape: PropTypes.shape(innerProps).isRequired,
+        oneOfType: PropTypes.oneOfType(arrayOfTypes).isRequired,
+    };
+    
+    type ExtractedProps = PropTypes.InferProps<typeof propTypes>;
+    
+    type ExtractedPropsWithoutAnnotation = PropTypes.InferProps<typeof propTypesWithoutAnnotation>;
+    
+    type ExtractPropsMatch = ExtractedProps extends ExtractedPropsWithoutAnnotation ? true : false;
+    const x: true = (null as any as ExtractPropsMatch);
\ No newline at end of file

From 0a207cc318a2d18aecdf5ba8decf76c2af39bfac Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Tue, 3 Mar 2020 14:10:32 -0800
Subject: [PATCH 4/6] Update test

---
 tests/cases/compiler/propTypeValidatorInference.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/cases/compiler/propTypeValidatorInference.ts b/tests/cases/compiler/propTypeValidatorInference.ts
index 54030ab91a916..9f6120a5d67ac 100644
--- a/tests/cases/compiler/propTypeValidatorInference.ts
+++ b/tests/cases/compiler/propTypeValidatorInference.ts
@@ -13,7 +13,7 @@ export interface Validator<T> {
     [nominalTypeHack]?: T;
 }
 
-export interface Requireable<T> extends Validator<T | undefined | null> {
+export interface Requireable<T> extends Validator<T> {
     isRequired: Validator<NonNullable<T>>;
 }
 

From adeb53237bd61c794f5738f639135950a198d7a6 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Tue, 3 Mar 2020 14:10:40 -0800
Subject: [PATCH 5/6] Accept new baselines

---
 .../propTypeValidatorInference.errors.txt     | 118 ------------------
 .../reference/propTypeValidatorInference.js   |   2 +-
 .../propTypeValidatorInference.symbols        |  44 +++----
 .../propTypeValidatorInference.types          |   4 +-
 4 files changed, 24 insertions(+), 144 deletions(-)
 delete mode 100644 tests/baselines/reference/propTypeValidatorInference.errors.txt

diff --git a/tests/baselines/reference/propTypeValidatorInference.errors.txt b/tests/baselines/reference/propTypeValidatorInference.errors.txt
deleted file mode 100644
index 277ac5ce532ea..0000000000000
--- a/tests/baselines/reference/propTypeValidatorInference.errors.txt
+++ /dev/null
@@ -1,118 +0,0 @@
-tests/cases/compiler/file.ts(35,5): error TS2322: Type 'Validator<InferProps<{ foo: Validator<string>; bar: Requireable<boolean>; baz: Requireable<any>; }>>' is not assignable to type 'Validator<{ foo: string; bar?: boolean | undefined; baz?: any; }>'.
-  Type 'InferProps<{ foo: Validator<string>; bar: Requireable<boolean>; baz: Requireable<any>; }>' is not assignable to type '{ foo: string; bar?: boolean | undefined; baz?: any; }'.
-    Types of property 'bar' are incompatible.
-      Type 'boolean | null | undefined' is not assignable to type 'boolean | undefined'.
-        Type 'null' is not assignable to type 'boolean | undefined'.
-tests/cases/compiler/file.ts(36,5): error TS2322: Type 'Validator<string | boolean | InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>>' is not assignable to type 'Validator<string | boolean | { foo?: string | undefined; bar: number; }>'.
-  Type 'string | boolean | InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>' is not assignable to type 'string | boolean | { foo?: string | undefined; bar: number; }'.
-    Type 'InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>' is not assignable to type 'string | boolean | { foo?: string | undefined; bar: number; }'.
-      Type 'InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>' is not assignable to type '{ foo?: string | undefined; bar: number; }'.
-        Types of property 'foo' are incompatible.
-          Type 'string | null | undefined' is not assignable to type 'string | undefined'.
-            Type 'null' is not assignable to type 'string | undefined'.
-
-
-==== tests/cases/compiler/node_modules/prop-types/index.d.ts (0 errors) ====
-    export const nominalTypeHack: unique symbol;
-    
-    export type IsOptional<T> = undefined | null extends T ? true : undefined extends T ? true : null extends T ? true : false;
-    
-    export type RequiredKeys<V> = { [K in keyof V]-?: Exclude<V[K], undefined> extends Validator<infer T> ? IsOptional<T> extends true ? never : K : never }[keyof V];
-    export type OptionalKeys<V> = Exclude<keyof V, RequiredKeys<V>>;
-    export type InferPropsInner<V> = { [K in keyof V]-?: InferType<V[K]>; };
-    
-    export interface Validator<T> {
-        (props: object, propName: string, componentName: string, location: string, propFullName: string): Error | null;
-        [nominalTypeHack]?: T;
-    }
-    
-    export interface Requireable<T> extends Validator<T | undefined | null> {
-        isRequired: Validator<NonNullable<T>>;
-    }
-    
-    export type ValidationMap<T> = { [K in keyof T]?: Validator<T[K]> };
-    
-    export type InferType<V> = V extends Validator<infer T> ? T : any;
-    export type InferProps<V> =
-        & InferPropsInner<Pick<V, RequiredKeys<V>>>
-        & Partial<InferPropsInner<Pick<V, OptionalKeys<V>>>>;
-    
-    export const any: Requireable<any>;
-    export const array: Requireable<any[]>;
-    export const bool: Requireable<boolean>;
-    export const string: Requireable<string>;
-    export const number: Requireable<number>;
-    export function shape<P extends ValidationMap<any>>(type: P): Requireable<InferProps<P>>;
-    export function oneOfType<T extends Validator<any>>(types: T[]): Requireable<NonNullable<InferType<T>>>;
-    
-    
-==== tests/cases/compiler/file.ts (2 errors) ====
-    import * as PropTypes from "prop-types";
-    interface Props {
-        any?: any;
-        array: string[];
-        bool: boolean;
-        shape: {
-            foo: string;
-            bar?: boolean;
-            baz?: any
-        };
-        oneOfType: string | boolean | {
-            foo?: string;
-            bar: number;
-        };
-    }
-    
-    type PropTypesMap = PropTypes.ValidationMap<Props>;
-    
-    const innerProps = {
-        foo: PropTypes.string.isRequired,
-        bar: PropTypes.bool,
-        baz: PropTypes.any
-    };
-    
-    const arrayOfTypes = [PropTypes.string, PropTypes.bool, PropTypes.shape({
-        foo: PropTypes.string,
-        bar: PropTypes.number.isRequired
-    })];
-    
-    // TS checking
-    const propTypes: PropTypesMap = {
-        any: PropTypes.any,
-        array: PropTypes.array.isRequired,
-        bool: PropTypes.bool.isRequired,
-        shape: PropTypes.shape(innerProps).isRequired,
-        ~~~~~
-!!! error TS2322: Type 'Validator<InferProps<{ foo: Validator<string>; bar: Requireable<boolean>; baz: Requireable<any>; }>>' is not assignable to type 'Validator<{ foo: string; bar?: boolean | undefined; baz?: any; }>'.
-!!! error TS2322:   Type 'InferProps<{ foo: Validator<string>; bar: Requireable<boolean>; baz: Requireable<any>; }>' is not assignable to type '{ foo: string; bar?: boolean | undefined; baz?: any; }'.
-!!! error TS2322:     Types of property 'bar' are incompatible.
-!!! error TS2322:       Type 'boolean | null | undefined' is not assignable to type 'boolean | undefined'.
-!!! error TS2322:         Type 'null' is not assignable to type 'boolean | undefined'.
-!!! related TS6500 tests/cases/compiler/file.ts:6:5: The expected type comes from property 'shape' which is declared here on type 'ValidationMap<Props>'
-        oneOfType: PropTypes.oneOfType(arrayOfTypes).isRequired,
-        ~~~~~~~~~
-!!! error TS2322: Type 'Validator<string | boolean | InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>>' is not assignable to type 'Validator<string | boolean | { foo?: string | undefined; bar: number; }>'.
-!!! error TS2322:   Type 'string | boolean | InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>' is not assignable to type 'string | boolean | { foo?: string | undefined; bar: number; }'.
-!!! error TS2322:     Type 'InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>' is not assignable to type 'string | boolean | { foo?: string | undefined; bar: number; }'.
-!!! error TS2322:       Type 'InferProps<{ foo: Requireable<string>; bar: Validator<number>; }>' is not assignable to type '{ foo?: string | undefined; bar: number; }'.
-!!! error TS2322:         Types of property 'foo' are incompatible.
-!!! error TS2322:           Type 'string | null | undefined' is not assignable to type 'string | undefined'.
-!!! error TS2322:             Type 'null' is not assignable to type 'string | undefined'.
-!!! related TS6500 tests/cases/compiler/file.ts:11:5: The expected type comes from property 'oneOfType' which is declared here on type 'ValidationMap<Props>'
-    };
-    
-    // JS checking
-    const propTypesWithoutAnnotation = {
-        any: PropTypes.any,
-        array: PropTypes.array.isRequired,
-        bool: PropTypes.bool.isRequired,
-        shape: PropTypes.shape(innerProps).isRequired,
-        oneOfType: PropTypes.oneOfType(arrayOfTypes).isRequired,
-    };
-    
-    type ExtractedProps = PropTypes.InferProps<typeof propTypes>;
-    
-    type ExtractedPropsWithoutAnnotation = PropTypes.InferProps<typeof propTypesWithoutAnnotation>;
-    
-    type ExtractPropsMatch = ExtractedProps extends ExtractedPropsWithoutAnnotation ? true : false;
-    const x: true = (null as any as ExtractPropsMatch);
\ No newline at end of file
diff --git a/tests/baselines/reference/propTypeValidatorInference.js b/tests/baselines/reference/propTypeValidatorInference.js
index 3a6fa04fbe183..de1b7e99e1fc2 100644
--- a/tests/baselines/reference/propTypeValidatorInference.js
+++ b/tests/baselines/reference/propTypeValidatorInference.js
@@ -14,7 +14,7 @@ export interface Validator<T> {
     [nominalTypeHack]?: T;
 }
 
-export interface Requireable<T> extends Validator<T | undefined | null> {
+export interface Requireable<T> extends Validator<T> {
     isRequired: Validator<NonNullable<T>>;
 }
 
diff --git a/tests/baselines/reference/propTypeValidatorInference.symbols b/tests/baselines/reference/propTypeValidatorInference.symbols
index 32a4a3c1abf3b..320c2c46bcd25 100644
--- a/tests/baselines/reference/propTypeValidatorInference.symbols
+++ b/tests/baselines/reference/propTypeValidatorInference.symbols
@@ -59,14 +59,14 @@ export interface Validator<T> {
 >T : Symbol(T, Decl(index.d.ts, 8, 27))
 }
 
-export interface Requireable<T> extends Validator<T | undefined | null> {
+export interface Requireable<T> extends Validator<T> {
 >Requireable : Symbol(Requireable, Decl(index.d.ts, 11, 1))
 >T : Symbol(T, Decl(index.d.ts, 13, 29))
 >Validator : Symbol(Validator, Decl(index.d.ts, 6, 72))
 >T : Symbol(T, Decl(index.d.ts, 13, 29))
 
     isRequired: Validator<NonNullable<T>>;
->isRequired : Symbol(Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>isRequired : Symbol(Requireable.isRequired, Decl(index.d.ts, 13, 54))
 >Validator : Symbol(Validator, Decl(index.d.ts, 6, 72))
 >NonNullable : Symbol(NonNullable, Decl(lib.es5.d.ts, --, --))
 >T : Symbol(T, Decl(index.d.ts, 13, 29))
@@ -202,11 +202,11 @@ const innerProps = {
 
     foo: PropTypes.string.isRequired,
 >foo : Symbol(foo, Decl(file.ts, 18, 20))
->PropTypes.string.isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>PropTypes.string.isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 >PropTypes.string : Symbol(PropTypes.string, Decl(index.d.ts, 27, 12))
 >PropTypes : Symbol(PropTypes, Decl(file.ts, 0, 6))
 >string : Symbol(PropTypes.string, Decl(index.d.ts, 27, 12))
->isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 
     bar: PropTypes.bool,
 >bar : Symbol(bar, Decl(file.ts, 19, 37))
@@ -242,11 +242,11 @@ const arrayOfTypes = [PropTypes.string, PropTypes.bool, PropTypes.shape({
 
     bar: PropTypes.number.isRequired
 >bar : Symbol(bar, Decl(file.ts, 25, 26))
->PropTypes.number.isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>PropTypes.number.isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 >PropTypes.number : Symbol(PropTypes.number, Decl(index.d.ts, 28, 12))
 >PropTypes : Symbol(PropTypes, Decl(file.ts, 0, 6))
 >number : Symbol(PropTypes.number, Decl(index.d.ts, 28, 12))
->isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 
 })];
 
@@ -263,37 +263,37 @@ const propTypes: PropTypesMap = {
 
     array: PropTypes.array.isRequired,
 >array : Symbol(array, Decl(file.ts, 31, 23))
->PropTypes.array.isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>PropTypes.array.isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 >PropTypes.array : Symbol(PropTypes.array, Decl(index.d.ts, 25, 12))
 >PropTypes : Symbol(PropTypes, Decl(file.ts, 0, 6))
 >array : Symbol(PropTypes.array, Decl(index.d.ts, 25, 12))
->isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 
     bool: PropTypes.bool.isRequired,
 >bool : Symbol(bool, Decl(file.ts, 32, 38))
->PropTypes.bool.isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>PropTypes.bool.isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 >PropTypes.bool : Symbol(PropTypes.bool, Decl(index.d.ts, 26, 12))
 >PropTypes : Symbol(PropTypes, Decl(file.ts, 0, 6))
 >bool : Symbol(PropTypes.bool, Decl(index.d.ts, 26, 12))
->isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 
     shape: PropTypes.shape(innerProps).isRequired,
 >shape : Symbol(shape, Decl(file.ts, 33, 36))
->PropTypes.shape(innerProps).isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>PropTypes.shape(innerProps).isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 >PropTypes.shape : Symbol(PropTypes.shape, Decl(index.d.ts, 28, 41))
 >PropTypes : Symbol(PropTypes, Decl(file.ts, 0, 6))
 >shape : Symbol(PropTypes.shape, Decl(index.d.ts, 28, 41))
 >innerProps : Symbol(innerProps, Decl(file.ts, 18, 5))
->isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 
     oneOfType: PropTypes.oneOfType(arrayOfTypes).isRequired,
 >oneOfType : Symbol(oneOfType, Decl(file.ts, 34, 50))
->PropTypes.oneOfType(arrayOfTypes).isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>PropTypes.oneOfType(arrayOfTypes).isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 >PropTypes.oneOfType : Symbol(PropTypes.oneOfType, Decl(index.d.ts, 29, 89))
 >PropTypes : Symbol(PropTypes, Decl(file.ts, 0, 6))
 >oneOfType : Symbol(PropTypes.oneOfType, Decl(index.d.ts, 29, 89))
 >arrayOfTypes : Symbol(arrayOfTypes, Decl(file.ts, 24, 5))
->isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 
 };
 
@@ -309,37 +309,37 @@ const propTypesWithoutAnnotation = {
 
     array: PropTypes.array.isRequired,
 >array : Symbol(array, Decl(file.ts, 40, 23))
->PropTypes.array.isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>PropTypes.array.isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 >PropTypes.array : Symbol(PropTypes.array, Decl(index.d.ts, 25, 12))
 >PropTypes : Symbol(PropTypes, Decl(file.ts, 0, 6))
 >array : Symbol(PropTypes.array, Decl(index.d.ts, 25, 12))
->isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 
     bool: PropTypes.bool.isRequired,
 >bool : Symbol(bool, Decl(file.ts, 41, 38))
->PropTypes.bool.isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>PropTypes.bool.isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 >PropTypes.bool : Symbol(PropTypes.bool, Decl(index.d.ts, 26, 12))
 >PropTypes : Symbol(PropTypes, Decl(file.ts, 0, 6))
 >bool : Symbol(PropTypes.bool, Decl(index.d.ts, 26, 12))
->isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 
     shape: PropTypes.shape(innerProps).isRequired,
 >shape : Symbol(shape, Decl(file.ts, 42, 36))
->PropTypes.shape(innerProps).isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>PropTypes.shape(innerProps).isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 >PropTypes.shape : Symbol(PropTypes.shape, Decl(index.d.ts, 28, 41))
 >PropTypes : Symbol(PropTypes, Decl(file.ts, 0, 6))
 >shape : Symbol(PropTypes.shape, Decl(index.d.ts, 28, 41))
 >innerProps : Symbol(innerProps, Decl(file.ts, 18, 5))
->isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 
     oneOfType: PropTypes.oneOfType(arrayOfTypes).isRequired,
 >oneOfType : Symbol(oneOfType, Decl(file.ts, 43, 50))
->PropTypes.oneOfType(arrayOfTypes).isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>PropTypes.oneOfType(arrayOfTypes).isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 >PropTypes.oneOfType : Symbol(PropTypes.oneOfType, Decl(index.d.ts, 29, 89))
 >PropTypes : Symbol(PropTypes, Decl(file.ts, 0, 6))
 >oneOfType : Symbol(PropTypes.oneOfType, Decl(index.d.ts, 29, 89))
 >arrayOfTypes : Symbol(arrayOfTypes, Decl(file.ts, 24, 5))
->isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 73))
+>isRequired : Symbol(PropTypes.Requireable.isRequired, Decl(index.d.ts, 13, 54))
 
 };
 
diff --git a/tests/baselines/reference/propTypeValidatorInference.types b/tests/baselines/reference/propTypeValidatorInference.types
index eb292dac5c486..5276e7837fbdd 100644
--- a/tests/baselines/reference/propTypeValidatorInference.types
+++ b/tests/baselines/reference/propTypeValidatorInference.types
@@ -35,9 +35,7 @@ export interface Validator<T> {
 >nominalTypeHack : unique symbol
 }
 
-export interface Requireable<T> extends Validator<T | undefined | null> {
->null : null
-
+export interface Requireable<T> extends Validator<T> {
     isRequired: Validator<NonNullable<T>>;
 >isRequired : Validator<NonNullable<T>>
 }

From f902f8ac6cfcb0df41166109d83f26e0678092ac Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Tue, 3 Mar 2020 14:24:43 -0800
Subject: [PATCH 6/6] Add tests

---
 ...ersectionsAndOptionalProperties.errors.txt | 49 ++++++++++++++
 .../intersectionsAndOptionalProperties.js     | 33 ++++++++++
 ...intersectionsAndOptionalProperties.symbols | 64 ++++++++++++++++++
 .../intersectionsAndOptionalProperties.types  | 65 +++++++++++++++++++
 .../intersectionsAndOptionalProperties.ts     | 23 +++++++
 5 files changed, 234 insertions(+)
 create mode 100644 tests/baselines/reference/intersectionsAndOptionalProperties.errors.txt
 create mode 100644 tests/baselines/reference/intersectionsAndOptionalProperties.js
 create mode 100644 tests/baselines/reference/intersectionsAndOptionalProperties.symbols
 create mode 100644 tests/baselines/reference/intersectionsAndOptionalProperties.types
 create mode 100644 tests/cases/compiler/intersectionsAndOptionalProperties.ts

diff --git a/tests/baselines/reference/intersectionsAndOptionalProperties.errors.txt b/tests/baselines/reference/intersectionsAndOptionalProperties.errors.txt
new file mode 100644
index 0000000000000..bcd0a6f841d88
--- /dev/null
+++ b/tests/baselines/reference/intersectionsAndOptionalProperties.errors.txt
@@ -0,0 +1,49 @@
+tests/cases/compiler/intersectionsAndOptionalProperties.ts(5,1): error TS2322: Type '{ a: null; b: string; }' is not assignable to type '{ a?: number | undefined; b: string; }'.
+  Types of property 'a' are incompatible.
+    Type 'null' is not assignable to type 'number | undefined'.
+tests/cases/compiler/intersectionsAndOptionalProperties.ts(6,1): error TS2322: Type '{ a: null; } & { b: string; }' is not assignable to type '{ a?: number | undefined; b: string; }'.
+  Types of property 'a' are incompatible.
+    Type 'null' is not assignable to type 'number | undefined'.
+tests/cases/compiler/intersectionsAndOptionalProperties.ts(19,5): error TS2322: Type 'From' is not assignable to type 'To'.
+  Types of property 'field' are incompatible.
+    Type 'null' is not assignable to type 'number | undefined'.
+tests/cases/compiler/intersectionsAndOptionalProperties.ts(20,5): error TS2322: Type 'null' is not assignable to type 'number | undefined'.
+
+
+==== tests/cases/compiler/intersectionsAndOptionalProperties.ts (4 errors) ====
+    declare let x: { a?: number, b: string };
+    declare let y: { a: null, b: string };
+    declare let z: { a: null } & { b: string };
+    
+    x = y;  // Error
+    ~
+!!! error TS2322: Type '{ a: null; b: string; }' is not assignable to type '{ a?: number | undefined; b: string; }'.
+!!! error TS2322:   Types of property 'a' are incompatible.
+!!! error TS2322:     Type 'null' is not assignable to type 'number | undefined'.
+    x = z;  // Error
+    ~
+!!! error TS2322: Type '{ a: null; } & { b: string; }' is not assignable to type '{ a?: number | undefined; b: string; }'.
+!!! error TS2322:   Types of property 'a' are incompatible.
+!!! error TS2322:     Type 'null' is not assignable to type 'number | undefined'.
+    
+    // Repro from #36604
+    
+    interface To {
+        field?: number;
+        anotherField: string;
+    }
+    
+    type From =  { field: null } & Omit<To, 'field'>;
+    
+    function foo(v: From) {
+        let x: To;
+        x = v;  // Error
+        ~
+!!! error TS2322: Type 'From' is not assignable to type 'To'.
+!!! error TS2322:   Types of property 'field' are incompatible.
+!!! error TS2322:     Type 'null' is not assignable to type 'number | undefined'.
+        x.field = v.field; // Error
+        ~~~~~~~
+!!! error TS2322: Type 'null' is not assignable to type 'number | undefined'.
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/intersectionsAndOptionalProperties.js b/tests/baselines/reference/intersectionsAndOptionalProperties.js
new file mode 100644
index 0000000000000..b2f13a9f67955
--- /dev/null
+++ b/tests/baselines/reference/intersectionsAndOptionalProperties.js
@@ -0,0 +1,33 @@
+//// [intersectionsAndOptionalProperties.ts]
+declare let x: { a?: number, b: string };
+declare let y: { a: null, b: string };
+declare let z: { a: null } & { b: string };
+
+x = y;  // Error
+x = z;  // Error
+
+// Repro from #36604
+
+interface To {
+    field?: number;
+    anotherField: string;
+}
+
+type From =  { field: null } & Omit<To, 'field'>;
+
+function foo(v: From) {
+    let x: To;
+    x = v;  // Error
+    x.field = v.field; // Error
+}
+
+
+//// [intersectionsAndOptionalProperties.js]
+"use strict";
+x = y; // Error
+x = z; // Error
+function foo(v) {
+    var x;
+    x = v; // Error
+    x.field = v.field; // Error
+}
diff --git a/tests/baselines/reference/intersectionsAndOptionalProperties.symbols b/tests/baselines/reference/intersectionsAndOptionalProperties.symbols
new file mode 100644
index 0000000000000..c5504794e6ea5
--- /dev/null
+++ b/tests/baselines/reference/intersectionsAndOptionalProperties.symbols
@@ -0,0 +1,64 @@
+=== tests/cases/compiler/intersectionsAndOptionalProperties.ts ===
+declare let x: { a?: number, b: string };
+>x : Symbol(x, Decl(intersectionsAndOptionalProperties.ts, 0, 11))
+>a : Symbol(a, Decl(intersectionsAndOptionalProperties.ts, 0, 16))
+>b : Symbol(b, Decl(intersectionsAndOptionalProperties.ts, 0, 28))
+
+declare let y: { a: null, b: string };
+>y : Symbol(y, Decl(intersectionsAndOptionalProperties.ts, 1, 11))
+>a : Symbol(a, Decl(intersectionsAndOptionalProperties.ts, 1, 16))
+>b : Symbol(b, Decl(intersectionsAndOptionalProperties.ts, 1, 25))
+
+declare let z: { a: null } & { b: string };
+>z : Symbol(z, Decl(intersectionsAndOptionalProperties.ts, 2, 11))
+>a : Symbol(a, Decl(intersectionsAndOptionalProperties.ts, 2, 16))
+>b : Symbol(b, Decl(intersectionsAndOptionalProperties.ts, 2, 30))
+
+x = y;  // Error
+>x : Symbol(x, Decl(intersectionsAndOptionalProperties.ts, 0, 11))
+>y : Symbol(y, Decl(intersectionsAndOptionalProperties.ts, 1, 11))
+
+x = z;  // Error
+>x : Symbol(x, Decl(intersectionsAndOptionalProperties.ts, 0, 11))
+>z : Symbol(z, Decl(intersectionsAndOptionalProperties.ts, 2, 11))
+
+// Repro from #36604
+
+interface To {
+>To : Symbol(To, Decl(intersectionsAndOptionalProperties.ts, 5, 6))
+
+    field?: number;
+>field : Symbol(To.field, Decl(intersectionsAndOptionalProperties.ts, 9, 14))
+
+    anotherField: string;
+>anotherField : Symbol(To.anotherField, Decl(intersectionsAndOptionalProperties.ts, 10, 19))
+}
+
+type From =  { field: null } & Omit<To, 'field'>;
+>From : Symbol(From, Decl(intersectionsAndOptionalProperties.ts, 12, 1))
+>field : Symbol(field, Decl(intersectionsAndOptionalProperties.ts, 14, 14))
+>Omit : Symbol(Omit, Decl(lib.es5.d.ts, --, --))
+>To : Symbol(To, Decl(intersectionsAndOptionalProperties.ts, 5, 6))
+
+function foo(v: From) {
+>foo : Symbol(foo, Decl(intersectionsAndOptionalProperties.ts, 14, 49))
+>v : Symbol(v, Decl(intersectionsAndOptionalProperties.ts, 16, 13))
+>From : Symbol(From, Decl(intersectionsAndOptionalProperties.ts, 12, 1))
+
+    let x: To;
+>x : Symbol(x, Decl(intersectionsAndOptionalProperties.ts, 17, 7))
+>To : Symbol(To, Decl(intersectionsAndOptionalProperties.ts, 5, 6))
+
+    x = v;  // Error
+>x : Symbol(x, Decl(intersectionsAndOptionalProperties.ts, 17, 7))
+>v : Symbol(v, Decl(intersectionsAndOptionalProperties.ts, 16, 13))
+
+    x.field = v.field; // Error
+>x.field : Symbol(To.field, Decl(intersectionsAndOptionalProperties.ts, 9, 14))
+>x : Symbol(x, Decl(intersectionsAndOptionalProperties.ts, 17, 7))
+>field : Symbol(To.field, Decl(intersectionsAndOptionalProperties.ts, 9, 14))
+>v.field : Symbol(field, Decl(intersectionsAndOptionalProperties.ts, 14, 14))
+>v : Symbol(v, Decl(intersectionsAndOptionalProperties.ts, 16, 13))
+>field : Symbol(field, Decl(intersectionsAndOptionalProperties.ts, 14, 14))
+}
+
diff --git a/tests/baselines/reference/intersectionsAndOptionalProperties.types b/tests/baselines/reference/intersectionsAndOptionalProperties.types
new file mode 100644
index 0000000000000..7f5af60c18e6f
--- /dev/null
+++ b/tests/baselines/reference/intersectionsAndOptionalProperties.types
@@ -0,0 +1,65 @@
+=== tests/cases/compiler/intersectionsAndOptionalProperties.ts ===
+declare let x: { a?: number, b: string };
+>x : { a?: number | undefined; b: string; }
+>a : number | undefined
+>b : string
+
+declare let y: { a: null, b: string };
+>y : { a: null; b: string; }
+>a : null
+>null : null
+>b : string
+
+declare let z: { a: null } & { b: string };
+>z : { a: null; } & { b: string; }
+>a : null
+>null : null
+>b : string
+
+x = y;  // Error
+>x = y : { a: null; b: string; }
+>x : { a?: number | undefined; b: string; }
+>y : { a: null; b: string; }
+
+x = z;  // Error
+>x = z : { a: null; } & { b: string; }
+>x : { a?: number | undefined; b: string; }
+>z : { a: null; } & { b: string; }
+
+// Repro from #36604
+
+interface To {
+    field?: number;
+>field : number | undefined
+
+    anotherField: string;
+>anotherField : string
+}
+
+type From =  { field: null } & Omit<To, 'field'>;
+>From : From
+>field : null
+>null : null
+
+function foo(v: From) {
+>foo : (v: From) => void
+>v : From
+
+    let x: To;
+>x : To
+
+    x = v;  // Error
+>x = v : From
+>x : To
+>v : From
+
+    x.field = v.field; // Error
+>x.field = v.field : null
+>x.field : number | undefined
+>x : To
+>field : number | undefined
+>v.field : null
+>v : From
+>field : null
+}
+
diff --git a/tests/cases/compiler/intersectionsAndOptionalProperties.ts b/tests/cases/compiler/intersectionsAndOptionalProperties.ts
new file mode 100644
index 0000000000000..a5bc4a1580af4
--- /dev/null
+++ b/tests/cases/compiler/intersectionsAndOptionalProperties.ts
@@ -0,0 +1,23 @@
+// @strict: true
+
+declare let x: { a?: number, b: string };
+declare let y: { a: null, b: string };
+declare let z: { a: null } & { b: string };
+
+x = y;  // Error
+x = z;  // Error
+
+// Repro from #36604
+
+interface To {
+    field?: number;
+    anotherField: string;
+}
+
+type From =  { field: null } & Omit<To, 'field'>;
+
+function foo(v: From) {
+    let x: To;
+    x = v;  // Error
+    x.field = v.field; // Error
+}

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