From ddf4d3a421d8a2de0aa740d0f96958d9eb8ade7c Mon Sep 17 00:00:00 2001
From: Andrew Branch <andrew@wheream.io>
Date: Mon, 22 Feb 2021 12:14:41 -0800
Subject: [PATCH 1/2] Never-reducing intersections are not untyped function
 call targets

---
 src/compiler/checker.ts                               |  2 +-
 .../reference/neverIntersectionNotCallable.errors.txt | 11 +++++++++++
 .../reference/neverIntersectionNotCallable.js         |  7 +++++++
 .../reference/neverIntersectionNotCallable.symbols    | 10 ++++++++++
 .../reference/neverIntersectionNotCallable.types      | 11 +++++++++++
 .../types/never/neverIntersectionNotCallable.ts       |  2 ++
 6 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/neverIntersectionNotCallable.errors.txt
 create mode 100644 tests/baselines/reference/neverIntersectionNotCallable.js
 create mode 100644 tests/baselines/reference/neverIntersectionNotCallable.symbols
 create mode 100644 tests/baselines/reference/neverIntersectionNotCallable.types
 create mode 100644 tests/cases/conformance/types/never/neverIntersectionNotCallable.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 7c7fab735856e..795189f4a109a 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -28359,7 +28359,7 @@ namespace ts {
         function isUntypedFunctionCall(funcType: Type, apparentFuncType: Type, numCallSignatures: number, numConstructSignatures: number): boolean {
             // We exclude union types because we may have a union of function types that happen to have no common signatures.
             return isTypeAny(funcType) || isTypeAny(apparentFuncType) && !!(funcType.flags & TypeFlags.TypeParameter) ||
-                !numCallSignatures && !numConstructSignatures && !(apparentFuncType.flags & (TypeFlags.Union | TypeFlags.Never)) && isTypeAssignableTo(funcType, globalFunctionType);
+                !numCallSignatures && !numConstructSignatures && !(getReducedType(apparentFuncType).flags & (TypeFlags.Union | TypeFlags.Never)) && isTypeAssignableTo(funcType, globalFunctionType);
         }
 
         function resolveNewExpression(node: NewExpression, candidatesOutArray: Signature[] | undefined, checkMode: CheckMode): Signature {
diff --git a/tests/baselines/reference/neverIntersectionNotCallable.errors.txt b/tests/baselines/reference/neverIntersectionNotCallable.errors.txt
new file mode 100644
index 0000000000000..5ae3d35a692aa
--- /dev/null
+++ b/tests/baselines/reference/neverIntersectionNotCallable.errors.txt
@@ -0,0 +1,11 @@
+tests/cases/conformance/types/never/neverIntersectionNotCallable.ts(2,1): error TS2349: This expression is not callable.
+  Type 'never' has no call signatures.
+
+
+==== tests/cases/conformance/types/never/neverIntersectionNotCallable.ts (1 errors) ====
+    declare const f: { (x: string): number, a: "" } & { a: number }
+    f()
+    ~
+!!! error TS2349: This expression is not callable.
+!!! error TS2349:   Type 'never' has no call signatures.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/neverIntersectionNotCallable.js b/tests/baselines/reference/neverIntersectionNotCallable.js
new file mode 100644
index 0000000000000..b06cd75ee4398
--- /dev/null
+++ b/tests/baselines/reference/neverIntersectionNotCallable.js
@@ -0,0 +1,7 @@
+//// [neverIntersectionNotCallable.ts]
+declare const f: { (x: string): number, a: "" } & { a: number }
+f()
+
+
+//// [neverIntersectionNotCallable.js]
+f();
diff --git a/tests/baselines/reference/neverIntersectionNotCallable.symbols b/tests/baselines/reference/neverIntersectionNotCallable.symbols
new file mode 100644
index 0000000000000..129b73cb84a99
--- /dev/null
+++ b/tests/baselines/reference/neverIntersectionNotCallable.symbols
@@ -0,0 +1,10 @@
+=== tests/cases/conformance/types/never/neverIntersectionNotCallable.ts ===
+declare const f: { (x: string): number, a: "" } & { a: number }
+>f : Symbol(f, Decl(neverIntersectionNotCallable.ts, 0, 13))
+>x : Symbol(x, Decl(neverIntersectionNotCallable.ts, 0, 20))
+>a : Symbol(a, Decl(neverIntersectionNotCallable.ts, 0, 39))
+>a : Symbol(a, Decl(neverIntersectionNotCallable.ts, 0, 51))
+
+f()
+>f : Symbol(f, Decl(neverIntersectionNotCallable.ts, 0, 13))
+
diff --git a/tests/baselines/reference/neverIntersectionNotCallable.types b/tests/baselines/reference/neverIntersectionNotCallable.types
new file mode 100644
index 0000000000000..1225532a5c406
--- /dev/null
+++ b/tests/baselines/reference/neverIntersectionNotCallable.types
@@ -0,0 +1,11 @@
+=== tests/cases/conformance/types/never/neverIntersectionNotCallable.ts ===
+declare const f: { (x: string): number, a: "" } & { a: number }
+>f : never
+>x : string
+>a : ""
+>a : number
+
+f()
+>f() : any
+>f : never
+
diff --git a/tests/cases/conformance/types/never/neverIntersectionNotCallable.ts b/tests/cases/conformance/types/never/neverIntersectionNotCallable.ts
new file mode 100644
index 0000000000000..1d38fdebde9b5
--- /dev/null
+++ b/tests/cases/conformance/types/never/neverIntersectionNotCallable.ts
@@ -0,0 +1,2 @@
+declare const f: { (x: string): number, a: "" } & { a: number }
+f()

From 5015a515471cd8b4f7f9186c7f8c15ae0de02b7d Mon Sep 17 00:00:00 2001
From: Andrew Branch <andrew@wheream.io>
Date: Mon, 22 Feb 2021 12:16:30 -0800
Subject: [PATCH 2/2] =?UTF-8?q?Don=E2=80=99t=20attempt=20to=20reduce=20uni?=
 =?UTF-8?q?on=20types?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 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 795189f4a109a..a64d6ebd1e786 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -28359,7 +28359,7 @@ namespace ts {
         function isUntypedFunctionCall(funcType: Type, apparentFuncType: Type, numCallSignatures: number, numConstructSignatures: number): boolean {
             // We exclude union types because we may have a union of function types that happen to have no common signatures.
             return isTypeAny(funcType) || isTypeAny(apparentFuncType) && !!(funcType.flags & TypeFlags.TypeParameter) ||
-                !numCallSignatures && !numConstructSignatures && !(getReducedType(apparentFuncType).flags & (TypeFlags.Union | TypeFlags.Never)) && isTypeAssignableTo(funcType, globalFunctionType);
+                !numCallSignatures && !numConstructSignatures && !(apparentFuncType.flags & TypeFlags.Union) && !(getReducedType(apparentFuncType).flags & TypeFlags.Never) && isTypeAssignableTo(funcType, globalFunctionType);
         }
 
         function resolveNewExpression(node: NewExpression, candidatesOutArray: Signature[] | undefined, checkMode: CheckMode): Signature {