Allow untyped calls on unions of untyped things

src/compiler/checker.ts

@@ -6930,7 +6930,7 @@ namespace ts {
         function resolveUnionTypeMembers(type: UnionType) {
             // The members and properties collections are empty for union types. To get all properties of a union
             // type use getPropertiesOfType (only the language service uses this).
-            const callSignatures = getUnionSignatures(map(type.types, t => getSignaturesOfType(t, SignatureKind.Call)));
+            const callSignatures = getUnionSignatures(map(type.types, t => t === globalFunctionType ? [unknownSignature] : getSignaturesOfType(t, SignatureKind.Call)));
             const constructSignatures = getUnionSignatures(map(type.types, t => getSignaturesOfType(t, SignatureKind.Construct)));
             const stringIndexInfo = getUnionIndexInfo(type.types, IndexKind.String);
             const numberIndexInfo = getUnionIndexInfo(type.types, IndexKind.Number);
@@ -20506,9 +20506,9 @@ namespace ts {
          * If FuncExpr is of type Any, or of an object type that has no call or construct signatures
          * but is a subtype of the Function interface, the call is an untyped function call.
          */
-        function isUntypedFunctionCall(funcType: Type, apparentFuncType: Type, numCallSignatures: number, numConstructSignatures: number) {
+        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 ||
+            return isTypeAny(funcType) || isTypeAny(apparentFuncType) && !!(funcType.flags & TypeFlags.TypeParameter) ||
                 !numCallSignatures && !numConstructSignatures && !(apparentFuncType.flags & (TypeFlags.Union | TypeFlags.Never)) && isTypeAssignableTo(funcType, globalFunctionType);
         }
 

tests/baselines/reference/unionOfFunctionAndSignatureIsCallable.js

@@ -0,0 +1,25 @@
+//// [unionOfFunctionAndSignatureIsCallable.ts]
+function f1(c1: Function, c2: () => object,  callable: typeof c1 | typeof c2) {
+    const a = c1();
+    const b = c2();
+    const c = callable();
+}
+
+function f2(fetcherParams: object | (() => object)) {
+    const data = typeof fetcherParams === 'function'
+        ? fetcherParams()
+        : fetcherParams
+}
+
+
+//// [unionOfFunctionAndSignatureIsCallable.js]
+function f1(c1, c2, callable) {
+    var a = c1();
+    var b = c2();
+    var c = callable();
+}
+function f2(fetcherParams) {
+    var data = typeof fetcherParams === 'function'
+        ? fetcherParams()
+        : fetcherParams;
+}

tests/baselines/reference/unionOfFunctionAndSignatureIsCallable.symbols

@@ -0,0 +1,38 @@
+=== tests/cases/compiler/unionOfFunctionAndSignatureIsCallable.ts ===
+function f1(c1: Function, c2: () => object,  callable: typeof c1 | typeof c2) {
+>f1 : Symbol(f1, Decl(unionOfFunctionAndSignatureIsCallable.ts, 0, 0))
+>c1 : Symbol(c1, Decl(unionOfFunctionAndSignatureIsCallable.ts, 0, 12))
+>Function : Symbol(Function, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>c2 : Symbol(c2, Decl(unionOfFunctionAndSignatureIsCallable.ts, 0, 25))
+>callable : Symbol(callable, Decl(unionOfFunctionAndSignatureIsCallable.ts, 0, 43))
+>c1 : Symbol(c1, Decl(unionOfFunctionAndSignatureIsCallable.ts, 0, 12))
+>c2 : Symbol(c2, Decl(unionOfFunctionAndSignatureIsCallable.ts, 0, 25))
+
+    const a = c1();
+>a : Symbol(a, Decl(unionOfFunctionAndSignatureIsCallable.ts, 1, 9))
+>c1 : Symbol(c1, Decl(unionOfFunctionAndSignatureIsCallable.ts, 0, 12))
+
+    const b = c2();
+>b : Symbol(b, Decl(unionOfFunctionAndSignatureIsCallable.ts, 2, 9))
+>c2 : Symbol(c2, Decl(unionOfFunctionAndSignatureIsCallable.ts, 0, 25))
+
+    const c = callable();
+>c : Symbol(c, Decl(unionOfFunctionAndSignatureIsCallable.ts, 3, 9))
+>callable : Symbol(callable, Decl(unionOfFunctionAndSignatureIsCallable.ts, 0, 43))
+}
+
+function f2(fetcherParams: object | (() => object)) {
+>f2 : Symbol(f2, Decl(unionOfFunctionAndSignatureIsCallable.ts, 4, 1))
+>fetcherParams : Symbol(fetcherParams, Decl(unionOfFunctionAndSignatureIsCallable.ts, 6, 12))
+
+    const data = typeof fetcherParams === 'function'
+>data : Symbol(data, Decl(unionOfFunctionAndSignatureIsCallable.ts, 7, 9))
+>fetcherParams : Symbol(fetcherParams, Decl(unionOfFunctionAndSignatureIsCallable.ts, 6, 12))
+
+        ? fetcherParams()
+>fetcherParams : Symbol(fetcherParams, Decl(unionOfFunctionAndSignatureIsCallable.ts, 6, 12))
+
+        : fetcherParams
+>fetcherParams : Symbol(fetcherParams, Decl(unionOfFunctionAndSignatureIsCallable.ts, 6, 12))
+}
+

tests/baselines/reference/unionOfFunctionAndSignatureIsCallable.types

@@ -0,0 +1,45 @@
+=== tests/cases/compiler/unionOfFunctionAndSignatureIsCallable.ts ===
+function f1(c1: Function, c2: () => object,  callable: typeof c1 | typeof c2) {
+>f1 : (c1: Function, c2: () => object, callable: Function | (() => object)) => void
+>c1 : Function
+>c2 : () => object
+>callable : Function | (() => object)
+>c1 : Function
+>c2 : () => object
+
+    const a = c1();
+>a : any
+>c1() : any
+>c1 : Function
+
+    const b = c2();
+>b : object
+>c2() : object
+>c2 : () => object
+
+    const c = callable();
+>c : any
+>callable() : any
+>callable : Function | (() => object)
+}
+
+function f2(fetcherParams: object | (() => object)) {
+>f2 : (fetcherParams: object | (() => object)) => void
+>fetcherParams : object | (() => object)
+
+    const data = typeof fetcherParams === 'function'
+>data : any
+>typeof fetcherParams === 'function'        ? fetcherParams()        : fetcherParams : any
+>typeof fetcherParams === 'function' : boolean
+>typeof fetcherParams : "string" | "number" | "bigint" | "boolean" | "symbol" | "undefined" | "object" | "function"
+>fetcherParams : object | (() => object)
+>'function' : "function"
+
+        ? fetcherParams()
+>fetcherParams() : any
+>fetcherParams : Function | (() => object)
+
+        : fetcherParams
+>fetcherParams : object
+}
+

tests/cases/compiler/unionOfFunctionAndSignatureIsCallable.ts

@@ -0,0 +1,11 @@
+function f1(c1: Function, c2: () => object,  callable: typeof c1 | typeof c2) {
+    const a = c1();
+    const b = c2();
+    const c = callable();
+}
+
+function f2(fetcherParams: object | (() => object)) {
+    const data = typeof fetcherParams === 'function'
+        ? fetcherParams()
+        : fetcherParams
+}