add check for function return unknow type

Author: Kingwl

src/compiler/checker.ts

@@ -20621,7 +20621,7 @@ namespace ts {
             }
 
             // Functions with with an explicitly specified 'void' or 'any' return type don't need any return expressions.
-            if (returnType && maybeTypeOfKind(returnType, TypeFlags.AnyOrUnknown | TypeFlags.Void)) {
+            if (returnType && maybeTypeOfKind(returnType, TypeFlags.Any | TypeFlags.Void)) {
                 return;
             }
 

tests/baselines/reference/explicitReturnUnknow.errors.txt

@@ -0,0 +1,12 @@
+tests/cases/compiler/explicitReturnUnknow.ts(1,15): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
+tests/cases/compiler/explicitReturnUnknow.ts(2,15): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
+
+
+==== tests/cases/compiler/explicitReturnUnknow.ts (2 errors) ====
+    function f(): unknown { ""; }
+                  ~~~~~~~
+!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
+    function g(): string | undefined { ""; }
+                  ~~~~~~~~~~~~~~~~~~
+!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
+    

tests/baselines/reference/explicitReturnUnknow.js

@@ -0,0 +1,12 @@
+//// [explicitReturnUnknow.ts]
+function f(): unknown { ""; }
+function g(): string | undefined { ""; }
+
+
+//// [explicitReturnUnknow.js]
+function f() {
+    "";
+}
+function g() {
+    "";
+}

tests/baselines/reference/explicitReturnUnknow.symbols

@@ -0,0 +1,7 @@
+=== tests/cases/compiler/explicitReturnUnknow.ts ===
+function f(): unknown { ""; }
+>f : Symbol(f, Decl(explicitReturnUnknow.ts, 0, 0))
+
+function g(): string | undefined { ""; }
+>g : Symbol(g, Decl(explicitReturnUnknow.ts, 0, 29))
+

tests/baselines/reference/explicitReturnUnknow.types

@@ -0,0 +1,9 @@
+=== tests/cases/compiler/explicitReturnUnknow.ts ===
+function f(): unknown { ""; }
+>f : () => unknown
+>"" : ""
+
+function g(): string | undefined { ""; }
+>g : () => string
+>"" : ""
+

tests/baselines/reference/unknownType1.errors.txt

@@ -18,11 +18,12 @@ tests/cases/conformance/types/unknown/unknownType1.ts(114,9): error TS2322: Type
   Type 'unknown' is not assignable to type '{}'.
 tests/cases/conformance/types/unknown/unknownType1.ts(120,9): error TS2322: Type 'T' is not assignable to type 'object'.
 tests/cases/conformance/types/unknown/unknownType1.ts(129,5): error TS2322: Type '123' is not assignable to type '{ [x: string]: unknown; }'.
+tests/cases/conformance/types/unknown/unknownType1.ts(149,17): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
 tests/cases/conformance/types/unknown/unknownType1.ts(155,14): error TS2700: Rest types may only be created from object types.
 tests/cases/conformance/types/unknown/unknownType1.ts(161,5): error TS2564: Property 'a' has no initializer and is not definitely assigned in the constructor.
 
 
-==== tests/cases/conformance/types/unknown/unknownType1.ts (21 errors) ====
+==== tests/cases/conformance/types/unknown/unknownType1.ts (22 errors) ====
     // In an intersection everything absorbs unknown
 
     type T00 = unknown & null;  // null
@@ -211,6 +212,8 @@ tests/cases/conformance/types/unknown/unknownType1.ts(161,5): error TS2564: Prop
     // Functions with unknown return type don't need return expressions
 
     function f27(): unknown {
+                    ~~~~~~~
+!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
     }
 
     // Rest type cannot be created from unknown

tests/cases/compiler/explicitReturnUnknow.ts

@@ -0,0 +1,2 @@
+function f(): unknown { ""; }
+function g(): string | undefined { ""; }