Fix #19257: Ensure a generated signature has a return type

Author: mhegazy

src/services/codefixes/inferFromUsage.ts

@@ -636,7 +636,7 @@ namespace ts.codefix {
                 symbol.type = checker.getWidenedType(checker.getBaseTypeOfLiteralType(callContext.argumentTypes[i]));
                 parameters.push(symbol);
             }
-            const returnType = getTypeFromUsageContext(callContext.returnType, checker);
+            const returnType = getTypeFromUsageContext(callContext.returnType, checker) || checker.getVoidType();
             return checker.createSignature(/*declaration*/ undefined, /*typeParameters*/ undefined, /*thisParameter*/ undefined, parameters, returnType, /*typePredicate*/ undefined, callContext.argumentTypes.length, /*hasRestParameter*/ false, /*hasLiteralTypes*/ false);
         }
 

tests/cases/fourslash/codeFixInferFromUsageCall.ts

@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts' />
+
+// @noImplicitAny: true
+////function wat([|b |]) {
+////    b();
+////}
+
+verify.rangeAfterCodeFix("b: () => void");