diff --git a/types/lodash/index.d.ts b/types/lodash/index.d.ts
index fafa7f6b5c..5be5358b4b 100644
--- a/types/lodash/index.d.ts
+++ b/types/lodash/index.d.ts
@@ -1234,7 +1234,7 @@ declare namespace _ {
          */
         findIndex<T>(
             array: List<T> | null | undefined,
-            predicate?: ListIterateeBoolean<T>,
+            predicate?: ListIterateeCustom<T, boolean>,
             fromIndex?: number
         ): number;
     }
@@ -1245,7 +1245,7 @@ declare namespace _ {
          */
         findIndex<T>(
             this: LoDashImplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>,
+            predicate?: ListIterateeCustom<T, boolean>,
             fromIndex?: number
         ): number;
     }
@@ -1256,7 +1256,7 @@ declare namespace _ {
          */
         findIndex<T>(
             this: LoDashExplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>,
+            predicate?: ListIterateeCustom<T, boolean>,
             fromIndex?: number
         ): LoDashExplicitWrapper<number>;
     }
@@ -1282,7 +1282,7 @@ declare namespace _ {
          */
         findLastIndex<T>(
             array: List<T> | null | undefined,
-            predicate?: ListIterateeBoolean<T>,
+            predicate?: ListIterateeCustom<T, boolean>,
             fromIndex?: number
         ): number;
     }
@@ -1293,7 +1293,7 @@ declare namespace _ {
          */
         findLastIndex<T>(
             this: LoDashImplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>,
+            predicate?: ListIterateeCustom<T, boolean>,
             fromIndex?: number
         ): number;
     }
@@ -1304,7 +1304,7 @@ declare namespace _ {
          */
         findLastIndex<T>(
             this: LoDashExplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>,
+            predicate?: ListIterateeCustom<T, boolean>,
             fromIndex?: number
         ): LoDashExplicitWrapper<number>;
     }
@@ -4315,6 +4315,14 @@ declare namespace _ {
          * @param thisArg The this binding of iteratee.
          * @return Returns the composed aggregate object.
          */
+        countBy<T>(
+            collection: string | null | undefined,
+            iteratee?: StringIterator<T>
+        ): Dictionary<number>;
+
+        /**
+         * @see _.countBy
+         */
         countBy<T>(
             collection: List<T> | null | undefined,
             iteratee?: ListIteratee<T>
@@ -4338,6 +4346,14 @@ declare namespace _ {
     }
 
     interface LoDashImplicitWrapper<TValue> {
+        /**
+         * @see _.countBy
+         */
+        countBy<T>(
+            this: LoDashImplicitWrapper<string | null | undefined>,
+            iteratee?: StringIterator<T>
+        ): LoDashImplicitWrapper<Dictionary<number>>;
+
         /**
          * @see _.countBy
          */
@@ -4364,6 +4380,14 @@ declare namespace _ {
     }
 
     interface LoDashExplicitWrapper<TValue> {
+        /**
+         * @see _.countBy
+         */
+        countBy<T>(
+            this: LoDashExplicitWrapper<string | null | undefined>,
+            iteratee?: StringIterator<T>
+        ): LoDashExplicitWrapper<Dictionary<number>>;
+
         /**
          * @see _.countBy
          */
@@ -4479,7 +4503,7 @@ declare namespace _ {
          */
         every<T>(
             collection: List<T> | null | undefined,
-            predicate?: ListIterateeBoolean<T>
+            predicate?: ListIterateeCustom<T, boolean>
         ): boolean;
 
         /**
@@ -4487,7 +4511,7 @@ declare namespace _ {
          */
         every<T>(
             collection: NumericDictionary<T> | null | undefined,
-            predicate?: NumericDictionaryIterateeBoolean<T>
+            predicate?: NumericDictionaryIterateeCustom<T, boolean>
         ): boolean;
 
         /**
@@ -4495,7 +4519,7 @@ declare namespace _ {
          */
         every<T extends object>(
             collection: T | null | undefined,
-            predicate?: ObjectIterateeBoolean<T>
+            predicate?: ObjectIterateeCustom<T, boolean>
         ): boolean;
     }
 
@@ -4505,7 +4529,7 @@ declare namespace _ {
          */
         every<T>(
             this: LoDashImplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>
+            predicate?: ListIterateeCustom<T, boolean>
         ): boolean;
 
         /**
@@ -4513,7 +4537,7 @@ declare namespace _ {
          */
         every<T extends object>(
             this: LoDashImplicitWrapper<T | null | undefined>,
-            predicate?: ObjectIterateeBoolean<T>
+            predicate?: ObjectIterateeCustom<T, boolean>
         ): boolean;
 
         /**
@@ -4521,7 +4545,7 @@ declare namespace _ {
          */
         every<T>(
             this: LoDashImplicitWrapper<NumericDictionary<T> | null | undefined>,
-            predicate?: NumericDictionaryIterateeBoolean<T>
+            predicate?: NumericDictionaryIterateeCustom<T, boolean>
         ): boolean;
     }
 
@@ -4531,7 +4555,7 @@ declare namespace _ {
          */
         every<T>(
             this: LoDashExplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>
+            predicate?: ListIterateeCustom<T, boolean>
         ): LoDashExplicitWrapper<boolean>;
 
         /**
@@ -4539,7 +4563,7 @@ declare namespace _ {
          */
         every<T extends object>(
             this: LoDashExplicitWrapper<T | null | undefined>,
-            predicate?: ObjectIterateeBoolean<T>
+            predicate?: ObjectIterateeCustom<T, boolean>
         ): LoDashExplicitWrapper<boolean>;
 
         /**
@@ -4547,7 +4571,7 @@ declare namespace _ {
          */
         every<T>(
             this: LoDashExplicitWrapper<NumericDictionary<T> | null | undefined>,
-            predicate?: NumericDictionaryIterateeBoolean<T>
+            predicate?: NumericDictionaryIterateeCustom<T, boolean>
         ): LoDashExplicitWrapper<boolean>;
     }
 
@@ -4589,7 +4613,7 @@ declare namespace _ {
          */
         filter<T>(
             collection: List<T> | null | undefined,
-            predicate?: ListIterateeBoolean<T>
+            predicate?: ListIterateeCustom<T, boolean>
         ): T[];
 
         /**
@@ -4605,7 +4629,7 @@ declare namespace _ {
          */
         filter<T extends object>(
             collection: T | null | undefined,
-            predicate?: ObjectIterateeBoolean<T>
+            predicate?: ObjectIterateeCustom<T, boolean>
         ): Array<T[keyof T]>;
     }
 
@@ -4631,7 +4655,7 @@ declare namespace _ {
          */
         filter<T>(
             this: LoDashImplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>
+            predicate?: ListIterateeCustom<T, boolean>
         ): LoDashImplicitWrapper<T[]>;
 
         /**
@@ -4647,7 +4671,7 @@ declare namespace _ {
          */
         filter<T extends object>(
             this: LoDashImplicitWrapper<T | null | undefined>,
-            predicate?: ObjectIterateeBoolean<T>
+            predicate?: ObjectIterateeCustom<T, boolean>
         ): LoDashImplicitWrapper<Array<T[keyof T]>>;
     }
 
@@ -4673,7 +4697,7 @@ declare namespace _ {
          */
         filter<T>(
             this: LoDashExplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>
+            predicate?: ListIterateeCustom<T, boolean>
         ): LoDashExplicitWrapper<T[]>;
 
         /**
@@ -4689,7 +4713,7 @@ declare namespace _ {
          */
         filter<T extends object>(
             this: LoDashExplicitWrapper<T | null | undefined>,
-            predicate?: ObjectIterateeBoolean<T>
+            predicate?: ObjectIterateeCustom<T, boolean>
         ): LoDashExplicitWrapper<Array<T[keyof T]>>;
     }
 
@@ -4724,7 +4748,7 @@ declare namespace _ {
          */
         find<T>(
             collection: List<T> | null | undefined,
-            predicate?: ListIterateeBoolean<T>,
+            predicate?: ListIterateeCustom<T, boolean>,
             fromIndex?: number
         ): T|undefined;
 
@@ -4742,7 +4766,7 @@ declare namespace _ {
          */
         find<T extends object>(
             collection: T | null | undefined,
-            predicate?: ObjectIterateeBoolean<T>,
+            predicate?: ObjectIterateeCustom<T, boolean>,
             fromIndex?: number
         ): T[keyof T]|undefined;
     }
@@ -4762,7 +4786,7 @@ declare namespace _ {
          */
         find<T>(
             this: LoDashImplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>,
+            predicate?: ListIterateeCustom<T, boolean>,
             fromIndex?: number
         ): T|undefined;
 
@@ -4780,7 +4804,7 @@ declare namespace _ {
          */
         find<T extends object>(
             this: LoDashImplicitWrapper<T | null | undefined>,
-            predicate?: ObjectIterateeBoolean<T>,
+            predicate?: ObjectIterateeCustom<T, boolean>,
             fromIndex?: number
         ): T[keyof T]|undefined;
     }
@@ -4800,7 +4824,7 @@ declare namespace _ {
          */
         find<T>(
             this: LoDashExplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>,
+            predicate?: ListIterateeCustom<T, boolean>,
             fromIndex?: number
         ): LoDashExplicitWrapper<T|undefined>;
 
@@ -4818,7 +4842,7 @@ declare namespace _ {
          */
         find<T extends object>(
             this: LoDashExplicitWrapper<T | null | undefined>,
-            predicate?: ObjectIterateeBoolean<T>,
+            predicate?: ObjectIterateeCustom<T, boolean>,
             fromIndex?: number
         ): LoDashExplicitWrapper<T[keyof T]|undefined>;
     }
@@ -4844,7 +4868,7 @@ declare namespace _ {
          */
         findLast<T>(
             collection: List<T> | null | undefined,
-            predicate?: ListIterateeBoolean<T>,
+            predicate?: ListIterateeCustom<T, boolean>,
             fromIndex?: number
         ): T|undefined;
 
@@ -4862,7 +4886,7 @@ declare namespace _ {
          */
         findLast<T extends object>(
             collection: T | null | undefined,
-            predicate?: ObjectIterateeBoolean<T>,
+            predicate?: ObjectIterateeCustom<T, boolean>,
             fromIndex?: number
         ): T[keyof T]|undefined;
     }
@@ -4882,7 +4906,7 @@ declare namespace _ {
          */
         findLast<T>(
             this: LoDashImplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>,
+            predicate?: ListIterateeCustom<T, boolean>,
             fromIndex?: number
         ): T | undefined;
 
@@ -4900,7 +4924,7 @@ declare namespace _ {
          */
         findLast<T extends object>(
             this: LoDashImplicitWrapper<T | null | undefined>,
-            predicate?: ObjectIterateeBoolean<T>,
+            predicate?: ObjectIterateeCustom<T, boolean>,
             fromIndex?: number
         ): T[keyof T]|undefined;
     }
@@ -4920,7 +4944,7 @@ declare namespace _ {
          */
         findLast<T>(
             this: LoDashExplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>,
+            predicate?: ListIterateeCustom<T, boolean>,
             fromIndex?: number
         ): LoDashExplicitWrapper<T | undefined>;
 
@@ -4938,7 +4962,7 @@ declare namespace _ {
          */
         findLast<T extends object>(
             this: LoDashExplicitWrapper<T | null | undefined>,
-            predicate?: ObjectIterateeBoolean<T>,
+            predicate?: ObjectIterateeCustom<T, boolean>,
             fromIndex?: number
         ): LoDashExplicitWrapper<T[keyof T]|undefined>;
     }
@@ -5849,9 +5873,17 @@ declare namespace _ {
          * @param thisArg The this binding of iteratee.
          * @return Returns the composed aggregate object.
          */
+        keyBy(
+            collection: string | null | undefined,
+            iteratee?: StringIterator<PropertyName>
+        ): Dictionary<string>;
+
+        /**
+         * @see _.keyBy
+         */
         keyBy<T>(
             collection: List<T> | null | undefined,
-            iteratee?: ListIteratee<T>
+            iteratee?: ListIterateeCustom<T, PropertyName>
         ): Dictionary<T>;
 
         /**
@@ -5859,7 +5891,7 @@ declare namespace _ {
          */
         keyBy<T extends object>(
             collection: T | null | undefined,
-            iteratee?: ObjectIteratee<T>
+            iteratee?: ObjectIterateeCustom<T, PropertyName>
         ): Dictionary<T[keyof T]>;
 
         /**
@@ -5867,17 +5899,25 @@ declare namespace _ {
          */
         keyBy<T>(
             collection: NumericDictionary<T> | null | undefined,
-            iteratee?: NumericDictionaryIteratee<T>
+            iteratee?: NumericDictionaryIterateeCustom<T, PropertyName>
         ): Dictionary<T>;
     }
 
     interface LoDashImplicitWrapper<TValue> {
+        /**
+         * @see _.keyBy
+         */
+        keyBy(
+            this: LoDashImplicitWrapper<string | null | undefined>,
+            iteratee?: StringIterator<PropertyName>
+        ): LoDashImplicitWrapper<Dictionary<string>>;
+
         /**
          * @see _.keyBy
          */
         keyBy<T>(
             this: LoDashImplicitWrapper<List<T> | null | undefined>,
-            iteratee?: ListIteratee<T>
+            iteratee?: ListIterateeCustom<T, PropertyName>
         ): LoDashImplicitWrapper<Dictionary<T>>;
 
         /**
@@ -5885,7 +5925,7 @@ declare namespace _ {
          */
         keyBy<T extends object>(
             this: LoDashImplicitWrapper<T | null | undefined>,
-            iteratee?: ObjectIteratee<T>
+            iteratee?: ObjectIterateeCustom<T, PropertyName>
         ): LoDashImplicitWrapper<Dictionary<T[keyof T]>>;
 
         /**
@@ -5893,17 +5933,25 @@ declare namespace _ {
          */
         keyBy<T>(
             this: LoDashImplicitWrapper<NumericDictionary<T> | null | undefined>,
-            iteratee?: NumericDictionaryIteratee<T>
+            iteratee?: NumericDictionaryIterateeCustom<T, PropertyName>
         ): LoDashImplicitWrapper<Dictionary<T>>;
     }
 
     interface LoDashExplicitWrapper<TValue> {
+        /**
+         * @see _.keyBy
+         */
+        keyBy(
+            this: LoDashExplicitWrapper<string | null | undefined>,
+            iteratee?: StringIterator<PropertyName>
+        ): LoDashExplicitWrapper<Dictionary<string>>;
+
         /**
          * @see _.keyBy
          */
         keyBy<T>(
             this: LoDashExplicitWrapper<List<T> | null | undefined>,
-            iteratee?: ListIteratee<T>
+            iteratee?: ListIterateeCustom<T, PropertyName>
         ): LoDashExplicitWrapper<Dictionary<T>>;
 
         /**
@@ -5911,7 +5959,7 @@ declare namespace _ {
          */
         keyBy<T extends object>(
             this: LoDashExplicitWrapper<T | null | undefined>,
-            iteratee?: ObjectIteratee<T>
+            iteratee?: ObjectIterateeCustom<T, PropertyName>
         ): LoDashExplicitWrapper<Dictionary<T[keyof T]>>;
 
         /**
@@ -5919,7 +5967,7 @@ declare namespace _ {
          */
         keyBy<T>(
             this: LoDashExplicitWrapper<NumericDictionary<T> | null | undefined>,
-            iteratee?: NumericDictionaryIteratee<T>
+            iteratee?: NumericDictionaryIterateeCustom<T, PropertyName>
         ): LoDashExplicitWrapper<Dictionary<T>>;
     }
 
@@ -6718,7 +6766,7 @@ declare namespace _ {
          */
         reject<T>(
             collection: List<T> | null | undefined,
-            predicate?: ListIterateeBoolean<T>
+            predicate?: ListIterateeCustom<T, boolean>
         ): T[];
 
         /**
@@ -6726,7 +6774,7 @@ declare namespace _ {
          */
         reject<T extends object>(
             collection: T | null | undefined,
-            predicate?: ObjectIterateeBoolean<T>
+            predicate?: ObjectIterateeCustom<T, boolean>
         ): Array<T[keyof T]>;
     }
 
@@ -6744,7 +6792,7 @@ declare namespace _ {
          */
         reject<T>(
             this: LoDashImplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>
+            predicate?: ListIterateeCustom<T, boolean>
         ): LoDashImplicitWrapper<T[]>;
 
         /**
@@ -6752,7 +6800,7 @@ declare namespace _ {
          */
         reject<T extends object>(
             this: LoDashImplicitWrapper<T | null | undefined>,
-            predicate?: ObjectIterateeBoolean<T>
+            predicate?: ObjectIterateeCustom<T, boolean>
         ): LoDashImplicitWrapper<Array<T[keyof T]>>;
     }
 
@@ -6770,7 +6818,7 @@ declare namespace _ {
          */
         reject<T>(
             this: LoDashExplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>
+            predicate?: ListIterateeCustom<T, boolean>
         ): LoDashExplicitWrapper<T[]>;
 
         /**
@@ -6778,7 +6826,7 @@ declare namespace _ {
          */
         reject<T extends object>(
             this: LoDashExplicitWrapper<T | null | undefined>,
-            predicate?: ObjectIterateeBoolean<T>
+            predicate?: ObjectIterateeCustom<T, boolean>
         ): LoDashExplicitWrapper<Array<T[keyof T]>>;
     }
 
@@ -6992,7 +7040,7 @@ declare namespace _ {
          */
         some<T>(
             collection: List<T> | null | undefined,
-            predicate?: ListIterateeBoolean<T>
+            predicate?: ListIterateeCustom<T, boolean>
         ): boolean;
 
         /**
@@ -7000,7 +7048,7 @@ declare namespace _ {
          */
         some<T extends object>(
             collection: T | null | undefined,
-            predicate?: ObjectIterateeBoolean<T>
+            predicate?: ObjectIterateeCustom<T, boolean>
         ): boolean;
 
         /**
@@ -7008,7 +7056,7 @@ declare namespace _ {
          */
         some<T>(
             collection: NumericDictionary<T> | null | undefined,
-            predicate?: NumericDictionaryIterateeBoolean<T>
+            predicate?: NumericDictionaryIterateeCustom<T, boolean>
         ): boolean;
     }
 
@@ -7018,7 +7066,7 @@ declare namespace _ {
          */
         some<T>(
             this: LoDashImplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>
+            predicate?: ListIterateeCustom<T, boolean>
         ): boolean;
 
         /**
@@ -7026,7 +7074,7 @@ declare namespace _ {
          */
         some<T extends object>(
             this: LoDashImplicitWrapper<T | null | undefined>,
-            predicate?: ObjectIterateeBoolean<T>
+            predicate?: ObjectIterateeCustom<T, boolean>
         ): boolean;
 
         /**
@@ -7034,7 +7082,7 @@ declare namespace _ {
          */
         some<T>(
             this: LoDashImplicitWrapper<NumericDictionary<T> | null | undefined>,
-            predicate?: NumericDictionaryIterateeBoolean<T>
+            predicate?: NumericDictionaryIterateeCustom<T, boolean>
         ): boolean;
     }
 
@@ -7044,7 +7092,7 @@ declare namespace _ {
          */
         some<T>(
             this: LoDashExplicitWrapper<List<T> | null | undefined>,
-            predicate?: ListIterateeBoolean<T>
+            predicate?: ListIterateeCustom<T, boolean>
         ): LoDashExplicitWrapper<boolean>;
 
         /**
@@ -7052,7 +7100,7 @@ declare namespace _ {
          */
         some<T extends object>(
             this: LoDashExplicitWrapper<T | null | undefined>,
-            predicate?: ObjectIterateeBoolean<T>
+            predicate?: ObjectIterateeCustom<T, boolean>
         ): LoDashExplicitWrapper<boolean>;
 
         /**
@@ -7060,7 +7108,7 @@ declare namespace _ {
          */
         some<T>(
             this: LoDashExplicitWrapper<NumericDictionary<T> | null | undefined>,
-            predicate?: NumericDictionaryIterateeBoolean<T>
+            predicate?: NumericDictionaryIterateeCustom<T, boolean>
         ): LoDashExplicitWrapper<boolean>;
     }
 
@@ -9315,14 +9363,16 @@ declare namespace _ {
         /**
          * @see _.conformsTo
          */
-        conformsTo(source: ConformsPredicateObject<TValue>): boolean;
+        conformsTo<T>(this: LoDashImplicitWrapper<T>, source: ConformsPredicateObject<T>): boolean;
+        // Note: we can't use TValue here,  because it generates a typescript error when strictFunctionTypes is enabled.
     }
 
     interface LoDashExplicitWrapper<TValue> {
         /**
          * @see _.conformsTo
          */
-        conformsTo(source: ConformsPredicateObject<TValue>): LoDashExplicitWrapper<boolean>;
+        conformsTo<T>(this: LoDashImplicitWrapper<T>, source: ConformsPredicateObject<T>): LoDashExplicitWrapper<boolean>;
+        // Note: we can't use TValue here,  because it generates a typescript error when strictFunctionTypes is enabled.
     }
 
     type CondPair<T, R> = [(val: T) => boolean, (val: T) => R]
@@ -10723,7 +10773,7 @@ declare namespace _ {
         /**
          * @see _.toArray
          */
-        //toArray(): LoDashImplicitWrapper<Array<TValue[keyof TValue]>>;
+        toArray<T extends object>(this: LoDashImplicitWrapper<T>): LoDashImplicitWrapper<Array<T[keyof T]>>;
     }
 
     interface LoDashExplicitWrapper<TValue> {
@@ -10735,7 +10785,7 @@ declare namespace _ {
         /**
          * @see _.toArray
          */
-        //toArray(): LoDashExplicitWrapper<Array<TValue[keyof TValue]>>;
+        toArray<T extends object>(this: LoDashImplicitWrapper<T>): LoDashExplicitWrapper<Array<T[keyof T]>>;
     }
 
     //_.toPlainObject
@@ -17019,13 +17069,13 @@ declare namespace _ {
     type ArrayIterator<T, TResult> = (value: T, index: number, collection: T[]) => TResult;
     type ListIterator<T, TResult> = (value: T, index: number, collection: List<T>) => TResult;
     type ListIteratee<T> = ListIterator<T, NotVoid> | string | [string, any] | PartialDeep<T>;
-    type ListIterateeBoolean<T> = ListIterator<T, boolean> | string | [string, any] | PartialDeep<T>;
+    type ListIterateeCustom<T, TResult> = ListIterator<T, TResult> | string | [string, any] | PartialDeep<T>;
     type ListIteratorTypeGuard<T, S extends T> = (value: T, index: number, collection: List<T>) => value is S;
 
     // Note: key should be string, not keyof T, because the actual object may contain extra properties that were not specified in the type.
     type ObjectIterator<TObject, TResult> = (value: TObject[keyof TObject], key: string, collection: TObject) => TResult;
     type ObjectIteratee<TObject> = ObjectIterator<TObject, NotVoid> | string | [string, any] | PartialDeep<TObject[keyof TObject]>;
-    type ObjectIterateeBoolean<TObject> = ObjectIterator<TObject, boolean> | string | [string, any] | PartialDeep<TObject[keyof TObject]>;
+    type ObjectIterateeCustom<TObject, TResult> = ObjectIterator<TObject, TResult> | string | [string, any] | PartialDeep<TObject[keyof TObject]>;
     type ObjectIteratorTypeGuard<TObject, S extends TObject[keyof TObject]> = (value: TObject[keyof TObject], key: string, collection: TObject) => value is S;
 
     type DictionaryIterator<T, TResult> = ObjectIterator<Dictionary<T>, TResult>;
@@ -17034,7 +17084,7 @@ declare namespace _ {
 
     type NumericDictionaryIterator<T, TResult> = (value: T, key: number, collection: NumericDictionary<T>) => TResult;
     type NumericDictionaryIteratee<T> = NumericDictionaryIterator<T, NotVoid> | string | [string, any] | PartialDeep<T>;
-    type NumericDictionaryIterateeBoolean<T> = NumericDictionaryIterator<T, boolean> | string | [string, any] | PartialDeep<T>;
+    type NumericDictionaryIterateeCustom<T, TResult> = NumericDictionaryIterator<T, TResult> | string | [string, any] | PartialDeep<T>;
 
     type StringIterator<TResult> = (char: string, index: number, string: string) => TResult;
 
diff --git a/types/lodash/lodash-tests.ts b/types/lodash/lodash-tests.ts
index e40569204d..cca7c239c7 100644
--- a/types/lodash/lodash-tests.ts
+++ b/types/lodash/lodash-tests.ts
@@ -4,86 +4,19 @@ interface IFoodOrganic {
     name: string;
     organic: boolean;
 }
-
-interface IFoodType {
-    name: string;
-    type: string;
-}
-
-interface IFoodCombined {
-    name: string;
-    organic: boolean;
-    type: string;
-}
-
-interface IStoogesQuote {
-    name: string;
-    quotes: string[];
-}
-
 interface IStoogesAge {
     name: string;
     age: number;
 }
 
-interface IStoogesCombined {
-    name: string;
-    age: number;
-    quotes: string[];
-}
-
-interface IKey {
-    dir: string;
-    code: number;
-}
-
-interface IDictionary<T> {
-    [index: string]: T;
-}
-
 const foodsOrganic: IFoodOrganic[] = [
     { name: 'banana', organic: true },
     { name: 'beet', organic: false },
 ];
-const foodsType: IFoodType[] = [
-    { name: 'apple', type: 'fruit' },
-    { name: 'banana', type: 'fruit' },
-    { name: 'beet', type: 'vegetable' }
-];
-const foodsCombined: IFoodCombined[] = [
-    { 'name': 'apple', 'organic': false, 'type': 'fruit' },
-    { 'name': 'carrot', 'organic': true, 'type': 'vegetable' }
-];
-
-const stoogesQuotes: IStoogesQuote[] = [
-    { 'name': 'curly', 'quotes': ['Oh, a wise guy, eh?', 'Poifect!'] },
-    { 'name': 'moe', 'quotes': ['Spread out!', 'You knucklehead!'] }
-];
 const stoogesAges: IStoogesAge[] = [
     { 'name': 'moe', 'age': 40 },
     { 'name': 'larry', 'age': 50 }
 ];
-const stoogesAgesDict: IDictionary<IStoogesAge> = {
-    first: { 'name': 'moe', 'age': 40 },
-    second: { 'name': 'larry', 'age': 50 }
-};
-const stoogesCombined: IStoogesCombined[] = [
-    { 'name': 'curly', 'age': 30, 'quotes': ['Oh, a wise guy, eh?', 'Poifect!'] },
-    { 'name': 'moe', 'age': 40, 'quotes': ['Spread out!', 'You knucklehead!'] }
-];
-
-const keys: IKey[] = [
-    { 'dir': 'left', 'code': 97 },
-    { 'dir': 'right', 'code': 100 }
-];
-
-class Dog {
-    constructor(public name: string) { }
-
-    bark() {
-        // Woof
-    }
-}
 
 let result: any;
 
@@ -4591,9 +4524,9 @@ namespace TestFilter {
     let obj: any = {};
     let dictionary: _.Dictionary<TResult> | null | undefined = obj;
 
-    let stringIterator: (char: string, index: number, string: string) => any = (char: string, index: number, string: string) => 1;
-    let listIterator: (value: TResult, index: number, collection: _.List<TResult>) => any = (value: TResult, index: number, collection: _.List<TResult>) => 1;
-    let dictionaryIterator: (value: TResult, key: string, collection: _.Dictionary<TResult>) => any = (value: TResult, key: string, collection: _.Dictionary<TResult>) => 1;
+    let stringIterator = (char: string, index: number, string: string) => true;
+    let listIterator = (value: TResult, index: number, collection: _.List<TResult>) => true;
+    let dictionaryIterator = (value: TResult, key: string, collection: _.Dictionary<TResult>) => true;
 
     {
         let result: string[];
@@ -5207,7 +5140,7 @@ namespace TestFlatMapDepth {
 
     let listIterator: (value: number|number[], index: number, collection: _.List<number|number[]>) => _.ListOfRecursiveArraysOrValues<number> = (a, b, c) =>[ 1];
 
-    let dictionaryIterator: (value: number|number[], key: number, collection: _.Dictionary<number|number[]>) => _.ListOfRecursiveArraysOrValues<number> = (a, b, c) => [1];
+    let dictionaryIterator: (value: number|number[], key: string, collection: _.Dictionary<number|number[]>) => _.ListOfRecursiveArraysOrValues<number> = (a, b, c) => [1];
 
     let numericDictionaryIterator: (value: number|number[], key: number, collection: _.NumericDictionary<number|number[]>) => _.ListOfRecursiveArraysOrValues<number> = (a, b, c) => [1];
 
@@ -5776,8 +5709,8 @@ namespace TestGroupBy {
     {
         let result: _.Dictionary<string[]>;
 
-        result = _.groupBy<string>('');
-        result = _.groupBy<string>('', stringIterator);
+        result = _.groupBy('');
+        result = _.groupBy('', stringIterator);
     }
 
     {
@@ -5909,16 +5842,16 @@ namespace TestKeyBy {
     let dictionary: _.Dictionary<SampleObject> | null | undefined = obj;
     let numericDictionary: _.NumericDictionary<SampleObject> | null | undefined = obj;
 
-    let stringIterator: (value: string, index: number, collection: string) => any = (value: string, index: number, collection: string) => 1;
-    let listIterator: (value: SampleObject, index: number, collection: _.List<SampleObject>) => any = (value: SampleObject, index: number, collection: _.List<SampleObject>) => 1;
-    let dictionaryIterator: (value: SampleObject, key: string, collection: _.Dictionary<SampleObject>) => any = (value: SampleObject, key: string, collection: _.Dictionary<SampleObject>) => 1;
-    let numericDictionaryIterator: (value: SampleObject, key: number, collection: _.NumericDictionary<SampleObject>) => any = (value: SampleObject, key: number, collection: _.NumericDictionary<SampleObject>) => 1;
+    let stringIterator = (value: string, index: number, collection: string) => "a";
+    let listIterator = (value: SampleObject, index: number, collection: _.List<SampleObject>) => 1;
+    let dictionaryIterator = (value: SampleObject, key: string, collection: _.Dictionary<SampleObject>) => Symbol.name;
+    let numericDictionaryIterator = (value: SampleObject, key: number, collection: _.NumericDictionary<SampleObject>) => "a";
 
     {
         let result: _.Dictionary<string>;
 
-        result = _.keyBy<string>('abcd');
-        result = _.keyBy<string>('abcd', stringIterator);
+        result = _.keyBy('abcd');
+        result = _.keyBy('abcd', stringIterator);
     }
 
     {
@@ -6464,9 +6397,9 @@ namespace TestReject {
     let obj: any = {};
     let dictionary: _.Dictionary<TResult> | null | undefined = obj;
 
-    let stringIterator: (char: string, index: number, string: string) => any = (char: string, index: number, string: string) => 1;
-    let listIterator: (value: TResult, index: number, collection: _.List<TResult>) => any = (value: TResult, index: number, collection: _.List<TResult>) => 1;
-    let dictionaryIterator: (value: TResult, key: string, collection: _.Dictionary<TResult>) => any = (value: TResult, key: string, collection: _.Dictionary<TResult>) => 1;
+    let stringIterator = (char: string, index: number, string: string) => true;
+    let listIterator = (value: TResult, index: number, collection: _.List<TResult>) => true;
+    let dictionaryIterator = (value: TResult, key: string, collection: _.Dictionary<TResult>) => true;
 
     {
         let result: string[];
@@ -8667,9 +8600,7 @@ namespace TestIsEqual {
 
 // _.isEqualWith
 namespace TestIsEqualWith {
-    let customizer = (value: any, other: any, indexOrKey: number|string|undefined, parent: any, otherParent: any, stack: any) => {
-        return value ? undefined : true;
-    };
+    let customizer = (value: any, other: any, indexOrKey: number|string|symbol|undefined, parent: any, otherParent: any, stack: any) => true;
 
     {
         let result: boolean;
@@ -8873,7 +8804,7 @@ namespace TestIsMatch {
 
 // _.isMatchWith
 namespace TestIsMatchWith {
-    let testIsMatchCustiomizerFn = (value: any, other: any, indexOrKey: number|string) => true;
+    let testIsMatchCustiomizerFn = (value: any, other: any, indexOrKey: number|string|symbol) => true;
 
     let result: boolean;