diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 4e4fc6919a0..f8bafa7a38f 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -3943,7 +3943,7 @@ namespace ts {
             let id = getTypeListId(elementTypes);
             let type = tupleTypes[id];
             if (!type) {
-                type = tupleTypes[id] = <TupleType>createObjectType(TypeFlags.Tuple);
+                type = tupleTypes[id] = <TupleType>createObjectType(TypeFlags.Tuple | getWideningFlagsOfTypes(elementTypes));
                 type.elementTypes = elementTypes;
             }
             return type;
@@ -5299,8 +5299,8 @@ namespace ts {
          * Check if a Type was written as a tuple type literal.
          * Prefer using isTupleLikeType() unless the use of `elementTypes` is required.
          */
-        function isTupleType(type: Type): boolean {
-            return (type.flags & TypeFlags.Tuple) && !!(<TupleType>type).elementTypes;
+        function isTupleType(type: Type): type is TupleType {
+            return !!(type.flags & TypeFlags.Tuple);
         }
 
         function getWidenedTypeOfObjectLiteral(type: Type): Type {
@@ -5341,26 +5341,45 @@ namespace ts {
                 if (isArrayType(type)) {
                     return createArrayType(getWidenedType((<TypeReference>type).typeArguments[0]));
                 }
+                if (isTupleType(type)) {
+                    return createTupleType(map(type.elementTypes, getWidenedType));
+                }
             }
             return type;
         }
 
+        /**
+         * Reports implicit any errors that occur as a result of widening 'null' and 'undefined'
+         * to 'any'. A call to reportWideningErrorsInType is normally accompanied by a call to
+         * getWidenedType. But in some cases getWidenedType is called without reporting errors
+         * (type argument inference is an example).
+         *
+         * The return value indicates whether an error was in fact reported. The particular circumstances
+         * are on a best effort basis. Currently, if the null or undefined that causes widening is inside
+         * an object literal property (arbitrarily deeply), this function reports an error. If no error is
+         * reported, reportImplicitAnyError is a suitable fallback to report a general error.
+         */
         function reportWideningErrorsInType(type: Type): boolean {
+            let errorReported = false;
             if (type.flags & TypeFlags.Union) {
-                let errorReported = false;
-                forEach((<UnionType>type).types, t => {
+                for (let t of (<UnionType>type).types) {
                     if (reportWideningErrorsInType(t)) {
                         errorReported = true;
                     }
-                });
-                return errorReported;
+                }
             }
             if (isArrayType(type)) {
                 return reportWideningErrorsInType((<TypeReference>type).typeArguments[0]);
             }
+            if (isTupleType(type)) {
+                for (let t of type.elementTypes) {
+                    if (reportWideningErrorsInType(t)) {
+                        errorReported = true;
+                    }
+                }
+            }
             if (type.flags & TypeFlags.ObjectLiteral) {
-                let errorReported = false;
-                forEach(getPropertiesOfObjectType(type), p => {
+                for (let p of getPropertiesOfObjectType(type)) {
                     let t = getTypeOfSymbol(p);
                     if (t.flags & TypeFlags.ContainsUndefinedOrNull) {
                         if (!reportWideningErrorsInType(t)) {
@@ -5368,10 +5387,9 @@ namespace ts {
                         }
                         errorReported = true;
                     }
-                });
-                return errorReported;
+                }
             }
-            return false;
+            return errorReported;
         }
 
         function reportImplicitAnyError(declaration: Declaration, type: Type) {
@@ -6964,7 +6982,6 @@ namespace ts {
             }
         }
 
-
         function checkJsxSelfClosingElement(node: JsxSelfClosingElement) {
             checkJsxOpeningLikeElement(node);
             return jsxElementType || anyType;
diff --git a/tests/baselines/reference/destructuringParameterDeclaration1ES5.errors.txt b/tests/baselines/reference/destructuringParameterDeclaration1ES5.errors.txt
index 269d2b5640d..8e51c2b6111 100644
--- a/tests/baselines/reference/destructuringParameterDeclaration1ES5.errors.txt
+++ b/tests/baselines/reference/destructuringParameterDeclaration1ES5.errors.txt
@@ -1,16 +1,8 @@
-tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration1ES5.ts(32,4): error TS2345: Argument of type '[string, number, number]' is not assignable to parameter of type '[undefined, null, undefined]'.
-  Types of property '0' are incompatible.
-    Type 'string' is not assignable to type 'undefined'.
-tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration1ES5.ts(33,4): error TS2345: Argument of type '[[string], number, [[boolean, boolean]]]' is not assignable to parameter of type '[[undefined], undefined, [[undefined, undefined]]]'.
-  Types of property '0' are incompatible.
-    Type '[string]' is not assignable to type '[undefined]'.
-      Types of property '0' are incompatible.
-        Type 'string' is not assignable to type 'undefined'.
 tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration1ES5.ts(62,10): error TS2393: Duplicate function implementation.
 tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration1ES5.ts(63,10): error TS2393: Duplicate function implementation.
 
 
-==== tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration1ES5.ts (4 errors) ====
+==== tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration1ES5.ts (2 errors) ====
     // A parameter declaration may specify either an identifier or a binding pattern.
     // The identifiers specified in parameter declarations and binding patterns
     // in a parameter list must be unique within that parameter list.
@@ -43,17 +35,7 @@ tests/cases/conformance/es6/destructuring/destructuringParameterDeclaration1ES5.
     b2("string", { x: 200, y: "string" });
     b2("string", { x: 200, y: true });
     b6(["string", 1, 2]);                    // Shouldn't be an error
-       ~~~~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '[string, number, number]' is not assignable to parameter of type '[undefined, null, undefined]'.
-!!! error TS2345:   Types of property '0' are incompatible.
-!!! error TS2345:     Type 'string' is not assignable to type 'undefined'.
     b7([["string"], 1, [[true, false]]]);    // Shouldn't be an error
-       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2345: Argument of type '[[string], number, [[boolean, boolean]]]' is not assignable to parameter of type '[[undefined], undefined, [[undefined, undefined]]]'.
-!!! error TS2345:   Types of property '0' are incompatible.
-!!! error TS2345:     Type '[string]' is not assignable to type '[undefined]'.
-!!! error TS2345:       Types of property '0' are incompatible.
-!!! error TS2345:         Type 'string' is not assignable to type 'undefined'.
     
     
     // If the declaration specifies a binding pattern, the parameter type is the implied type of that binding pattern (section 5.1.3)
diff --git a/tests/baselines/reference/wideningTuples1.js b/tests/baselines/reference/wideningTuples1.js
new file mode 100644
index 00000000000..ed39a735bfe
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples1.js
@@ -0,0 +1,9 @@
+//// [wideningTuples1.ts]
+declare function foo<T extends [any]>(x: T): T;
+
+var y = foo([undefined]);
+y = [""];
+
+//// [wideningTuples1.js]
+var y = foo([undefined]);
+y = [""];
diff --git a/tests/baselines/reference/wideningTuples1.symbols b/tests/baselines/reference/wideningTuples1.symbols
new file mode 100644
index 00000000000..819510b7319
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples1.symbols
@@ -0,0 +1,16 @@
+=== tests/cases/conformance/types/tuple/wideningTuples1.ts ===
+declare function foo<T extends [any]>(x: T): T;
+>foo : Symbol(foo, Decl(wideningTuples1.ts, 0, 0))
+>T : Symbol(T, Decl(wideningTuples1.ts, 0, 21))
+>x : Symbol(x, Decl(wideningTuples1.ts, 0, 38))
+>T : Symbol(T, Decl(wideningTuples1.ts, 0, 21))
+>T : Symbol(T, Decl(wideningTuples1.ts, 0, 21))
+
+var y = foo([undefined]);
+>y : Symbol(y, Decl(wideningTuples1.ts, 2, 3))
+>foo : Symbol(foo, Decl(wideningTuples1.ts, 0, 0))
+>undefined : Symbol(undefined)
+
+y = [""];
+>y : Symbol(y, Decl(wideningTuples1.ts, 2, 3))
+
diff --git a/tests/baselines/reference/wideningTuples1.types b/tests/baselines/reference/wideningTuples1.types
new file mode 100644
index 00000000000..1fdd4a6cb53
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples1.types
@@ -0,0 +1,21 @@
+=== tests/cases/conformance/types/tuple/wideningTuples1.ts ===
+declare function foo<T extends [any]>(x: T): T;
+>foo : <T extends [any]>(x: T) => T
+>T : T
+>x : T
+>T : T
+>T : T
+
+var y = foo([undefined]);
+>y : [any]
+>foo([undefined]) : [any]
+>foo : <T extends [any]>(x: T) => T
+>[undefined] : [undefined]
+>undefined : undefined
+
+y = [""];
+>y = [""] : [string]
+>y : [any]
+>[""] : [string]
+>"" : string
+
diff --git a/tests/baselines/reference/wideningTuples2.js b/tests/baselines/reference/wideningTuples2.js
new file mode 100644
index 00000000000..fa74e089961
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples2.js
@@ -0,0 +1,13 @@
+//// [wideningTuples2.ts]
+var foo: () => [any] = function bar() {
+    let intermediate = bar();
+    intermediate = [""];
+    return [undefined];
+};
+
+//// [wideningTuples2.js]
+var foo = function bar() {
+    var intermediate = bar();
+    intermediate = [""];
+    return [undefined];
+};
diff --git a/tests/baselines/reference/wideningTuples2.symbols b/tests/baselines/reference/wideningTuples2.symbols
new file mode 100644
index 00000000000..74186045e90
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples2.symbols
@@ -0,0 +1,16 @@
+=== tests/cases/conformance/types/tuple/wideningTuples2.ts ===
+var foo: () => [any] = function bar() {
+>foo : Symbol(foo, Decl(wideningTuples2.ts, 0, 3))
+>bar : Symbol(bar, Decl(wideningTuples2.ts, 0, 22))
+
+    let intermediate = bar();
+>intermediate : Symbol(intermediate, Decl(wideningTuples2.ts, 1, 7))
+>bar : Symbol(bar, Decl(wideningTuples2.ts, 0, 22))
+
+    intermediate = [""];
+>intermediate : Symbol(intermediate, Decl(wideningTuples2.ts, 1, 7))
+
+    return [undefined];
+>undefined : Symbol(undefined)
+
+};
diff --git a/tests/baselines/reference/wideningTuples2.types b/tests/baselines/reference/wideningTuples2.types
new file mode 100644
index 00000000000..c07166c53f0
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples2.types
@@ -0,0 +1,22 @@
+=== tests/cases/conformance/types/tuple/wideningTuples2.ts ===
+var foo: () => [any] = function bar() {
+>foo : () => [any]
+>function bar() {    let intermediate = bar();    intermediate = [""];    return [undefined];} : () => [any]
+>bar : () => [any]
+
+    let intermediate = bar();
+>intermediate : [any]
+>bar() : [any]
+>bar : () => [any]
+
+    intermediate = [""];
+>intermediate = [""] : [string]
+>intermediate : [any]
+>[""] : [string]
+>"" : string
+
+    return [undefined];
+>[undefined] : [undefined]
+>undefined : undefined
+
+};
diff --git a/tests/baselines/reference/wideningTuples3.errors.txt b/tests/baselines/reference/wideningTuples3.errors.txt
new file mode 100644
index 00000000000..43c7e349a0c
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples3.errors.txt
@@ -0,0 +1,9 @@
+tests/cases/conformance/types/tuple/wideningTuples3.ts(3,5): error TS7005: Variable 'b' implicitly has an '[any, any]' type.
+
+
+==== tests/cases/conformance/types/tuple/wideningTuples3.ts (1 errors) ====
+    var a: [any];
+    
+    var b = a = [undefined, null];
+        ~
+!!! error TS7005: Variable 'b' implicitly has an '[any, any]' type.
\ No newline at end of file
diff --git a/tests/baselines/reference/wideningTuples3.js b/tests/baselines/reference/wideningTuples3.js
new file mode 100644
index 00000000000..dfeaae745d4
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples3.js
@@ -0,0 +1,8 @@
+//// [wideningTuples3.ts]
+var a: [any];
+
+var b = a = [undefined, null];
+
+//// [wideningTuples3.js]
+var a;
+var b = a = [undefined, null];
diff --git a/tests/baselines/reference/wideningTuples4.js b/tests/baselines/reference/wideningTuples4.js
new file mode 100644
index 00000000000..b4d16a3058b
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples4.js
@@ -0,0 +1,10 @@
+//// [wideningTuples4.ts]
+var a: [any];
+
+var b = a = [undefined, null];
+b = ["", ""];
+
+//// [wideningTuples4.js]
+var a;
+var b = a = [undefined, null];
+b = ["", ""];
diff --git a/tests/baselines/reference/wideningTuples4.symbols b/tests/baselines/reference/wideningTuples4.symbols
new file mode 100644
index 00000000000..95e7cc3cff8
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples4.symbols
@@ -0,0 +1,12 @@
+=== tests/cases/conformance/types/tuple/wideningTuples4.ts ===
+var a: [any];
+>a : Symbol(a, Decl(wideningTuples4.ts, 0, 3))
+
+var b = a = [undefined, null];
+>b : Symbol(b, Decl(wideningTuples4.ts, 2, 3))
+>a : Symbol(a, Decl(wideningTuples4.ts, 0, 3))
+>undefined : Symbol(undefined)
+
+b = ["", ""];
+>b : Symbol(b, Decl(wideningTuples4.ts, 2, 3))
+
diff --git a/tests/baselines/reference/wideningTuples4.types b/tests/baselines/reference/wideningTuples4.types
new file mode 100644
index 00000000000..6d101dd1e01
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples4.types
@@ -0,0 +1,19 @@
+=== tests/cases/conformance/types/tuple/wideningTuples4.ts ===
+var a: [any];
+>a : [any]
+
+var b = a = [undefined, null];
+>b : [any, any]
+>a = [undefined, null] : [undefined, null]
+>a : [any]
+>[undefined, null] : [undefined, null]
+>undefined : undefined
+>null : null
+
+b = ["", ""];
+>b = ["", ""] : [string, string]
+>b : [any, any]
+>["", ""] : [string, string]
+>"" : string
+>"" : string
+
diff --git a/tests/baselines/reference/wideningTuples5.errors.txt b/tests/baselines/reference/wideningTuples5.errors.txt
new file mode 100644
index 00000000000..bfd72079f55
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples5.errors.txt
@@ -0,0 +1,10 @@
+tests/cases/conformance/types/tuple/wideningTuples5.ts(1,6): error TS7005: Variable 'a' implicitly has an 'any' type.
+tests/cases/conformance/types/tuple/wideningTuples5.ts(1,9): error TS7005: Variable 'b' implicitly has an 'any' type.
+
+
+==== tests/cases/conformance/types/tuple/wideningTuples5.ts (2 errors) ====
+    var [a, b] = [undefined, null];
+         ~
+!!! error TS7005: Variable 'a' implicitly has an 'any' type.
+            ~
+!!! error TS7005: Variable 'b' implicitly has an 'any' type.
\ No newline at end of file
diff --git a/tests/baselines/reference/wideningTuples5.js b/tests/baselines/reference/wideningTuples5.js
new file mode 100644
index 00000000000..5763fb3340f
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples5.js
@@ -0,0 +1,5 @@
+//// [wideningTuples5.ts]
+var [a, b] = [undefined, null];
+
+//// [wideningTuples5.js]
+var _a = [undefined, null], a = _a[0], b = _a[1];
diff --git a/tests/baselines/reference/wideningTuples6.js b/tests/baselines/reference/wideningTuples6.js
new file mode 100644
index 00000000000..b1d5e8ec0bd
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples6.js
@@ -0,0 +1,9 @@
+//// [wideningTuples6.ts]
+var [a, b] = [undefined, null];
+a = "";
+b = "";
+
+//// [wideningTuples6.js]
+var _a = [undefined, null], a = _a[0], b = _a[1];
+a = "";
+b = "";
diff --git a/tests/baselines/reference/wideningTuples6.symbols b/tests/baselines/reference/wideningTuples6.symbols
new file mode 100644
index 00000000000..88de6a7b9b7
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples6.symbols
@@ -0,0 +1,12 @@
+=== tests/cases/conformance/types/tuple/wideningTuples6.ts ===
+var [a, b] = [undefined, null];
+>a : Symbol(a, Decl(wideningTuples6.ts, 0, 5))
+>b : Symbol(b, Decl(wideningTuples6.ts, 0, 7))
+>undefined : Symbol(undefined)
+
+a = "";
+>a : Symbol(a, Decl(wideningTuples6.ts, 0, 5))
+
+b = "";
+>b : Symbol(b, Decl(wideningTuples6.ts, 0, 7))
+
diff --git a/tests/baselines/reference/wideningTuples6.types b/tests/baselines/reference/wideningTuples6.types
new file mode 100644
index 00000000000..d75c0b49e9e
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples6.types
@@ -0,0 +1,18 @@
+=== tests/cases/conformance/types/tuple/wideningTuples6.ts ===
+var [a, b] = [undefined, null];
+>a : any
+>b : any
+>[undefined, null] : [undefined, null]
+>undefined : undefined
+>null : null
+
+a = "";
+>a = "" : string
+>a : any
+>"" : string
+
+b = "";
+>b = "" : string
+>b : any
+>"" : string
+
diff --git a/tests/baselines/reference/wideningTuples7.errors.txt b/tests/baselines/reference/wideningTuples7.errors.txt
new file mode 100644
index 00000000000..25fd1f58e64
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples7.errors.txt
@@ -0,0 +1,10 @@
+tests/cases/conformance/types/tuple/wideningTuples7.ts(1,20): error TS7010: 'bar', which lacks return-type annotation, implicitly has an '[any]' return type.
+
+
+==== tests/cases/conformance/types/tuple/wideningTuples7.ts (1 errors) ====
+    var foo = function bar() {
+                       ~~~
+!!! error TS7010: 'bar', which lacks return-type annotation, implicitly has an '[any]' return type.
+        let intermediate: [string];
+        return intermediate = [undefined];
+    };
\ No newline at end of file
diff --git a/tests/baselines/reference/wideningTuples7.js b/tests/baselines/reference/wideningTuples7.js
new file mode 100644
index 00000000000..4d94a1909ad
--- /dev/null
+++ b/tests/baselines/reference/wideningTuples7.js
@@ -0,0 +1,11 @@
+//// [wideningTuples7.ts]
+var foo = function bar() {
+    let intermediate: [string];
+    return intermediate = [undefined];
+};
+
+//// [wideningTuples7.js]
+var foo = function bar() {
+    var intermediate;
+    return intermediate = [undefined];
+};
diff --git a/tests/cases/conformance/types/tuple/wideningTuples1.ts b/tests/cases/conformance/types/tuple/wideningTuples1.ts
new file mode 100644
index 00000000000..f4885435dcf
--- /dev/null
+++ b/tests/cases/conformance/types/tuple/wideningTuples1.ts
@@ -0,0 +1,5 @@
+//@noImplicitAny: true
+declare function foo<T extends [any]>(x: T): T;
+
+var y = foo([undefined]);
+y = [""];
\ No newline at end of file
diff --git a/tests/cases/conformance/types/tuple/wideningTuples2.ts b/tests/cases/conformance/types/tuple/wideningTuples2.ts
new file mode 100644
index 00000000000..d8bf1248546
--- /dev/null
+++ b/tests/cases/conformance/types/tuple/wideningTuples2.ts
@@ -0,0 +1,6 @@
+//@noImplicitAny: true
+var foo: () => [any] = function bar() {
+    let intermediate = bar();
+    intermediate = [""];
+    return [undefined];
+};
\ No newline at end of file
diff --git a/tests/cases/conformance/types/tuple/wideningTuples3.ts b/tests/cases/conformance/types/tuple/wideningTuples3.ts
new file mode 100644
index 00000000000..a6837be2a0f
--- /dev/null
+++ b/tests/cases/conformance/types/tuple/wideningTuples3.ts
@@ -0,0 +1,4 @@
+//@noImplicitAny: true
+var a: [any];
+
+var b = a = [undefined, null];
\ No newline at end of file
diff --git a/tests/cases/conformance/types/tuple/wideningTuples4.ts b/tests/cases/conformance/types/tuple/wideningTuples4.ts
new file mode 100644
index 00000000000..550ba07f600
--- /dev/null
+++ b/tests/cases/conformance/types/tuple/wideningTuples4.ts
@@ -0,0 +1,4 @@
+var a: [any];
+
+var b = a = [undefined, null];
+b = ["", ""];
\ No newline at end of file
diff --git a/tests/cases/conformance/types/tuple/wideningTuples5.ts b/tests/cases/conformance/types/tuple/wideningTuples5.ts
new file mode 100644
index 00000000000..36434c6eafe
--- /dev/null
+++ b/tests/cases/conformance/types/tuple/wideningTuples5.ts
@@ -0,0 +1,2 @@
+//@noImplicitAny: true
+var [a, b] = [undefined, null];
\ No newline at end of file
diff --git a/tests/cases/conformance/types/tuple/wideningTuples6.ts b/tests/cases/conformance/types/tuple/wideningTuples6.ts
new file mode 100644
index 00000000000..cac228ecb4d
--- /dev/null
+++ b/tests/cases/conformance/types/tuple/wideningTuples6.ts
@@ -0,0 +1,3 @@
+var [a, b] = [undefined, null];
+a = "";
+b = "";
\ No newline at end of file
diff --git a/tests/cases/conformance/types/tuple/wideningTuples7.ts b/tests/cases/conformance/types/tuple/wideningTuples7.ts
new file mode 100644
index 00000000000..1a4d212d362
--- /dev/null
+++ b/tests/cases/conformance/types/tuple/wideningTuples7.ts
@@ -0,0 +1,5 @@
+//@noImplicitAny: true
+var foo = function bar() {
+    let intermediate: [string];
+    return intermediate = [undefined];
+};
\ No newline at end of file