Ignore empty binding patterns for contextual typing

Author: andrewbranch

src/compiler/checker.ts

@@ -25274,7 +25274,8 @@ namespace ts {
                 if (result) {
                     return result;
                 }
-                if (!(contextFlags! & ContextFlags.SkipBindingPatterns) && isBindingPattern(declaration.name)) { // This is less a contextual type and more an implied shape - in some cases, this may be undesirable
+                if (!(contextFlags! & ContextFlags.SkipBindingPatterns) && isBindingPattern(declaration.name) && declaration.name.elements.length > 0) {
+                    // This is less a contextual type and more an implied shape - in some cases, this may be undesirable
                     return getTypeFromBindingPattern(declaration.name, /*includePatternInType*/ true, /*reportErrors*/ false);
                 }
             }

tests/baselines/reference/declarationEmitDestructuring4.errors.txt

@@ -1,17 +1,11 @@
-tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern.ts(1,13): error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{}'.
-tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern.ts(1,19): error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{}'.
 tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern.ts(2,23): error TS2353: Object literal may only specify known properties, and 'y4' does not exist in type '{ x4: any; }'.
 tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern.ts(3,16): error TS2353: Object literal may only specify known properties, and 'x5' does not exist in type '{ y5: any; }'.
 tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern.ts(5,27): error TS2353: Object literal may only specify known properties, and 'y7' does not exist in type '{ x7: any; }'.
 tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern.ts(6,20): error TS2353: Object literal may only specify known properties, and 'x8' does not exist in type '{ y8: any; }'.
 
 
-==== tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern.ts (6 errors) ====
+==== tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern.ts (4 errors) ====
     var { } = { x: 5, y: "hello" };
-                ~
-!!! error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{}'.
-                      ~
-!!! error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{}'.
     var { x4 } = { x4: 5, y4: "hello" };
                           ~~
 !!! error TS2353: Object literal may only specify known properties, and 'y4' does not exist in type '{ x4: any; }'.

tests/baselines/reference/declarationEmitDestructuringObjectLiteralPattern.errors.txt

@@ -1,17 +1,11 @@
-tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern1.ts(1,13): error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{}'.
-tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern1.ts(1,19): error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{}'.
 tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern1.ts(2,23): error TS2353: Object literal may only specify known properties, and 'y4' does not exist in type '{ x4: any; }'.
 tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern1.ts(3,16): error TS2353: Object literal may only specify known properties, and 'x5' does not exist in type '{ y5: any; }'.
 tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern1.ts(5,27): error TS2353: Object literal may only specify known properties, and 'y7' does not exist in type '{ x7: any; }'.
 tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern1.ts(6,20): error TS2353: Object literal may only specify known properties, and 'x8' does not exist in type '{ y8: any; }'.
 
 
-==== tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern1.ts (6 errors) ====
+==== tests/cases/compiler/declarationEmitDestructuringObjectLiteralPattern1.ts (4 errors) ====
     var { } = { x: 5, y: "hello" };
-                ~
-!!! error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{}'.
-                      ~
-!!! error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{}'.
     var { x4 } = { x4: 5, y4: "hello" };
                           ~~
 !!! error TS2353: Object literal may only specify known properties, and 'y4' does not exist in type '{ x4: any; }'.

tests/baselines/reference/declarationEmitDestructuringObjectLiteralPattern1.errors.txt

@@ -1,6 +1,4 @@
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(5,16): error TS2493: Tuple type '[number, string]' of length '2' has no element at index '2'.
-tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(22,17): error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{}'.
-tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(22,23): error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{}'.
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(23,25): error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{ x: any; }'.
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(24,19): error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{ y: any; }'.
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(28,28): error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{ x: any; }'.
@@ -22,7 +20,7 @@ tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(138,6):
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(138,9): error TS2322: Type 'number' is not assignable to type 'string'.
 
 
-==== tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts (22 errors) ====
+==== tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts (20 errors) ====
     function f0() {
         var [] = [1, "hello"];
         var [x] = [1, "hello"];
@@ -47,10 +45,6 @@ tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(138,9):
 
     function f2() {
         var { } = { x: 5, y: "hello" };       // Error, no x and y in target
-                    ~
-!!! error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{}'.
-                          ~
-!!! error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{}'.
         var { x } = { x: 5, y: "hello" };     // Error, no y in target
                             ~
 !!! error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{ x: any; }'.

tests/baselines/reference/declarationsAndAssignments.errors.txt

@@ -10,8 +10,6 @@ tests/cases/conformance/es6/destructuring/missingAndExcessProperties.ts(12,8): e
 tests/cases/conformance/es6/destructuring/missingAndExcessProperties.ts(12,11): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
 tests/cases/conformance/es6/destructuring/missingAndExcessProperties.ts(13,18): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
 tests/cases/conformance/es6/destructuring/missingAndExcessProperties.ts(14,8): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/conformance/es6/destructuring/missingAndExcessProperties.ts(20,17): error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{}'.
-tests/cases/conformance/es6/destructuring/missingAndExcessProperties.ts(20,23): error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{}'.
 tests/cases/conformance/es6/destructuring/missingAndExcessProperties.ts(21,25): error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{ x: any; }'.
 tests/cases/conformance/es6/destructuring/missingAndExcessProperties.ts(22,19): error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{ y: any; }'.
 tests/cases/conformance/es6/destructuring/missingAndExcessProperties.ts(29,14): error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{}'.
@@ -20,7 +18,7 @@ tests/cases/conformance/es6/destructuring/missingAndExcessProperties.ts(30,22):
 tests/cases/conformance/es6/destructuring/missingAndExcessProperties.ts(31,16): error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{ y: number; }'.
 
 
-==== tests/cases/conformance/es6/destructuring/missingAndExcessProperties.ts (20 errors) ====
+==== tests/cases/conformance/es6/destructuring/missingAndExcessProperties.ts (18 errors) ====
     // Missing properties
     function f1() {
         var { x, y } = {};
@@ -69,10 +67,6 @@ tests/cases/conformance/es6/destructuring/missingAndExcessProperties.ts(31,16):
     // Excess properties
     function f3() {
         var { } = { x: 0, y: 0 };
-                    ~
-!!! error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{}'.
-                          ~
-!!! error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{}'.
         var { x } = { x: 0, y: 0 };
                             ~
 !!! error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{ x: any; }'.

tests/baselines/reference/emptyObjectBindingPatternParameter04.errors.txt

@@ -0,0 +1,9 @@
+/// <reference path="fourslash.ts" />
+
+//// declare function pick<T, K extends keyof T>(keys: K[], obj: T): Pick<T, K>;
+//// const { /**/ } = pick(['b'], { a: 'a', b: 'b' });
+
+verify.completions({
+  marker: "",
+  exact: ["b"]
+});