Merge pull request #3209 from Microsoft/merge3137

Merge PR #3137 into release-1.5

Author: mhegazy

src/compiler/emitter.ts

@@ -1366,7 +1366,7 @@ var __param = (this && this.__param) || function (paramIndex, decorator) {
                 return true;
             }
 
-            function emitListWithSpread(elements: Expression[], multiLine: boolean, trailingComma: boolean) {
+            function emitListWithSpread(elements: Expression[], alwaysCopy: boolean, multiLine: boolean, trailingComma: boolean) {
                 let pos = 0;
                 let group = 0;
                 let length = elements.length;
@@ -1383,6 +1383,9 @@ var __param = (this && this.__param) || function (paramIndex, decorator) {
                         e = (<SpreadElementExpression>e).expression;
                         emitParenthesizedIf(e, /*parenthesized*/ group === 0 && needsParenthesisForPropertyAccessOrInvocation(e));
                         pos++;
+                        if (pos === length && group === 0 && alwaysCopy && e.kind !== SyntaxKind.ArrayLiteralExpression) {
+                            write(".slice()");
+                        }
                     }
                     else {
                         let i = pos;
@@ -1422,7 +1425,7 @@ var __param = (this && this.__param) || function (paramIndex, decorator) {
                     write("]");
                 }
                 else {
-                    emitListWithSpread(elements, /*multiLine*/(node.flags & NodeFlags.MultiLine) !== 0,
+                    emitListWithSpread(elements, /*alwaysCopy*/ true, /*multiLine*/(node.flags & NodeFlags.MultiLine) !== 0,
                         /*trailingComma*/ elements.hasTrailingComma);
                 }
             }
@@ -1847,7 +1850,7 @@ var __param = (this && this.__param) || function (paramIndex, decorator) {
                     write("void 0");
                 }
                 write(", ");
-                emitListWithSpread(node.arguments, /*multiLine*/ false, /*trailingComma*/ false);
+                emitListWithSpread(node.arguments, /*alwaysCopy*/ false, /*multiLine*/ false, /*trailingComma*/ false);
                 write(")");
             }
 

tests/baselines/reference/arrayLiteralSpread.js

@@ -26,7 +26,7 @@ function f2() {
 //// [arrayLiteralSpread.js]
 function f0() {
     var a = [1, 2, 3];
-    var a1 = a;
+    var a1 = a.slice();
     var a2 = [1].concat(a);
     var a3 = [1, 2].concat(a);
     var a4 = a.concat([1]);

tests/baselines/reference/arrayLiterals2ES5.js

@@ -93,12 +93,12 @@ var temp2 = [[1, 2, 3], ["hello", "string"]];
 var temp3 = [undefined, null, undefined];
 var temp4 = [];
 var d0 = [1, true].concat(temp); // has type (string|number|boolean)[]
-var d1 = temp; // has type string[]
-var d2 = temp1;
-var d3 = temp1;
+var d1 = temp.slice(); // has type string[]
+var d2 = temp1.slice();
+var d3 = temp1.slice();
 var d4 = temp.concat(temp1);
-var d5 = temp3;
-var d6 = temp4;
-var d7 = temp1;
-var d8 = [temp1];
-var d9 = [temp1].concat(["hello"]);
+var d5 = temp3.slice();
+var d6 = temp4.slice();
+var d7 = temp1.slice();
+var d8 = [temp1.slice()];
+var d9 = [temp1.slice()].concat(["hello"]);

tests/baselines/reference/arrayLiterals3.js

@@ -55,6 +55,6 @@ var _a = [1, 2, "string", true], b1 = _a[0], b2 = _a[1];
 var temp = ["s", "t", "r"];
 var temp1 = [1, 2, 3];
 var temp2 = [[1, 2, 3], ["hello", "string"]];
-var c0 = temp2; // Error
-var c1 = temp1; // Error cannot assign number[] to [number, number, number]
+var c0 = temp2.slice(); // Error
+var c1 = temp1.slice(); // Error cannot assign number[] to [number, number, number]
 var c2 = temp1.concat(temp); // Error cannot assign (number|string)[] to number[]

tests/baselines/reference/destructuringArrayBindingPatternAndAssignment1ES5.js

@@ -88,7 +88,7 @@ var _e = foo(), b6 = _e[0], b7 = _e[1];
 var b8 = foo().slice(0);
 //      S is not a tuple- like type and the numeric index signature type of S is assignable to the target given in E.
 var temp = [1, 2, 3];
-var _f = temp, c0 = _f[0], c1 = _f[1];
+var _f = temp.slice(), c0 = _f[0], c1 = _f[1];
 var c2 = [][0];
 var _g = [[[]], [[[[]]]]], c3 = _g[0][0][0], c4 = _g[1][0][0][0][0];
 var _h = [[1], true], c5 = _h[0][0], c6 = _h[1];

tests/baselines/reference/destructuringArrayBindingPatternAndAssignment2.js

@@ -50,8 +50,8 @@ var _c = bar(), _d = _c[0], b3 = _d === void 0 ? "string" : _d, b4 = _c[1], b5 =
 // V is an array assignment pattern, S is the type Any or an array-like type (section 3.3.2), and, for each assignment element E in V,
 //      S is not a tuple- like type and the numeric index signature type of S is assignable to the target given in E.
 var temp = [1, 2, 3];
-var _e = temp, c0 = _e[0], c1 = _e[1]; // Error
-var _f = temp, c2 = _f[0], c3 = _f[1]; // Error
+var _e = temp.slice(), c0 = _e[0], c1 = _e[1]; // Error
+var _f = temp.slice(), c2 = _f[0], c3 = _f[1]; // Error
 function foo(idx) {
     return {
         2: true