Revert "Workaround flow bug around trailing comma" (#429)

src/printer.js

@@ -609,24 +609,12 @@ function genericPrintNoParens(path, options, print) {
     case "Decorator":
       return concat([ "@", path.call(print, "expression") ]);
     case "ArrayExpression":
-    case "ArrayPattern": {
+    case "ArrayPattern":
       if (n.elements.length === 0) {
         parts.push("[]");
       } else {
         const lastElem = util.getLast(n.elements);
-        let canHaveTrailingComma = !(lastElem && lastElem.type === "RestElement");
-
-        // There's a bug with flow 0.38 where trailing commas are triggering
-        // parse errors for array patterns in arguments of a function
-        const parent = path.getParentNode(0);
-        if (options.parser === 'flow' &&
-          n.type === "ArrayPattern" &&
-          parent && (
-          parent.type === 'FunctionExpression' ||
-          parent.type === 'FunctionDeclaration' ||
-          parent.type === 'ArrowFunctionExpression')) {
-          canHaveTrailingComma = false;
-        }
+        const canHaveTrailingComma = !(lastElem && lastElem.type === "RestElement");
 
         // JavaScript allows you to have empty elements in an array which
         // changes its length based on the number of commas. The algorithm
@@ -667,7 +655,6 @@ function genericPrintNoParens(path, options, print) {
       if (n.typeAnnotation) parts.push(path.call(print, "typeAnnotation"));
 
       return concat(parts);
-    }
     case "SequenceExpression":
       return join(", ", path.map(print, "expressions"));
     case "ThisExpression":

tests/array_trailing_comma/__snapshots__/jsfmt.spec.js.snap

@@ -1,69 +0,0 @@
-exports[`test trailing_comma.js 1`] = `
-"f = ([s=1]) => 1;
-function f([s=1]){};
-f = function([s=1]){};
-class c {a([s=1]){}}
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-f = (
-  [
-    s = 1
-  ],
-) =>
-  1;
-function f(
-  [
-    s = 1
-  ],
-) {
-}
-f = function(
-  [
-    s = 1
-  ],
-) {
-};
-class c {
-  a(
-    [
-      s = 1
-    ],
-  ) {
-  }
-}
-"
-`;
-
-exports[`test trailing_comma.js 2`] = `
-"f = ([s=1]) => 1;
-function f([s=1]){};
-f = function([s=1]){};
-class c {a([s=1]){}}
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-f = (
-  [
-    s = 1,
-  ],
-) =>
-  1;
-function f(
-  [
-    s = 1,
-  ],
-) {
-}
-f = function(
-  [
-    s = 1,
-  ],
-) {
-};
-class c {
-  a(
-    [
-      s = 1,
-    ],
-  ) {
-  }
-}
-"
-`;

tests/array_trailing_comma/jsfmt.spec.js

@@ -1,2 +0,0 @@
-run_spec(__dirname, {printWidth: 1, trailingComma: true});
-run_spec(__dirname, {printWidth: 1, trailingComma: true, parser: 'babylon'});

tests/array_trailing_comma/trailing_comma.js

@@ -1,4 +0,0 @@
-f = ([s=1]) => 1;
-function f([s=1]){};
-f = function([s=1]){};
-class c {a([s=1]){}}