Do not inline arrow when argument has a leading comment (#1660)

Fixes #1614

src/printer.js

@@ -392,12 +392,13 @@ function genericPrintNoParens(path, options, print, args) {
       // We want to always keep these types of nodes on the same line
       // as the arrow.
       if (
-        n.body.type === "ArrayExpression" ||
-        n.body.type === "ObjectExpression" ||
-        n.body.type === "JSXElement" ||
-        n.body.type === "BlockStatement" ||
-        isTemplateOnItsOwnLine(n.body, options.originalText) ||
-        n.body.type === "ArrowFunctionExpression"
+        !hasLeadingOwnLineComment(options.originalText, n.body) &&
+        (n.body.type === "ArrayExpression" ||
+          n.body.type === "ObjectExpression" ||
+          n.body.type === "JSXElement" ||
+          n.body.type === "BlockStatement" ||
+          isTemplateOnItsOwnLine(n.body, options.originalText) ||
+          n.body.type === "ArrowFunctionExpression")
       ) {
         return group(collapsed);
       }

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

@@ -239,6 +239,57 @@ jest.mock(
 
 `;
 
+exports[`comment.js 1`] = `
+/**
+ * Curried function that ends with a BEM CSS Selector
+ *
+ * @param {String} block - the BEM Block you'd like to select.
+ * @returns {Function}
+ */
+export const bem = block =>
+  /**
+   * @param {String} [element] - the BEM Element within that block; if undefined, selects the block itself.
+   * @returns {Function}
+   */
+  element =>
+    /**
+     * @param {?String} [modifier] - the BEM Modifier for the Block or Element; if undefined, selects the Block or Element unmodified.
+     * @returns {String}
+     */
+    modifier =>
+      [
+        ".",
+        css(block),
+        element ? \`__\${css(element)}\` : "",
+        modifier ? \`--\${css(modifier)}\` : ""
+      ].join("");
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+/**
+ * Curried function that ends with a BEM CSS Selector
+ *
+ * @param {String} block - the BEM Block you'd like to select.
+ * @returns {Function}
+ */
+export const bem = block =>
+  /**
+   * @param {String} [element] - the BEM Element within that block; if undefined, selects the block itself.
+   * @returns {Function}
+   */
+  element =>
+    /**
+     * @param {?String} [modifier] - the BEM Modifier for the Block or Element; if undefined, selects the Block or Element unmodified.
+     * @returns {String}
+     */
+    modifier =>
+      [
+        ".",
+        css(block),
+        element ? \`__\${css(element)}\` : "",
+        modifier ? \`--\${css(modifier)}\` : ""
+      ].join("");
+
+`;
+
 exports[`currying.js 1`] = `
 const fn = b => c => d => {
   return 3;

tests/arrows/comment.js

@@ -0,0 +1,23 @@
+/**
+ * Curried function that ends with a BEM CSS Selector
+ *
+ * @param {String} block - the BEM Block you'd like to select.
+ * @returns {Function}
+ */
+export const bem = block =>
+  /**
+   * @param {String} [element] - the BEM Element within that block; if undefined, selects the block itself.
+   * @returns {Function}
+   */
+  element =>
+    /**
+     * @param {?String} [modifier] - the BEM Modifier for the Block or Element; if undefined, selects the Block or Element unmodified.
+     * @returns {String}
+     */
+    modifier =>
+      [
+        ".",
+        css(block),
+        element ? `__${css(element)}` : "",
+        modifier ? `--${css(modifier)}` : ""
+      ].join("");