clang-format: [JS] handle destructuring `of`.

[mprobst]

Summary

Previously, clang-format would drop a space character between of and
then following (non-identifier) token if the preceding token was part of
a destructuring assignment (} or ]).

Before:

for (const [a, b] of[]) {}

After:

for (const [a, b] of []) {}

[djasper]

Looks good.

cfe/trunk/lib/Format/TokenAnnotator.cpp

if (Right.is(tok::l_paren)) {
       // Additional unary JavaScript operators that need a space after.
       if (Left.isOneOf(tok::kw_throw, Keywords.kw_await, Keywords.kw_typeof,
                        tok::kw_void))
         return true;
     }
     if ((Left.isOneOf(Keywords.kw_let, Keywords.kw_var, Keywords.kw_in,
                       tok::kw_const) ||
          // "of" is only a keyword if it appears after another identifier
-         // (e.g. as "const x of y" in a for loop).
+         // (e.g. as "const x of y" in a for loop), or after a destructuring
+         // operation (const [x, y] of z, const {a, b} of c).
          (Left.is(Keywords.kw_of) && Left.Previous &&
-          Left.Previous->Tok.getIdentifierInfo())) &&
+          (Left.Previous->Tok.getIdentifierInfo() ||
+           Left.Previous->isOneOf(tok::r_square, tok::r_brace)))) &&
         (!Left.Previous || !Left.Previous->is(tok::period)))
       return true;
     if (Left.isOneOf(tok::kw_for, Keywords.kw_as) && Left.Previous &&
         Left.Previous->is(tok::period) && Right.is(tok::l_paren))
       return false;
     if (Left.is(Keywords.kw_as) &&
         Right.isOneOf(tok::l_square, tok::l_brace, tok::l_paren))
       return true;

cfe/trunk/unittests/Format/FormatTestJS.cpp

 
 TEST_F(FormatTestJS, ForLoops) {
   verifyFormat("for (var i in [2, 3]) {\n"
                "}");
   verifyFormat("for (var i of [2, 3]) {\n"
                "}");
   verifyFormat("for (let {a, b} of x) {\n"
                "}");
+  verifyFormat("for (let {a, b} of [x]) {\n"
+               "}");
+  verifyFormat("for (let [a, b] of [x]) {\n"
+               "}");
   verifyFormat("for (let {a, b} in x) {\n"
                "}");
 }
 
 TEST_F(FormatTestJS, WrapRespectsAutomaticSemicolonInsertion) {
   // The following statements must not wrap, as otherwise the program meaning
   // would change due to automatic semicolon insertion.
   // See http://www.ecma-international.org/ecma-262/5.1/#sec-7.9.1.