clang-format: [JS] Prevent ASI before [ and (.

[mprobst]

Summary

JavaScript automatic semicolon insertion can trigger before [ and (, so
avoid breaking before them if the previous token is likely to terminate
an expression.

[djasper]

Makes sense.

lib/Format/TokenAnnotator.cpp

if (Style.Language == FormatStyle::LK_Java) {
     if (NonComment &&
         NonComment->isOneOf(
             tok::kw_return, Keywords.kw_yield, tok::kw_continue, tok::kw_break,
             tok::kw_throw, Keywords.kw_interface, Keywords.kw_type,
             tok::kw_static, tok::kw_public, tok::kw_private, tok::kw_protected,
             Keywords.kw_readonly, Keywords.kw_abstract, Keywords.kw_get,
             Keywords.kw_set, Keywords.kw_async, Keywords.kw_await))
       return false; // Otherwise automatic semicolon insertion would trigger.
-    if (Left.Tok.getIdentifierInfo() &&
-        Right.startsSequence(tok::l_square, tok::r_square))
-      return false;  // breaking in "foo[]" creates illegal TS type syntax.
+    if (Right.NestingLevel == 0 &&
+        (Left.Tok.getIdentifierInfo() ||
+         Left.isOneOf(tok::r_square, tok::r_paren)) &&
+        Right.isOneOf(tok::l_square, tok::l_paren))
+      return false; // Otherwise automatic semicolon insertion would trigger.
     if (Left.is(TT_JsFatArrow) && Right.is(tok::l_brace))
       return false;
     if (Left.is(TT_JsTypeColon))
       return true;
     if (Right.NestingLevel == 0 && Right.is(Keywords.kw_is))
       return false;
     if (Left.is(Keywords.kw_in))
       return Style.BreakBeforeBinaryOperators == FormatStyle::BOS_None;

unittests/Format/FormatTestJS.cpp

verifyFormat("const x = (5 + 9)\n"
                "const y = 3\n",
                "const x = (   5 +    9)\n"
                "const y = 3\n");
   // Ideally the foo() bit should be indented relative to the async function().
   verifyFormat("async function\n"
                "foo() {}",
                getGoogleJSStyleWithColumns(10));
   verifyFormat("await theReckoning;", getGoogleJSStyleWithColumns(10));
+  verifyFormat("some['a']['b']", getGoogleJSStyleWithColumns(10));
+  verifyFormat("x = (a['a']\n"
+               "      ['b']);", getGoogleJSStyleWithColumns(10));
 }
 
 TEST_F(FormatTestJS, AutomaticSemicolonInsertionHeuristic) {
   verifyFormat("a\n"
                "b;",
                " a \n"
                " b ;");
   verifyFormat("a()\n"