clang-format: [JS/TS] Properly understand cast expressions.

Many things were wrong:
- We didn't always allow wrapping after "as", which can be necessary.
- We used to Undestand the identifier after "as" as a start of a name.
- We didn't properly parse the structure of the expression with "as"
  having the precedence of relational operators

llvm-svn: 296659

clang/lib/Format/TokenAnnotator.cpp

@@ -1158,7 +1158,8 @@ private:
     if (Tok.isNot(tok::identifier) || !Tok.Previous)
       return false;
 
-    if (Tok.Previous->isOneOf(TT_LeadingJavaAnnotation, Keywords.kw_instanceof))
+    if (Tok.Previous->isOneOf(TT_LeadingJavaAnnotation, Keywords.kw_instanceof,
+                              Keywords.kw_as))
       return false;
     if (Style.Language == FormatStyle::LK_JavaScript &&
         Tok.Previous->is(Keywords.kw_in))
@@ -1533,7 +1534,7 @@ private:
           Current->is(Keywords.kw_instanceof))
         return prec::Relational;
       if (Style.Language == FormatStyle::LK_JavaScript &&
-          Current->is(Keywords.kw_in))
+          Current->isOneOf(Keywords.kw_in, Keywords.kw_as))
         return prec::Relational;
       if (Current->is(TT_BinaryOperator) || Current->is(tok::comma))
         return Current->getPrecedence();
@@ -2531,6 +2532,8 @@ bool TokenAnnotator::canBreakBefore(const AnnotatedLine &Line,
       return Style.BreakBeforeBinaryOperators != FormatStyle::BOS_None;
     if (Right.is(Keywords.kw_as))
       return false; // must not break before as in 'x as type' casts
+    if (Left.is(Keywords.kw_as))
+      return true;
     if (Left.is(Keywords.kw_declare) &&
         Right.isOneOf(Keywords.kw_module, tok::kw_namespace,
                       Keywords.kw_function, tok::kw_class, tok::kw_enum,

clang/unittests/Format/FormatTestJS.cpp

@@ -1502,6 +1502,9 @@ TEST_F(FormatTestJS, CastSyntax) {
   verifyFormat("x = x as {a: string};");
   verifyFormat("x = x as (string);");
   verifyFormat("x = x! as (string);");
+  verifyFormat("var x = something.someFunction() as\n"
+               "    something;",
+               getGoogleJSStyleWithColumns(40));
 }
 
 TEST_F(FormatTestJS, TypeArguments) {