[clang-format][NFC] Use Prev instead of Current->Previous

[curdeius]

LGTM.

clang/lib/Format/TokenAnnotator.cpp

bool AlignArrayOfStructures =
       (Style.AlignArrayOfStructures != FormatStyle::AIAS_None &&
        Line.Type == LT_ArrayOfStructInitializer);
   if (AlignArrayOfStructures)
     calculateArrayInitializerColumnList(Line);
 
   while (Current) {
     if (isFunctionDeclarationName(Style.isCpp(), *Current, Line))
       Current->setType(TT_FunctionDeclarationName);
+    const FormatToken *Prev = Current->Previous;
     if (Current->is(TT_LineComment)) {
-      if (Current->Previous->is(BK_BracedInit) &&
-          Current->Previous->opensScope())
+      if (Prev->is(BK_BracedInit) && Prev->opensScope())
         Current->SpacesRequiredBefore =
             (Style.Cpp11BracedListStyle && !Style.SpacesInParentheses) ? 0 : 1;
       else
         Current->SpacesRequiredBefore = Style.SpacesBeforeTrailingComments;
 
       // If we find a trailing comment, iterate backwards to determine whether
       // it seems to relate to a specific parameter. If so, break before that
       // parameter to avoid changing the comment's meaning. E.g. don't move 'b'
while (Current) {
 
     if (!Current->MustBreakBefore && InFunctionDecl &&
         Current->is(TT_FunctionDeclarationName))
       Current->MustBreakBefore = mustBreakForReturnType(Line);
 
     Current->CanBreakBefore =
         Current->MustBreakBefore || canBreakBefore(Line, *Current);
     unsigned ChildSize = 0;
-    if (Current->Previous->Children.size() == 1) {
-      FormatToken &LastOfChild = *Current->Previous->Children[0]->Last;
+    if (Prev->Children.size() == 1) {
+      FormatToken &LastOfChild = *Prev->Children[0]->Last;
       ChildSize = LastOfChild.isTrailingComment() ? Style.ColumnLimit
                                                   : LastOfChild.TotalLength + 1;
     }
-    const FormatToken *Prev = Current->Previous;
     if (Current->MustBreakBefore || Prev->Children.size() > 1 ||
         (Prev->Children.size() == 1 &&
          Prev->Children[0]->First->MustBreakBefore) ||
         Current->IsMultiline)
       Current->TotalLength = Prev->TotalLength + Style.ColumnLimit;
     else
       Current->TotalLength = Prev->TotalLength + Current->ColumnWidth +
                              ChildSize + Current->SpacesRequiredBefore;