[AST] Remove unparsed case from FuncDecl::getSourceRange

This wasn't really sound since it could result in source ranges that
have different buffers for the start and end loc. Instead, adjust
the parser logic to look at the brace range.

Author: hamishknight

lib/AST/Decl.cpp

@@ -11481,9 +11481,6 @@ SourceRange FuncDecl::getSourceRange() const {
   if (startLoc.isInvalid())
     return SourceRange();
 
-  if (getBodyKind() == BodyKind::Unparsed)
-    return { startLoc, BodyRange.End };
-
   SourceLoc endLoc = getOriginalBodySourceRange().End;
   if (endLoc.isInvalid()) {
     if (isa<AccessorDecl>(this))

lib/Parse/ParseDecl.cpp

@@ -9009,7 +9009,7 @@ Parser::parseAbstractFunctionBodyDelayed(AbstractFunctionDecl *AFD) {
   auto bodyRange = AFD->getBodySourceRange();
   auto BeginParserPosition = getParserPosition(bodyRange.Start,
                                                /*previousLoc*/ SourceLoc());
-  auto EndLexerState = L->getStateForEndOfTokenLoc(AFD->getEndLoc());
+  auto EndLexerState = L->getStateForEndOfTokenLoc(bodyRange.End);
 
   // ParserPositionRAII needs a primed parser to restore to.
   if (Tok.is(tok::NUM_TOKENS))