Fix preprocessor for Arduino sketch when function returns certain type // Resolve #1683

platformio/builder/tools/piomisc.py

@@ -33,7 +33,7 @@ class InoToCPPConverter(object):
     PROTOTYPE_RE = re.compile(
         r"""^(
         (?:template\<.*\>\s*)?      # template
-        ([a-z_\d]+\*?\s+){1,2}      # return type
+        ([a-z_\d\&]+\*?\s+){1,2}      # return type
         ([a-z_\d]+\s*)              # name of prototype
         \([a-z_,\.\*\&\[\]\s\d]*\)  # arguments
         )\s*\{                      # must end with {