add test for #2302

testsuite/tests/ghc-regress/parser/unicode/2302.hs

+f = À

testsuite/tests/ghc-regress/parser/unicode/2302.stderr

+
+2302.hs:1:4: Not in scope: data constructor `À'

testsuite/tests/ghc-regress/parser/unicode/all.T

@@ -18,3 +18,4 @@ test('unicode001', normal, compile_and_run, [''])
 
 test('1744', normal, compile_and_run, [''])
 test('1103', normal, compile, [''])
+test('2302', only_ways(['normal']), compile_fail, [''])