Add missing specialization for constructing bytes from buffer

Author: msimacek

graalpython/com.oracle.graal.python.test/src/tests/unittest_tags/test_gzip.txt

@@ -42,10 +42,13 @@
 *graalpython.lib-python.3.test.test_gzip.TestGzip.test_textio_readlines
 *graalpython.lib-python.3.test.test_gzip.TestGzip.test_with_open
 *graalpython.lib-python.3.test.test_gzip.TestGzip.test_write
+*graalpython.lib-python.3.test.test_gzip.TestGzip.test_write_array
 *graalpython.lib-python.3.test.test_gzip.TestGzip.test_write_bytearray
 *graalpython.lib-python.3.test.test_gzip.TestGzip.test_write_incompatible_type
+*graalpython.lib-python.3.test.test_gzip.TestGzip.test_write_memoryview
 *graalpython.lib-python.3.test.test_gzip.TestGzip.test_write_read_with_pathlike_file
 *graalpython.lib-python.3.test.test_gzip.TestGzip.test_zero_padded_file
+*graalpython.lib-python.3.test.test_gzip.TestMain.test_main
 *graalpython.lib-python.3.test.test_gzip.TestOpen.test_bad_params
 *graalpython.lib-python.3.test.test_gzip.TestOpen.test_binary_modes
 *graalpython.lib-python.3.test.test_gzip.TestOpen.test_encoding

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/bytes/BytesNodes.java

@@ -598,6 +598,16 @@ static byte[] fromIndex(VirtualFrame frame, Object source, @SuppressWarnings("un
             return BytesUtils.fromSize(getCore(), cap);
         }
 
+        @Specialization(guards = {"lib.isBuffer(source)", "!lib.canBeIndex(source)"}, limit = "3")
+        static byte[] fromBuffer(Object source, @SuppressWarnings("unused") PNone encoding, @SuppressWarnings("unused") PNone errors,
+                        @CachedLibrary("source") PythonObjectLibrary lib) {
+            try {
+                return lib.getBufferBytes(source);
+            } catch (UnsupportedMessageException e) {
+                throw CompilerDirectives.shouldNotReachHere();
+            }
+        }
+
         @Specialization(guards = {"!isString(source)", "!isNoValue(source)", "!lib.canBeIndex(source)", "!lib.isBuffer(source)"}, limit = "3")
         static byte[] fromIterable(VirtualFrame frame, Object source, @SuppressWarnings("unused") PNone encoding, @SuppressWarnings("unused") PNone errors,
                         @Cached IteratorNodes.GetLength lenNode,