[build] fatal on warnings 21, 52, 57

Summary:
Went through the trouble of killing these warnings, make sure they do not creep
up again in the future.

Reviewed By: mbouaziz

Differential Revision: D4937493

fbshipit-source-id: 0e2eda4

infer/src/Makefile

@@ -22,7 +22,7 @@ ATDGEN_SUFFIXES = _t.ml _t.mli _j.ml _j.mli
 
 #### ocamlbuild options ####
 
-OCAML_FATAL_WARNINGS = +3+5+6+8+10+11+12+18+19+20+23+26+29+27+33+34+35+37+38+39+50
+OCAML_FATAL_WARNINGS = +3+5+6+8+10+11+12+18+19+20+21+23+26+29+27+33+34+35+37+38+39+50+52+57
 
 # options for ocamlbuild
 # Notice that use-ocamlfind is used here to avoid a linker bug in ocamlbuild when using -tag thread

infer/src/unit/accessPathTests.ml

@@ -115,8 +115,7 @@ let tests =
           assert_equal ~cmp:AccessPath.Raw.equal ap1 xFG;
           assert_equal ~cmp:AccessPath.Raw.equal ap2 xF;
       | _ ->
-          assert false;
-          () in
+          assert false in
     "of_exp">::of_exp_test_ in
 
   let abstraction_test =