Add support for improper list patterns

Summary: Remove a crash when elaborating an improper list pattern.

Reviewed By: ilya-klyuchnikov

Differential Revision: D41551007

fbshipit-source-id: c765558fe3472654d4ec94f9b009191b543e64c6

Author: VLanvin

eqwalizer/src/main/scala/com/whatsapp/eqwalizer/tc/ElabPat.scala

@@ -82,8 +82,10 @@ final class ElabPat(pipelineContext: PipelineContext) {
           case Some(ListType(elemType)) =>
             val (hType, env1) = elabPat(hPat, elemType, env)
             val (tType, env2) = elabPat(tPat, ListType(elemType), env1)
-            val ListType(refinedT) = narrow.asListType(tType).get
-            (ListType(subtype.join(hType, refinedT)), env2)
+            narrow.asListType(tType) match {
+              case Some(ListType(refinedT)) => (ListType(subtype.join(hType, refinedT)), env2)
+              case None                     => (AnyType, env2)
+            }
         }
       case PatMatch(p1: PatVar, p2) =>
         val (t2, env1) = elabPat(p2, t, env)

eqwalizer/test_projects/_cli/checkable_funs.cli

@@ -1,7 +1,7 @@
 all funs:
-                                               All : 2838
-                                         Checkable : 2573
-                              Well-typed checkable : 1642
+                                               All : 2839
+                                         Checkable : 2574
+                              Well-typed checkable : 1643
                                    Checkable ratio : 91%
                          Health ratio of checkable : 64%
                                        error count : 930
@@ -26,18 +26,18 @@ generated non-test funs:
 
 --------------------------------------------
 non-generated funs:
-                                               All : 2838
-                                         Checkable : 2573
-                              Well-typed checkable : 1642
+                                               All : 2839
+                                         Checkable : 2574
+                              Well-typed checkable : 1643
                                    Checkable ratio : 91%
                          Health ratio of checkable : 64%
                                        error count : 930
 
 --------------------------------------------
 non-generated non-test funs (most important):
-                                               All : 2836
-                                         Checkable : 2571
-                              Well-typed checkable : 1641
+                                               All : 2837
+                                         Checkable : 2572
+                              Well-typed checkable : 1642
                                    Checkable ratio : 91%
                          Health ratio of checkable : 64%
                                        error count : 929

eqwalizer/test_projects/_cli/discarded_specs.cli

@@ -49,5 +49,5 @@ type_aliases:uses_trans_unbound_var/2
 type_aliases:uses_ty_w_unbound_var/2
 type_aliases:uses_ty_w_unbound_var2/0
 Discarded specs: 49
-Total specs: 2711
-Discarded ratio: 1.8075 %
+Total specs: 2712
+Discarded ratio: 1.8068 %

eqwalizer/test_projects/_cli/misc.json

@@ -2563,7 +2563,8 @@
           "f/1",
           "g/1",
           "fuzz01/0",
-          "fuzz02/0"
+          "fuzz02/0",
+          "fuzz03/1"
         ]
       },
       {

eqwalizer/test_projects/_cli/numbers.cli

@@ -1,8 +1,8 @@
 all specs:
-    containing number: 13.16%
-    containing integer: 10.72%
+    containing number: 13.15%
+    containing integer: 10.71%
     containing pos_integer: 3.25%
-    containing non_neg_integer: 2.00%
+    containing non_neg_integer: 1.99%
     containing neg_integer: 1.48%
     containing byte: 0.26%
     containing char: 0.22%
@@ -21,10 +21,10 @@ generated specs:
     containing range: 0.00%
     containing int lit: 0.00%
 non-generated specs:
-    containing number: 13.16%
-    containing integer: 10.72%
+    containing number: 13.15%
+    containing integer: 10.71%
     containing pos_integer: 3.25%
-    containing non_neg_integer: 2.00%
+    containing non_neg_integer: 1.99%
     containing neg_integer: 1.48%
     containing byte: 0.26%
     containing char: 0.22%

eqwalizer/test_projects/check_gradual/src/gradual_misc.erl

@@ -36,3 +36,7 @@ fuzz01() when #{(true andalso false) => {}} ->
 -spec fuzz02() -> ok.
 fuzz02() ->
     <<X || X <- [], (X ++ X) >>.
+
+-spec fuzz03(term()) -> ok.
+fuzz03([_ | {}]) -> 
+    ok.

eqwalizer/test_projects/check_gradual/src/gradual_misc.erl.check

@@ -40,3 +40,7 @@ fuzz02() ->                                | ERROR   |
     <<X || X <- [], (X ++ X) >>.           |         | << || >>.
                                            |         | Expected: 'ok'
                                            |         | Got     : binary()
+                                           |         |
+-spec fuzz03(term()) -> ok.                |         |
+fuzz03([_ | {}]) ->                        | OK      |
+    ok.                                    |         |