Improve eqWAlizer coverage

Summary:
As title, improve types and specs for eqWAlizer clause coverage.

Uncovers a limitation of eqWAlizer T192344722.

Differential Revision: D58519984

fbshipit-source-id: 309d3ded77b9b5b702e710debf46349cea23fabe

finer_taint/src/taint_abstract_machine.erl

@@ -194,7 +194,7 @@
     | {capture_closure, {[string()]}}
     % Pops a value of the stack, if untainted push an empty scope
     % If the value is {lambda_closure, Scope}, push the Scope
-    | {restore_capture, {string()}}
+    | {restore_capture, {mfa(), string()}}
     % Store VarName - Pop a value of the stack and store it in scope with VarName
     | {store, {string(), string()}}
     | {set_element, {integer(), integer(), string()}}.
@@ -582,6 +582,7 @@ propagate(
     ?NOT_TRY_ENTER(Capture)
 ->
     % Note: maybe add a marker to taint history that it went through restore_capture
+    % eqwalizer:fixme handle negative guard above T192344722
     Capture1 = append_taint_history_base(Capture, {call_site, {Module, Function, Arity}, Loc}),
     NewScope =
         case Capture1 of