Snapshot tests -- better maps:map/2

Summary: A snapshot test for more precise support of `maps:map/2`

Reviewed By: RobinMorisset

Differential Revision: D85677708

fbshipit-source-id: 1520e78419c51ae26604768fd78d787e06301a61

Author: VLanvin

crates/elp/src/resources/test/eqwalizer_tests/check/custom-OTP-27.pretty

@@ -3255,4 +3255,34 @@ error: incompatible_types (See https://fb.me/eqwalizer_errors#incompatible_types
 Expression has type:   number()
 Context expected type: binary()
 
-202 ERRORS
+error: incompatible_types (See https://fb.me/eqwalizer_errors#incompatible_types)
+     ┌─ check/src/custom.erl:2722:5
+     │    
+2722 │ ╭ ╭     maps:map(fun
+2723 │ │ │         (ka, va) -> va2;
+2724 │ │ │         (_K, V) -> V
+2725 │ │ │     end, M).
+     │ ╰─│───────────^ maps:map(fun, M).
+Expression has type:   #{ka => 'va' | 'vb' | 'vc' | 'va2', kb => 'va' | 'vb' | 'vc' | 'va2', kc => 'va' | 'vb' | 'vc' | 'va2'}
+Context expected type: #{ka => 'va2', kb => 'vb', kc => 'vc'}
+     │   ╰───────────' 
+
+Because in the expression's type:
+  #{ ka =>
+    Here the type is a union type with some valid candidates: 'va2'
+    However the following candidate: 'va'
+    Differs from the expected type:  'va2'
+  , ... }
+
+------------------------------ Detailed message ------------------------------
+
+  #{ka => 'va' | 'vb' | 'vc' | 'va2', kb => 'va' | 'vb' | 'vc' | 'va2', kc => 'va' | 'vb' | 'vc' | 'va2'} is not compatible with #{ka => 'va2', kb => 'vb', kc => 'vc'}
+  because
+  at key `ka`:
+  #{ka => 'va' | 'vb' | 'vc' | 'va2', kb => 'va' | 'vb' | 'vc' | 'va2', kc => 'va' | 'vb' | 'vc' | 'va2'} is not compatible with #{ka => 'va2', kb => 'vb', kc => 'vc'}
+  because
+  'va' | 'vb' | 'vc' | 'va2' is not compatible with 'va2'
+  because
+  'va' is not compatible with 'va2'
+
+203 ERRORS

test_projects/eqwalizer_tests/check/src/custom.erl

@@ -2713,3 +2713,13 @@ maps_foreach_neg(M) ->
         end,
         M
     ).
+
+-spec maps_map_2_13(
+    #{ka => va, kb => vb, kc => vc}
+) ->
+    #{ka => va2, kb => vb, kc => vc}.
+maps_map_2_13(M) ->
+    maps:map(fun
+        (ka, va) -> va2;
+        (_K, V) -> V
+    end, M).