Better scoring for map mismatches

Summary: Error messages should always choose a map with common keys if possible. The case where there are no keys in common was badly handled, leading to it being sometimes chosen.

Reviewed By: TD5

Differential Revision: D69980751

fbshipit-source-id: f8f0b6893e023b7555ef9c5419a73295455b78c8

Author: VLanvin

crates/elp/src/resources/test/eqwalizer_tests/check/custom.pretty

@@ -669,13 +669,6 @@ Expression has type:   #{'a' | 'b' => atom() | number()}
 Context expected type: #{a := atom(), b := number()} | #{a := atom()}
     │                         
 
-Because in the expression's type:
-  Here the type is:     #{...}
-  Context expects type: #{a := ..., ...}
-  The type of the expression is missing the following required keys: a.
-
------------------------------- Detailed message ------------------------------
-
   #{'a' | 'b' => atom() | number()} is not compatible with #{a := atom(), b := number()} | #{a := atom()}
   because
   #{'a' | 'b' => atom() | number()} is not compatible with #{a := atom(), b := number()}

crates/elp/src/resources/test/eqwalizer_tests/check/error_messages.pretty

@@ -10,9 +10,10 @@ Context expected type: foo_map() | #{foo => atom()}
    │                      
 
 Because in the expression's type:
-  Here the type is:     #{baz := ...}
-  Context expects type: #{...}
-  The expected map has no corresponding key for: baz.
+  #{ baz =>
+    Here the type is:     atom()
+    Context expects type: number()
+  , ... }
 
 ------------------------------ Detailed message ------------------------------
 

crates/elp/src/resources/test/eqwalizer_tests/check/recursive_aliases.pretty

@@ -158,9 +158,9 @@ Context expected type: mChainA()
     │                       
 
 Because in the expression's type:
-  Here the type is:     #{...}
-  Context expects type: #{a := ..., ...}
-  The type of the expression is missing the following required keys: a.
+  Here the type is:     #{b := mChainB()}
+  Context expects type: 'nil' | #{a := mChainA()}
+  No candidate matches in the expected union.
 
 ------------------------------ Detailed message ------------------------------