[ruby/prism] Make equality operators non-associative

Fix https://github.com/ruby/prism/pull/2073

https://github.com/ruby/prism/commit/0f747d9240

prism/prism.c

@@ -10287,12 +10287,12 @@ pm_binding_powers_t pm_binding_powers[PM_TOKEN_MAXIMUM] = {
     [PM_TOKEN_AMPERSAND_AMPERSAND] = LEFT_ASSOCIATIVE(PM_BINDING_POWER_LOGICAL_AND),
 
     // != !~ == === =~ <=>
-    [PM_TOKEN_BANG_EQUAL] = LEFT_ASSOCIATIVE(PM_BINDING_POWER_EQUALITY),
-    [PM_TOKEN_BANG_TILDE] = LEFT_ASSOCIATIVE(PM_BINDING_POWER_EQUALITY),
-    [PM_TOKEN_EQUAL_EQUAL] = LEFT_ASSOCIATIVE(PM_BINDING_POWER_EQUALITY),
-    [PM_TOKEN_EQUAL_EQUAL_EQUAL] = LEFT_ASSOCIATIVE(PM_BINDING_POWER_EQUALITY),
-    [PM_TOKEN_EQUAL_TILDE] = LEFT_ASSOCIATIVE(PM_BINDING_POWER_EQUALITY),
-    [PM_TOKEN_LESS_EQUAL_GREATER] = LEFT_ASSOCIATIVE(PM_BINDING_POWER_EQUALITY),
+    [PM_TOKEN_BANG_EQUAL] = NON_ASSOCIATIVE(PM_BINDING_POWER_EQUALITY),
+    [PM_TOKEN_BANG_TILDE] = NON_ASSOCIATIVE(PM_BINDING_POWER_EQUALITY),
+    [PM_TOKEN_EQUAL_EQUAL] = NON_ASSOCIATIVE(PM_BINDING_POWER_EQUALITY),
+    [PM_TOKEN_EQUAL_EQUAL_EQUAL] = NON_ASSOCIATIVE(PM_BINDING_POWER_EQUALITY),
+    [PM_TOKEN_EQUAL_TILDE] = NON_ASSOCIATIVE(PM_BINDING_POWER_EQUALITY),
+    [PM_TOKEN_LESS_EQUAL_GREATER] = NON_ASSOCIATIVE(PM_BINDING_POWER_EQUALITY),
 
     // > >= < <=
     [PM_TOKEN_GREATER] = LEFT_ASSOCIATIVE(PM_BINDING_POWER_COMPARISON),

test/prism/errors_test.rb

@@ -2004,6 +2004,33 @@ module Prism
       ]
     end
 
+    def test_non_assoc_equality
+      source = <<~RUBY
+        1 == 2 == 3
+        1 != 2 != 3
+        1 === 2 === 3
+        1 =~ 2 =~ 3
+        1 !~ 2 !~ 3
+        1 <=> 2 <=> 3
+      RUBY
+      message1 = 'expected a newline or semicolon after the statement'
+      message2 = 'cannot parse the expression'
+      assert_errors expression(source), source, [
+        [message1, 6..6],
+        [message2, 6..6],
+        [message1, 18..18],
+        [message2, 18..18],
+        [message1, 31..31],
+        [message2, 31..31],
+        [message1, 44..44],
+        [message2, 44..44],
+        [message1, 56..56],
+        [message2, 56..56],
+        [message1, 69..69],
+        [message2, 69..69],
+      ]
+    end
+
     private
 
     def assert_errors(expected, source, errors, compare_ripper: RUBY_ENGINE == "ruby")