+ ruby34.y: reject return in singleton class (#1048)

This tracks upstream commit ruby/ruby@e642ddf

Author: Earlopain

lib/parser/context.rb

@@ -24,6 +24,7 @@ class Context
       in_class
       in_block
       in_lambda
+      cant_return
     ]
 
     def initialize
@@ -38,6 +39,7 @@ def reset
       @in_class = false
       @in_block = false
       @in_lambda = false
+      @cant_return = false
     end
 
     attr_accessor(*FLAGS)

lib/parser/ruby34.y

@@ -366,6 +366,7 @@ rule
 
                       result = [ val[0], @context.dup ]
                       @context.in_def = true
+                      @context.cant_return = false
                     }
 
        defn_head: k_def def_name
@@ -1319,6 +1320,7 @@ rule
                 | k_class cpath superclass
                     {
                       @context.in_class = true
+                      @context.cant_return = true
                       local_push
                     }
                     bodystmt kEND
@@ -1334,11 +1336,13 @@ rule
 
                       local_pop
                       @context.in_class = ctx.in_class
+                      @context.cant_return = ctx.cant_return
                     }
                 | k_class tLSHFT expr_value term
                     {
                       @context.in_def = false
                       @context.in_class = false
+                      @context.cant_return = true
                       local_push
                     }
                     bodystmt kEND
@@ -1350,10 +1354,12 @@ rule
                       local_pop
                       @context.in_def = ctx.in_def
                       @context.in_class = ctx.in_class
+                      @context.cant_return = ctx.cant_return
                     }
                 | k_module cpath
                     {
                       @context.in_class = true
+                      @context.cant_return = true
                       local_push
                     }
                     bodystmt kEND
@@ -1367,6 +1373,7 @@ rule
 
                       local_pop
                       @context.in_class = ctx.in_class
+                      @context.cant_return = ctx.cant_return
                     }
                 | defn_head f_arglist bodystmt kEND
                     {
@@ -1425,7 +1432,7 @@ rule
 
         k_return: kRETURN
                     {
-                      if @context.in_class && !@context.in_def && !(context.in_block || context.in_lambda)
+                      if @context.cant_return && !(context.in_block || context.in_lambda)
                         diagnostic :error, :invalid_return, nil, val[0]
                       end
                     }

test/test_parser.rb

@@ -6805,15 +6805,29 @@ def test_context_class
       %q{class A; get_context; end},
       %q{class A < B; get_context; end}
     ].each do |code|
-      assert_context([:in_class], code, ALL_VERSIONS)
+      assert_context([:in_class], code, ALL_VERSIONS - SINCE_3_4)
+      assert_context([:in_class, :cant_return], code, SINCE_3_4)
     end
   end
 
   def test_context_module
     assert_context(
       [:in_class],
       %q{module M; get_context; end},
-      ALL_VERSIONS)
+      ALL_VERSIONS - SINCE_3_4)
+    assert_context(
+      [:in_class, :cant_return],
+      %q{module M; get_context; end},
+      SINCE_3_4)
+  end
+
+  def test_context_sclass
+    [
+      %q{class << foo; get_context; end},
+      %q{class A; class << self; get_context; end; end}
+    ].each do |code|
+      assert_context([:cant_return], code, SINCE_3_4)
+    end
   end
 
   def test_context_def
@@ -6900,15 +6914,21 @@ def test_return_in_class
       SINCE_2_5)
 
     [
-      %q{class << foo; return; end},
       %q{def m; return; end},
       %q{tap { return }},
-      %q{class A; class << self; return; end; end},
+      %q{class A; class << self; def m; return; end; end; end},
       %q{class A; def m; return; end; end},
     ].each do |code|
       refute_diagnoses(code, ALL_VERSIONS)
     end
 
+    [
+      %q{class << foo; return; end},
+      %q{class A; class << self; return; end; end},
+    ].each do |code|
+      refute_diagnoses(code, ALL_VERSIONS - SINCE_3_4)
+    end
+
     [
       %q{-> do return end},
       %q{class A; -> do return end; end},
@@ -6917,6 +6937,20 @@ def test_return_in_class
     end
   end
 
+  def test_return_in_sclass_since_34
+    assert_diagnoses(
+      [:error, :invalid_return, {}],
+      %q{class << foo; return; end},
+      %q{              ^^^^^^ location},
+      SINCE_3_4)
+    
+    assert_diagnoses(
+      [:error, :invalid_return, {}],
+      %q{class A; class << self; return; end; end},
+      %q{                        ^^^^^^ location},
+      SINCE_3_4)
+  end
+
   def test_method_definition_in_while_cond
     assert_parses(
       s(:while,