Raise NameError instead of SyntaxError when Regexp-related read-only global variables are assigned

Author: andrykonchin

spec/ruby/language/predefined_spec.rb

@@ -142,6 +142,13 @@ def obj.foo2(&proc); proc.call; end
       eval %q{$& = ""}
     }.should raise_error(SyntaxError, /Can't set variable \$&/)
   end
+
+  it "is read-only when aliased" do
+    alias $predefined_spec_ampersand $&
+    -> {
+      $predefined_spec_ampersand = ""
+    }.should raise_error(NameError, '$predefined_spec_ampersand is a read-only variable')
+  end
 end
 
 describe "Predefined global $`" do
@@ -166,6 +173,13 @@ def obj.foo2(&proc); proc.call; end
       eval %q{$` = ""}
     }.should raise_error(SyntaxError, /Can't set variable \$`/)
   end
+
+  it "is read-only when aliased" do
+    alias $predefined_spec_backquote $`
+    -> {
+      $predefined_spec_backquote = ""
+    }.should raise_error(NameError, '$predefined_spec_backquote is a read-only variable')
+  end
 end
 
 describe "Predefined global $'" do
@@ -190,6 +204,13 @@ def obj.foo2(&proc); proc.call; end
       eval %q{$' = ""}
     }.should raise_error(SyntaxError, /Can't set variable \$'/)
   end
+
+  it "is read-only when aliased" do
+    alias $predefined_spec_single_quote $'
+    -> {
+      $predefined_spec_single_quote = ""
+    }.should raise_error(NameError, '$predefined_spec_single_quote is a read-only variable')
+  end
 end
 
 describe "Predefined global $+" do
@@ -214,6 +235,13 @@ def obj.foo2(&proc); proc.call; end
       eval %q{$+ = ""}
     }.should raise_error(SyntaxError, /Can't set variable \$\+/)
   end
+
+  it "is read-only when aliased" do
+    alias $predefined_spec_plus $+
+    -> {
+      $predefined_spec_plus = ""
+    }.should raise_error(NameError, '$predefined_spec_plus is a read-only variable')
+  end
 end
 
 describe "Predefined globals $1..N" do
@@ -1198,7 +1226,7 @@ def obj.foo2; yield; end
   end
 
   it "raises a SyntaxError if assigned to" do
-    -> { eval("nil = true") }.should raise_error(SyntaxError)
+    -> { eval("nil = true") }.should raise_error(SyntaxError, /Can't assign to nil/)
   end
 end
 
@@ -1208,7 +1236,7 @@ def obj.foo2; yield; end
   end
 
   it "raises a SyntaxError if assigned to" do
-    -> { eval("true = false") }.should raise_error(SyntaxError)
+    -> { eval("true = false") }.should raise_error(SyntaxError, /Can't assign to true/)
   end
 end
 
@@ -1218,13 +1246,13 @@ def obj.foo2; yield; end
   end
 
   it "raises a SyntaxError if assigned to" do
-    -> { eval("false = nil") }.should raise_error(SyntaxError)
+    -> { eval("false = nil") }.should raise_error(SyntaxError, /Can't assign to false/)
   end
 end
 
 describe "The self pseudo-variable" do
   it "raises a SyntaxError if assigned to" do
-    -> { eval("self = 1") }.should raise_error(SyntaxError)
+    -> { eval("self = 1") }.should raise_error(SyntaxError, /Can't change the value of self/)
   end
 end
 

src/main/ruby/truffleruby/core/match_data.rb

@@ -188,30 +188,34 @@ def backref_from_arg(index)
   -> s { Primitive.regexp_last_match_get(s) },
   Truffle::RegexpOperations::LAST_MATCH_SET)
 
+# Prism gives a SyntaxError if $` is not aliased
 Truffle::KernelOperations.define_hooked_variable(
   :'$`',
   -> s { match = Primitive.regexp_last_match_get(s)
          match.pre_match if match },
-  -> { raise SyntaxError, "Can't set variable $`" },
+  -> name, _ { raise NameError, "#{name} is a read-only variable" },
   -> s { 'global-variable' if Primitive.regexp_last_match_get(s) })
 
+# Prism gives a SyntaxError if $' is not aliased
 Truffle::KernelOperations.define_hooked_variable(
   :"$'",
   -> s { match = Primitive.regexp_last_match_get(s)
          match.post_match if match },
-  -> { raise SyntaxError, "Can't set variable $'" },
+  -> name, _ { raise NameError, "#{name} is a read-only variable" },
   -> s { 'global-variable' if Primitive.regexp_last_match_get(s) })
 
+# Prism gives a SyntaxError if $& is not aliased
 Truffle::KernelOperations.define_hooked_variable(
   :'$&',
   -> s { match = Primitive.regexp_last_match_get(s)
          match[0] if match },
-  -> { raise SyntaxError, "Can't set variable $&" },
+  -> name, _ { raise NameError, "#{name} is a read-only variable" },
   -> s { 'global-variable' if Primitive.regexp_last_match_get(s) })
 
+# Prism gives a SyntaxError if $+ is not aliased
 Truffle::KernelOperations.define_hooked_variable(
   :'$+',
   -> s { match = Primitive.regexp_last_match_get(s)
          match.captures.reverse.find { |m| !Primitive.nil?(m) } if match },
-  -> { raise SyntaxError, "Can't set variable $+" },
+  -> name, _ { raise NameError, "#{name} is a read-only variable" },
   -> s { 'global-variable' if Primitive.regexp_last_match_get(s) })