Fix exception messages and use global variable alias names.

Fix TestString#test_fs_setter

Original error:
```
  1) Failure:
TestString#test_fs_setter [/b/b/e/main/test/mri/tests/ruby/test_string.rb:2704]:
Expected Exception(TypeError) was raised, but the message doesn't match.
Expected /\$分行/ to match "$/ must be a String".
```

Author: andrykonchin

lib/truffle/truffle/cext.rb

@@ -2113,7 +2113,7 @@ def rb_backref_get
   end
 
   def rb_backref_set(value)
-    Truffle::RegexpOperations::LAST_MATCH_SET.call(value, rb_get_special_vars())
+    Truffle::RegexpOperations::LAST_MATCH_SET.call(nil, value, rb_get_special_vars())
   end
 
   def rb_gv_set(name, value)
@@ -2152,7 +2152,7 @@ def rb_define_hooked_variable(name, gvar, getter, setter)
         nil)
     }
 
-    setter_proc = -> value {
+    setter_proc = -> _, value {
       Primitive.call_with_c_mutex_and_frame(
         POINTER3_TO_VOID_WRAPPER,
         [setter, Primitive.cext_wrap(value), Primitive.cext_wrap(id), gvar],

spec/ruby/language/predefined_spec.rb

@@ -88,8 +88,8 @@ def obj.foo2(&proc); proc.call; end
     $~ = /foo/.match("foo")
     $~.should be_an_instance_of(MatchData)
 
-    -> { $~ = Object.new }.should raise_error(TypeError)
-    -> { $~ = 1 }.should raise_error(TypeError)
+    -> { $~ = Object.new }.should raise_error(TypeError, 'wrong argument type Object (expected MatchData)')
+    -> { $~ = 1 }.should raise_error(TypeError, 'wrong argument type Integer (expected MatchData)')
   end
 
   it "changes the value of derived capture globals when assigned" do
@@ -136,6 +136,12 @@ def obj.foo2(&proc); proc.call; end
     "abc".dup.force_encoding(Encoding::EUC_JP) =~ /b/
     $&.encoding.should equal(Encoding::EUC_JP)
   end
+
+  it "is read-only" do
+    -> {
+      eval %q{$& = ""}
+    }.should raise_error(SyntaxError, /Can't set variable \$&/)
+  end
 end
 
 describe "Predefined global $`" do
@@ -154,6 +160,12 @@ def obj.foo2(&proc); proc.call; end
     "abc".dup.force_encoding(Encoding::ISO_8859_1) =~ /a/
     $`.encoding.should equal(Encoding::ISO_8859_1)
   end
+
+  it "is read-only" do
+    -> {
+      eval %q{$` = ""}
+    }.should raise_error(SyntaxError, /Can't set variable \$`/)
+  end
 end
 
 describe "Predefined global $'" do
@@ -172,6 +184,12 @@ def obj.foo2(&proc); proc.call; end
     "abc".dup.force_encoding(Encoding::ISO_8859_1) =~ /c/
     $'.encoding.should equal(Encoding::ISO_8859_1)
   end
+
+  it "is read-only" do
+    -> {
+      eval %q{$' = ""}
+    }.should raise_error(SyntaxError, /Can't set variable \$'/)
+  end
 end
 
 describe "Predefined global $+" do
@@ -190,6 +208,12 @@ def obj.foo2(&proc); proc.call; end
     "abc".dup.force_encoding(Encoding::EUC_JP) =~ /(b)/
     $+.encoding.should equal(Encoding::EUC_JP)
   end
+
+  it "is read-only" do
+    -> {
+      eval %q{$+ = ""}
+    }.should raise_error(SyntaxError, /Can't set variable \$\+/)
+  end
 end
 
 describe "Predefined globals $1..N" do
@@ -229,7 +253,7 @@ def test(arg)
   end
 
   it "raises TypeError error if assigned to nil" do
-    -> { $stdout = nil }.should raise_error(TypeError)
+    -> { $stdout = nil }.should raise_error(TypeError, '$stdout must have write method, NilClass given')
   end
 
   it "raises TypeError error if assigned to object that doesn't respond to #write" do
@@ -253,6 +277,12 @@ def test(arg)
     $!.should == nil
   end
 
+  it "is read-only" do
+    -> {
+      $! = []
+    }.should raise_error(NameError, '$! is a read-only variable')
+  end
+
   # See http://jira.codehaus.org/browse/JRUBY-5550
   it "remains nil after a failed core class \"checked\" coercion against a class that defines method_missing" do
     $!.should == nil
@@ -512,6 +542,64 @@ def foo
   end
 end
 
+describe "Predefined global $@" do
+  it "is Fiber-local" do
+    Fiber.new do
+      raise "hi"
+    rescue
+      Fiber.yield
+    end.resume
+
+    $@.should == nil
+  end
+
+  it "is set to a backtrace of a rescued exception" do
+    begin
+      raise
+    rescue
+      $@.should be_an_instance_of(Array)
+      $@.should == $!.backtrace
+    end
+  end
+
+  it "is cleared when an exception is rescued" do
+    begin
+      raise
+    rescue
+    end
+
+    $@.should == nil
+  end
+
+  it "is not set when there is no current exception" do
+    $@.should == nil
+  end
+
+  it "is set to a backtrace of a rescued exception" do
+    begin
+      raise
+    rescue
+      $@.should be_an_instance_of(Array)
+      $@.should == $!.backtrace
+    end
+  end
+
+  it "is not read-only" do
+    begin
+      raise
+    rescue
+      $@ = []
+      $@.should == []
+    end
+  end
+
+  it "cannot be assigned when there is no a rescued exception" do
+    -> {
+      $@ = []
+    }.should raise_error(ArgumentError, '$! not set')
+  end
+end
+
 # Input/Output Variables
 # ---------------------------------------------------------------------------------------------------
 #
@@ -583,15 +671,15 @@ def foo
     obj = mock("$/ value")
     obj.should_not_receive(:to_str)
 
-    -> { $/ = obj }.should raise_error(TypeError)
+    -> { $/ = obj }.should raise_error(TypeError, 'value of $/ must be String')
   end
 
   it "raises a TypeError if assigned an Integer" do
-    -> { $/ = 1 }.should raise_error(TypeError)
+    -> { $/ = 1 }.should raise_error(TypeError, 'value of $/ must be String')
   end
 
   it "raises a TypeError if assigned a boolean" do
-    -> { $/ = true }.should raise_error(TypeError)
+    -> { $/ = true }.should raise_error(TypeError, 'value of $/ must be String')
   end
 end
 
@@ -632,15 +720,15 @@ def foo
     obj = mock("$-0 value")
     obj.should_not_receive(:to_str)
 
-    -> { $-0 = obj }.should raise_error(TypeError)
+    -> { $-0 = obj }.should raise_error(TypeError, 'value of $-0 must be String')
   end
 
   it "raises a TypeError if assigned an Integer" do
-    -> { $-0 = 1 }.should raise_error(TypeError)
+    -> { $-0 = 1 }.should raise_error(TypeError, 'value of $-0 must be String')
   end
 
   it "raises a TypeError if assigned a boolean" do
-    -> { $-0 = true }.should raise_error(TypeError)
+    -> { $-0 = true }.should raise_error(TypeError, 'value of $-0 must be String')
   end
 end
 
@@ -674,12 +762,12 @@ def foo
     obj = mock("$\\ value")
     obj.should_not_receive(:to_str)
 
-    -> { $\ = obj }.should raise_error(TypeError)
+    -> { $\ = obj }.should raise_error(TypeError, 'value of $\ must be String')
   end
 
   it "raises a TypeError if assigned not String" do
-    -> { $\ = 1 }.should raise_error(TypeError)
-    -> { $\ = true }.should raise_error(TypeError)
+    -> { $\ = 1 }.should raise_error(TypeError, 'value of $\ must be String')
+    -> { $\ = true }.should raise_error(TypeError, 'value of $\ must be String')
   end
 end
 
@@ -693,7 +781,7 @@ def foo
   end
 
   it "raises TypeError if assigned a non-String" do
-    -> { $, = Object.new }.should raise_error(TypeError)
+    -> { $, = Object.new }.should raise_error(TypeError, 'value of $, must be String')
   end
 
   it "warns if assigned non-nil" do
@@ -878,15 +966,15 @@ def obj.foo2; yield; end
   it "is read-only" do
     -> {
       $: = []
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$: is a read-only variable')
 
     -> {
       $LOAD_PATH = []
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$LOAD_PATH is a read-only variable')
 
     -> {
       $-I = []
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$-I is a read-only variable')
   end
 
   it "default $LOAD_PATH entries until sitelibdir included have @gem_prelude_index set" do
@@ -908,35 +996,35 @@ def obj.foo2; yield; end
   it "is read-only" do
     -> {
       $" = []
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$" is a read-only variable')
 
     -> {
       $LOADED_FEATURES = []
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$LOADED_FEATURES is a read-only variable')
   end
 end
 
 describe "Global variable $<" do
   it "is read-only" do
     -> {
       $< = nil
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$< is a read-only variable')
   end
 end
 
 describe "Global variable $FILENAME" do
   it "is read-only" do
     -> {
       $FILENAME = "-"
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$FILENAME is a read-only variable')
   end
 end
 
 describe "Global variable $?" do
   it "is read-only" do
     -> {
       $? = nil
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$? is a read-only variable')
   end
 
   it "is thread-local" do
@@ -947,19 +1035,19 @@ def obj.foo2; yield; end
 
 describe "Global variable $-a" do
   it "is read-only" do
-    -> { $-a = true }.should raise_error(NameError)
+    -> { $-a = true }.should raise_error(NameError, '$-a is a read-only variable')
   end
 end
 
 describe "Global variable $-l" do
   it "is read-only" do
-    -> { $-l = true }.should raise_error(NameError)
+    -> { $-l = true }.should raise_error(NameError, '$-l is a read-only variable')
   end
 end
 
 describe "Global variable $-p" do
   it "is read-only" do
-    -> { $-p = true }.should raise_error(NameError)
+    -> { $-p = true }.should raise_error(NameError, '$-p is a read-only variable')
   end
 end
 

src/main/java/org/truffleruby/language/globals/WriteGlobalVariableNode.java

@@ -52,24 +52,27 @@ Object write(VirtualFrame frame, Object value,
         return value;
     }
 
-    @Specialization(guards = { "storage.hasHooks()", "arity != 2" })
+    @Specialization(guards = { "storage.hasHooks()", "arity != 3" })
     Object writeHooks(VirtualFrame frame, Object value,
             @Bind("getStorage(frame)") GlobalVariableStorage storage,
             @Bind("setterArity(storage)") int arity,
+            @Bind("name") String boundName,
             @Cached @Exclusive CallBlockNode yieldNode) {
-        yieldNode.yield(this, storage.getSetter(), value);
+        yieldNode.yield(this, storage.getSetter(), boundName, value);
         return value;
     }
 
-    @Specialization(guards = { "storage.hasHooks()", "arity == 2" })
-    static Object writeHooksWithStorage(VirtualFrame frame, Object value,
+    @Specialization(guards = { "storage.hasHooks()", "arity == 3" })
+    Object writeHooksWithStorage(VirtualFrame frame, Object value,
             @Bind("getStorage(frame)") GlobalVariableStorage storage,
             @Bind("setterArity(storage)") int arity,
+            @Bind("name") String boundName,
             @Cached @Exclusive CallBlockNode yieldNode,
             @Cached GetSpecialVariableStorage storageNode,
             @Bind Node node) {
         yieldNode.yield(node,
                 storage.getSetter(),
+                boundName,
                 value,
                 storageNode.execute(frame, node));
         return value;

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

@@ -637,5 +637,5 @@ def advance!
 Truffle::KernelOperations.define_hooked_variable(
   :$.,
   -> { ARGF.instance_variable_get(:@last_lineno) },
-  -> value { value = Primitive.rb_to_int(value)
-             ARGF.instance_variable_set(:@last_lineno, value) } )
+  -> _, value { value = Primitive.rb_to_int(value)
+                ARGF.instance_variable_set(:@last_lineno, value) } )

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

@@ -2488,4 +2488,4 @@ def write_nonblock(data, **options)
 Truffle::KernelOperations.define_hooked_variable(
   :$_,
   -> s { Primitive.io_last_line_get(s) },
-  -> v, s { Primitive.io_last_line_set(s, v) })
+  -> _, v, s { Primitive.io_last_line_set(s, v) })

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

@@ -927,7 +927,7 @@ def switch
 Truffle::KernelOperations.define_hooked_variable(
   :'$0',
   -> { Primitive.global_variable_get :'$0' },
-  -> v {
+  -> _, v {
     v = StringValue(v)
     Process.setproctitle(v)
     Primitive.global_variable_set :'$0', v

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

@@ -377,6 +377,6 @@ def marshal_dump
 Truffle::KernelOperations.define_hooked_variable(
   :$@,
   -> { $!.backtrace if $! },
-  -> value { raise ArgumentError, '$! not set' unless $!
-             $!.set_backtrace value }
+  -> _, value { raise ArgumentError, '$! not set' unless $!
+                $!.set_backtrace value }
 )