Fixed #228: incorrect SymbolLiteral#to_s. Also fixed Symbol#inspect

spec/compiler/parser/to_s_spec.cr

@@ -29,4 +29,12 @@ describe "ASTNode#to_s" do
   it "puts parenthesis in call argument if it's a cast" do
     Parser.parse("foo(a as Int32)").to_s.should eq("foo((a as Int32))")
   end
+
+  it "correctly convert a symbol that doesn't need qoutes" do
+    Parser.parse(%(:foo)).to_s.should eq(%(:foo))
+  end
+
+  it "correctly convert a symbol that needs qoutes" do
+    Parser.parse(%(:"{")).to_s.should eq(%(:"{"))
+  end
 end

spec/std/symbol_spec.cr

@@ -0,0 +1,10 @@
+require "spec"
+
+describe Symbol do
+  it "inspects" do
+    :foo.inspect.should eq(%(:foo))
+    :"{".inspect.should eq(%(:"{"))
+    :"hi there".inspect.should eq(%(:"hi there"))
+    # :かたな.inspect.should eq(%(:かたな))
+  end
+end

src/compiler/crystal/syntax/to_s.cr

@@ -40,15 +40,22 @@ module Crystal
     end
 
     def visit(node : CharLiteral)
-      @str << node.value.inspect
+      node.value.inspect(@str)
     end
 
     def visit(node : SymbolLiteral)
-      @str << ":" << node.value
+      @str << ':'
+
+      value = node.value
+      if Symbol.needs_quotes?(value)
+        value.inspect(@str)
+      else
+        value.to_s(@str)
+      end
     end
 
     def visit(node : StringLiteral)
-      @str << node.value.inspect
+      node.value.inspect(@str)
     end
 
     def visit(node : StringInterpolation)

src/symbol.cr

@@ -1,10 +1,29 @@
 struct Symbol
   def inspect(io : IO)
     io << ":"
-    to_s io
+
+    value = to_s
+    if Symbol.needs_quotes?(value)
+      value.inspect(io)
+    else
+      value.to_s(io)
+    end
   end
 
   def to_s(io : IO)
     io << to_s
   end
+
+  # Determines if a string needs to be quoted to be used for a symbol.
+  def self.needs_quotes?(string)
+    string.each_char do |char|
+      case char
+      when '0'..'9', 'A'..'Z', 'a'..'z', '_'
+        # Nothing
+      else
+        return true
+      end
+    end
+    false
+  end
 end