Use Char for single char strings (crystal-lang#5882)

samples/sdl/tv.cr

@@ -87,7 +87,7 @@ end
 
 def parse_rectangles
   rects = [] of Rectangle
-  lines = File.read("#{__DIR__}/tv.txt").split("\n").map { |line| line.rstrip }
+  lines = File.read("#{__DIR__}/tv.txt").split('\n').map { |line| line.rstrip }
   lines.each_with_index do |line, y|
     x = 0
     line.each_char do |c|

samples/sudoku.cr

@@ -148,7 +148,7 @@ sudoku = "
 
 def solve_all(sudoku)
   mr, mc = sd_genmat()
-  sudoku.split("\n").map do |line|
+  sudoku.split('\n').map do |line|
     if line.size >= 81
       ret = sd_solve(mr, mc, line)
       ret.map { |s2| s2.join }

scripts/generate_windows_zone_names.cr

@@ -51,7 +51,7 @@ hash_items = String.build do |io|
     entry[:key].inspect(io)
     io << " => "
     entry[:zones].inspect(io)
-    io << ", # " << entry[:tzdata_name] << "\n"
+    io << ", # " << entry[:tzdata_name] << '\n'
   end
 end
 

spec/compiler/crystal/tools/expand_spec.cr

@@ -620,6 +620,6 @@ describe "expand" do
     end
     CODE
 
-    assert_expand_simple code, original: "foo(hello)", expanded: expanded + "\n"
+    assert_expand_simple code, original: "foo(hello)", expanded: expanded + '\n'
   end
 end

spec/std/ecr/ecr_spec.cr

@@ -27,7 +27,7 @@ describe "ECR" do
       %(__str__ << " "),
       %(__str__ << "<% \\"string\\" %>"),
     ]
-    program.should eq(pieces.join("\n") + "\n")
+    program.should eq(pieces.join('\n') + '\n')
   end
 
   it "does ECR.def_to_s" do

spec/std/http/formdata/builder_spec.cr

@@ -35,7 +35,7 @@ describe HTTP::FormData::Builder do
       --fixed-boundary--
       MULTIPART
 
-    generated.should eq(expected.gsub("\n", "\r\n"))
+    generated.should eq(expected.gsub('\n', "\r\n"))
   end
 
   describe "#field" do
@@ -54,7 +54,7 @@ describe HTTP::FormData::Builder do
         --fixed-boundary--
         MULTIPART
 
-      generated.should eq(expected.gsub("\n", "\r\n"))
+      generated.should eq(expected.gsub('\n', "\r\n"))
     end
   end
 

spec/std/http/formdata/parser_spec.cr

@@ -23,7 +23,7 @@ describe HTTP::FormData::Parser do
       -----------------------------735323031399963166993862150--
       FORMDATA
 
-    parser = HTTP::FormData::Parser.new IO::Memory.new(formdata.gsub("\n", "\r\n")), "---------------------------735323031399963166993862150"
+    parser = HTTP::FormData::Parser.new IO::Memory.new(formdata.gsub('\n', "\r\n")), "---------------------------735323031399963166993862150"
 
     runs = 0
     while parser.has_next?

spec/std/http/headers_spec.cr

@@ -28,7 +28,7 @@ describe HTTP::Headers do
     headers = HTTP::Headers{"FOO_BAR" => "bar", "Foobar-foo" => "baz"}
     serialized = String.build do |io|
       headers.each do |name, values|
-        io << name << ": " << values.first << ";"
+        io << name << ": " << values.first << ';'
       end
     end
 

spec/std/http/multipart/builder_spec.cr

@@ -25,7 +25,7 @@ describe HTTP::Multipart::Builder do
       --fixed-boundary--
       MULTIPART
 
-    io.to_s.should eq(expected_message.gsub("\n", "\r\n"))
+    io.to_s.should eq(expected_message.gsub('\n', "\r\n"))
   end
 
   it "generates valid multipart messages with preamble and epilogue" do
@@ -59,7 +59,7 @@ describe HTTP::Multipart::Builder do
       Irelevant textMuch more irelevant text
       MULTIPART
 
-    io.to_s.should eq(expected_message.gsub("\n", "\r\n"))
+    io.to_s.should eq(expected_message.gsub('\n', "\r\n"))
   end
 
   describe "#content_type" do
@@ -99,7 +99,7 @@ describe HTTP::Multipart::Builder do
         --boundary--
         MULTIPART
 
-      generated_multipart.should eq(expected_multipart.gsub("\n", "\r\n"))
+      generated_multipart.should eq(expected_multipart.gsub('\n', "\r\n"))
     end
 
     it "raises when called after starting the body" do
@@ -156,7 +156,7 @@ describe HTTP::Multipart::Builder do
         --boundary--
         MULTIPART
 
-      generated_multipart.should eq(expected_multipart.gsub("\n", "\r\n"))
+      generated_multipart.should eq(expected_multipart.gsub('\n', "\r\n"))
     end
 
     it "raises when called after finishing" do
@@ -211,7 +211,7 @@ describe HTTP::Multipart::Builder do
 
         MULTIPART
 
-      generated_multipart.should eq(expected_multipart.gsub("\n", "\r\n"))
+      generated_multipart.should eq(expected_multipart.gsub('\n', "\r\n"))
     end
 
     it "raises when called after finishing" do

spec/std/http/multipart/parser_spec.cr

@@ -2,7 +2,7 @@ require "spec"
 require "http"
 
 private def parse(delim, data, *, gsub = true)
-  data_io = IO::Memory.new(gsub ? data.gsub("\n", "\r\n") : data)
+  data_io = IO::Memory.new(gsub ? data.gsub('\n', "\r\n") : data)
   parser = HTTP::Multipart::Parser.new(data_io, delim)
 
   parsed = [] of {headers: HTTP::Headers, body: String}
@@ -89,7 +89,7 @@ describe HTTP::Multipart::Parser do
       Foo
       --AaB03x--
       MULTIPART
-    parser = HTTP::Multipart::Parser.new(IO::Memory.new(input.gsub("\n", "\r\n")), "AaB03x")
+    parser = HTTP::Multipart::Parser.new(IO::Memory.new(input.gsub('\n', "\r\n")), "AaB03x")
 
     parser.next { }
     parser.has_next?.should eq(false)
@@ -126,7 +126,7 @@ describe HTTP::Multipart::Parser do
       --b--
       MULTIPART
 
-    parser = HTTP::Multipart::Parser.new(IO::Memory.new(input.gsub("\n", "\r\n")), "b")
+    parser = HTTP::Multipart::Parser.new(IO::Memory.new(input.gsub('\n', "\r\n")), "b")
 
     ios = [] of IO
 

spec/std/http/server/server_spec.cr

@@ -350,5 +350,5 @@ module HTTP
 end
 
 private def requestize(string)
-  string.gsub("\n", "\r\n")
+  string.gsub('\n', "\r\n")
 end

spec/std/io/io_spec.cr

@@ -243,9 +243,9 @@ describe IO do
 
     it "gets with single byte string as delimiter" do
       io = SimpleIOMemory.new("hello\nworld\nbye")
-      io.gets("\n").should eq("hello\n")
-      io.gets("\n").should eq("world\n")
-      io.gets("\n").should eq("bye")
+      io.gets('\n').should eq("hello\n")
+      io.gets('\n').should eq("world\n")
+      io.gets('\n').should eq("bye")
     end
 
     it "does gets with limit" do

spec/std/logger_spec.cr

@@ -45,7 +45,7 @@ describe "Logger" do
     IO.pipe do |r, w|
       logger = Logger.new(w)
       logger.formatter = Logger::Formatter.new do |severity, datetime, progname, message, io|
-        io << severity.to_s[0] << " " << progname << ": " << message
+        io << severity.to_s[0] << ' ' << progname << ": " << message
       end
       logger.warn "message", "prog"
 

spec/std/spec/junit_formatter_spec.cr

@@ -100,7 +100,7 @@ describe "JUnit Formatter" do
     name.should eq("Something happened")
 
     backtrace = xml.xpath_string("string(//testsuite/testcase[1]/failure/text())")
-    backtrace.should eq(cause.backtrace.join("\n"))
+    backtrace.should eq(cause.backtrace.join('\n'))
   end
 
   it "report error stacktrace if present" do
@@ -115,7 +115,7 @@ describe "JUnit Formatter" do
     name.should eq("Something happened")
 
     backtrace = xml.xpath_string("string(//testsuite/testcase[1]/error/text())")
-    backtrace.should eq(cause.backtrace.join("\n"))
+    backtrace.should eq(cause.backtrace.join('\n'))
   end
 end
 

src/array.cr

@@ -1657,9 +1657,9 @@ class Array(T)
 
   def to_s(io : IO)
     executed = exec_recursive(:to_s) do
-      io << "["
+      io << '['
       join ", ", io, &.inspect(io)
-      io << "]"
+      io << ']'
     end
     io << "[...]" unless executed
   end

src/bit_array.cr

@@ -209,9 +209,9 @@ struct BitArray
   def to_s(io : IO)
     io << "BitArray["
     each do |value|
-      io << (value ? "1" : "0")
+      io << (value ? '1' : '0')
     end
-    io << "]"
+    io << ']'
   end
 
   # ditto

src/char.cr

@@ -479,7 +479,7 @@ struct Char
       if ascii_control?
         io << "\\u{"
         ord.to_s(16, io)
-        io << "}"
+        io << '}'
       else
         to_s(io)
       end
@@ -507,7 +507,7 @@ struct Char
       if ascii_control? || ord >= 0x80
         io << "\\u{"
         ord.to_s(16, io)
-        io << "}"
+        io << '}'
       else
         to_s(io)
       end

src/colorize.cr

@@ -160,14 +160,14 @@ struct Colorize::Object(T)
   private BACK_LIGHT_CYAN    = "106"
   private BACK_WHITE         = "107"
 
-  private MODE_DEFAULT   = "0"
-  private MODE_BOLD      = "1"
-  private MODE_BRIGHT    = "1"
-  private MODE_DIM       = "2"
-  private MODE_UNDERLINE = "4"
-  private MODE_BLINK     = "5"
-  private MODE_REVERSE   = "7"
-  private MODE_HIDDEN    = "8"
+  private MODE_DEFAULT   = '0'
+  private MODE_BOLD      = '1'
+  private MODE_BRIGHT    = '1'
+  private MODE_DIM       = '2'
+  private MODE_UNDERLINE = '4'
+  private MODE_BLINK     = '5'
+  private MODE_REVERSE   = '7'
+  private MODE_HIDDEN    = '8'
 
   private MODE_BOLD_FLAG      =  1
   private MODE_BRIGHT_FLAG    =  1
@@ -304,13 +304,13 @@ struct Colorize::Object(T)
       end
 
       unless fore_is_default
-        io << ";" if printed
+        io << ';' if printed
         io << @fore
         printed = true
       end
 
       unless back_is_default
-        io << ";" if printed
+        io << ';' if printed
         io << @back
         printed = true
       end
@@ -319,14 +319,14 @@ struct Colorize::Object(T)
         # Can't reuse MODES constant because it has bold/bright duplicated
         {% for name in %w(bold dim underline blink reverse hidden) %}
           if @mode.bits_set? MODE_{{name.upcase.id}}_FLAG
-            io << ";" if printed
+            io << ';' if printed
             io << MODE_{{name.upcase.id}}
             printed = true
           end
         {% end %}
       end
 
-      io << "m"
+      io << 'm'
 
       true
     end

src/compiler/crystal/codegen/asm.cr

@@ -16,22 +16,22 @@ class Crystal::CodeGenVisitor
     input_values = [] of LLVM::Value
 
     if inputs = node.inputs
-      constraints << "," unless constraints.empty?
+      constraints << ',' unless constraints.empty?
 
       inputs.each_with_index do |input, i|
         accept input.exp
         input_types << llvm_type(input.exp.type)
         input_values << @last
-        constraints << "," if i > 0
+        constraints << ',' if i > 0
         constraints << input.constraint
       end
     end
 
     if clobbers = node.clobbers
-      constraints << "," unless constraints.empty?
+      constraints << ',' unless constraints.empty?
 
       clobbers.each_with_index do |clobber, i|
-        constraints << "," if i > 0
+        constraints << ',' if i > 0
         constraints << "~{"
         constraints << clobber
         constraints << '}'

src/compiler/crystal/codegen/ast.cr

@@ -37,36 +37,36 @@ module Crystal
 
     def mangled_name(program, self_type)
       name = String.build do |str|
-        str << "*"
+        str << '*'
 
         if owner = @owner
           if owner.metaclass?
             self_type.instance_type.llvm_name(str)
             if original_owner != self_type
-              str << "@"
+              str << '@'
               original_owner.instance_type.llvm_name(str)
             end
             str << "::"
           elsif !owner.is_a?(Crystal::Program)
             self_type.llvm_name(str)
             if original_owner != self_type
-              str << "@"
+              str << '@'
               original_owner.llvm_name(str)
             end
-            str << "#"
+            str << '#'
           end
         end
 
         str << self.name.gsub('@', '.')
 
         next_def = self.next
         while next_def
-          str << "'"
+          str << '\''
           next_def = next_def.next
         end
 
         if args.size > 0 || uses_block_arg?
-          str << "<"
+          str << '<'
           if args.size > 0
             args.each_with_index do |arg, i|
               str << ", " if i > 0
@@ -75,13 +75,13 @@ module Crystal
           end
           if uses_block_arg?
             str << ", " if args.size > 0
-            str << "&"
+            str << '&'
             block_arg.not_nil!.type.llvm_name(str)
           end
-          str << ">"
+          str << '>'
         end
         if return_type = @type
-          str << ":"
+          str << ':'
           return_type.llvm_name(str)
         end
       end

src/compiler/crystal/codegen/cache_dir.cr

@@ -92,7 +92,7 @@ module Crystal
         io.puts "Crystal needs a cache directory. These directories were candidates for it:"
         io.puts
         candidates.each do |candidate|
-          io << " - " << candidate << "\n"
+          io << " - " << candidate << '\n'
         end
         io.puts
         io.puts "but none of them are writable."