render Regex and SubstitionString correctly for repr (#39422)

Fixes #29580

(cherry picked from commit 26fd3c8)

Author: vtjnash

base/regex.jl

@@ -119,8 +119,9 @@ function show(io::IO, re::Regex)
     imsxa = PCRE.CASELESS|PCRE.MULTILINE|PCRE.DOTALL|PCRE.EXTENDED|PCRE.UCP
     opts = re.compile_options
     if (opts & ~imsxa) == (DEFAULT_COMPILER_OPTS & ~imsxa)
-        print(io, 'r')
-        print_quoted_literal(io, re.pattern)
+        print(io, "r\"")
+        escape_raw_string(io, re.pattern)
+        print(io, "\"")
         if (opts & PCRE.CASELESS ) != 0; print(io, 'i'); end
         if (opts & PCRE.MULTILINE) != 0; print(io, 'm'); end
         if (opts & PCRE.DOTALL   ) != 0; print(io, 's'); end
@@ -456,8 +457,9 @@ isvalid(s::SubstitutionString, i::Integer) = isvalid(s.string, i)::Bool
 iterate(s::SubstitutionString, i::Integer...) = iterate(s.string, i...)::Union{Nothing,Tuple{AbstractChar,Int}}
 
 function show(io::IO, s::SubstitutionString)
-    print(io, "s")
-    print_quoted_literal(io, s.string)
+    print(io, "s\"")
+    escape_raw_string(io, s.string)
+    print(io, "\"")
 end
 
 """

base/strings/io.jl

@@ -186,16 +186,6 @@ write(io::IO, s::Union{String,SubString{String}}) =
     GC.@preserve s Int(unsafe_write(io, pointer(s), reinterpret(UInt, sizeof(s))))::Int
 print(io::IO, s::Union{String,SubString{String}}) = (write(io, s); nothing)
 
-## printing literal quoted string data ##
-
-# this is the inverse of print_unescaped_chars(io, s, "\\\")
-
-function print_quoted_literal(io, s::AbstractString)
-    print(io, '"')
-    for c = s; c == '"' ? print(io, "\\\"") : print(io, c); end
-    print(io, '"')
-end
-
 """
     repr(x; context=nothing)
 

test/regex.jl

@@ -34,11 +34,6 @@
     @test map(m -> m.match, eachmatch(r"(\p{L}+)", "Tú lees.")) == ["Tú", "lees"]
     @test map(m -> m.match, eachmatch(r"(\p{L}+)", "¿Cuál es tu pregunta?")) == ["Cuál", "es", "tu", "pregunta"]
 
-    # Issue 9545 (32 bit)
-    buf = PipeBuffer()
-    show(buf, r"")
-    @test read(buf, String) == "r\"\""
-
     # see #10994, #11447: PCRE2 allows NUL chars in the pattern
     @test occursin(Regex("^a\0b\$"), "a\0b")
 
@@ -52,12 +47,17 @@
     subst = s"FROM: \g<name>\n MESSAGE: \1"
     @test replace(msg, re => subst) == "FROM: Julia\n MESSAGE: Hello"
 
+    # Issue #9545 (32 bit)
+    @test repr(r"") == "r\"\""
     # Issue #36550
-    @test repr(s"\x") == "s\"\\x\""
-    @test repr(s"\\x") == "s\"\\\\x\""
-    @test repr(s"\\\x") == "s\"\\\\\\x\""
-    @test repr(s"x\\") == "s\"x\\\""
-    @test repr(s"a\1b") == "s\"a\\1b\""
+    @test repr(s"\x") == raw"s\"\x\""
+    @test repr(s"\\x") == raw"s\"\\x\""
+    @test repr(s"\\\x") == raw"s\"\\\x\""
+    @test repr(s"x\\") == raw"s\"x\\\\\""
+    @test repr(s"a\1b") == raw"s\"a\1b\""
+    # Issue #29580
+    @test repr(r"\\\"") == raw"r\"\\\\\\\"\""
+    @test repr(s"\\\"\\") == raw"s\"\\\\\\\"\\\\\""
 
     # findall
     @test findall(r"\w+", "foo bar") == [1:3, 5:7]