[stdlib] Faster repr() logic for String, StringRef, UInt, DType and others

docs/changelog.md

@@ -16,6 +16,9 @@ what we publish.
 
 ### ⭐️ New
 
+- `StringRef` is now representable so `repr(StringRef("hello"))` will return
+  `StringRef('hello')`.
+
 - Mojo can now interpret simple LLVM intrinsics in parameter expressions,
   enabling things like `count_leading_zeros` to work at compile time:
   [Issue #933](https://github.com/modularml/mojo/issues/933).

stdlib/src/builtin/dtype.mojo

@@ -217,7 +217,7 @@ struct DType(
         Returns:
             The representation of the dtype.
         """
-        return "DType." + str(self)
+        return String.write("DType.", self)
 
     @always_inline("nodebug")
     fn get_value(self) -> __mlir_type.`!kgen.dtype`:

stdlib/src/builtin/error.mojo

@@ -180,7 +180,7 @@ struct Error(
         Returns:
             A printable representation of the error message.
         """
-        return "Error(" + repr(self._message()) + ")"
+        return String.write("Error(", repr(self._message()), ")")
 
     # ===-------------------------------------------------------------------===#
     # Methods

stdlib/src/builtin/uint.mojo

@@ -149,7 +149,7 @@ struct UInt(IntLike, _HashableWithHasher):
         Returns:
             The string representation of this UInt.
         """
-        return "UInt(" + str(self) + ")"
+        return String.write("UInt(", str(self), ")")
 
     fn __hash__(self) -> UInt:
         """Hash the UInt using builtin hash.

stdlib/src/os/fstat.mojo

@@ -46,7 +46,7 @@ fn _constrain_unix():
 
 
 @value
-struct stat_result(Stringable):
+struct stat_result(Stringable, Writable):
     """Object whose fields correspond  to the members of the stat structure."""
 
     var st_mode: Int
@@ -150,30 +150,43 @@ struct stat_result(Stringable):
         self.st_rdev = st_rdev
         self.st_flags = st_flags
 
+    @no_inline
+    fn write_to[W: Writer](self, inout writer: W):
+        """
+        Formats this path to the provided Writer.
+
+        Parameters:
+            W: A type conforming to the Writable trait.
+
+        Args:
+            writer: The object to write to.
+        """
+        writer.write("os.stat_result(")
+        writer.write("st_mode=", self.st_mode)
+        writer.write(", st_ino=", self.st_ino)
+        writer.write(", st_dev=", self.st_dev)
+        writer.write(", st_nlink=", self.st_nlink)
+        writer.write(", st_uid=", self.st_uid)
+        writer.write(", st_gid=", self.st_gid)
+        writer.write(", st_size=", self.st_size)
+        writer.write(", st_atime=", str(self.st_atimespec))
+        writer.write(", st_mtime=", str(self.st_mtimespec))
+        writer.write(", st_ctime=", str(self.st_ctimespec))
+        writer.write(", st_birthtime=", str(self.st_birthtimespec))
+        writer.write(", st_blocks=", self.st_blocks)
+        writer.write(", st_blksize=", self.st_blksize)
+        writer.write(", st_rdev=", self.st_rdev)
+        writer.write(", st_flags=", self.st_flags)
+        writer.write(")")
+
     @no_inline
     fn __str__(self) -> String:
         """Constructs a string representation of stat_result.
 
         Returns:
           A string representation of stat_result.
         """
-        var res = String("os.stat_result(")
-        res += "st_mode=" + str(self.st_mode)
-        res += ", st_ino=" + str(self.st_ino)
-        res += ", st_dev=" + str(self.st_dev)
-        res += ", st_nlink=" + str(self.st_nlink)
-        res += ", st_uid=" + str(self.st_uid)
-        res += ", st_gid=" + str(self.st_gid)
-        res += ", st_size=" + str(self.st_size)
-        res += ", st_atime=" + str(self.st_atimespec)
-        res += ", st_mtime=" + str(self.st_mtimespec)
-        res += ", st_ctime=" + str(self.st_ctimespec)
-        res += ", st_birthtime=" + str(self.st_birthtimespec)
-        res += ", st_blocks=" + str(self.st_blocks)
-        res += ", st_blksize=" + str(self.st_blksize)
-        res += ", st_rdev=" + str(self.st_rdev)
-        res += ", st_flags=" + str(self.st_flags)
-        return res + ")"
+        return String.write(self)
 
     fn __repr__(self) -> String:
         """Constructs a representation of stat_result.

stdlib/src/utils/stringref.mojo

@@ -41,17 +41,18 @@ fn _align_down(value: Int, alignment: Int) -> Int:
 @value
 @register_passable("trivial")
 struct StringRef(
-    Sized,
-    IntableRaising,
+    AsBytes,
+    Boolable,
     CollectionElement,
     CollectionElementNew,
+    Comparable,
+    Hashable,
+    IntableRaising,
+    Representable,
+    Sized,
     Stringable,
     Writable,
-    Hashable,
     _HashableWithHasher,
-    Boolable,
-    Comparable,
-    AsBytes,
 ):
     """
     Represent a constant reference to a string, i.e. a sequence of characters
@@ -396,6 +397,15 @@ struct StringRef(
         """
         return String.write(self)
 
+    @no_inline
+    fn __repr__(self) -> String:
+        """Convert the string reference to a string.
+
+        Returns:
+            The String representation of the StringRef.
+        """
+        return String.write("StringRef(", repr(str(self)), ")")
+
     @no_inline
     fn write_to[W: Writer](self, inout writer: W):
         """

stdlib/test/pathlib/test_pathlib.mojo

@@ -148,6 +148,34 @@ def test_home():
     set_home(original_home)
 
 
+def test_stat():
+    var path = Path(__source_location().file_name)
+    var stat = path.stat()
+    assert_equal(
+        str(stat),
+        "os.stat_result(st_mode={}, st_ino={}, st_dev={}, st_nlink={},"
+        " st_uid={}, st_gid={}, st_size={}, st_atime={}, st_mtime={},"
+        " st_ctime={}, st_birthtime={}, st_blocks={}, st_blksize={},"
+        " st_rdev={}, st_flags={})".format(
+            stat.st_mode,
+            stat.st_ino,
+            stat.st_dev,
+            stat.st_nlink,
+            stat.st_uid,
+            stat.st_gid,
+            stat.st_size,
+            str(stat.st_atimespec),
+            str(stat.st_mtimespec),
+            str(stat.st_ctimespec),
+            str(stat.st_birthtimespec),
+            stat.st_blocks,
+            stat.st_blksize,
+            stat.st_rdev,
+            stat.st_flags,
+        ),
+    )
+
+
 def main():
     test_cwd()
     test_path()
@@ -159,3 +187,4 @@ def main():
     test_read_write()
     test_expand_user()
     test_home()
+    test_stat()

stdlib/test/utils/test_stringref.mojo

@@ -169,6 +169,25 @@ fn test_stringref_split() raises:
     assert_equal(res4[1], "o")
 
 
+def test_str_and_ref():
+    assert_equal(StringRef("abc").__str__(), "abc")
+    assert_equal(StringRef("abc").__repr__(), "StringRef('abc')")
+    assert_equal(StringRef("\0").__repr__(), r"StringRef('\x00')")
+    assert_equal(StringRef("\x09").__repr__(), r"StringRef('\t')")
+    assert_equal(StringRef("\n").__repr__(), r"StringRef('\n')")
+    assert_equal(StringRef("\x0d").__repr__(), r"StringRef('\r')")
+    assert_equal(StringRef("'").__repr__(), 'StringRef("\'")')
+
+    # Multi-byte characters.__repr__()
+    assert_equal(
+        StringRef("Örnsköldsvik").__repr__(), "StringRef('Örnsköldsvik')"
+    )  # 2-byte
+    assert_equal(StringRef("你好!").__repr__(), "StringRef('你好!')")  # 3-byte
+    assert_equal(
+        StringRef("hello 🔥!").__repr__(), "StringRef('hello 🔥!')"
+    )  # 4-byte
+
+
 def main():
     test_strref_from_start()
     test_stringref_split()
@@ -177,3 +196,4 @@ def main():
     test_indexing()
     test_find()
     test_endswith()
+    test_str_and_ref()