String/Character escape sequence \e

[!INCLUDESpecletdisclaimer]

Champion issue: https://github.com/dotnet/csharplang/issues/8657

Summary

An addition of the string/character escape sequence \e as a shortcut/short-hand replacement for the character code point 0x1b, commonly known as the ESCAPE (or ESC) character.
This character is currently accessible using one of the following escape sequences:

• \u001b
• \U0000001b
• \x1b (not recommended, see the picture attached at the bottom.)

With the implementation of this proposal, the following assertions should be true:

char escape_char = '\e';

Assert.IsTrue(escape_char == (char)0x1b, "...");
Assert.IsTrue(escape_char == '\u001b', "...");
Assert.IsTrue(escape_char == '\U0000001b', "...");
Assert.IsTrue(escape_char == '\x1b', "...");

Detailed design

The language syntax specification is changed as follows in section 6.4.5.5:

fragment Simple_Escape_Sequence
-    : '\\\'' | '\\"' | '\\\\' | '\\0' | '\\a' | '\\b' | '\\f' | '\\n' | '\\r' | '\\t' | '\\v'
+    : '\\\'' | '\\"' | '\\\\' | '\\0' | '\\a' | '\\b' | '\\f' | '\\n' | '\\r' | '\\t' | '\\v' | '\\e'
    ;

As well as the addition of the last line to the following table in the specifications:

A simple escape sequence represents a Unicode character, as described in the table below.

Escape sequence	Character name	Unicode code point
\'	Single quote	U+0027
...	...	...
\e	Escape character	U+001B

The type of a Character_Literal is char.