Add spec identifier syntax to input-format.md

src/input-format.md

@@ -1,26 +1,41 @@
 # Input format
 
+r[input]
+
+r[input.intro]
 This chapter describes how a source file is interpreted as a sequence of tokens.
 
 See [Crates and source files] for a description of how programs are organised into files.
 
 ## Source encoding
 
+r[input.encoding]
+
+r[input.encoding.utf8]
 Each source file is interpreted as a sequence of Unicode characters encoded in UTF-8.
+
+r[input.encoding.invalid]
 It is an error if the file is not valid UTF-8.
 
 ## Byte order mark removal
 
+r[input.byte-order-mark]
+
 If the first character in the sequence is `U+FEFF` ([BYTE ORDER MARK]), it is removed.
 
 ## CRLF normalization
 
+r[input.crlf]
+
 Each pair of characters `U+000D` (CR) immediately followed by `U+000A` (LF) is replaced by a single `U+000A` (LF).
 
 Other occurrences of the character `U+000D` (CR) are left in place (they are treated as [whitespace]).
 
 ## Shebang removal
 
+r[input.shebang]
+
+r[input.shebang.intro]
 If the remaining sequence begins with the characters `#!`, the characters up to and including the first `U+000A` (LF) are removed from the sequence.
 
 For example, the first line of the following file would be ignored:
@@ -34,15 +49,17 @@ fn main() {
 }
 ```
 
+r[input.shebang.inner-attribute]
 As an exception, if the `#!` characters are followed (ignoring intervening [comments] or [whitespace]) by a `[` token, nothing is removed.
 This prevents an [inner attribute] at the start of a source file being removed.
 
 > **Note**: The standard library [`include!`] macro applies byte order mark removal, CRLF normalization, and shebang removal to the file it reads. The [`include_str!`] and [`include_bytes!`] macros do not.
 
 ## Tokenization
 
-The resulting sequence of characters is then converted into tokens as described in the remainder of this chapter.
+r[input.tokenization]
 
+The resulting sequence of characters is then converted into tokens as described in the remainder of this chapter.
 
 [`include!`]: ../std/macro.include.md
 [`include_bytes!`]: ../std/macro.include_bytes.md