Add float literal's grammar
@@ -264,6 +264,22 @@ a single integer literal.
#### Floating-point literals
+> **<sup>Lexer</sup>**
+> FLOAT_LITERAL :
+> &nbsp;&nbsp; &nbsp;&nbsp; DEC_LITERAL `.`
+> _(not immediately followed by `.`, `_` or an identifier_)
+> &nbsp;&nbsp; | DEC_LITERAL FLOAT_EXPONENT
+> &nbsp;&nbsp; | DEC_LITERAL `.` DEC_LITERAL FLOAT_EXPONENT<sup>?</sup>
+> &nbsp;&nbsp; | DEC_LITERAL (`.` DEC_LITERAL)<sup>?</sup>
+> FLOAT_EXPONENT<sup>?</sup> FLOAT_SUFFIX
+>
+> FLOAT_EXPONENT :
+> &nbsp;&nbsp; (`e`|`E`) (`+`|`-`)?
+> (DEC_DIGIT|`_`)<sup>\*</sup> DEC_DIGIT (DEC_DIGIT|`_`)<sup>\*</sup>
+>
+> FLOAT_SUFFIX :
+> &nbsp;&nbsp; `f32` | `f64`
+
A _floating-point literal_ has one of two forms:
* A _decimal literal_ followed by a period character `U+002E` (`.`). This is
