Doctest column name reference (#918)

* Doctest column name reference
* Document rusqlite assumption on column name reference
And move doctest as a test.
* Document when columns metadata should be extracted.
* Rustfmt doc (wrap_comments)

src/types/mod.rs

@@ -15,9 +15,11 @@
 //! [`FromSql`] has different behaviour depending on the SQL and Rust types, and
 //! the value.
 //!
-//! * `INTEGER` to integer: returns an [`Error::IntegralValueOutOfRange`](crate::Error::IntegralValueOutOfRange) error if
-//!   the value does not fit in the Rust type.
-//! * `REAL` to integer: always returns an [`Error::InvalidColumnType`](crate::Error::InvalidColumnType) error.
+//! * `INTEGER` to integer: returns an
+//!   [`Error::IntegralValueOutOfRange`](crate::Error::IntegralValueOutOfRange)
+//!   error if the value does not fit in the Rust type.
+//! * `REAL` to integer: always returns an
+//!   [`Error::InvalidColumnType`](crate::Error::InvalidColumnType) error.
 //! * `INTEGER` to float: casts using `as` operator. Never fails.
 //! * `REAL` to float: casts using `as` operator. Never fails.
 //!
@@ -62,8 +64,8 @@ impl ToSql for DateTimeSql {
 "##
 )]
 //! [`ToSql`] and [`FromSql`] are also implemented for `Option<T>` where `T`
-//! implements [`ToSql`] or [`FromSql`] for the cases where you want to know if a
-//! value was NULL (which gets translated to `None`).
+//! implements [`ToSql`] or [`FromSql`] for the cases where you want to know if
+//! a value was NULL (which gets translated to `None`).
 
 pub use self::from_sql::{FromSql, FromSqlError, FromSqlResult};
 pub use self::to_sql::{ToSql, ToSqlOutput};

src/types/value.rs

@@ -3,7 +3,8 @@ use super::{Null, Type};
 /// Owning [dynamic type value](http://sqlite.org/datatype3.html). Value's type is typically
 /// dictated by SQLite (not by the caller).
 ///
-/// See [`ValueRef`](crate::types::ValueRef) for a non-owning dynamic type value.
+/// See [`ValueRef`](crate::types::ValueRef) for a non-owning dynamic type
+/// value.
 #[derive(Clone, Debug, PartialEq)]
 pub enum Value {
     /// The value is a `NULL` value.

src/types/value_ref.rs

@@ -35,7 +35,8 @@ impl ValueRef<'_> {
 
 impl<'a> ValueRef<'a> {
     /// If `self` is case `Integer`, returns the integral value. Otherwise,
-    /// returns [`Err(Error::InvalidColumnType)`](crate::Error::InvalidColumnType).
+    /// returns [`Err(Error::InvalidColumnType)`](crate::Error::
+    /// InvalidColumnType).
     #[inline]
     pub fn as_i64(&self) -> FromSqlResult<i64> {
         match *self {
@@ -45,7 +46,8 @@ impl<'a> ValueRef<'a> {
     }
 
     /// If `self` is case `Real`, returns the floating point value. Otherwise,
-    /// returns [`Err(Error::InvalidColumnType)`](crate::Error::InvalidColumnType).
+    /// returns [`Err(Error::InvalidColumnType)`](crate::Error::
+    /// InvalidColumnType).
     #[inline]
     pub fn as_f64(&self) -> FromSqlResult<f64> {
         match *self {