Allow raw identifiers for SqlIdentifier (column-name)

This allows using the `r#identifier` syntax for SqlIdentifier
(column-name), which is used in derive macros.
Previously the derive macros would panic when encountering such an
identifier:
    `"r#identifier"` is not a valid identifier

diesel_derives/src/attrs.rs

@@ -75,7 +75,11 @@ impl SqlIdentifier {
 
 impl ToTokens for SqlIdentifier {
     fn to_tokens(&self, tokens: &mut TokenStream) {
-        Ident::new(&self.field_name, self.span).to_tokens(tokens)
+        if self.field_name.starts_with("r#") {
+            Ident::new_raw(&self.field_name[2..], self.span).to_tokens(tokens)
+        } else {
+            Ident::new(&self.field_name, self.span).to_tokens(tokens)
+        }
     }
 }
 

diesel_derives/tests/queryable.rs

@@ -30,6 +30,26 @@ fn tuple_struct() {
     assert_eq!(Ok(MyStruct(1, 2)), data);
 }
 
+#[test]
+fn raw_ident_struct() {
+    #[derive(Debug, Clone, Copy, PartialEq, Eq, Queryable)]
+    struct MyStruct {
+        r#foo: i32,
+        #[diesel(column_name = bar)]
+        r#struct: i32,
+    }
+
+    let conn = &mut connection();
+    let data = select(sql::<(Integer, Integer)>("1, 2")).get_result(conn);
+    assert_eq!(
+        Ok(MyStruct {
+            foo: 1,
+            r#struct: 2
+        }),
+        data
+    );
+}
+
 #[test]
 fn tuple_struct_without_column_name_annotations() {
     #[derive(Debug, Clone, Copy, PartialEq, Eq, Queryable)]
@@ -63,3 +83,15 @@ fn multiple_tables() {
         data
     );
 }
+
+#[test]
+fn raw_ident_table() {
+    #[derive(Debug, Clone, PartialEq, Eq, Queryable)]
+    struct Car {
+        r#type: i32,
+    }
+
+    let conn = &mut connection();
+    let data = select(sql::<(diesel::sql_types::Integer,)>("0")).get_result(conn);
+    assert_eq!(Ok(Car { r#type: 0 }), data);
+}

diesel_derives/tests/schema.rs

@@ -13,3 +13,9 @@ table! {
         hair_color -> Nullable<Text>,
     }
 }
+
+table! {
+    cars {
+        r#type -> Integer,
+    }
+}