add tests that show improved spans

salsa-2022-tests/tests/compile-fail/input_struct_id_fields_no_setters.stderr

@@ -1,8 +1,8 @@
 error[E0599]: no method named `set_id_one` found for struct `MyInput` in the current scope
   --> tests/compile-fail/input_struct_id_fields_no_setters.rs:30:11
    |
-7  | #[salsa::input(jar = Jar)]
-   | -------------------------- method `set_id_one` not found for this struct
+8  | struct MyInput {
+   |        ------- method `set_id_one` not found for this struct
 ...
 30 |     input.set_id_one(1);
    |           ^^^^^^^^^^ help: there is a method with a similar name: `id_one`

salsa-2022-tests/tests/compile-fail/span-input-setter.rs

@@ -0,0 +1,27 @@
+#[salsa::jar(db = Db)]
+pub struct Jar(MyInput);
+
+pub trait Db: salsa::DbWithJar<Jar> {}
+
+#[salsa::db(Jar)]
+#[derive(Default)]
+struct Database {
+    storage: salsa::Storage<Self>,
+}
+
+impl salsa::Database for Database {}
+
+impl Db for Database {}
+
+#[salsa::input]
+pub struct MyInput {
+    field: u32,
+}
+
+fn main() {
+    let mut db = Database::default();
+    let input = MyInput::new(&mut db, 22);
+
+    input.field(&db);
+    input.set_field(22);
+}

salsa-2022-tests/tests/compile-fail/span-input-setter.stderr

@@ -0,0 +1,18 @@
+error[E0308]: mismatched types
+  --> tests/compile-fail/span-input-setter.rs:26:21
+   |
+26 |     input.set_field(22);
+   |           --------- ^^ expected `&mut dyn Db`, found integer
+   |           |
+   |           arguments to this method are incorrect
+   |
+   = note: expected mutable reference `&mut dyn Db`
+                           found type `{integer}`
+note: method defined here
+  --> tests/compile-fail/span-input-setter.rs:18:5
+   |
+16 | #[salsa::input]
+   | ---------------
+17 | pub struct MyInput {
+18 |     field: u32,
+   |     ^^^^^

salsa-2022-tests/tests/compile-fail/span-tracked-getter.rs

@@ -0,0 +1,30 @@
+#[salsa::jar(db = Db)]
+pub struct Jar(MyTracked, my_fn);
+
+pub trait Db: salsa::DbWithJar<Jar> {}
+
+#[salsa::db(Jar)]
+#[derive(Default)]
+struct Database {
+    storage: salsa::Storage<Self>,
+}
+
+impl salsa::Database for Database {}
+
+impl Db for Database {}
+
+#[salsa::tracked]
+pub struct MyTracked {
+    field: u32,
+}
+
+#[salsa::tracked]
+fn my_fn(db: &dyn crate::Db) {
+    let x = MyTracked::new(db, 22);
+    x.field(22);
+}
+
+fn main() {
+    let mut db = Database::default();
+    my_fn(&db);
+}

salsa-2022-tests/tests/compile-fail/span-tracked-getter.stderr

@@ -0,0 +1,18 @@
+error[E0308]: mismatched types
+  --> tests/compile-fail/span-tracked-getter.rs:24:13
+   |
+24 |     x.field(22);
+   |       ----- ^^ expected `&dyn Db`, found integer
+   |       |
+   |       arguments to this method are incorrect
+   |
+   = note: expected reference `&dyn Db`
+                   found type `{integer}`
+note: method defined here
+  --> tests/compile-fail/span-tracked-getter.rs:18:5
+   |
+16 | #[salsa::tracked]
+   | -----------------
+17 | pub struct MyTracked {
+18 |     field: u32,
+   |     ^^^^^