Refine codegen error positions.

codegen/ui_tests/rhai_fn_getter_signature.stderr

@@ -2,7 +2,7 @@ error: property getter requires exactly 1 parameter
   --> $DIR/rhai_fn_getter_signature.rs:13:9
    |
 13 |     pub fn test_fn(input: Point, value: bool) -> bool {
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0433]: failed to resolve: use of undeclared crate or module `test_module`
   --> $DIR/rhai_fn_getter_signature.rs:23:8

codegen/ui_tests/rhai_fn_global_multiple.stderr

@@ -1,4 +1,4 @@
-error: conflicting namespace
+error: namespace is already set to 'global'
   --> $DIR/rhai_fn_global_multiple.rs:12:23
    |
 12 |     #[rhai_fn(global, internal)]

codegen/ui_tests/rhai_fn_index_getter_signature.stderr

@@ -2,7 +2,7 @@ error: index getter requires exactly 2 parameters
   --> $DIR/rhai_fn_index_getter_signature.rs:13:9
    |
 13 |     pub fn test_fn(input: Point) -> bool {
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                    ^^^^^^^^^^^^
 
 error[E0433]: failed to resolve: use of undeclared crate or module `test_module`
   --> $DIR/rhai_fn_index_getter_signature.rs:23:8

codegen/ui_tests/rhai_fn_setter_index_signature.stderr

@@ -2,7 +2,7 @@ error: index setter requires exactly 3 parameters
   --> $DIR/rhai_fn_setter_index_signature.rs:13:9
    |
 13 |     pub fn test_fn(input: Point) -> bool {
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                    ^^^^^^^^^^^^
 
 error[E0433]: failed to resolve: use of undeclared crate or module `test_module`
   --> $DIR/rhai_fn_setter_index_signature.rs:23:8

codegen/ui_tests/rhai_fn_setter_return.stderr

@@ -2,7 +2,7 @@ error: property setter cannot return any value
   --> $DIR/rhai_fn_setter_return.rs:13:9
    |
 13 |     pub fn test_fn(input: &mut Point, value: f32) -> bool {
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                                                   ^^^^^^^
 
 error[E0433]: failed to resolve: use of undeclared crate or module `test_module`
   --> $DIR/rhai_fn_setter_return.rs:24:8

codegen/ui_tests/rhai_fn_setter_signature.stderr

@@ -2,7 +2,7 @@ error: property setter requires exactly 2 parameters
   --> $DIR/rhai_fn_setter_signature.rs:13:9
    |
 13 |     pub fn test_fn(input: Point) -> bool {
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                    ^^^^^^^^^^^^
 
 error[E0433]: failed to resolve: use of undeclared crate or module `test_module`
   --> $DIR/rhai_fn_setter_signature.rs:23:8