Merge #7970

7970: Fix incorrect diagnostics for failing built in macros r=jonas-schievink a=brandondong

**Reproduction:**
1. Use a built in macro in such a way that rust-analyzer fails to expand it. For example:

**lib.rs**
```
include!("<valid file but without a .rs extension so it is not indexed by rust-analyzer>");
```
2. rust-analyzer highlights the macro call and says the macro itself cannot be resolved even though include! is in the standard library (unresolved-macro-call diagnostic).
3. No macro-error diagnostic is raised.

**Root cause for incorrect unresolved-macro-call diagnostic:**
1. collector:collect_macro_call is able to resolve include! in legacy scope but the expansion fails. Therefore, it's pushed into unexpanded_macros to be retried with module scope.
2. include! fails at the resolution step in collector:resolve_macros now that it's using module scope. Therefore, it's retained in unexpanded_macros.
3. Finally, collector:finish tries resolving the remaining unexpanded macros but only with module scope. include! again fails at the resolution step so a diagnostic is created.

**Root cause for missing macro-error diagnostic:**
1. In collector:resolve_macros, directive.legacy is None since eager expansion failed in collector:collect_macro_call. The macro_call_as_call_id fails to resolve since we're retrying in module scope. Therefore, collect_macro_expansion is not called for the macro and no macro-error diagnostic is generated.

**Fix:**
- In collector:collect_macro_call, do not add failing built-in macros to the unexpanded_macros list and immediately raise the macro-error diagnostic. This is in contrast to lazy macros which are resolved in collector::resolve_macros and later expanded in collect_macro_expansion where a macro-error diagnostic may be raised.

Co-authored-by: Brandon <[email protected]>
Co-authored-by: brandondong <[email protected]>

1 files changed, 45 insertions, 0 deletions

diff --git a/crates/hir_def/src/nameres/tests/diagnostics.rs b/crates/hir_def/src/nameres/tests/diagnostics.rs
index 1b8e885b0..c22ef46fd 100644
--- a/crates/hir_def/src/nameres/tests/diagnostics.rs
+++ b/crates/hir_def/src/nameres/tests/diagnostics.rs
@@ -155,3 +155,48 @@ fn inactive_via_cfg_attr() {
         "#,
     );
 }
+
+#[test]
+fn unresolved_legacy_scope_macro() {
+    check_diagnostics(
+        r#"
+        //- /lib.rs
+          macro_rules! m { () => {} }
+
+          m!();
+          m2!();
+        //^^^^^^ unresolved macro call
+        "#,
+    );
+}
+
+#[test]
+fn unresolved_module_scope_macro() {
+    check_diagnostics(
+        r#"
+        //- /lib.rs
+          mod mac {
+            #[macro_export]
+            macro_rules! m { () => {} }
+          }
+
+          self::m!();
+          self::m2!();
+        //^^^^^^^^^^^^ unresolved macro call
+        "#,
+    );
+}
+
+#[test]
+fn builtin_macro_fails_expansion() {
+    check_diagnostics(
+        r#"
+        //- /lib.rs
+          #[rustc_builtin_macro]
+          macro_rules! include { () => {} }
+
+          include!("doesntexist");
+        //^^^^^^^^^^^^^^^^^^^^^^^^ could not convert tokens
+        "#,
+    );
+}