1 files changed, 62 insertions, 0 deletions
diff --git a/src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/unresolved_proc_macro.rs b/src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/unresolved_proc_macro.rs
new file mode 100644
index 000000000..760f51f90
--- /dev/null
+++ b/src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/unresolved_proc_macro.rs
@@ -0,0 +1,62 @@
+use hir::db::DefDatabase;
+use syntax::NodeOrToken;
+
+use crate::{Diagnostic, DiagnosticsContext, Severity};
+
+// Diagnostic: unresolved-proc-macro
+//
+// This diagnostic is shown when a procedural macro can not be found. This usually means that
+// procedural macro support is simply disabled (and hence is only a weak hint instead of an error),
+// but can also indicate project setup problems.
+//
+// If you are seeing a lot of "proc macro not expanded" warnings, you can add this option to the
+// `rust-analyzer.diagnostics.disabled` list to prevent them from showing. Alternatively you can
+// enable support for procedural macros (see `rust-analyzer.procMacro.attributes.enable`).
+pub(crate) fn unresolved_proc_macro(
+    ctx: &DiagnosticsContext<'_>,
+    d: &hir::UnresolvedProcMacro,
+    proc_macros_enabled: bool,
+    proc_attr_macros_enabled: bool,
+) -> Diagnostic {
+    // Use more accurate position if available.
+    let display_range = (|| {
+        let precise_location = d.precise_location?;
+        let root = ctx.sema.parse_or_expand(d.node.file_id)?;
+        match root.covering_element(precise_location) {
+            NodeOrToken::Node(it) => Some(ctx.sema.original_range(&it)),
+            NodeOrToken::Token(it) => d.node.with_value(it).original_file_range_opt(ctx.sema.db),
+        }
+    })()
+    .unwrap_or_else(|| ctx.sema.diagnostics_display_range(d.node.clone()))
+    .range;
+
+    let config_enabled = match d.kind {
+        hir::MacroKind::Attr => proc_macros_enabled && proc_attr_macros_enabled,
+        _ => proc_macros_enabled,
+    };
+
+    let message = match &d.macro_name {
+        Some(name) => format!("proc macro `{}` not expanded", name),
+        None => "proc macro not expanded".to_string(),
+    };
+    let severity = if config_enabled { Severity::Error } else { Severity::WeakWarning };
+    let def_map = ctx.sema.db.crate_def_map(d.krate);
+    let message = format!(
+        "{message}: {}",
+        if config_enabled {
+            match def_map.proc_macro_loading_error() {
+                Some(e) => e,
+                None => "proc macro not found in the built dylib",
+            }
+        } else {
+            match d.kind {
+                hir::MacroKind::Attr if proc_macros_enabled => {
+                    "attribute macro expansion is disabled"
+                }
+                _ => "proc-macro expansion is disabled",
+            }
+        },
+    );
+
+    Diagnostic::new("unresolved-proc-macro", message, display_range).severity(severity)
+}