3 files changed, 48 insertions, 8 deletions

diff --git a/crates/hir_def/src/diagnostics.rs b/crates/hir_def/src/diagnostics.rs
index dd06e3f20..c71266dc0 100644
--- a/crates/hir_def/src/diagnostics.rs
+++ b/crates/hir_def/src/diagnostics.rs
@@ -6,7 +6,7 @@ use stdx::format_to;
 use cfg::{CfgExpr, CfgOptions, DnfExpr};
 use hir_expand::diagnostics::{Diagnostic, DiagnosticCode, DiagnosticSink};
 use hir_expand::{HirFileId, InFile};
-use syntax::{ast, AstPtr, SyntaxNodePtr};
+use syntax::{ast, AstPtr, SyntaxNodePtr, TextRange};
 
 use crate::{db::DefDatabase, DefWithBodyId};
 
@@ -137,6 +137,9 @@ impl Diagnostic for InactiveCode {
 pub struct UnresolvedProcMacro {
     pub file: HirFileId,
     pub node: SyntaxNodePtr,
+    /// If the diagnostic can be pinpointed more accurately than via `node`, this is the `TextRange`
+    /// to use instead.
+    pub precise_location: Option<TextRange>,
     pub macro_name: Option<String>,
 }
 
diff --git a/crates/hir_def/src/nameres.rs b/crates/hir_def/src/nameres.rs
index 3d65a46bf..ffd0381d4 100644
--- a/crates/hir_def/src/nameres.rs
+++ b/crates/hir_def/src/nameres.rs
@@ -287,7 +287,8 @@ mod diagnostics {
     use hir_expand::diagnostics::DiagnosticSink;
     use hir_expand::hygiene::Hygiene;
     use hir_expand::{InFile, MacroCallKind};
-    use syntax::{ast, AstPtr, SyntaxNodePtr};
+    use syntax::ast::AttrsOwner;
+    use syntax::{ast, AstNode, AstPtr, SyntaxKind, SyntaxNodePtr};
 
     use crate::path::ModPath;
     use crate::{db::DefDatabase, diagnostics::*, nameres::LocalModuleId, AstId};
@@ -425,6 +426,7 @@ mod diagnostics {
                 }
 
                 DiagnosticKind::UnresolvedProcMacro { ast } => {
+                    let mut precise_location = None;
                     let (file, ast, name) = match ast {
                         MacroCallKind::FnLike(ast) => {
                             let node = ast.to_node(db.upcast());
@@ -432,14 +434,47 @@ mod diagnostics {
                         }
                         MacroCallKind::Attr(ast, name) => {
                             let node = ast.to_node(db.upcast());
+
+                            // Compute the precise location of the macro name's token in the derive
+                            // list.
+                            // FIXME: This does not handle paths to the macro, but neither does the
+                            // rest of r-a.
+                            let derive_attrs =
+                                node.attrs().filter_map(|attr| match attr.as_simple_call() {
+                                    Some((name, args)) if name == "derive" => Some(args),
+                                    _ => None,
+                                });
+                            'outer: for attr in derive_attrs {
+                                let tokens =
+                                    attr.syntax().children_with_tokens().filter_map(|elem| {
+                                        match elem {
+                                            syntax::NodeOrToken::Node(_) => None,
+                                            syntax::NodeOrToken::Token(tok) => Some(tok),
+                                        }
+                                    });
+                                for token in tokens {
+                                    if token.kind() == SyntaxKind::IDENT
+                                        && token.to_string() == *name
+                                    {
+                                        precise_location = Some(token.text_range());
+                                        break 'outer;
+                                    }
+                                }
+                            }
+
                             (
                                 ast.file_id,
                                 SyntaxNodePtr::from(AstPtr::new(&node)),
-                                Some(name.to_string()),
+                                Some(name.clone()),
                             )
                         }
                     };
-                    sink.push(UnresolvedProcMacro { file, node: ast, macro_name: name });
+                    sink.push(UnresolvedProcMacro {
+                        file,
+                        node: ast,
+                        precise_location,
+                        macro_name: name,
+                    });
                 }
 
                 DiagnosticKind::MacroError { ast, message } => {
diff --git a/crates/ide/src/diagnostics.rs b/crates/ide/src/diagnostics.rs
index 8b4ceb9a1..9d3d88289 100644
--- a/crates/ide/src/diagnostics.rs
+++ b/crates/ide/src/diagnostics.rs
@@ -143,11 +143,13 @@ pub(crate) fn diagnostics(
             );
         })
         .on::<hir::diagnostics::UnresolvedProcMacro, _>(|d| {
+            // Use more accurate position if available.
+            let display_range =
+                d.precise_location.unwrap_or_else(|| sema.diagnostics_display_range(d).range);
+
             // FIXME: it would be nice to tell the user whether proc macros are currently disabled
-            res.borrow_mut().push(
-                Diagnostic::hint(sema.diagnostics_display_range(d).range, d.message())
-                    .with_code(Some(d.code())),
-            );
+            res.borrow_mut()
+                .push(Diagnostic::hint(display_range, d.message()).with_code(Some(d.code())));
         })
         // Only collect experimental diagnostics when they're enabled.
         .filter(|diag| !(diag.is_experimental() && config.disable_experimental))