fix: prefer resolving parser alias over declaration

src/Lean/Elab/Syntax.lean

@@ -191,26 +191,31 @@ where
     return (stx, stackSz)
 
   processNullaryOrCat (stx : Syntax) := do
-    match (← elabParserName? stx[0]) with
+    let ident := stx[0]
+    let id := ident.getId.eraseMacroScopes
+    -- run when parser is neither a decl nor a cat
+    let default := do
+      if (← Parser.isParserAlias id) then
+        ensureNoPrec stx
+        return (← processAlias ident #[])
+      throwError "unknown parser declaration/category/alias '{id}'"
+    match (← elabParserName? ident) with
     | some (.parser c (isDescr := true)) =>
       ensureNoPrec stx
       -- `syntax _ :=` at least enforces this
       let stackSz := 1
       return (mkIdentFrom stx c, stackSz)
     | some (.parser c (isDescr := false)) =>
+      if (← Parser.getParserAliasInfo id).declName == c then
+        -- prefer parser alias over base declaration because it has more metadata, #2249
+        return (← default)
       ensureNoPrec stx
       -- as usual, we assume that people using `Parser` know what they are doing
       let stackSz := 1
       return (← `(ParserDescr.parser $(quote c)), stackSz)
     | some (.category _) =>
       processParserCategory stx
-    | none =>
-      let id := stx[0].getId.eraseMacroScopes
-      if (← Parser.isParserAlias id) then
-        ensureNoPrec stx
-        processAlias stx[0] #[]
-      else
-        throwError "unknown parser declaration/category/alias '{id}'"
+    | none => default
 
   processSepBy (stx : Syntax) := do
     let p ← ensureUnaryOutput <$> withNestedParser do process stx[1]

tests/lean/run/2249.lean

@@ -0,0 +1,12 @@
+import Lean
+
+macro (name := fooParser) "foo" x:(ppSpace ident)* : term =>
+  `([$(x.map (Lean.mkIdent ·.getId)),*])
+
+namespace Lean.Parser.Term
+macro (name := barParser) "bar" x:(ppSpace ident)* : term =>
+  `([$(x.map (Lean.mkIdent ·.getId)),*])
+
+variable (a : Nat)
+#check foo a -- ok
+#check bar a -- ok (used to be: unknown identifier '[anonymous]')