[ASTGen] Unique "unimplemented" fatal error message

Author: rintaro

lib/ASTGen/Sources/ASTGen/BuiltinPound.swift

@@ -195,10 +195,10 @@ extension ASTGenVisitor {
   }
 
   func generateObjCSelectorExpr(freestandingMacroExpansion node: some FreestandingMacroExpansionSyntax) -> BridgedObjCSelectorExpr {
-    fatalError("unimplemented")
+    fatalError("unimplemented (objc selector)")
   }
 
   func generateObjCKeyPathExpr(freestandingMacroExpansion node: some FreestandingMacroExpansionSyntax) -> BridgedKeyPathExpr {
-    fatalError("unimplemented")
+    fatalError("unimplemented (objc keypath)")
   }
 }

lib/ASTGen/Sources/ASTGen/DeclAttrs.swift

@@ -302,7 +302,7 @@ extension ASTGenVisitor {
       // Modifers.
       case .accessControl:
         // TODO: Diagnose and generateAccessControl().
-        fatalError("unimplemented")
+        fatalError("unimplemented (access control modifier parsed as attributes)")
       case .nonisolated:
         // TODO: Diagnose.
         return handle(self.generateNonisolatedAttr(attribute: node)?.asDeclAttribute)

lib/ASTGen/Sources/ASTGen/Exprs.swift

@@ -738,7 +738,7 @@ extension ASTGenVisitor {
       ).asExpr
 
     case .method(_):
-      fatalError("unimplemented")
+      fatalError("unimplemented (method keypath)")
     }
   }
 

lib/ASTGen/Sources/ASTGen/Stmts.swift

@@ -50,7 +50,7 @@ extension ASTGenVisitor {
     case .labeledStmt(let node):
       return self.generate(labeledStmt: node)
     case .missingStmt:
-      fatalError("unimplemented")
+      fatalError("unimplemented (missing statement)")
     case .repeatStmt(let node):
       return self.generate(repeatStmt: node).asStmt
     case .returnStmt(let node):
@@ -234,7 +234,7 @@ extension ASTGenVisitor {
           // FIXME: Implement.
           // For `if let foo.bar {`, diagnose and convert it to `if let _ =  foo.bar`
           // For `if let (a, b) {`, diagnose it and create an error expression.
-          fatalError("unimplemented")
+          fatalError("unimplemented (optional binding recovery)")
         }
       }
       return .createPatternBinding(