From 17c7163c2ae8fc290e70b43d8700b68ef18b1ee1 Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Fri, 6 Oct 2023 14:03:18 -0700
Subject: Small type system fixes. (#3265)

---
 source/slang/slang-check-expr.cpp | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

(limited to 'source/slang/slang-check-expr.cpp')

diff --git a/source/slang/slang-check-expr.cpp b/source/slang/slang-check-expr.cpp
index 05a6ed249..22bc2cae8 100644
--- a/source/slang/slang-check-expr.cpp
+++ b/source/slang/slang-check-expr.cpp
@@ -372,7 +372,24 @@ namespace Slang
                 {
                     expr->type.isLeftValue = false;
                 }
-
+                else
+                {
+                    // If we are accessing a readonly property, then the result
+                    // is not an l-value.
+                    if (auto propertyDecl = as<PropertyDecl>(declRef.getDecl()))
+                    {
+                        bool isLValue = false;
+                        for (auto member : propertyDecl->members)
+                        {
+                            if (as<SetterDecl>(member) || as< RefAccessorDecl>(member))
+                            {
+                                isLValue = true;
+                                break;
+                            }
+                        }
+                        expr->type.isLeftValue = isLValue;
+                    }
+                }
                 return expr;
             }
         }
@@ -3322,7 +3339,10 @@ namespace Slang
 
         // A swizzle can be used as an l-value as long as there
         // were no duplicates in the list of components
-        swizExpr->type.isLeftValue = !anyDuplicates;
+        swizExpr->type.isLeftValue = !anyDuplicates &&
+            swizExpr->base &&
+            swizExpr->base->type &&
+            swizExpr->base->type.isLeftValue;
 
         return swizExpr;
     }
-- 
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