Fix zero size array handling in slangc (#6399)

* Fix zero size array handling in slangc

Fixes #2890

1. Fix zero size array handling in slangc
2. Add new zero size array diagnostic test.

* format code

* fix review comments

---------

Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>
Co-authored-by: Ellie Hermaszewska <ellieh@nvidia.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/source/slang/slang-check-expr.cpp b/source/slang/slang-check-expr.cpp
index 7d4fbdf4c..1fb2b336f 100644
--- a/source/slang/slang-check-expr.cpp
+++ b/source/slang/slang-check-expr.cpp
@@ -2378,6 +2378,18 @@ Expr* SemanticsExprVisitor::visitIndexExpr(IndexExpr* subscriptExpr)
                 IntegerConstantExpressionCoercionType::AnyInteger,
                 nullptr,
                 ConstantFoldingKind::LinkTime);
+
+            // Validate that array size is greater than zero
+            if (auto constElementCount = as<ConstantIntVal>(elementCount))
+            {
+                if (constElementCount->getValue() <= 0)
+                {
+                    getSink()->diagnose(
+                        subscriptExpr->indexExprs[0],
+                        Diagnostics::invalidArraySize);
+                    return CreateErrorExpr(subscriptExpr);
+                }
+            }
         }
         else if (subscriptExpr->indexExprs.getCount() != 0)
         {