Fix some resources-in-structs bugs

Fixes #171
Fixes #172

These two bugs related to bad logic in handling of splitting resource-containing `cbuffer` declarations.

- Issue #171 was the case where a `cbuffer` *only* had resource fields, in which case we crashed whenever referencing any field (some code was assuming there had to be non-resource fields)

- Issue #172 was a case where two fields were declared with a single declaration (`Texture2D a, b;`), and the logic we had for tracking resource-type fields was accidentally tagging *both* fields with a single modifier so that field `b` would get confused for `a` in some contexts, and attempts to access `b` would crash.

Both issues are now fixed, and regression tests have been added.

2 files changed, 51 insertions, 1 deletions

diff --git a/source/slang/lower.cpp b/source/slang/lower.cpp
index 70c153902..a1b6dcf17 100644
--- a/source/slang/lower.cpp
+++ b/source/slang/lower.cpp
@@ -308,6 +308,11 @@ struct LoweredExpr
         return (getFlavor() == Flavor::VaryingTuple) ? getVaryingTupleExpr() : nullptr;
     }
 
+    bool operator!()
+    {
+        return !value;
+    }
+
 private:
     RefPtr<RefObject>   value;
     Flavor              flavor;
@@ -1820,6 +1825,12 @@ struct LoweringVisitor
                 baseTuple->primaryExpr = loweredPrimary;
                 return baseTuple;
             }
+            else
+            {
+                // No primary expression? Then there is nothing
+                // to dereference.
+                return baseTuple;
+            }
         }
         else if (auto baseVaryingTuple = loweredBase.asVaryingTuple())
         {
@@ -1847,8 +1858,16 @@ struct LoweringVisitor
     LoweredExpr visitMemberExpr(
         MemberExpr* expr)
     {
+        assert(expr->BaseExpression);
         auto loweredBase = lowerExprOrTuple(expr->BaseExpression);
 
+        if( !loweredBase )
+        {
+            loweredBase = lowerExprOrTuple(expr->BaseExpression);
+        }
+
+        assert(loweredBase);
+
         auto loweredDeclRef = translateDeclRef(expr->declRef);
 
 
@@ -1872,7 +1891,11 @@ struct LoweringVisitor
                 }
 
                 if (!tupleFieldMod->hasAnyNonTupleFields)
+                {
+                    // We need to have found something!
+                    assert(tupleFieldExpr);
                     return tupleFieldExpr;
+                }
 
                 auto tupleFieldTupleExpr = tupleFieldExpr.asTuple();
                 SLANG_RELEASE_ASSERT(tupleFieldTupleExpr);
@@ -1885,6 +1908,8 @@ struct LoweringVisitor
                 loweredPrimaryExpr->declRef = loweredDeclRef.As<Decl>();
                 loweredPrimaryExpr->name = expr->name;
 
+                assert(loweredPrimaryExpr->BaseExpression);
+
                 tupleFieldTupleExpr->primaryExpr = loweredPrimaryExpr;
                 return tupleFieldTupleExpr;
             }
@@ -1892,6 +1917,7 @@ struct LoweringVisitor
             // If the field was a non-tuple field, then we can
             // simply fall through to the ordinary case below.
             loweredBase = LoweredExpr(baseTuple->primaryExpr);
+            assert(baseTuple->primaryExpr);
         }
         else if (auto baseVaryingTuple = loweredBase.asVaryingTuple())
         {
@@ -1901,6 +1927,7 @@ struct LoweringVisitor
                 if (expr->declRef.getDecl() == elem.originalFieldDeclRef.getDecl())
                 {
                     // We found the field!
+                    assert(elem.expr);
                     return elem.expr;
                 }
             }
@@ -1916,6 +1943,8 @@ struct LoweringVisitor
         loweredExpr->declRef = loweredDeclRef.As<Decl>();
         loweredExpr->name = expr->name;
 
+        assert(loweredExpr->BaseExpression);
+
         return LoweredExpr(loweredExpr);
     }
 
diff --git a/source/slang/parser.cpp b/source/slang/parser.cpp
index 7ea3fe864..c3969be42 100644
--- a/source/slang/parser.cpp
+++ b/source/slang/parser.cpp
@@ -549,9 +549,30 @@ namespace Slang
     {
         RefPtr<Modifier>*& modifierLink = *ioModifierLink;
 
-        while(*modifierLink)
+        // We'd like to add the modifier to the end of the list,
+        // but we need to be careful, in case there is a "shared"
+        // section of modifiers for multiple declarations.
+        //
+        // TODO: This whole approach is a mess because we are "accidentally quadratic"
+        // when adding many modifiers.
+        for(;;)
+        {
+            // At end of the chain? Done.
+            if(!*modifierLink)
+                break;
+
+            // About to look at shared modifiers? Done.
+            RefPtr<Modifier> linkMod = *modifierLink;
+            if(linkMod.As<SharedModifiers>())
+                break;
+
+            // Otherwise: keep traversing the modifier list.
             modifierLink = &(*modifierLink)->next;
+        }
+
+        // Splice the modifier into the linked list
 
+        modifier->next = *modifierLink;
         *modifierLink = modifier;
         modifierLink = &modifier->next;
     }