Complete removal of DifferentialBottom type. (#2537)

Co-authored-by: Yong He <yhe@nvidia.com>

1 files changed, 42 insertions, 80 deletions

diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index 4d2839b8d..5e6c6eedf 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -259,8 +259,6 @@ namespace Slang
 
         void visitParamDecl(ParamDecl* paramDecl);
 
-        void _maybeRegisterDifferentialBottomTypeConformance(SemanticsContext& context);
-
         void checkDerivativeOfAttribute(FunctionDeclBase* funcDecl);
 
         void checkDerivativeAttribute(FunctionDeclBase* funcDecl, ForwardDerivativeAttribute* attr);
@@ -3317,73 +3315,52 @@ namespace Slang
         auto seqStmt = synth.pushSeqStmtScope();
         blockStmt->body = seqStmt;
 
-        if (synFunc->returnType.type->equals(m_astBuilder->getDifferentialBottomType()))
-        {
-            // Trivial case, the `Differential` type is `DifferentialBottom`.
-            // We will just return `DifferentialBottom.dzero()`.
-            auto resultExpr = m_astBuilder->create<InvokeExpr>();
-            auto dzeroMember = m_astBuilder->create<StaticMemberExpr>();
-            auto base = m_astBuilder->create<SharedTypeExpr>();
-            auto typetype = m_astBuilder->create<TypeType>();
-            typetype->type = m_astBuilder->getDifferentialBottomType();
-            base->type.type = typetype;
-            dzeroMember->baseExpression = base;
-            dzeroMember->name = getName("dzero");
-            resultExpr->functionExpr = dzeroMember;
-            auto synReturn = m_astBuilder->create<ReturnStmt>();
-            synReturn->expression = resultExpr;
-            seqStmt->stmts.add(synReturn);
-        }
-        else
-        {
-            // The general case. 
-            // Create a variable for return value.
-            synth.pushVarScope();
-            auto varStmt = synth.emitVarDeclStmt(synFunc->returnType.type, getName("result"));
-            auto resultVarExpr = synth.emitVarExpr(varStmt, synFunc->returnType.type);
+        // Create a variable for return value.
+        synth.pushVarScope();
+        auto varStmt = synth.emitVarDeclStmt(synFunc->returnType.type, getName("result"));
+        auto resultVarExpr = synth.emitVarExpr(varStmt, synFunc->returnType.type);
 
-            for (auto member : context->parentDecl->members)
-            {
-                auto derivativeAttr = member->findModifier<DerivativeMemberAttribute>();
-                if (!derivativeAttr)
-                    continue;
-                auto varMember = as<VarDeclBase>(member);
-                if (!varMember)
-                    continue;
-                ensureDecl(varMember, DeclCheckState::ReadyForReference);
-                auto memberType = varMember->getType();
-                auto diffMemberType = tryGetDifferentialType(m_astBuilder, memberType);
-                if (!diffMemberType)
-                    continue;
-
-                // Construct reference exprs to the member's corresponding fields in each parameter.
-                List<Expr*> paramFields;
-                int paramIndex = 0;
-                for (auto arg : synArgs)
-                {
-                    auto memberExpr = m_astBuilder->create<MemberExpr>();
-                    memberExpr->baseExpression = arg;
-                    // TODO: we should probably fetch the name from `[DerivativeMember]` if `arg` is
-                    // Differential type.
-                    memberExpr->name = varMember->getName();
-                    paramFields.add(memberExpr);
-                    paramIndex++;
-                }
+        for (auto member : context->parentDecl->members)
+        {
+            auto derivativeAttr = member->findModifier<DerivativeMemberAttribute>();
+            if (!derivativeAttr)
+                continue;
+            auto varMember = as<VarDeclBase>(member);
+            if (!varMember)
+                continue;
+            ensureDecl(varMember, DeclCheckState::ReadyForReference);
+            auto memberType = varMember->getType();
+            auto diffMemberType = tryGetDifferentialType(m_astBuilder, memberType);
+            if (!diffMemberType)
+                continue;
 
-                // Invoke the method for the field and assign the value to resultVar.
-                // TODO: we should probably fetch the name from `[DerivativeMember]` if `resultVarExpr`
-                // is Differential type.
-                auto leftVal = synth.emitMemberExpr(resultVarExpr, varMember->getName());
-                if (!_synthesizeMemberAssignMemberHelper(synth, requirementDeclRef.getName(), memberType, leftVal, _Move(paramFields)))
-                    return false;
-            }
+            // Construct reference exprs to the member's corresponding fields in each parameter.
+            List<Expr*> paramFields;
+            int paramIndex = 0;
+            for (auto arg : synArgs)
+            {
+                auto memberExpr = m_astBuilder->create<MemberExpr>();
+                memberExpr->baseExpression = arg;
+                // TODO: we should probably fetch the name from `[DerivativeMember]` if `arg` is
+                // Differential type.
+                memberExpr->name = varMember->getName();
+                paramFields.add(memberExpr);
+                paramIndex++;
+            }
+
+            // Invoke the method for the field and assign the value to resultVar.
+            // TODO: we should probably fetch the name from `[DerivativeMember]` if `resultVarExpr`
+            // is Differential type.
+            auto leftVal = synth.emitMemberExpr(resultVarExpr, varMember->getName());
+            if (!_synthesizeMemberAssignMemberHelper(synth, requirementDeclRef.getName(), memberType, leftVal, _Move(paramFields)))
+                return false;
+        }
 
-            // TODO: synthesize assignments for inherited members here.
+        // TODO: synthesize assignments for inherited members here.
 
-            auto synReturn = m_astBuilder->create<ReturnStmt>();
-            synReturn->expression = resultVarExpr;
-            seqStmt->stmts.add(synReturn);
-        }
+        auto synReturn = m_astBuilder->create<ReturnStmt>();
+        synReturn->expression = resultVarExpr;
+        seqStmt->stmts.add(synReturn);
         
         context->parentDecl->members.add(synFunc);
         context->parentDecl->invalidateMemberDictionary();
@@ -4633,21 +4610,6 @@ namespace Slang
             getSink()->diagnose(decl, Slang::Diagnostics::assocTypeInInterfaceOnly);
     }
 
-    void SemanticsDeclBodyVisitor::_maybeRegisterDifferentialBottomTypeConformance(SemanticsContext& context)
-    {
-        auto parentDifferentiableAttr = context.getParentDifferentiableAttribute();
-        if (parentDifferentiableAttr)
-        {
-            auto diffBottomType = m_astBuilder->getDifferentialBottomType();
-            auto idifferentiable = DeclRef<InterfaceDecl>(m_astBuilder->getDifferentiableInterface(), nullptr);
-            auto witness = as<SubtypeWitness>(tryGetInterfaceConformanceWitness(diffBottomType, idifferentiable));
-            SLANG_ASSERT(witness);
-            parentDifferentiableAttr->m_mapTypeToIDifferentiableWitness.Add(
-                as<DeclRefType>(diffBottomType)->declRef,
-                witness);
-        }
-    }
-
     void SemanticsDeclBodyVisitor::checkDerivativeOfAttribute(FunctionDeclBase* funcDecl)
     {
         auto attr = funcDecl->findModifier<ForwardDerivativeOfAttribute>();