[Heavy] Fix nbdl ADT identity types

Author: ricejasonf

heavy/include/nbdl_gen/Nbdl.td

@@ -21,20 +21,20 @@ def Nbdl_Dialect : Dialect {
 def Nbdl_Empty : TypeDef<Nbdl_Dialect, "Empty", []> {
   let mnemonic = "empty";
   let description = [{
-    We define empty_type as a type with no information either
-    compile-time or run-time.
+    We define empty_type as a type whose with no
+    state either compile-time or run-time.
 
-    This serves as the identity element for product types.
+    This serves as the identity element for sum types.
   }];
 }
 
-def Nbdl_Void : TypeDef<Nbdl_Dialect, "Void", []> {
-  let mnemonic = "void";
+def Nbdl_Unit : TypeDef<Nbdl_Dialect, "Unit", []> {
+  let mnemonic = "unit";
   let description = [{
-    We define void_type as a unit type with no run-time information
-    and no run-time instantiation.
+    We define unit_type to have a single possible
+    compile-time and run-time state.
 
-    This serves as the identity element for sum types.
+    This serves as the identity element for product types.
   }];
 }
 
@@ -113,9 +113,9 @@ def Nbdl_Symbol : TypeDef<Nbdl_Dialect, "Symbol"> {
 // Keys are optional, but we are using variadic arguments
 // so we resort to using this sum type.
 def Nbdl_KeyType : AnyTypeOf<[Nbdl_Opaque, Nbdl_Tag,
-                              Nbdl_Symbol, Nbdl_Empty]>;
+                              Nbdl_Symbol, Nbdl_Unit]>;
 
-def Nbdl_Type : AnyTypeOf<[Nbdl_Void, Nbdl_Empty, Nbdl_Opaque,
+def Nbdl_Type : AnyTypeOf<[Nbdl_Unit, Nbdl_Empty, Nbdl_Opaque,
                            Nbdl_Store, Nbdl_Tag]>;
 
 class Nbdl_Op<string mnemonic, list<Trait> traits = []> :
@@ -312,6 +312,15 @@ def Nbdl_EmptyOp : Nbdl_Op<"empty", []> {
   let results = (outs Nbdl_Empty:$result);
 }
 
+def Nbdl_UnitOp : Nbdl_Op<"unit", []> {
+  let description = [{
+    An operation that produces an object of the unit type.
+  }];
+
+  let arguments = (ins);
+  let results = (outs Nbdl_Unit:$result);
+}
+
 def Nbdl_ApplyOp : Nbdl_Op<"apply", []> {
   let description = [{
     Apply a function.

heavy/lib/Nbdl/NbdlWriter.cpp

@@ -209,7 +209,7 @@ class NbdlWriter {
       else if (isa<ConstexprOp>(Op))
         return VisitType(cast<ConstexprOp>(Op));
       else
-        SetError("unhandled operation (VisitType)", Op);
+        SetError("unhandled operation (VisitType): {}", Op);
     } else {
       // Handle mlir::BlockArgument.
       // Arguments cannot be `decltype(auto)`
@@ -285,8 +285,11 @@ class FuncWriter : public NbdlWriter<FuncWriter> {
     else if (isa<FuncOp>(Op))         return Visit(cast<FuncOp>(Op));
     else if (isa<MemberNameOp>(Op))   return Visit(cast<MemberNameOp>(Op));
     else if (isa<ConstexprOp, LiteralOp>(Op)) return;
+    else if (isa<UnitOp>(Op)) return;
+    else if (isa<EmptyOp>(Op))
+      return SetError("empty type does not map to c++", Op);
     else
-      SetError("unhandled operation", Op);
+      return SetError("unhandled operation: {}", Op);
   }
 
   void VisitRegion(mlir::Region& R) {
@@ -342,8 +345,10 @@ class FuncWriter : public NbdlWriter<FuncWriter> {
     } else {
       OS << "nbdl::get(";
       WriteForwardedExpr(Op.getState());
-      OS << ',';
-      WriteForwardedExpr(Op.getKey());
+      if (!isa<nbdl_gen::UnitType>(Op.getKey().getType())) {
+        OS << ", ";
+        WriteForwardedExpr(Op.getKey());
+      }
       OS << ");\n";
     }
   }
@@ -361,8 +366,10 @@ class FuncWriter : public NbdlWriter<FuncWriter> {
   void Visit(MatchOp Op) {
     OS << "nbdl::match(";
     WriteForwardedExpr(Op.getStore());
-    OS << ", ";
-    WriteForwardedExpr(Op.getKey());
+    if (!isa<nbdl_gen::UnitType>(Op.getKey().getType())) {
+      OS << ", ";
+      WriteForwardedExpr(Op.getKey());
+    }
     OS << ", ";
     OS << "\nboost::hana::overload_linearly(";
 
@@ -494,7 +501,7 @@ class ContextWriter : public NbdlWriter<ContextWriter> {
       return;
     } else {
       mlir::Operation* Irr = Val.getDefiningOp();
-      SetError("unhandled operation", Irr);
+      SetError("unhandled operation: (WriteMemberDecl) {}", Irr);
     }
   }
 
@@ -533,7 +540,6 @@ class ContextWriter : public NbdlWriter<ContextWriter> {
     if (!ContOp)
       return;
 
-
     OS << Op.getName();
     OS << '(';
     llvm::interleaveComma(Op.getBody().getArguments(), OS,