[flang] Add passArg to ProcEntityDetails and ProcBindingDetails

Add `passArg` to `ProcEntityDetails` and `ProcBindingDetails`.
The is the symbols that represents the passed-object dummy argument,
or nullptr if none.

As both of these classes need `passName` and `passArg`, create a mixin
class, `WithPassArg` for the shared content.

Change passName_ from optional to pointer because that makes it a little
easier to work with and there is no need to have a copy of the name.

Original-commit: flang-compiler/f18@1cdd1a5b87
Reviewed-on: https://github.com/flang-compiler/f18/pull/521
Tree-same-pre-rewrite: false

flang/lib/semantics/mod-file.cc

@@ -43,7 +43,7 @@ static std::vector<const Symbol *> CollectSymbols(const Scope &);
 static void PutEntity(std::ostream &, const Symbol &);
 static void PutObjectEntity(std::ostream &, const Symbol &);
 static void PutProcEntity(std::ostream &, const Symbol &);
-static void PutPassName(std::ostream &, const std::optional<SourceName> &);
+static void PutPassName(std::ostream &, const SourceName *);
 static void PutTypeParam(std::ostream &, const Symbol &);
 static void PutEntity(std::ostream &, const Symbol &, std::function<void()>);
 static void PutInit(std::ostream &, const MaybeExpr &);
@@ -488,7 +488,7 @@ void PutProcEntity(std::ostream &os, const Symbol &symbol) {
   });
 }
 
-void PutPassName(std::ostream &os, const std::optional<SourceName> &passName) {
+void PutPassName(std::ostream &os, const SourceName *passName) {
   if (passName) {
     PutLower(os << ",pass(", passName->ToString()) << ')';
   }

flang/lib/semantics/resolve-names.cc

@@ -270,7 +270,7 @@ protected:
 
 private:
   MaybeExpr bindName_;  // from BIND(C, NAME="...")
-  std::optional<SourceName> passName_;  // from PASS(...)
+  const SourceName *passName_{nullptr};  // from PASS(...)
 };
 
 // Find and create types from declaration-type-spec nodes.
@@ -1159,10 +1159,9 @@ Attrs AttrsVisitor::GetAttrs() {
   return *attrs_;
 }
 Attrs AttrsVisitor::EndAttrs() {
-  CHECK(attrs_);
-  Attrs result{*attrs_};
+  Attrs result{GetAttrs()};
   attrs_.reset();
-  passName_.reset();
+  passName_ = nullptr;
   bindName_.reset();
   return result;
 }
@@ -1216,7 +1215,7 @@ bool AttrsVisitor::Pre(const parser::IntentSpec &x) {
 }
 bool AttrsVisitor::Pre(const parser::Pass &x) {
   if (x.v) {
-    passName_ = x.v->source;
+    passName_ = &x.v->source;
     MakePlaceholder(*x.v, MiscDetails::Kind::PassName);
   } else {
     attrs_->set(Attr::PASS);

flang/lib/semantics/symbol.cc

@@ -27,8 +27,7 @@ std::ostream &operator<<(std::ostream &os, const parser::CharBlock &name) {
 }
 
 template<typename T>
-static void DumpOptional(
-    std::ostream &os, const char *label, const std::optional<T> &x) {
+static void DumpOptional(std::ostream &os, const char *label, const T &x) {
   if (x) {
     os << ' ' << label << ':' << *x;
   }
@@ -435,9 +434,7 @@ std::ostream &operator<<(std::ostream &os, const Details &details) {
           },
           [&](const FinalProcDetails &) {},
           [&](const TypeParamDetails &x) {
-            if (x.type()) {
-              os << ' ' << *x.type();
-            }
+            DumpOptional(os, "type", x.type());
             os << ' ' << common::EnumToString(x.attr());
             DumpOptional(os, "init", x.init());
           },

flang/lib/semantics/symbol.h

@@ -189,8 +189,21 @@ private:
   friend std::ostream &operator<<(std::ostream &, const ObjectEntityDetails &);
 };
 
+// Mixin for details with passed-object dummy argument.
+class WithPassArg {
+public:
+  const SourceName *passName() const { return passName_; }
+  void set_passName(const SourceName &passName) { passName_ = &passName; }
+  const Symbol *passArg() const { return passArg_; }
+  void set_passArg(const Symbol *passArg) { passArg_ = passArg; }
+
+private:
+  const SourceName *passName_{nullptr};
+  const Symbol *passArg_{nullptr};
+};
+
 // A procedure pointer, dummy procedure, or external procedure
-class ProcEntityDetails : public EntityDetails {
+class ProcEntityDetails : public EntityDetails, public WithPassArg {
 public:
   ProcEntityDetails() = default;
   explicit ProcEntityDetails(EntityDetails &&d);
@@ -198,13 +211,10 @@ public:
   const ProcInterface &interface() const { return interface_; }
   ProcInterface &interface() { return interface_; }
   void set_interface(const ProcInterface &interface) { interface_ = interface; }
-  const std::optional<SourceName> &passName() const { return passName_; }
-  void set_passName(const SourceName &passName) { passName_ = passName; }
   inline bool HasExplicitInterface() const;
 
 private:
   ProcInterface interface_;
-  std::optional<SourceName> passName_;
   friend std::ostream &operator<<(std::ostream &, const ProcEntityDetails &);
 };
 
@@ -263,16 +273,13 @@ private:
   friend std::ostream &operator<<(std::ostream &, const DerivedTypeDetails &);
 };
 
-class ProcBindingDetails {
+class ProcBindingDetails : public WithPassArg {
 public:
   explicit ProcBindingDetails(const Symbol &symbol) : symbol_{&symbol} {}
   const Symbol &symbol() const { return *symbol_; }
-  std::optional<SourceName> passName() const { return passName_; }
-  void set_passName(const SourceName &passName) { passName_ = passName; }
 
 private:
   const Symbol *symbol_;  // procedure bound to
-  std::optional<SourceName> passName_;  // name in PASS attribute
 };
 
 ENUM_CLASS(GenericKind,  // Kinds of generic-spec