[flang] Implicitly convert result of statement function

[tskeith]

Summary

The result of a statement function may require an implicit conversion
to match its result type. Add that to the expression that represents
the statement function body in SubprogramDetails.

Extract the analysis of that expression into a separate function.

Dump the statement function expression as part of the dump of
SubprogramDetails.

[klausler]

flang/lib/Semantics/resolve-names.cpp

6119

Singular/plural conflict here in comment ("the symbol" vs. "have").

6134

ConvertToType() should do the right thing (nothing) if the types already match, so maybe you can simplify that if predicate.

[PeteSteinfeld]

Is there a test for this?

[tskeith]

Address review comments.

[tskeith]

In D84452#2170402, @PeteSteinfeld wrote:

Is there a test for this?

We don't currently have a way to test the expression that implements a statement function. Once they are lowered the generated code can be verified.

flang/lib/Semantics/resolve-names.cpp

 private:
   // Kind of procedure we are expecting to see in a ProcedureDesignator
   std::optional<Symbol::Flag> expectedProcFlag_;
   std::optional<SourceName> prevImportStmt_;
 
   void PreSpecificationConstruct(const parser::SpecificationConstruct &);
   void CreateGeneric(const parser::GenericSpec &);
   void FinishSpecificationPart(const std::list<parser::DeclarationConstruct> &);
+  void AnalyzeStmtFunctionStmt(const parser::StmtFunctionStmt &);
   void CheckImports();
   void CheckImport(const SourceName &, const SourceName &);
   void HandleCall(Symbol::Flag, const parser::Call &);
   void HandleProcedureName(Symbol::Flag, const parser::Name &);
   bool SetProcFlag(const parser::Name &, Symbol &, Symbol::Flag);
   void ResolveSpecificationParts(ProgramTree &);
   void AddSubpNames(ProgramTree &);
   bool BeginScopeForNode(const ProgramTree &);
if (inModule && symbol.attrs().test(Attr::EXTERNAL) &&
         !symbol.test(Symbol::Flag::Function) &&
         !symbol.test(Symbol::Flag::Subroutine)) {
       // in a module, external proc without return type is subroutine
       symbol.set(
           symbol.GetType() ? Symbol::Flag::Function : Symbol::Flag::Subroutine);
     }
   }
   currScope().InstantiateDerivedTypes(context());
-  // Analyze the bodies of statement functions now that the symbol in this
-  // specification part have been fully declared and implicitly typed.
   for (const auto &decl : decls) {
     if (const auto *statement{std::get_if<
             parser::Statement<common::Indirection<parser::StmtFunctionStmt>>>(
             &decl.u)}) {
-      const parser::StmtFunctionStmt &stmtFunc{statement->statement.value()};
-      if (Symbol * symbol{std::get<parser::Name>(stmtFunc.t).symbol}) {
-        if (auto *details{symbol->detailsIf<SubprogramDetails>()}) {
-          if (auto expr{AnalyzeExpr(context(),
-                  std::get<parser::Scalar<parser::Expr>>(stmtFunc.t))}) {
-            details->set_stmtFunction(std::move(*expr));
-          } else {
-            context().SetError(*symbol);
-          }
-        }
-      }
+      AnalyzeStmtFunctionStmt(statement->statement.value());
     }
   }
   // TODO: what about instantiations in BLOCK?
   CheckSaveStmts();
   CheckCommonBlocks();
   CheckEquivalenceSets();
 }
 
+// Analyze the bodies of statement functions now that the symbols in this
+// specification part have been fully declared and implicitly typed.
+void ResolveNamesVisitor::AnalyzeStmtFunctionStmt(
+    const parser::StmtFunctionStmt &stmtFunc) {
+  Symbol *symbol{std::get<parser::Name>(stmtFunc.t).symbol};
+  if (!symbol || !symbol->has<SubprogramDetails>()) {
+    return;
+  }
+  auto &details{symbol->get<SubprogramDetails>()};
+  auto expr{AnalyzeExpr(
+      context(), std::get<parser::Scalar<parser::Expr>>(stmtFunc.t))};
+  if (!expr) {
+    context().SetError(*symbol);
+    return;
+  }
+  if (auto type{evaluate::DynamicType::From(*symbol)}) {
+    auto converted{ConvertToType(*type, std::move(*expr))};
+    if (!converted) {
+      context().SetError(*symbol);
+      return;
+    }
+    details.set_stmtFunction(std::move(*converted));
+  } else {
+    details.set_stmtFunction(std::move(*expr));
+  }
+}
+
 void ResolveNamesVisitor::CheckImports() {
   auto &scope{currScope()};
   switch (scope.GetImportKind()) {
   case common::ImportKind::None:
     break;
   case common::ImportKind::All:
     // C8102: all entities in host must not be hidden
     for (const auto &pair : scope.parent()) {

flang/lib/Semantics/symbol.cpp

for (const Symbol *arg : x.dummyArgs_) {
     if (arg) {
       DumpType(os, *arg);
       os << arg->name();
     } else {
       os << '*';
     }
   }
   os << (sep == '(' ? "()" : ")");
+  if (x.stmtFunction_) {
+    os << " -> " << x.stmtFunction_->AsFortran();
+  }
   return os;
 }
 
 void EntityDetails::set_type(const DeclTypeSpec &type) {
   CHECK(!type_);
   type_ = &type;
 }