[flang] Move check for statement function in BLOCK construct

[klausler]

Summary

A BLOCK construct may not contain a statement function definition;
but it may of course contain an assignment statement with an array
element on its left-hand side that looks like a statement function
definition. These misparsed statement functions are converted
into assignment statements during semantics once it is clear what
they are. Move the C1107 check for a statement function definition
in a block construct into declaration checking, which is where it
probably should have been in the first place anyway.

[vdonaldson]

Thanks for the fix!

flang/lib/Semantics/check-declarations.cpp

if (auto msg{evaluate::CheckStatementFunction(
       if (const Symbol *
           host{symbol.owner().parent().FindSymbol(symbol.name())}) {
         evaluate::AttachDeclaration(
             messages_.Say(symbol.name(),
                 "An implicitly typed statement function should not appear when the same symbol is available in its host scope"_port_en_US),
             *host);
       }
     }
+    if (GetProgramUnitOrBlockConstructContaining(symbol).kind() ==
+        Scope::Kind::BlockConstruct) { // C1107
+      messages_.Say(symbol.name(),
+          "A statement function definition may not appear in a BLOCK construct"_err_en_US);
+    }
   }
   if (IsElementalProcedure(symbol)) {
     // See comment on the similar check in CheckProcEntity()
     if (details.isDummy()) {
       messages_.Say("A dummy procedure may not be ELEMENTAL"_err_en_US);
     } else {
       for (const Symbol *dummy : details.dummyArgs()) {
         if (!dummy) { // C15100

flang/lib/Semantics/resolve-names.cpp

 void ResolveNamesVisitor::Post(const parser::ProcComponentRef &x) {
   ResolveStructureComponent(x.v.thing);
 }
 void ResolveNamesVisitor::Post(const parser::TypeGuardStmt &x) {
   DeclTypeSpecVisitor::Post(x);
   ConstructVisitor::Post(x);
 }
 bool ResolveNamesVisitor::Pre(const parser::StmtFunctionStmt &x) {
-  CheckNotInBlock("STATEMENT FUNCTION"); // C1107
   if (HandleStmtFunction(x)) {
     return false;
   } else {
     // This is an array element assignment: resolve names of indices
     const auto &names{std::get<std::list<parser::Name>>(x.t)};
     for (auto &name : names) {
       ResolveName(name);
     }

flang/test/Semantics/blockconstruct01.f90

subroutine s6_c1107(x, y)
   optional x
   block
     !ERROR: OPTIONAL statement is not allowed in a BLOCK construct
     optional y
   end block
 end
 
 subroutine s7_c1107
- integer x
+ integer x, arr(1)
  inc(x) = x + 1
   block
-    !ERROR: STATEMENT FUNCTION statement is not allowed in a BLOCK construct
+    !ERROR: A statement function definition may not appear in a BLOCK construct
     dec(x) = x - 1
+    arr(x) = x - 1 ! ok
   end block
 end
-