[flang] Prevent lowering crash by properly updating symbol pointer

Kind of an edge case.  When a MODULE FUNCTION or SUBROUTINE
interface is defined by a MODULE PROCEDURE in the same program
unit, ensure that the symbol table pointer in the parse tree is
updated to point to the SubprogramDetails symbol for the
interface, and not left pointing to what should soon become
a dead SubprogramNameDetails symbol.

Differential Revision: https://reviews.llvm.org/D154380

Author: klausler

flang/lib/Semantics/resolve-names.cpp

@@ -4005,6 +4005,7 @@ bool SubprogramVisitor::BeginMpSubprogram(const parser::Name &name) {
     // Convert the module procedure's interface into a subprogram.
     SetScope(DEREF(symbol->scope()));
     symbol->get<SubprogramDetails>().set_isInterface(false);
+    name.symbol = symbol;
   } else {
     // Copy the interface into a new subprogram scope.
     EraseSymbol(name);
@@ -4025,7 +4026,8 @@ bool SubprogramVisitor::BeginSubprogram(const parser::Name &name,
     Symbol::Flag subpFlag, bool hasModulePrefix,
     const parser::LanguageBindingSpec *bindingSpec,
     const ProgramTree::EntryStmtList *entryStmts) {
-  if (hasModulePrefix && currScope().IsGlobal()) { // C1547
+  if (hasModulePrefix && !currScope().IsModule() &&
+      !currScope().IsSubmodule()) { // C1547
     Say(name,
         "'%s' is a MODULE procedure which must be declared within a "
         "MODULE or SUBMODULE"_err_en_US);

flang/test/Semantics/symbol28.f90

@@ -43,7 +43,7 @@ module subroutine s2 (j)
   end subroutine
  end interface
 contains
- !DEF: /m2/s MODULE SubprogramName
+ !REF:/m2/s
  module procedure s
  end procedure
  !DEF: /m2/s2 MODULE, PUBLIC (Subroutine) Subprogram