[flang] Support kind/index lookup inside of EQUIVALENCE (#170056)

Turn off "in EQUIVALENCE" check for processing of array subscripts,
since subscripts themselves are not part of the EQUIVALENCE.

Fixes #169590

Author: eugeneepshteyn

flang/lib/Semantics/resolve-names.cpp

@@ -2153,6 +2153,8 @@ class ResolveNamesVisitor : public virtual ScopeHandler,
   void Post(const parser::AssignedGotoStmt &);
   void Post(const parser::CompilerDirective &);
 
+  bool Pre(const parser::SectionSubscript &);
+
   // These nodes should never be reached: they are handled in ProgramUnit
   bool Pre(const parser::MainProgram &) {
     llvm_unreachable("This node is handled in ProgramUnit");
@@ -10218,6 +10220,14 @@ template <typename A> std::set<SourceName> GetUses(const A &x) {
   return uses;
 }
 
+bool ResolveNamesVisitor::Pre(const parser::SectionSubscript &x) {
+  // Turn off "in EQUIVALENCE" check for array indexing, because
+  // the indices themselves are not part of the EQUIVALENCE.
+  auto restorer{common::ScopedSet(inEquivalenceStmt_, false)};
+  Walk(x.u);
+  return false;
+}
+
 bool ResolveNamesVisitor::Pre(const parser::Program &x) {
   if (Scope * hermetic{context().currentHermeticModuleFileScope()}) {
     // Processing either the dependent modules or first module of a

flang/test/Semantics/equiv-kind.f90

@@ -0,0 +1,19 @@
+! RUN: %flang_fc1 -fdebug-unparse %s 2>&1 | FileCheck %s
+module equiv_kind_m
+  implicit none
+  integer, parameter :: knd = kind(42)
+  integer, parameter :: dim_2 = 1_knd
+  integer, parameter :: n = 3_knd
+  integer, parameter :: i_start = 1_knd
+contains
+subroutine test()
+  integer(knd) :: a(n),b(n,n)
+  character(len=5) :: small_ch
+  character(len=20) :: large_ch
+
+  equivalence (a(1_knd),b(1_knd,dim_2))
+  !CHECK: EQUIVALENCE (a(1_4), b(1_4,1_4))
+  equivalence (small_ch, large_ch(i_start:5_knd))
+  !CHECK: EQUIVALENCE (small_ch, large_ch(1_4:5_4))
+end subroutine test
+end module equiv_kind_m