[flang] Allow nested scopes for implied DO loops with DATA statements

[eugeneepshteyn]

Previously, nested scopes for implied DO loops with DATA statements were disallowed, which meant that the following code couldn't compile due to re-use of j loop variable name:

DATA (a(i),(b(i,j),j=1,3),(c(i,j),j=1,3),i=0,4)/

This change allows nested scopes implied DO loops, which allows the code above to compile.

Tests modified to in accordance with this change: Semantics/resolve40.f90, Semantics/symbol09.f90

[llvmbot]

@llvm/pr-subscribers-flang-semantics

Author: Eugene Epshteyn (eugeneepshteyn)

Changes

Previously, nested scopes for implied DO loops with DATA statements were disallowed, which meant that the following code couldn't compile due to re-use of j loop variable name:

DATA (a(i),(b(i,j),j=1,3),(c(i,j),j=1,3),i=0,4)/

This change allows nested scopes implied DO loops, which allows the code above to compile.

Tests modified to in accordance with this change: Semantics/resolve40.f90, Semantics/symbol09.f90

---

Full diff: https://github.com/llvm/llvm-project/pull/129410.diff

3 Files Affected:

• (modified) flang/lib/Semantics/resolve-names.cpp (+4-9)
• (modified) flang/test/Semantics/resolve40.f90 (+2-2)
• (modified) flang/test/Semantics/symbol09.f90 (+1-1)

diff --git a/flang/lib/Semantics/resolve-names.cpp b/flang/lib/Semantics/resolve-names.cpp
index 1514c01a49528..d29e04869e615 100644
--- a/flang/lib/Semantics/resolve-names.cpp
+++ b/flang/lib/Semantics/resolve-names.cpp
@@ -7477,15 +7477,10 @@ bool ConstructVisitor::Pre(const parser::DataImpliedDo &x) {
   Walk(bounds.upper);
   Walk(bounds.step);
   EndCheckOnIndexUseInOwnBounds(restore);
-  bool pushScope{currScope().kind() != Scope::Kind::ImpliedDos};
-  if (pushScope) {
-    PushScope(Scope::Kind::ImpliedDos, nullptr);
-  }
+  PushScope(Scope::Kind::ImpliedDos, nullptr);
   DeclareStatementEntity(bounds.name, type);
   Walk(objects);
-  if (pushScope) {
-    PopScope();
-  }
+  PopScope();
   return false;
 }
 
@@ -7526,9 +7521,9 @@ bool ConstructVisitor::Pre(const parser::DataStmtObject &x) {
             }
           },
           [&](const parser::DataImpliedDo &y) {
-            PushScope(Scope::Kind::ImpliedDos, nullptr);
+            // Don't push scope here, since it's done when visiting
+            // DataImpliedDo.
             Walk(y);
-            PopScope();
           },
       },
       x.u);
diff --git a/flang/test/Semantics/resolve40.f90 b/flang/test/Semantics/resolve40.f90
index b3384a91097d7..a91507aa62282 100644
--- a/flang/test/Semantics/resolve40.f90
+++ b/flang/test/Semantics/resolve40.f90
@@ -69,8 +69,8 @@ subroutine s8
 
 subroutine s9
   real :: x(2,2)
-  !ERROR: 'i' is already declared in this scoping unit
-  data ((x(i,i),i=1,2),i=1,2)/4*0.0/
+  ! Nested implied DO loops have their own scope
+  data ((x(i,j),j=1,2),(x(i,j),j=1,2),i=1,2)/8*0.0/
 end
 
 module m10
diff --git a/flang/test/Semantics/symbol09.f90 b/flang/test/Semantics/symbol09.f90
index 98cd1d954c3e7..0ed80b55b34d1 100644
--- a/flang/test/Semantics/symbol09.f90
+++ b/flang/test/Semantics/symbol09.f90
@@ -51,7 +51,7 @@ subroutine s3
  real, dimension(n,n) :: x
  !REF: /s3/x
  !DEF: /s3/ImpliedDos1/k (Implicit) ObjectEntity INTEGER(4)
- !DEF: /s3/ImpliedDos1/j ObjectEntity INTEGER(8)
+ !DEF: /s3/ImpliedDos1/ImpliedDos1/j ObjectEntity INTEGER(8)
  !REF: /s3/n
  !REF: /s3/n2
  data ((x(k,j),integer(kind=8)::j=1,n),k=1,n)/n2*3.0/