[flang] Prioritize DATA object error messages a little better (llvm#66258)

When a DATA statement object is not valid, there's a number of possible
reasons. Emit an error message for the most egregious violation, so that
an unlucky user doesn't fix something easy (due to a less-severe error
message masking one that is worse) and then run into something that
might be more serious.

Author: klausler

flang/lib/Semantics/check-data.cpp

@@ -58,21 +58,24 @@ class DataVarChecker : public evaluate::AllTraverse<DataVarChecker, true> {
     const Scope &scope{context_.FindScope(source_)};
     bool isFirstSymbol{isFirstSymbol_};
     isFirstSymbol_ = false;
-    if (const char *whyNot{IsAutomatic(symbol) ? "Automatic variable"
-                : IsDummy(symbol)              ? "Dummy argument"
-                : IsFunctionResult(symbol)     ? "Function result"
-                : IsAllocatable(symbol)        ? "Allocatable"
+    // Ordered so that most egregious errors are first
+    if (const char *whyNot{IsProcedure(symbol) && !IsPointer(symbol)
+                ? "Procedure"
+                : isFirstSymbol && IsHostAssociated(symbol, scope)
+                ? "Host-associated object"
+                : isFirstSymbol && IsUseAssociated(symbol, scope)
+                ? "USE-associated object"
+                : IsDummy(symbol)          ? "Dummy argument"
+                : IsFunctionResult(symbol) ? "Function result"
+                : IsAutomatic(symbol)      ? "Automatic variable"
+                : IsAllocatable(symbol)    ? "Allocatable"
                 : IsInitialized(symbol, true /*ignore DATA*/,
                       true /*ignore allocatable components*/,
                       true /*ignore uninitialized pointer components*/)
                 ? "Default-initialized"
-                : IsProcedure(symbol) && !IsPointer(symbol) ? "Procedure"
-                // remaining checks don't apply to components
-                : !isFirstSymbol                   ? nullptr
-                : IsHostAssociated(symbol, scope)  ? "Host-associated object"
-                : IsUseAssociated(symbol, scope)   ? "USE-associated object"
                 : symbol.has<AssocEntityDetails>() ? "Construct association"
-                : IsPointer(symbol) && (hasComponent_ || hasSubscript_)
+                : isFirstSymbol && IsPointer(symbol) &&
+                    (hasComponent_ || hasSubscript_)
                 ? "Target of pointer"
                 : nullptr}) {
       context_.Say(source_,

flang/test/Semantics/data18.f90

@@ -0,0 +1,59 @@
+! RUN: %python %S/test_errors.py %s %flang_fc1
+! Test error message priorities for DATA problems
+module m
+  integer useAlloc
+  allocatable useAlloc
+  integer, pointer :: usePtr(:)
+ contains
+  subroutine useProc
+  end
+end
+function f(hostDummy, hostProc) result(hostResult)
+  integer hostDummy, hostResult
+  external hostProc
+  integer hostAuto(hostDummy)
+  integer, allocatable :: hostAlloc
+  integer :: hostInit = 1
+  integer, pointer :: hostPtr(:)
+ contains
+  subroutine test(innerDummy, innerProc)
+    use m
+    external innerProc
+    integer innerAuto(innerDummy)
+    integer, allocatable :: innerAlloc
+    integer :: innerInit = 1
+    integer, pointer :: innerPtr(:)
+    !ERROR: Procedure 'useproc' must not be initialized in a DATA statement
+    data useProc/0/
+    !ERROR: Procedure 'hostproc' must not be initialized in a DATA statement
+    data hostProc/0/
+    !ERROR: Procedure 'innerproc' must not be initialized in a DATA statement
+    data innerProc/0/
+    !ERROR: Host-associated object 'hostdummy' must not be initialized in a DATA statement
+    data hostDummy/1/
+    !ERROR: Host-associated object 'hostresult' must not be initialized in a DATA statement
+    data hostResult/1/
+    !ERROR: Host-associated object 'hostauto' must not be initialized in a DATA statement
+    data hostAuto/1/
+    !ERROR: Host-associated object 'hostalloc' must not be initialized in a DATA statement
+    data hostAlloc/1/
+    !ERROR: Host-associated object 'hostinit' must not be initialized in a DATA statement
+    data hostInit/1/
+    !ERROR: Host-associated object 'hostptr' must not be initialized in a DATA statement
+    data hostPtr(1)/1/
+    !ERROR: USE-associated object 'usealloc' must not be initialized in a DATA statement
+    data useAlloc/1/
+    !ERROR: USE-associated object 'useptr' must not be initialized in a DATA statement
+    data usePtr(1)/1/
+    !ERROR: Dummy argument 'innerdummy' must not be initialized in a DATA statement
+    data innerDummy/1/
+    !ERROR: Automatic variable 'innerauto' must not be initialized in a DATA statement
+    data innerAuto/1/
+    !ERROR: Allocatable 'inneralloc' must not be initialized in a DATA statement
+    data innerAlloc/1/
+    !ERROR: Default-initialized 'innerinit' must not be initialized in a DATA statement
+    data innerInit/1/
+    !ERROR: Target of pointer 'innerptr' must not be initialized in a DATA statement
+    data innerptr(1)/1/
+  end
+end