[flang] Recognize complex-part-designator

The "%RE" or "%IM" is parsed as a structure-component.
If the base has type COMPLEX and the component name is one
of those, allow it without comment.

Note that the `parser::Name` for these components don't get
symbols filled in, so we still get a warning that they are
unresolved. We have to figure out how to deal with names
like this that we won't have symbols for.

Fixes flang-compiler/f18#188.

Original-commit: flang-compiler/f18@1d4a84fe3c
Reviewed-on: https://github.com/flang-compiler/f18/pull/194
Tree-same-pre-rewrite: false

flang/lib/semantics/resolve-names.cc

@@ -2595,6 +2595,13 @@ Symbol *ResolveNamesVisitor::FindComponent(
   if (!type) {
     return nullptr;  // should have already reported error
   }
+  if (type->category() == DeclTypeSpec::Intrinsic &&
+      type->intrinsicTypeSpec().category() == TypeCategory::Complex) {
+    auto name{component.ToString()};
+    if (name == "re" || name == "im") {
+      return nullptr;  // complex-part-designator, not structure-component
+    }
+  }
   if (type->category() != DeclTypeSpec::TypeDerived) {
     if (base.test(Symbol::Flag::Implicit)) {
       Say(base.lastOccurrence(),

flang/test/semantics/CMakeLists.txt

@@ -69,6 +69,7 @@ set(SYMBOL_TESTS
   symbol04.f90
   symbol05.f90
   symbol06.f90
+  symbol07.f90
 )
 
 # These test files have expected .mod file contents in the source

flang/test/semantics/symbol07.f90

@@ -0,0 +1,53 @@
+! Copyright (c) 2018, NVIDIA CORPORATION.  All rights reserved.
+!
+! Licensed under the Apache License, Version 2.0 (the "License");
+! you may not use this file except in compliance with the License.
+! You may obtain a copy of the License at
+!
+!     http://www.apache.org/licenses/LICENSE-2.0
+!
+! Unless required by applicable law or agreed to in writing, software
+! distributed under the License is distributed on an "AS IS" BASIS,
+! WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+! See the License for the specific language governing permissions and
+! limitations under the License.
+
+!DEF: /main MainProgram
+program main
+ implicit complex(z)
+ !DEF: /main/t DerivedType
+ type :: t
+  !DEF: /main/t/re ObjectEntity REAL(4)
+  real :: re
+  !DEF: /main/t/im ObjectEntity REAL(4)
+  real :: im
+ end type
+ !DEF: /main/z1 ObjectEntity COMPLEX(4)
+ complex z1
+ !DEF: /main/w ObjectEntity TYPE(t)
+ !REF: /main/t
+ type(t) :: w
+ !DEF: /main/x ObjectEntity REAL(4)
+ !DEF: /main/y ObjectEntity REAL(4)
+ real x, y
+ !REF: /main/x
+ !REF: /main/z1
+ x = z1%re
+ !REF: /main/y
+ !REF: /main/z1
+ y = z1%im
+ !DEF: /main/z2 (implicit) ObjectEntity COMPLEX(4)
+ !REF: /main/x
+ z2%re = x
+ !REF: /main/z2
+ !REF: /main/y
+ z2%im = y
+ !REF: /main/x
+ !REF: /main/w
+ !REF: /main/t/re
+ x = w%re
+ !REF: /main/y
+ !REF: /main/w
+ !REF: /main/t/im
+ y = w%im
+end program