(Closes #466) Fix for "==" when matching implicit loop in array constructor

CHANGELOG.md

@@ -19,6 +19,8 @@ Modifications by (in alphabetical order):
 * P. Vitt, University of Siegen, Germany
 * A. Voysey, UK Met Office
 
+21/07/2025 PR #467 for #466. Fix "==" when matching implicit loops in array constructors.
+
 26/06/2025 PR #471 for #470. Drop support for Python 3.7 and 3.8.
 
 25/06/2025 PR #459 for #458. Improvements to the 'make public' example script.

src/fparser/two/Fortran2003.py

@@ -2945,13 +2945,24 @@ class Ac_Implied_Do(Base):
     use_names = ["Ac_Value_List", "Ac_Implied_Do_Control"]
 
     @staticmethod
-    def match(string):
+    def match(string: str):
+        """
+        Attempts to match the supplied string as an implicit do within an
+        array constructor.
+
+        :param string: the text to match against.
+
+        :returns: a tuple describing the match or None if there is no match.
+        :rtype: Optional[Tuple[Ac_Value_List, Ac_Implied_Do_Control]]
+
+        """
         if string[0] + string[-1] != "()":
-            return
+            return None
         line, repmap = string_replace_map(string[1:-1].strip())
         i = line.rfind("=")
-        if i == -1:
-            return
+        if i == -1 or (i > 0 and line[i - 1] == "="):
+            # No "=" or it is "==" so no match.
+            return None
         j = line[:i].rfind(",")
         assert j != -1
         s1 = repmap(line[:j].rstrip())

src/fparser/two/tests/fortran2003/test_array_constructor_implied_do_r470.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2020-2021 Science and Technology Facilities Council.
+# Copyright (c) 2020-2025 Science and Technology Facilities Council.
 #
 # All rights reserved.
 #
@@ -57,6 +57,18 @@ def test_implicit_loop_constructor_no_parentheses():
     assert ast is None
 
 
+@pytest.mark.usefixtures("f2003_create")
+def test_no_implicit_loop_constructor_with_is_equal_to():
+    """Test that the parser does not match an implicit loop if the
+    array constructor contains '=='."""
+    fcode = "(/lval1, ival1==ival2/)"
+    reader = FortranStringReader(fcode)
+    ast = Fortran2003.Array_Constructor(reader)
+    # Should have an array constructor without an implicit loop.
+    assert isinstance(ast, Fortran2003.Array_Constructor)
+    assert isinstance(ast.children[1], Fortran2003.Ac_Value_List)
+
+
 @pytest.mark.xfail(reason="#257 Constraint C497 is not checked.")
 @pytest.mark.usefixtures("f2003_create")
 def test_nested_implied_do():

src/fparser/two/tests/fortran2003/test_intrinsics.py

@@ -1,7 +1,7 @@
 # -----------------------------------------------------------------------------
 # BSD 3-Clause License
 #
-# Copyright (c) 2019-2023, Science and Technology Facilities Council.
+# Copyright (c) 2019-2025, Science and Technology Facilities Council.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -206,6 +206,17 @@ def test_intrinsic_function_reference_unlimited_args():
         assert str(result) == f"MAX({args})"
 
 
+@pytest.mark.usefixtures("f2003_create")
+def test_intrinsic_function_reference_all_args():
+    """Check that we match a call to ALL containing an array constructor
+    of logical type.
+
+    """
+    code = "all( (/ var1, var2, (i1==i2) /) )"
+    result = Intrinsic_Function_Reference(code)
+    assert isinstance(result, Intrinsic_Function_Reference)
+
+
 @pytest.mark.usefixtures("f2003_create")
 def test_intrinsic_function_reference_error1():
     """Test that class Intrinsic_Function_Reference raises the expected