interpreterbase: protect string division with FeatureNew

Meson is not warning if you join paths with / but you are requesting a
version older than 0.49.0; fix this before adding more features to the
division operator.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

mesonbuild/interpreterbase.py

@@ -606,6 +606,23 @@ The result of this is undefined and will become a hard error in a future Meson r
             raise InterpreterException('Argument to negation is not an integer.')
         return -v
 
+    @FeatureNew('/ with string arguments', '0.49.0')
+    def evaluate_path_join(self, l, r):
+        if not isinstance(l, str):
+            raise InvalidCode('The division operator can only append to a string.')
+        if not isinstance(r, str):
+            raise InvalidCode('The division operator can only append a string.')
+        return self.join_path_strings((l, r))
+
+    def evaluate_division(self, l, r):
+        if isinstance(l, str) or isinstance(r, str):
+            return self.evaluate_path_join(l, r)
+        if isinstance(l, int) and isinstance(r, int):
+            if r == 0:
+                raise InvalidCode('Division by zero.')
+            return l // r
+        raise InvalidCode('Division works only with strings or integers.')
+
     def evaluate_arithmeticstatement(self, cur):
         l = self.evaluate_statement(cur.left)
         if is_disabler(l):
@@ -630,13 +647,7 @@ The result of this is undefined and will become a hard error in a future Meson r
                 raise InvalidCode('Multiplication works only with integers.')
             return l * r
         elif cur.operation == 'div':
-            if isinstance(l, str) and isinstance(r, str):
-                return self.join_path_strings((l, r))
-            if isinstance(l, int) and isinstance(r, int):
-                if r == 0:
-                    raise InvalidCode('Division by zero.')
-                return l // r
-            raise InvalidCode('Division works only with strings or integers.')
+            return self.evaluate_division(l, r)
         elif cur.operation == 'mod':
             if not isinstance(l, int) or not isinstance(r, int):
                 raise InvalidCode('Modulo works only with integers.')

run_project_tests.py

@@ -547,6 +547,7 @@ def detect_tests_to_run():
     # Name, subdirectory, skip condition.
     all_tests = [
         ('common', 'common', False),
+        ('warning-meson', 'warning', False),
         ('failing-meson', 'failing', False),
         ('failing-build', 'failing build', False),
         ('failing-test',  'failing test', False),
@@ -623,9 +624,14 @@ def _run_tests(all_tests, log_name_base, failfast, extra_args):
             (testnum, testbase) = t.name.split(' ', 1)
             testname = '%.3d %s' % (int(testnum), testbase)
             should_fail = False
+            suite_args = []
             if name.startswith('failing'):
                 should_fail = name.split('failing-')[1]
-            result = executor.submit(run_test, skipped, t.as_posix(), extra_args, system_compiler, backend, backend_flags, commands, should_fail)
+            if name.startswith('warning'):
+                suite_args = ['--fatal-meson-warnings']
+                should_fail = name.split('warning-')[1]
+            result = executor.submit(run_test, skipped, t.as_posix(), extra_args + suite_args,
+                                     system_compiler, backend, backend_flags, commands, should_fail)
             futures.append((testname, t, result))
         for (testname, t, result) in futures:
             sys.stdout.flush()

test cases/warning/1 version for string div/a/b.c

@@ -0,0 +1,3 @@
+int main()
+{
+}

test cases/warning/1 version for string div/meson.build

@@ -0,0 +1,3 @@
+project('warn on string division', 'c', meson_version: '>=0.48.0')
+
+executable('prog', 'a' / 'b.c')