Merge branch 'topic/fix_use_if_expr' into 'master'

Fix the "Use_If_Expressions" rule

Closes #406

See merge request eng/libadalang/langkit-query-language!347

Author: HugoGGuerrier

lkql_checker/share/lkql/use_if_expressions.lkql

@@ -1,6 +1,6 @@
-fun simple_return(l) = l.children_count == 1 and l[1] is ReturnStmt
+fun simple_return(l) = l != null and l.children_count == 1 and l[1] is ReturnStmt
 fun simple_assignment(l) =
-    l.children_count == 1 and l[1] is AssignStmt(f_dest: Name)
+    l != null and l.children_count == 1 and l[1] is AssignStmt(f_dest: Name)
 
 @check(message="IF statement may be replaced by an IF expression",
        category="Style", subcategory="Programming Practice")
@@ -52,11 +52,11 @@ fun use_if_expressions(node) =
     |"    end if;
     node is IfStmt
     when (simple_return(node.f_then_stmts) and
-          simple_return(node.f_else_part.f_stmts) and
+          simple_return(node.f_else_part?.f_stmts) and
           not [s for s in node.f_alternatives.children
                if not simple_return(s.f_stmts)])
       or (simple_assignment(node.f_then_stmts) and
-          simple_assignment(node.f_else_part.f_stmts) and
+          simple_assignment(node.f_else_part?.f_stmts) and
           not [s for s in node.f_alternatives.children
                if not simple_assignment(s.f_stmts)] and {
           val stmts = from node select AssignStmt;

testsuite/tests/checks/use_if_expressions/stmt.adb

@@ -45,5 +45,9 @@ begin
       X := 0;
    end if;
 
+   if X > 0 then    --  NOFLAG
+      return 2;
+   end if:
+
    return X;
 end Stmt;