karm-io: fix Re::negate, update gitignore for intelliJ

.gitignore

@@ -5,3 +5,5 @@ __pycache__/
 .python-version
 book/
 *.code-workspace
+.idea/
+skift.iml

src/libs/karm-io/expr.h

@@ -52,7 +52,15 @@ auto operator&(Expr auto a, Expr auto b) {
 /// Inverts the result of the expression.
 inline auto negate(Expr auto expr) {
     return [=](auto &scan) {
-        return not expr(scan);
+        auto saved = scan;
+        if (not expr(scan)) {
+            if (scan.ended())
+                return false;
+            scan.next();
+            return true;
+        }
+        scan = saved;
+        return false;
     };
 }
 

src/libs/karm-io/tests/text-expr.cpp

@@ -24,4 +24,14 @@ test$(exprSingle) {
     return Ok();
 }
 
+test$(exprNegate) {
+    expect$(Re::match(~'a'_re, "") == Match::NO);
+    expect$(Re::match(~'a'_re, "b") == Match::YES);
+    expect$(Re::match(~'a'_re, "a") == Match::NO);
+    expect$(Re::match((~'a'_re) & 'a'_re, "ba") == Match::YES);
+    expect$(Re::match((~'a'_re) & 'a'_re, "aa") == Match::NO);
+
+    return Ok();
+}
+
 } // namespace Karm::Io::Tests