Add regression tests for var locals and yielded refined constructors (#344, #346, #347)

These reproducers already verify on main: since Spoon parses at the
project's compliance level (21 by default, #352, #368), a var local gets
the static type of its initialiser instead of a type named "var", and
switch expressions with yield are modelled correctly. With a pre-10
compliance level, the null type of a var comparison is now also handled
as an unresolved type (#388).

Fixes #344
Fixes #346
Fixes #347

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: CatarinaGamboa

liquidjava-example/src/main/java/testSuite/CorrectVarLocal.java

@@ -0,0 +1,28 @@
+package testSuite;
+
+import liquidjava.specification.Refinement;
+import liquidjava.specification.RefinementAlias;
+
+// A var local has the static type of its initialiser (#344, #347)
+@SuppressWarnings("unused")
+@RefinementAlias("Port(int x) { 0 <= x && x <= 65535 }")
+public class CorrectVarLocal {
+    static String name() {
+        return "x";
+    }
+
+    static void connect(@Refinement("Port(_)") int port) {
+    }
+
+    static void nullCheck() {
+        var n = name();
+        if (n == null) {
+            throw new IllegalArgumentException("no name");
+        }
+    }
+
+    static void refinedArgument() {
+        var port = 80;
+        connect(port);
+    }
+}

liquidjava-example/src/main/java/testSuite/CorrectYieldRefinedConstructor.java

@@ -0,0 +1,21 @@
+package testSuite;
+
+import liquidjava.specification.Refinement;
+
+// Yielding a call to a refined constructor from a switch expression (#346)
+@SuppressWarnings("unused")
+public class CorrectYieldRefinedConstructor {
+    static class Conn {
+        public Conn(@Refinement("_ > 0") int port) {
+        }
+    }
+
+    static Conn open(String scheme) {
+        return switch (scheme) {
+        case "tcp" -> {
+            yield new Conn(80);
+        }
+        default -> new Conn(1);
+        };
+    }
+}

liquidjava-example/src/main/java/testSuite/ErrorVarLocal.java

@@ -0,0 +1,17 @@
+package testSuite;
+
+import liquidjava.specification.Refinement;
+import liquidjava.specification.RefinementAlias;
+
+// The value of a var local is still checked against a refined parameter (#347)
+@SuppressWarnings("unused")
+@RefinementAlias("Port(int x) { 0 <= x && x <= 65535 }")
+public class ErrorVarLocal {
+    static void connect(@Refinement("Port(_)") int port) {
+    }
+
+    static void refinedArgument() {
+        var port = 70000;
+        connect(port); // Expect: Refinement Error
+    }
+}

liquidjava-example/src/main/java/testSuite/ErrorYieldRefinedConstructor.java

@@ -0,0 +1,21 @@
+package testSuite;
+
+import liquidjava.specification.Refinement;
+
+// The arguments of a refined constructor yielded from a switch expression are checked (#346)
+@SuppressWarnings("unused")
+public class ErrorYieldRefinedConstructor {
+    static class Conn {
+        public Conn(@Refinement("_ > 0") int port) {
+        }
+    }
+
+    static Conn open(String scheme) {
+        return switch (scheme) {
+        case "tcp" -> {
+            yield new Conn(-1); // Expect: Refinement Error
+        }
+        default -> new Conn(1);
+        };
+    }
+}