test: characterize method symbol info

src/test/fixtures/README.md

@@ -405,3 +405,17 @@ Compiled with Scala 2.11.5 under Java 8, `-target:jvm-1.8`, against the untouche
 | --- | --- |
 | `ReferenceScalaMethodSymbolDescriptor` | `47731de0986ab2701a3d5acae0b0a93b24c979495c288383fcab4a925370c192` |
 | `ReferenceScalaMethodSymbolDescriptor$$anon$1` | `9fbfb463190e14a9be53a27add9d460d2e8e45bedb0054059806798aa098d2e1` |
+
+### `ReferenceScalaMethodSymbolInfo`
+
+`scala/codechicken/multipart/compat/ReferenceScalaMethodSymbolInfo.scala` freezes a Scala caller of
+`MethodSymbol.info`. Tests preserve the path-dependent return descriptor, virtual info-ID evaluation and failures.
+
+Compiled with Scala 2.11.5 under Java 8, `-target:jvm-1.8`, against the untouched dev jar at `257d0e4`
+(SHA-256 `1d671a402ec0fe06fcf44c0edbcca350372c05886ad2a7b3cb5fb8688ab95267`). Source SHA-256 is
+`53c16080dcd7fe271a9c89b2c869bcb8410baad88e72641d73668aea1cbfd8b8`. The frozen class file is under
+`src/test/resources/compat/`; do not regenerate it against the port.
+
+| Class | SHA-256 |
+| --- | --- |
+| `ReferenceScalaMethodSymbolInfo` | `0d89ef63187efc9f7959e292ba8e6cee1f4b68794891b913c53c3e96032c869e` |

src/test/fixtures/scala/codechicken/multipart/compat/ReferenceScalaMethodSymbolInfo.scala

@@ -0,0 +1,7 @@
+package codechicken.multipart.compat
+
+import codechicken.multipart.asm.ScalaSignature
+
+class ReferenceScalaMethodSymbolInfo {
+  def info(ref: ScalaSignature#MethodSymbol): ScalaSignature#TMethodType = ref.info
+}

src/test/java/codechicken/multipart/asm/ScalaSignatureMethodSymbolInfoTest.java

@@ -0,0 +1,209 @@
+package codechicken.multipart.asm;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.io.InputStream;
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Base64;
+import java.util.List;
+import java.util.Objects;
+import java.util.Scanner;
+import java.util.function.IntFunction;
+
+import org.junit.jupiter.api.Test;
+
+import codechicken.multipart.asm.ScalaSignature.Bytes;
+import codechicken.multipart.asm.ScalaSignature.MethodSymbol;
+import codechicken.multipart.asm.ScalaSignature.SymbolRef;
+import codechicken.multipart.asm.ScalaSignature.TMethodType;
+
+class ScalaSignatureMethodSymbolInfoTest {
+
+    private static final Fixture FIXTURE = new Fixture();
+
+    @Test
+    void returnsEvaluatedMethodTypeAndNullLiterally() throws Throwable {
+        TMethodType expected = method();
+        ProbeSignature sig = signature(index -> index == 37 ? expected : null, new ArrayList<>());
+        assertSame(expected, info(sig.new MethodSymbol(null, null, 0, 37)));
+        assertNull(info(sig.new MethodSymbol(null, null, 0, -1)));
+    }
+
+    @Test
+    void readsInfoIdThenEvalOnEveryQuery() throws Throwable {
+        List<String> calls = new ArrayList<>();
+        TMethodType expected = method();
+        ProbeSignature sig = signature(index -> expected, calls);
+        MethodSymbol ref = sig.new MethodSymbol(null, null, 0, 0) {
+
+            @Override
+            public int infoId() {
+                calls.add("infoId");
+                return 19;
+            }
+        };
+        assertSame(expected, info(ref));
+        assertSame(expected, info(ref));
+        assertEquals(Arrays.asList("infoId", "eval:19", "infoId", "eval:19"), calls);
+    }
+
+    @Test
+    void changingInfoIdsAndResultsAreNotCached() throws Throwable {
+        TMethodType first = method();
+        TMethodType second = method();
+        int[] query = { 0 };
+        ProbeSignature sig = signature(index -> index == 4 ? first : second, new ArrayList<>());
+        MethodSymbol ref = sig.new MethodSymbol(null, null, 0, 0) {
+
+            @Override
+            public int infoId() {
+                return query[0]++ == 0 ? 4 : 9;
+            }
+        };
+        assertSame(first, info(ref));
+        assertSame(second, info(ref));
+        assertEquals(2, query[0]);
+    }
+
+    @Test
+    void rejectsAnEvaluatedNonMethodType() {
+        ProbeSignature sig = signature(index -> "not a method type", new ArrayList<>());
+        assertThrows(ClassCastException.class, () -> info(sig.new MethodSymbol(null, null, 0, 0)));
+    }
+
+    @Test
+    void failuresStopAtInfoIdOrEval() {
+        RuntimeException failure = new IllegalStateException("method info lookup");
+        List<String> calls = new ArrayList<>();
+        ProbeSignature sig = signature(index -> {
+            calls.add("value");
+            throw failure;
+        }, calls);
+
+        MethodSymbol idFailure = sig.new MethodSymbol(null, null, 0, 0) {
+
+            @Override
+            public int infoId() {
+                calls.add("infoId");
+                throw failure;
+            }
+        };
+        assertSame(failure, assertThrows(RuntimeException.class, () -> info(idFailure)));
+        assertEquals(Arrays.asList("infoId"), calls);
+
+        calls.clear();
+        MethodSymbol evalFailure = sig.new MethodSymbol(null, null, 0, 8) {
+
+            @Override
+            public int infoId() {
+                calls.add("infoId");
+                return 8;
+            }
+        };
+        assertSame(failure, assertThrows(RuntimeException.class, () -> info(evalFailure)));
+        assertEquals(Arrays.asList("infoId", "eval:8", "value"), calls);
+    }
+
+    @Test
+    void infoDoesNotReadOtherSymbolOrMethodTypeMembers() throws Throwable {
+        TMethodType expected = method();
+        ProbeSignature sig = signature(index -> expected, new ArrayList<>());
+        MethodSymbol ref = sig.new MethodSymbol(null, null, 0, 3) {
+
+            @Override
+            public String name() {
+                throw new AssertionError("name");
+            }
+
+            @Override
+            public SymbolRef owner() {
+                throw new AssertionError("owner");
+            }
+
+            @Override
+            public int flags() {
+                throw new AssertionError("flags");
+            }
+
+            @Override
+            public String full() {
+                throw new AssertionError("full");
+            }
+
+            @Override
+            public String jDesc() {
+                throw new AssertionError("jDesc");
+            }
+        };
+        assertSame(expected, info(ref));
+    }
+
+    @Test
+    void frozenScalaCallerKeepsItsReturnDescriptorAndNullReceiverFailure() throws Throwable {
+        assertEquals(TMethodType.class, FIXTURE.returnType);
+        assertThrows(NullPointerException.class, () -> info(null));
+    }
+
+    private static TMethodType method() {
+        return (TMethodType) java.lang.reflect.Proxy.newProxyInstance(
+                TMethodType.class.getClassLoader(),
+                new Class<?>[] { TMethodType.class },
+                (proxy, method, args) -> { throw new AssertionError(method.getName()); });
+    }
+
+    private static TMethodType info(MethodSymbol ref) throws Throwable {
+        return (TMethodType) FIXTURE.info.invoke(ref);
+    }
+
+    private static ProbeSignature signature(IntFunction<Object> values, List<String> calls) {
+        return new ProbeSignature(values, calls);
+    }
+
+    private static final class ProbeSignature extends ScalaSignature {
+
+        private final IntFunction<Object> values;
+        private final List<String> calls;
+
+        ProbeSignature(IntFunction<Object> values, List<String> calls) {
+            super(new Bytes(new byte[] { 5, 0, 0 }, 0, 3));
+            this.values = values;
+            this.calls = calls;
+        }
+
+        @Override
+        @SuppressWarnings("unchecked")
+        public <T> T evalT(int index) {
+            calls.add("eval:" + index);
+            return (T) values.apply(index);
+        }
+    }
+
+    private static final class Fixture extends ClassLoader {
+
+        final MethodHandle info;
+        final Class<?> returnType;
+
+        Fixture() {
+            super(ScalaSignatureMethodSymbolInfoTest.class.getClassLoader());
+            try {
+                String base = "ReferenceScalaMethodSymbolInfo";
+                byte[] bytes;
+                try (InputStream stream = Objects.requireNonNull(getResourceAsStream("compat/" + base + ".class.b64"));
+                        Scanner scanner = new Scanner(stream, StandardCharsets.UTF_8.name()).useDelimiter("\\A")) {
+                    bytes = Base64.getMimeDecoder().decode(scanner.next());
+                }
+                Class<?> type = defineClass(null, bytes, 0, bytes.length);
+                Object instance = type.getConstructor().newInstance();
+                java.lang.reflect.Method method = type.getMethod("info", MethodSymbol.class);
+                returnType = method.getReturnType();
+                info = MethodHandles.publicLookup().unreflect(method).bindTo(instance);
+            } catch (ReflectiveOperationException | java.io.IOException e) {
+                throw new AssertionError(e);
+            }
+        }
+    }
+}

src/test/resources/compat/ReferenceScalaMethodSymbolInfo.class.b64

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