do not fully validate parameter indices in hasEntry (#238)

* do not fully validate parameter indices in hasEntry

* checkstyle

enigma/src/main/java/org/quiltmc/enigma/api/EnigmaProject.java

@@ -170,7 +170,7 @@ public boolean isNavigable(Entry<?> obfEntry) {
 			return false;
 		}
 
-		return this.jarIndex.getIndex(EntryIndex.class).hasEntry(obfEntry, this);
+		return this.jarIndex.getIndex(EntryIndex.class).hasEntry(obfEntry);
 	}
 
 	public boolean isRenamable(Entry<?> obfEntry) {
@@ -211,7 +211,7 @@ public boolean isRenamable(Entry<?> obfEntry) {
 			return false;
 		}
 
-		return this.jarIndex.getIndex(EntryIndex.class).hasEntry(obfEntry, this);
+		return this.jarIndex.getIndex(EntryIndex.class).hasEntry(obfEntry);
 	}
 
 	private static boolean isEnumValueOfMethod(ClassDefEntry parent, MethodEntry method) {
@@ -237,7 +237,7 @@ public boolean isObfuscated(Entry<?> entry) {
 	}
 
 	public boolean isSynthetic(Entry<?> entry) {
-		return this.jarIndex.getIndex(EntryIndex.class).hasEntry(entry, this) && this.jarIndex.getIndex(EntryIndex.class).getEntryAccess(entry).isSynthetic();
+		return this.jarIndex.getIndex(EntryIndex.class).hasEntry(entry) && this.jarIndex.getIndex(EntryIndex.class).getEntryAccess(entry).isSynthetic();
 	}
 
 	public boolean isAnonymousOrLocal(ClassEntry classEntry) {
@@ -246,6 +246,42 @@ public boolean isAnonymousOrLocal(ClassEntry classEntry) {
 		return enclosingMethodIndex.hasEnclosingMethod(classEntry);
 	}
 
+	/**
+	 * Verifies that the provided {@code parameter} has a valid index for its parent method.
+	 * This method validates both the upper and lower bounds of the parent method's index range.
+	 *
+	 * <p>Note that this method could still return {@code true} for an invalid index in the case that the index is impossible due to double-size parameters --
+	 * for example, if the index is 4 and there's a double at index 3, the index would be invalid.
+	 * But honestly, we at <a href=https://quiltmc.org>QuiltMC</a> doubt that that's a situation you'll ever be running into.
+	 * If it is, complain <a href=https://github.com/QuiltMC/enigma/issues>in our issue tracker</a> about us writing this whole comment instead of implementing that functionality.
+	 *
+	 * @param parameter the parameter to validate
+	 * @return whether the index is valid
+	 */
+	public boolean validateParameterIndex(LocalVariableEntry parameter) {
+		MethodEntry parent = parameter.getParent();
+		EntryIndex index = this.jarIndex.getIndex(EntryIndex.class);
+
+		if (index.hasMethod(parent)) {
+			AtomicInteger maxLocals = new AtomicInteger(-1);
+			ClassEntry parentClass = parent != null ? parent.getParent() : null;
+
+			// find max_locals for method, representing the number of parameters it receives (JVMS§4.7.3)
+			// note: parent class cannot be null, warning suppressed
+			ClassNode classNode = this.getClassProvider().get(parentClass.getFullName());
+			if (classNode != null) {
+				classNode.methods.stream()
+					.filter(node -> node.name.equals(parent.getName()) && node.desc.equals(parent.getDesc().toString()))
+					.findFirst().ifPresent(node -> maxLocals.set(node.maxLocals));
+			}
+
+			// if maxLocals is -1 it's not found for the method and should be ignored
+			return index.validateParameterIndex(parameter) && (maxLocals.get() == -1 || parameter.getIndex() <= maxLocals.get() - 1);
+		}
+
+		return false;
+	}
+
 	public JarExport exportRemappedJar(ProgressListener progress) {
 		Collection<ClassEntry> classEntries = this.jarIndex.getIndex(EntryIndex.class).getClasses();
 		ClassProvider fixingClassProvider = new ObfuscationFixClassProvider(this.classProvider, this.jarIndex);

enigma/src/main/java/org/quiltmc/enigma/api/analysis/index/jar/EntryIndex.java

@@ -1,6 +1,5 @@
 package org.quiltmc.enigma.api.analysis.index.jar;
 
-import org.objectweb.asm.tree.ClassNode;
 import org.quiltmc.enigma.api.EnigmaProject;
 import org.quiltmc.enigma.api.translation.mapping.EntryMapping;
 import org.quiltmc.enigma.api.translation.mapping.tree.EntryTree;
@@ -19,7 +18,6 @@
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.Map;
-import java.util.concurrent.atomic.AtomicInteger;
 
 public class EntryIndex implements JarIndexer {
 	private final EntryTree<EntryMapping> tree = new HashEntryTree<>();
@@ -73,26 +71,13 @@ public boolean hasField(FieldEntry entry) {
 	/**
 	 * Checks whether the entry has been indexed and therefore exists in the JAR file.
 	 * <br>
-	 * Parameters are not indexed, and this method does not fully verify validity of parameter indices.
-	 * Therefore, it is possible that this method returns {@code true} for an invalid parameter.
+	 * For parameters, which are not indexed, checks the parent method and partially verifies their indices.
+	 * To fully validate a parameter's index, use {@link EnigmaProject#validateParameterIndex(LocalVariableEntry)}.
+	 *
 	 * @param entry the entry to check
 	 * @return whether the entry exists
-	 * @see #hasEntry(Entry, EnigmaProject)
 	 */
 	public boolean hasEntry(Entry<?> entry) {
-		return this.hasEntry(entry, null);
-	}
-
-	/**
-	 * Checks whether the entry has been indexed and therefore exists in the JAR file.
-	 * <br>
-	 * For parameters, which are not indexed, verifies that they have a valid index and therefore could exist.
-	 * @param entry the entry to check
-	 * @param project the current project
-	 * @return whether the entry exists
-	 */
-	@SuppressWarnings("ConstantConditions")
-	public boolean hasEntry(Entry<?> entry, @Nullable EnigmaProject project) {
 		if (entry instanceof ClassEntry classEntry) {
 			return this.hasClass(classEntry);
 		} else if (entry instanceof MethodEntry methodEntry) {
@@ -101,32 +86,30 @@ public boolean hasEntry(Entry<?> entry, @Nullable EnigmaProject project) {
 			return this.hasField(fieldEntry);
 		} else if (entry instanceof LocalVariableEntry localVariableEntry) {
 			MethodEntry parent = localVariableEntry.getParent();
-			if (this.hasMethod(parent)) {
-				AtomicInteger maxLocals = new AtomicInteger(-1);
-				ClassEntry parentClass = parent != null ? parent.getParent() : null;
-
-				if (project != null) {
-					// find max_locals for method, representing the number of parameters it receives (JVMS§4.7.3)
-					// note: parent class cannot be null, warning suppressed
-					ClassNode classNode = project.getClassProvider().get(parentClass.getFullName());
-					if (classNode != null) {
-						classNode.methods.stream()
-							.filter(node -> node.name.equals(parent.getName()) && node.desc.equals(parent.getDesc().toString()))
-							.findFirst().ifPresent(node -> maxLocals.set(node.maxLocals));
-					}
-				}
-
-				AccessFlags parentAccess = this.getMethodAccess(parent);
-				int startIndex = parentAccess != null && parentAccess.isStatic() ? 0 : 1;
-
-				// if maxLocals is -1 it's not found for the method and should be ignored
-				return localVariableEntry.getIndex() >= startIndex && (maxLocals.get() == -1 || localVariableEntry.getIndex() <= maxLocals.get() - 1);
+			if (this.hasEntry(parent)) {
+				return this.validateParameterIndex(localVariableEntry);
 			}
 		}
 
 		return false;
 	}
 
+	/**
+	 * Validates that the parameter index is not below the minimum index for its parent method and therefore could be valid.
+	 * <br>Note that this method does not guarantee the index is valid -- for full validation, call {@link EnigmaProject#validateParameterIndex(LocalVariableEntry)}.
+	 *
+	 * @param parameter the parameter to validate
+	 * @return whether the index could be valid
+	 * @see EnigmaProject#validateParameterIndex(LocalVariableEntry)
+	 */
+	public boolean validateParameterIndex(LocalVariableEntry parameter) {
+		MethodEntry parent = parameter.getParent();
+		AccessFlags parentAccess = this.getMethodAccess(parent);
+
+		int startIndex = parentAccess != null && parentAccess.isStatic() ? 0 : 1;
+		return parameter.getIndex() >= startIndex;
+	}
+
 	@Nullable
 	public AccessFlags getMethodAccess(MethodEntry entry) {
 		var def = this.methodDefinitions.get(entry);

enigma/src/main/java/org/quiltmc/enigma/impl/translation/mapping/MappingsChecker.java

@@ -9,6 +9,7 @@
 import org.quiltmc.enigma.api.translation.mapping.tree.EntryTree;
 import org.quiltmc.enigma.api.translation.mapping.tree.EntryTreeNode;
 import org.quiltmc.enigma.api.translation.representation.entry.Entry;
+import org.quiltmc.enigma.api.translation.representation.entry.LocalVariableEntry;
 import org.quiltmc.enigma.api.translation.representation.entry.MethodEntry;
 
 import java.util.Collection;
@@ -62,7 +63,8 @@ private void tryDropBrokenEntry(Dropped dropped, Entry<?> entry) {
 	}
 
 	private boolean shouldDropBrokenEntry(Dropped dropped, Entry<?> entry) {
-		if (!this.index.getIndex(EntryIndex.class).hasEntry(entry, this.project)) {
+		if (!this.index.getIndex(EntryIndex.class).hasEntry(entry)
+				|| (entry instanceof LocalVariableEntry parameter && !this.project.validateParameterIndex(parameter))) {
 			return true;
 		}