Update checkstyle to prevent using var expect for new instance creation.

checkstyle.xml

@@ -158,5 +158,10 @@
 		<module name="AtclauseOrder">
 			<property name="tagOrder" value="@param,@return,@throws,@deprecated"/>
 		</module>
+
+		<!-- Prevent var for all cases other than new instance creation -->
+		<module name="MatchXpath">
+			<property name="query" value="//VARIABLE_DEF[./TYPE/IDENT[@text='var'] and not(./ASSIGN/EXPR/LITERAL_NEW)]"/>
+		</module>
 	</module>
 </module>

src/main/java/net/fabricmc/loom/LoomGradlePlugin.java

@@ -78,7 +78,7 @@ public class LoomGradlePlugin implements BootstrappedPlugin {
 		project.apply(ImmutableMap.of("plugin", "idea"));
 
 		// Setup extensions, minecraft wraps loom
-		var extension = project.getExtensions().create(LoomGradleExtensionAPI.class, "loom", LoomGradleExtensionImpl.class, project, LoomFiles.create(project));
+		LoomGradleExtensionAPI extension = project.getExtensions().create(LoomGradleExtensionAPI.class, "loom", LoomGradleExtensionImpl.class, project, LoomFiles.create(project));
 		project.getExtensions().create(LoomGradleExtensionAPI.class, "minecraft", MinecraftGradleExtension.class, extension);
 		project.getExtensions().create("fabricApi", FabricApiExtension.class, project);
 

src/main/java/net/fabricmc/loom/build/nesting/NestedDependencyProvider.java

@@ -43,6 +43,7 @@ import org.gradle.api.artifacts.Configuration;
 import org.gradle.api.artifacts.Dependency;
 import org.gradle.api.artifacts.DependencySet;
 import org.gradle.api.artifacts.ProjectDependency;
+import org.gradle.api.artifacts.ResolvedArtifact;
 import org.gradle.api.artifacts.ResolvedConfiguration;
 import org.gradle.api.artifacts.ResolvedDependency;
 import org.gradle.api.tasks.bundling.AbstractArchiveTask;
@@ -133,7 +134,7 @@ public final class NestedDependencyProvider implements NestedJarProvider {
 				continue;
 			}
 
-			for (var artifact : dependency.getModuleArtifacts()) {
+			for (ResolvedArtifact artifact : dependency.getModuleArtifacts()) {
 				fileList.add(new DependencyInfo<>(
 						dependency,
 						new ResolvedDependencyMetaExtractor(),

src/main/java/net/fabricmc/loom/configuration/CompileConfiguration.java

@@ -139,10 +139,18 @@ public final class CompileConfiguration {
 
 			MixinExtension mixin = LoomGradleExtension.get(project).getMixin();
 
-			if (!mixin.getUseLegacyMixinAp().get()) {
+			if (mixin.getUseLegacyMixinAp().get()) {
-				return;
+				setupMixinAp(project, mixin);
+			}
+		});
+
+		if (p.getPluginManager().hasPlugin("org.jetbrains.kotlin.kapt")) {
+			// If loom is applied after kapt, then kapt will use the AP arguments too early for loom to pass the arguments we need for mixin.
+			throw new IllegalArgumentException("fabric-loom must be applied BEFORE kapt in the plugins { } block.");
+		}
 	}
 
+	private static void setupMixinAp(Project project, MixinExtension mixin) {
 		mixin.init();
 
 		// Disable some things used by log4j via the mixin AP that prevent it from being garbage collected
@@ -163,12 +171,6 @@ public final class CompileConfiguration {
 			project.getLogger().info("Configuring compiler arguments for Kapt plugin");
 			new KaptApInvoker(project).configureMixin();
 		}
-		});
-
-		if (p.getPluginManager().hasPlugin("org.jetbrains.kotlin.kapt")) {
-			// If loom is applied after kapt, then kapt will use the AP arguments too early for loom to pass the arguments we need for mixin.
-			throw new IllegalArgumentException("fabric-loom must be applied BEFORE kapt in the plugins { } block.");
-		}
 	}
 
 	private static void extendsFrom(String a, String b, Project project) {

src/main/java/net/fabricmc/loom/configuration/JarManifestConfiguration.java

@@ -29,6 +29,7 @@ import java.util.jar.Attributes;
 import java.util.jar.Manifest;
 
 import org.gradle.api.Project;
+import org.gradle.api.artifacts.Dependency;
 import org.gradle.util.GradleVersion;
 
 import net.fabricmc.loom.LoomGradleExtension;
@@ -46,7 +47,7 @@ public final record JarManifestConfiguration(Project project) {
 		LoomGradleExtension extension = LoomGradleExtension.get(project);
 
 		Attributes attributes = manifest.getMainAttributes();
-		var tinyRemapperVersion = Optional.ofNullable(TinyRemapper.class.getPackage().getImplementationVersion());
+		Optional<String> tinyRemapperVersion = Optional.ofNullable(TinyRemapper.class.getPackage().getImplementationVersion());
 
 		attributes.putValue("Fabric-Gradle-Version", GradleVersion.current().getVersion());
 		attributes.putValue("Fabric-Loom-Version", LoomGradlePlugin.LOOM_VERSION);
@@ -63,7 +64,7 @@ public final record JarManifestConfiguration(Project project) {
 
 	private void addMixinVersion(Attributes attributes) {
 		// Not super ideal that this uses the mod compile classpath, should prob look into making this not a thing at somepoint
-		var dependency = project.getConfigurations().getByName(Constants.Configurations.LOADER_DEPENDENCIES)
+		Optional<Dependency> dependency = project.getConfigurations().getByName(Constants.Configurations.LOADER_DEPENDENCIES)
 				.getDependencies()
 				.stream()
 				.filter(dep -> "sponge-mixin".equals(dep.getName()))

src/main/java/net/fabricmc/loom/configuration/MavenPublication.java

@@ -44,6 +44,7 @@ import org.gradle.api.publish.Publication;
 import org.gradle.api.publish.PublishingExtension;
 
 import net.fabricmc.loom.LoomGradleExtension;
+import net.fabricmc.loom.util.DeprecationHelper;
 import net.fabricmc.loom.util.GroovyXmlUtil;
 
 public final class MavenPublication {
@@ -94,7 +95,7 @@ public final class MavenPublication {
 				if (hasSoftwareComponent(publication) || EXCLUDED_PUBLICATIONS.contains(publication)) {
 					continue;
 				} else if (!reportedDeprecation.get()) {
-					var deprecationHelper = LoomGradleExtension.get(project).getDeprecationHelper();
+					DeprecationHelper deprecationHelper = LoomGradleExtension.get(project).getDeprecationHelper();
 					deprecationHelper.warn("Loom is applying dependency data manually to publications instead of using a software component (from(components[\"java\"])). This is deprecated and will be removed in Loom 0.12.");
 					reportedDeprecation.set(true);
 				}

src/main/java/net/fabricmc/loom/configuration/providers/MinecraftProviderImpl.java

@@ -206,7 +206,7 @@ public class MinecraftProviderImpl extends DependencyProvider implements Minecra
 		String expVersionManifest = Files.asCharSource(experimentalVersionsJson, StandardCharsets.UTF_8).read();
 		ManifestVersion expManifest = LoomGradlePlugin.OBJECT_MAPPER.readValue(expVersionManifest, ManifestVersion.class);
 
-		var result = expManifest.versions().stream().filter(versions -> versions.id.equalsIgnoreCase(minecraftVersion)).findFirst();
+		Optional<ManifestVersion.Versions> result = expManifest.versions().stream().filter(versions -> versions.id.equalsIgnoreCase(minecraftVersion)).findFirst();
 
 		if (result.isPresent()) {
 			getProject().getLogger().lifecycle("Using fallback experimental version {}", minecraftVersion);

src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingSpecBuilder.java

@@ -48,7 +48,7 @@ public class LayeredMappingSpecBuilder {
 	}
 
 	public LayeredMappingSpecBuilder parchment(String mavenNotation, Action<ParchmentMappingsSpecBuilder> action) {
-		var builder = ParchmentMappingsSpecBuilder.builder(mavenNotation);
+		ParchmentMappingsSpecBuilder builder = ParchmentMappingsSpecBuilder.builder(mavenNotation);
 		action.execute(builder);
 		layers.add(builder.build());
 		return this;