fix most nullness annotations and errors in VSCode

.gitignore

@@ -17,7 +17,8 @@ target/
 .classpath
 .factorypath
 .project
-.settings
+# We actually want to sync this to ensure NonNullByDefault
+# .settings
 .springBeans
 .sts4-cache
 

.settings/org.eclipse.jdt.core.prefs

@@ -0,0 +1,11 @@
+eclipse.preferences.version=1
+org.eclipse.jdt.core.compiler.annotation.missingNonNullByDefaultAnnotation=disabled
+org.eclipse.jdt.core.compiler.annotation.nonnull=javax.annotation.Nonnull
+org.eclipse.jdt.core.compiler.annotation.nonnullbydefault=org.eclipse.jdt.annotation.NonNullByDefault
+org.eclipse.jdt.core.compiler.annotation.nullable=javax.annotation.Nullable
+org.eclipse.jdt.core.compiler.annotation.nullanalysis=enabled
+org.eclipse.jdt.core.compiler.problem.nullAnnotationInferenceConflict=warning
+org.eclipse.jdt.core.compiler.problem.nullReference=warning
+org.eclipse.jdt.core.compiler.problem.nullSpecViolation=warning
+org.eclipse.jdt.core.compiler.problem.potentialNullReference=warning
+org.eclipse.jdt.core.compiler.problem.syntacticNullAnalysisForFields=enabled

src/main/java/org/prlprg/bc/ConstPool.java

@@ -64,7 +64,7 @@ public <S extends SEXP> S get(TypedIdx<S> idx) {
 
 
     /** If the SEXP is a constant, returns its index. Otherwise returns null. */
-    public <S extends SEXP> @Nullable TypedIdx<S> indexOf(S c) {
+    public @Nullable <S extends SEXP> TypedIdx<S> indexOf(S c) {
         if (consts == null) {
             throw new IllegalStateException("ConstPool is not yet built");
         }
@@ -280,7 +280,7 @@ private <S extends SEXP> TypedIdx<S> of(int i, Class<S> sexpInterface) {
             return idx;
         }
 
-        private <S extends SEXP> @Nullable TypedIdx<S> tryOf(int i, Class<S> sexpInterface) {
+        private @Nullable <S extends SEXP> TypedIdx<S> tryOf(int i, Class<S> sexpInterface) {
             var idx = new TypedIdx<>(pool, i, sexpInterface);
             if (!idx.checkType()) {
                 return null;
@@ -316,7 +316,7 @@ public Builder() {
         public <S extends SEXP> TypedIdx<S> add(S c) {
             // This only works because TypedIdx is covariant the and generic gets erased.
             // We actually cast TypedIdx<something more specific than S> into TypedIdx<S>.
-            @SuppressWarnings("unchecked") var idx = (TypedIdx<S>)consts.computeIfAbsent(c, (ignored) -> new TypedIdx<S>(pool, consts.size(), (Class<S>)c.getClass()));
+            @SuppressWarnings("unchecked") var idx = (TypedIdx<S>)consts.computeIfAbsent(c, (ignored) -> new TypedIdx<>(pool, consts.size(), (Class<S>)c.getClass()));
             return idx;
         }
 

src/main/java/org/prlprg/sexp/SimpleScalarSXPImpl.java

@@ -8,27 +8,24 @@
 
 /** Class for representing a scalar SEXP of a primitive type with no attributes. */
 @Immutable
-abstract non-sealed class SimpleScalarSXPImpl<T> implements VectorSXP<T> {
+abstract class SimpleScalarSXPImpl<T> {
     final T data;
 
     protected SimpleScalarSXPImpl(T data) {
         this.data = data;
     }
 
-    @Override
     public UnmodifiableIterator<T> iterator() {
         return Iterators.forArray(data);
     }
 
-    @Override
     public T get(int i) {
         if (i != 0) {
             throw new IndexOutOfBoundsException();
         }
         return data;
     }
 
-    @Override
     public int size() {
         return 1;
     }
@@ -38,7 +35,6 @@ public String toString() {
         return data.toString();
     }
 
-    @Override
     public Attributes attributes() {
         return Attributes.NONE;
     }

src/main/java/org/prlprg/sexp/VectorSXP.java

@@ -2,7 +2,7 @@
 
 import java.util.stream.BaseStream;
 
-public sealed interface VectorSXP<T> extends ListOrVectorSXP<T> permits ComplexSXP, ExprSXP, IntSXP, LglSXP, RealSXP, StrSXP, VecSXP, SimpleScalarSXPImpl, EmptyVectorSXPImpl {
+public sealed interface VectorSXP<T> extends ListOrVectorSXP<T> permits ComplexSXP, ExprSXP, IntSXP, LglSXP, RealSXP, StrSXP, VecSXP, EmptyVectorSXPImpl {
     @Override Attributes attributes();
 
     @Override