Prevent NPEs in completion tests

- Prevent NPE when completing name of the last parameter in a method
  declaration
  - This uses the existing "suggest a name for this variable" logic
- Prevent various NPEs when completing the first parameter of a
  parameterized type
  - eg.
    ```java
    List<| asdf = new ArrayList<>();
    ```
- move private check before deprecated check to avoid NPE trying to
  access the `IMethod` for a private JDK class member.
  (I think the root cause is that the private method doesn't exist in the
  stubbed jar, so we can't access the associated `IMethod`, but it does
  exist in javac's internal bindings, since javac has access to the real
  JDK class)
- when completing throws clause, add null checks when accessing the
  return type and name to compute the scanning index
  - constructors don't have a return type node, and an incomplete method
    declaration might not have a name
- replace a use of "Ljava/lang/Object;" with the constant from KeyUtils

Should fix 5 cases, and switch several test errors over to failures.

Signed-off-by: David Thompson <[email protected]>

Author: datho7561

org.eclipse.jdt.core.javac/src/org/eclipse/jdt/internal/codeassist/DOMCompletionEngine.java

@@ -96,6 +96,7 @@
 import org.eclipse.jdt.core.dom.IfStatement;
 import org.eclipse.jdt.core.dom.ImportDeclaration;
 import org.eclipse.jdt.core.dom.InfixExpression;
+import org.eclipse.jdt.core.dom.InfixExpression.Operator;
 import org.eclipse.jdt.core.dom.Initializer;
 import org.eclipse.jdt.core.dom.InstanceofExpression;
 import org.eclipse.jdt.core.dom.Javadoc;
@@ -107,6 +108,7 @@
 import org.eclipse.jdt.core.dom.MethodInvocation;
 import org.eclipse.jdt.core.dom.MethodRef;
 import org.eclipse.jdt.core.dom.Modifier;
+import org.eclipse.jdt.core.dom.Modifier.ModifierKeyword;
 import org.eclipse.jdt.core.dom.ModuleDeclaration;
 import org.eclipse.jdt.core.dom.Name;
 import org.eclipse.jdt.core.dom.NodeFinder;
@@ -147,8 +149,6 @@
 import org.eclipse.jdt.core.dom.VariableDeclarationFragment;
 import org.eclipse.jdt.core.dom.VariableDeclarationStatement;
 import org.eclipse.jdt.core.dom.WhileStatement;
-import org.eclipse.jdt.core.dom.InfixExpression.Operator;
-import org.eclipse.jdt.core.dom.Modifier.ModifierKeyword;
 import org.eclipse.jdt.core.formatter.DefaultCodeFormatterConstants;
 import org.eclipse.jdt.core.search.IJavaSearchConstants;
 import org.eclipse.jdt.core.search.IJavaSearchScope;
@@ -1335,6 +1335,21 @@ public void complete(org.eclipse.jdt.internal.compiler.env.ICompilationUnit sour
 				suggestDefaultCompletions = false;
 			}
 			if (context instanceof MethodDeclaration methodDeclaration) {
+				int closingParenLocation = methodDeclaration.getName().getStartPosition() + methodDeclaration.getName().getLength();
+				boolean afterComma = true;
+				while (closingParenLocation < this.textContent.length() && this.textContent.charAt(closingParenLocation) != ')') {
+					if (afterComma) {
+						if (!Character.isWhitespace(this.textContent.charAt(closingParenLocation))) {
+							afterComma = false;
+						}
+					} else {
+						// TODO: handle \u002C
+						if (this.textContent.charAt(closingParenLocation) == ',') {
+							afterComma = true;
+						}
+					}
+					closingParenLocation++;
+				}
 				if (this.offset < methodDeclaration.getName().getStartPosition()) {
 					completeMethodModifiers(methodDeclaration);
 					// return type: suggest types from current CU
@@ -1347,9 +1362,22 @@ public void complete(org.eclipse.jdt.internal.compiler.env.ICompilationUnit sour
 						publishFromScope(specificCompletionBindings);
 					}
 					suggestDefaultCompletions = false;
-				} else if (methodDeclaration.getBody() == null || (methodDeclaration.getBody() != null && this.offset <= methodDeclaration.getBody().getStartPosition())) {
+				} else if (methodDeclaration.getBody() == null || (methodDeclaration.getBody() != null && this.offset <= methodDeclaration.getBody().getStartPosition()) && closingParenLocation < this.offset) {
 					completeThrowsClause(methodDeclaration, specificCompletionBindings);
 					suggestDefaultCompletions = false;
+				} else if (methodDeclaration.getName().getStartPosition() + methodDeclaration.getName().getLength() < this.offset && this.offset <= closingParenLocation && !afterComma) {
+					// void myMethod(Integer a, Boolean |) { ...
+					SingleVariableDeclaration svd = (SingleVariableDeclaration)methodDeclaration.parameters().get(methodDeclaration.parameters().size() - 1);
+					ITypeBinding typeBinding = svd.getType().resolveBinding();
+					Block block = methodDeclaration.getBody();
+					Set<String> alreadySuggestedNames = new HashSet<>();
+					if (block != null) {
+						suggestUndeclaredVariableNames(block, typeBinding, alreadySuggestedNames);
+					} else {
+						suggestUndeclaredVariableNames(typeBinding, alreadySuggestedNames);
+					}
+					suggestVariableNamesForType(typeBinding, alreadySuggestedNames);
+					suggestDefaultCompletions = false;
 				} else if (this.offset > methodDeclaration.getStartPosition() + methodDeclaration.getLength()) {
 					suggestModifierKeywords(0);
 				}
@@ -2705,7 +2733,9 @@ private boolean filterTypeBasedOnAccess(IType type, String currentPackage, IType
 	}
 
 	private boolean isParameterInNonParameterizedType(ASTNode context) {
-		if (DOMCompletionUtil.findParent(context, new int[] { ASTNode.PARAMETERIZED_TYPE }) != null) {
+		if (context instanceof ParameterizedType) {
+			return true;
+		} else if (DOMCompletionUtil.findParent(context, new int[] { ASTNode.PARAMETERIZED_TYPE }) != null) {
 			ASTNode cursor1 = context;
 			ASTNode cursor2 = context.getParent();
 			while (!(cursor2 instanceof ParameterizedType paramType)) {
@@ -3137,9 +3167,13 @@ private void completeJavadocInlineTags(TagElement tagNode) {
 
 	private void completeThrowsClause(MethodDeclaration methodDeclaration, Bindings scope) {
 		if (methodDeclaration.thrownExceptionTypes().size() == 0) {
-			int startScanIndex = Math.max(
-					methodDeclaration.getName().getStartPosition() + methodDeclaration.getName().getLength(),
-					methodDeclaration.getReturnType2().getStartPosition() + methodDeclaration.getReturnType2().getLength());
+			int startScanIndex = -1;
+			if (methodDeclaration.getReturnType2() != null) {
+				startScanIndex = methodDeclaration.getReturnType2().getStartPosition() + methodDeclaration.getReturnType2().getLength();
+			}
+			if (methodDeclaration.getName() != null) {
+				startScanIndex = methodDeclaration.getName().getStartPosition() + methodDeclaration.getName().getLength();
+			}
 			if (!methodDeclaration.parameters().isEmpty()) {
 				SingleVariableDeclaration lastParam = (SingleVariableDeclaration)methodDeclaration.parameters().get(methodDeclaration.parameters().size() - 1);
 				startScanIndex = lastParam.getName().getStartPosition() + lastParam.getName().getLength();
@@ -3470,9 +3504,9 @@ private void findOverridableMethods0(ITypeBinding currentType, ITypeBinding type
 				continue next;
 			}
 			if (method.isSynthetic() || method.isConstructor()
+					|| Modifier.isPrivate(method.getModifiers())
 					|| (this.assistOptions.checkDeprecation && isDeprecated(method.getJavaElement()))
 					|| Modifier.isStatic(method.getModifiers())
-					|| Modifier.isPrivate(method.getModifiers())
 					|| ((method.getModifiers() & (Modifier.PUBLIC | Modifier.PRIVATE | Modifier.PROTECTED)) == 0) && !typeBinding.getPackage().getKey().equals(originalPackageKey)) {
 				continue next;
 			}

org.eclipse.jdt.core.javac/src/org/eclipse/jdt/internal/codeassist/ExpectedTypes.java

@@ -194,6 +194,16 @@ private void computeExpectedTypes(){
 				}
 				break;
 			}
+			if (parent2 instanceof ParameterizedType parameterizedType) {
+				ITypeBinding typeBinding = parameterizedType.getType().resolveBinding().getTypeDeclaration();
+				// TODO: does this ever happen for other entries?
+				if (typeBinding.getTypeParameters()[0].isWildcardType() && typeBinding.getTypeParameters()[0].getBound() != null) {
+					this.expectedTypes.add(typeBinding.getTypeParameters()[0].getBound());
+				} else {
+					this.expectedTypes.add(parent2.getAST().resolveWellKnownType(Object.class.getName()));
+				}
+				return;
+			}
 			if (parent2.getLocationInParent() == MemberValuePair.VALUE_PROPERTY && parent2.getParent() instanceof MemberValuePair mvp) {
 				var binding = mvp.resolveMemberValuePairBinding();
 				if (binding != null) {

org.eclipse.jdt.core.javac/src/org/eclipse/jdt/internal/codeassist/KeyUtils.java

@@ -17,6 +17,8 @@
  * Utility methods for manipulating binding keys.
  */
 public class KeyUtils {
+	
+	public static final String OBJECT_KEY = "Ljava/lang/Object;";
 
 	/**
 	 * Returns the given method key with the owner type and return type removed.

org.eclipse.jdt.core.javac/src/org/eclipse/jdt/internal/codeassist/RelevanceUtils.java

@@ -131,7 +131,7 @@ static int computeRelevanceForExpectingType(ITypeBinding proposalType, ExpectedT
 						relevance = CompletionEngine.R_EXPECTED_TYPE;
 					}
 				}
-				if ("Ljava/lang/Object;".equals(expectedType.getKey()) && proposalType.isPrimitive()) {
+				if (KeyUtils.OBJECT_KEY.equals(expectedType.getKey()) && proposalType.isPrimitive()) {
 					// can be autoboxed
 					relevance = CompletionEngine.R_EXPECTED_TYPE;
 				}

org.eclipse.jdt.core.javac/src/org/eclipse/jdt/internal/javac/dom/JavacTypeBinding.java

@@ -58,6 +58,7 @@
 import org.eclipse.jdt.core.dom.Modifier;
 import org.eclipse.jdt.core.dom.RecordDeclaration;
 import org.eclipse.jdt.core.dom.TypeDeclaration;
+import org.eclipse.jdt.internal.codeassist.KeyUtils;
 import org.eclipse.jdt.internal.compiler.codegen.ConstantPool;
 import org.eclipse.jdt.internal.core.BinaryType;
 import org.eclipse.jdt.internal.core.JavaElement;
@@ -314,10 +315,10 @@ public String getKey() {
 	}
 
 	private String computeKey() {
-		return getKeyWithPossibleGenerics(this.type, this.typeSymbol, ITypeBinding::getKey, true);
+		return getKeyWithPossibleGenerics(this.type, this.typeSymbol, tb -> tb != null ? tb.getKey() : KeyUtils.OBJECT_KEY, true);
 	}
 	public String getKeyWithPossibleGenerics(Type t, TypeSymbol s) {
-		return getKeyWithPossibleGenerics(t, s, ITypeBinding::getKey);
+		return getKeyWithPossibleGenerics(t, s, tb -> tb != null ? tb.getKey() : KeyUtils.OBJECT_KEY);
 	}
 	private String getKeyWithPossibleGenerics(Type t, TypeSymbol s, Function<ITypeBinding, String> parameterizedCallback) {
 		return getKeyWithPossibleGenerics(t, s, parameterizedCallback, false);
@@ -373,7 +374,7 @@ public String getGenericTypeSignature(Type t, TypeSymbol s, boolean useSlashes)
 			return '[' + componentBinding.getGenericTypeSignature(useSlashes);
 		}
 		String ret = getKeyWithPossibleGenerics(t, s, 
-				x -> x instanceof JavacTypeBinding jtb ? jtb.getGenericTypeSignature(useSlashes) : x.getKey(),
+				x -> x instanceof JavacTypeBinding jtb ? jtb.getGenericTypeSignature(useSlashes) : x != null ? x.getKey() : KeyUtils.OBJECT_KEY,
 						useSlashes);
 		return ret;
 	}