Bug 578167 - fix completion for arguments inside lambdaI20220123-1800I20220122-1800I20220121-1800I20220120-1800

When a method CompletionOnMessageSend is inside a lambda block, The
first expected types computations seems to empty the expected types
array, which should be in length of 1. This cause later computations to
find expected types for current argument position fails with an AIOB.
The fix guard the array copy which erroneously resize the expected types
array to zero length in first computation.


Change-Id: I34bc9a6409d8c6623d3de008764b1cd93a2520ca
Signed-off-by: Gayan Perera <gayanper@gmail.com>
Reviewed-on: https://git.eclipse.org/r/c/jdt/eclipse.jdt.core/+/189486
Tested-by: JDT Bot <jdt-bot@eclipse.org>

2 files changed, 29 insertions, 3 deletions

diff --git a/org.eclipse.jdt.core.tests.model/src/org/eclipse/jdt/core/tests/model/CompletionTests18.java b/org.eclipse.jdt.core.tests.model/src/org/eclipse/jdt/core/tests/model/CompletionTests18.java
index 0d7dd30165..b8b9d4e12d 100644
--- a/org.eclipse.jdt.core.tests.model/src/org/eclipse/jdt/core/tests/model/CompletionTests18.java
+++ b/org.eclipse.jdt.core.tests.model/src/org/eclipse/jdt/core/tests/model/CompletionTests18.java
@@ -6393,10 +6393,10 @@ public void testBug577883_expectCompletions_onOuterLambdaVars_inNestedLambdas()
 public void testBug577885_expectCompletions_onMethodArguments_followingMethodInvocationWithMethodRefArguments() throws JavaModelException {
 	this.workingCopies = new ICompilationUnit[1];
 	this.workingCopies[0] = getWorkingCopy(
-			"Completion/src/Bug443091.java",
+			"Completion/src/Bug577885.java",
 			"import java.util.stream.Stream;\n" +
 			"\n" +
-			"public class Bug443091 {\n" +
+			"public class Bug577885 {\n" +
 			"	private void foo() {\n" +
 			" 		Stream.of(\"1\").map(Long::valueOf).filter()\n" +
 			"	}\n" +
@@ -6413,6 +6413,31 @@ public void testBug577885_expectCompletions_onMethodArguments_followingMethodInv
 			+ "[LAMBDA_EXPRESSION]{->, Ljava.util.function.Predicate<Ljava.lang.Long;>;, (Ljava.lang.Long;)Z, test, (arg0), 89}",
 			result);
 }
+public void testBug577885_expectCompletions_onMethodArguments_followingMethodInvocationWithMethodRefArguments_InsideLambda() throws JavaModelException {
+	this.workingCopies = new ICompilationUnit[1];
+	this.workingCopies[0] = getWorkingCopy(
+			"Completion/src/Bug577885.java",
+			"import java.util.stream.Stream;\n" +
+			"\n" +
+			"public class Bug577885 {\n" +
+			"	private void foo() {\n" +
+			"		Runnable run = () -> {\n" +
+			" 			Stream.of(\"1\").map(Long::valueOf).filter()\n" +
+			"		};\n" +
+			"	}\n" +
+			"}\n");
+
+	CompletionTestsRequestor2 requestor = new CompletionTestsRequestor2(true);
+	requestor.allowAllRequiredProposals();
+	String str = this.workingCopies[0].getSource();
+	String completeBehind = "filter(";
+	int cursorLocation = str.indexOf(completeBehind) + completeBehind.length();
+	this.workingCopies[0].codeComplete(cursorLocation, requestor, this.wcOwner);
+	String result = requestor.getResults();
+	assertResults("filter[METHOD_REF]{, Ljava.util.stream.Stream<Ljava.lang.Long;>;, (Ljava.util.function.Predicate<-Ljava.lang.Long;>;)Ljava.util.stream.Stream<Ljava.lang.Long;>;, filter, (arg0), 56}\n"
+			+ "[LAMBDA_EXPRESSION]{->, Ljava.util.function.Predicate<Ljava.lang.Long;>;, (Ljava.lang.Long;)Z, test, (arg0), 89}",
+			result);
+}
 public void testBug578116_expectCompletions_forConstructorsInsideLamndaBlock() throws JavaModelException {
 	this.workingCopies = new ICompilationUnit[1];
 	this.workingCopies[0] = getWorkingCopy(
diff --git a/org.eclipse.jdt.core/codeassist/org/eclipse/jdt/internal/codeassist/CompletionEngine.java b/org.eclipse.jdt.core/codeassist/org/eclipse/jdt/internal/codeassist/CompletionEngine.java
index eafc1e5beb..a5d50c36f1 100644
--- a/org.eclipse.jdt.core/codeassist/org/eclipse/jdt/internal/codeassist/CompletionEngine.java
+++ b/org.eclipse.jdt.core/codeassist/org/eclipse/jdt/internal/codeassist/CompletionEngine.java
@@ -4602,7 +4602,8 @@ public final class CompletionEngine
 			}
 		}
 
-		if(this.expectedTypesPtr + 1 != this.expectedTypes.length) {
+		// Guard it, otherwise we end up with a empty array which cause issues down the line
+		if((this.expectedTypesPtr > -1) && ((this.expectedTypesPtr + 1) != this.expectedTypes.length)) {
 			System.arraycopy(this.expectedTypes, 0, this.expectedTypes = new TypeBinding[this.expectedTypesPtr + 1], 0, this.expectedTypesPtr + 1);
 		}
 	}