Bug 562758 - [14] Pattern variable conflicts with lambda parameter even

when not in scope

Change-Id: I151a46e258131a56a358065b909fd09b3c692603
Signed-off-by: Jay Arthanareeswaran <jarthana@in.ibm.com>

4 files changed, 87 insertions, 4 deletions

diff --git a/org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/PatternMatching14Test.java b/org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/PatternMatching14Test.java
index 2a8383fde1..9dc03a4a46 100644
--- a/org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/PatternMatching14Test.java
+++ b/org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/PatternMatching14Test.java
@@ -2211,7 +2211,8 @@ public class PatternMatching14Test extends AbstractRegressionTest {
 				"PASS",
 				compilerOptions);
 	}
-	public void _test056() {
+	// Positive - Test conflicting pattern variable and lambda argument in for loop
+	public void test056() {
 		Map<String, String> compilerOptions = getCompilerOptions(true);
 		runConformTest(
 				new String[] {
@@ -2240,6 +2241,7 @@ public class PatternMatching14Test extends AbstractRegressionTest {
 				"PASS",
 				compilerOptions);
 	}
+	// Positive - Test conflicting pattern variable and lambda argument in for loop (block)
 	public void test056a() {
 		Map<String, String> compilerOptions = getCompilerOptions(true);
 		runConformTest(
@@ -2272,6 +2274,74 @@ public class PatternMatching14Test extends AbstractRegressionTest {
 				"PASS",
 				compilerOptions);
 	}
+	// Positive - Test conflicting pattern variable and lambda argument in if
+	public void test056b() {
+		Map<String, String> compilerOptions = getCompilerOptions(true);
+		runConformTest(
+				new String[] {
+						"X.java",
+						"@SuppressWarnings(\"preview\")\n" +
+						"public class X {\n" +
+						"	public static int impl(I a) {\n" +
+						"		return a.foo(\"Default\");\n" +
+						"	}\n" +
+						"	public static void main(String argv[]) {\n" +
+						"		String result = \"\";\n" +
+						"		Object obj = \"a\";\n" +
+						"		if (!(obj instanceof String a)) {\n" +
+						"			  int i = impl(a -> a.length());\n" +
+						"		}\n" +
+						"		if (!result.equals(\"\"))\n" +
+						"			System.out.println(\"FAIL\");\n" +
+						"		else\n" +
+						"			System.out.println(\"PASS\");\n" +
+						"	}\n" +
+						"}\n" +
+						"interface I {\n" +
+						"	int foo(String s);\n" +
+						"}\n",
+				},
+				"PASS",
+				compilerOptions);
+	}
+	// Positive - Test conflicting pattern variable and lambda argument in if
+	public void test056d() {
+		Map<String, String> compilerOptions = getCompilerOptions(true);
+		runNegativeTest(
+				new String[] {
+						"X.java",
+						"@SuppressWarnings(\"preview\")\n" +
+						"public class X {\n" +
+						"	public static int impl(I a) {\n" +
+						"		return a.foo(\"Default\");\n" +
+						"	}\n" +
+						"	public static void main(String argv[]) {\n" +
+						"		String result = \"\";\n" +
+						"		Object obj = \"a\";\n" +
+						"		for (int i = 0; (obj instanceof String a); i = impl(a -> a.length())) {\n" +
+						"			obj = null;\n" +
+						"		}\n" +
+						"		if (!result.equals(\"\"))\n" +
+						"			System.out.println(\"FAIL\");\n" +
+						"		else\n" +
+						"			System.out.println(\"PASS\");\n" +
+						"	}\n" +
+						"}\n" +
+						"interface I {\n" +
+						"	int foo(String s);\n" +
+						"}\n",
+				},
+				"----------\n" +
+				"1. ERROR in X.java (at line 9)\n" +
+				"	for (int i = 0; (obj instanceof String a); i = impl(a -> a.length())) {\n" +
+				"	                                                    ^\n" +
+				"Lambda expression\'s parameter a cannot redeclare another local variable defined in an enclosing scope. \n" +
+				"----------\n",
+				"",
+				null,
+				true,
+				compilerOptions);
+	}
 	/*
 	 * Test we report only one duplicate variable, i.e., in THEN stmt
 	 * where pattern variable is in scope.
diff --git a/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/ast/AbstractMethodDeclaration.java b/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/ast/AbstractMethodDeclaration.java
index 93955b1419..91e91be98d 100644
--- a/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/ast/AbstractMethodDeclaration.java
+++ b/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/ast/AbstractMethodDeclaration.java
@@ -240,6 +240,9 @@ public abstract class AbstractMethodDeclaration
 						}
 					}
 				}
+				if (methodArguments[i].duplicateCheckObligation != null) {
+					methodArguments[i].duplicateCheckObligation.accept(flowInfo);
+				}
 				// tag parameters as being set:
 				flowInfo.markAsDefinitelyAssigned(methodArguments[i].binding);
 			}
diff --git a/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/ast/Argument.java b/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/ast/Argument.java
index 82ae705d15..2a00cbc764 100644
--- a/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/ast/Argument.java
+++ b/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/ast/Argument.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2019 IBM Corporation and others.
+ * Copyright (c) 2000, 2020 IBM Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -118,7 +118,15 @@ public class Argument extends LocalDeclaration {
 			final boolean localExists = existingVariable instanceof LocalVariableBinding;
 			if (localExists && this.hiddenVariableDepth == 0) {
 				if ((this.bits & ASTNode.ShadowsOuterLocal) != 0 && scope.isLambdaSubscope()) {
-					scope.problemReporter().lambdaRedeclaresArgument(this);
+					if ((((LocalVariableBinding) existingVariable).modifiers & ExtraCompilerModifiers.AccPatternVariable) != 0) {
+						this.duplicateCheckObligation = (flowInfo) -> {
+							if (flowInfo.isDefinitelyAssigned((LocalVariableBinding) existingVariable)) {
+								scope.problemReporter().lambdaRedeclaresArgument(this);
+							}
+						};
+					} else {
+						scope.problemReporter().lambdaRedeclaresArgument(this);
+					}
 				} else if (scope.referenceContext instanceof CompactConstructorDeclaration) {
 					// skip error reporting - hidden params - already reported in record components
 				} else {
diff --git a/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/ast/LocalDeclaration.java b/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/ast/LocalDeclaration.java
index 4a889766c2..de737e275e 100644
--- a/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/ast/LocalDeclaration.java
+++ b/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/ast/LocalDeclaration.java
@@ -309,8 +309,10 @@ public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, Fl
 		Binding existingVariable = scope.getBinding(this.name, Binding.VARIABLE, this, false /*do not resolve hidden field*/);
 		if (existingVariable != null && existingVariable.isValidBinding()){
 			boolean localExists = existingVariable instanceof LocalVariableBinding;
-			if (localExists && (((LocalVariableBinding) existingVariable).modifiers & ExtraCompilerModifiers.AccPatternVariable) != 0)
+			if (localExists && (isPatternVariable
+					|| (((LocalVariableBinding) existingVariable).modifiers & ExtraCompilerModifiers.AccPatternVariable) != 0))
 			{
+				// Do this only if either one of them is a pattern variable.
 				this.duplicateCheckObligation = (flowInfo) -> {
 					if (flowInfo.isDefinitelyAssigned((LocalVariableBinding) existingVariable)) {
 						scope.problemReporter().redefineLocal(this);