diff --git a/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/GuardedPattern.java b/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/GuardedPattern.java
index 6db84d30b35..921d5dc6851 100644
--- a/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/GuardedPattern.java
+++ b/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/GuardedPattern.java
@@ -210,6 +210,10 @@ public void wrapupGeneration(CodeStream codeStream) {
 		this.primaryPattern.wrapupGeneration(codeStream);
 	}
 	@Override
+	public void fullWrapupGeneration(CodeStream codeStream) {
+		this.primaryPattern.fullWrapupGeneration(codeStream);
+	}
+	@Override
 	protected void generatePatternVariable(BlockScope currentScope, CodeStream codeStream, BranchLabel trueLabel,
 			BranchLabel falseLabel) {
 		this.primaryPattern.generatePatternVariable(currentScope, codeStream, trueLabel, falseLabel);
diff --git a/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/InstanceOfExpression.java b/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/InstanceOfExpression.java
index 0cb159691b4..7f15fe694bc 100644
--- a/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/InstanceOfExpression.java
+++ b/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/InstanceOfExpression.java
@@ -117,7 +117,7 @@ public void generateCode(BlockScope currentScope, CodeStream codeStream, boolean
 
 	int pc = codeStream.position;
 
-	if (this.elementVariable != null) {
+	if (this.elementVariable != null || this.pattern != null) {
 		addAssignment(currentScope, codeStream, this.secretInstanceOfPatternExpressionValue);
 		codeStream.load(this.secretInstanceOfPatternExpressionValue);
 	} else {
@@ -125,7 +125,22 @@ public void generateCode(BlockScope currentScope, CodeStream codeStream, boolean
 	}
 
 	codeStream.instance_of(this.type, this.type.resolvedType);
-	if (this.elementVariable != null) {
+	if (this.pattern != null) {
+		BranchLabel trueLabel = new BranchLabel(codeStream);
+		BranchLabel falseLabel = new BranchLabel(codeStream);
+		BranchLabel continueLabel = new BranchLabel(codeStream);
+		codeStream.ifeq(falseLabel);
+		codeStream.load(this.secretInstanceOfPatternExpressionValue);
+		this.pattern.generateOptimizedBoolean(currentScope, codeStream, trueLabel, falseLabel);
+		this.pattern.fullWrapupGeneration(codeStream);
+		codeStream.removeVariable(this.secretInstanceOfPatternExpressionValue);
+		trueLabel.place();
+		codeStream.iconst_1();
+		codeStream.goto_(continueLabel);
+		falseLabel.place();
+		codeStream.iconst_0();
+		continueLabel.place();
+	} else if (this.elementVariable != null) {
 		BranchLabel actionLabel = new BranchLabel(codeStream);
 		codeStream.dup();
 		codeStream.ifeq(actionLabel);
diff --git a/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/Pattern.java b/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/Pattern.java
index 19b2b994eeb..9bbecb7a59f 100644
--- a/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/Pattern.java
+++ b/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/Pattern.java
@@ -118,6 +118,11 @@ public void resumeVariables(CodeStream codeStream, BlockScope scope) {
 	protected abstract void generatePatternVariable(BlockScope currentScope, CodeStream codeStream, BranchLabel trueLabel, BranchLabel falseLabel);
 	protected abstract void wrapupGeneration(CodeStream codeStream);
 
+	/**
+	 * Clean up all variables (actual and secret) used in this pattern and child patterns.
+	 */
+	protected abstract void fullWrapupGeneration(CodeStream codeStream);
+
 	public TypeReference getType() {
 		return null;
 	}
diff --git a/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/RecordPattern.java b/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/RecordPattern.java
index 48d4b5aabfe..c1eed49c471 100644
--- a/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/RecordPattern.java
+++ b/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/RecordPattern.java
@@ -413,6 +413,13 @@ public void wrapupGeneration(CodeStream codeStream) {
 		super.wrapupGeneration(codeStream);
 	}
 	@Override
+	public void fullWrapupGeneration(CodeStream codeStream) {
+		for (Pattern p : this.patterns) {
+			p.fullWrapupGeneration(codeStream);
+		}
+		super.fullWrapupGeneration(codeStream);
+	}
+	@Override
 	public void suspendVariables(CodeStream codeStream, BlockScope scope) {
 		codeStream.removeNotDefinitelyAssignedVariables(scope, this.thenInitStateIndex1);
 	}
diff --git a/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/TypePattern.java b/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/TypePattern.java
index bbae1d167a5..75fe39ba885 100644
--- a/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/TypePattern.java
+++ b/org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/TypePattern.java
@@ -136,6 +136,13 @@ public void wrapupGeneration(CodeStream codeStream) {
 		codeStream.removeVariable(this.secretPatternVariable);
 	}
 	@Override
+	public void fullWrapupGeneration(CodeStream codeStream) {
+		this.wrapupGeneration(codeStream);
+		if (this.local != null) {
+			codeStream.removeVariable(this.local.binding);
+		}
+	}
+	@Override
 	public LocalDeclaration getPatternVariable() {
 		return this.local;
 	}
@@ -269,7 +276,7 @@ private static LocalVariableBinding getNewLocalVariableBinding(BlockScope scope,
 //		int delta =  ((TypeBinding.equalsEquals(type, TypeBinding.LONG)) ||
 //				(TypeBinding.equalsEquals(type, TypeBinding.DOUBLE))) ?
 //				2 : 1;
-		l.resolvedPosition = scope.localIndex;
+		l.resolvedPosition = scope.startIndex + scope.localIndex;
 		return l;
 	}
 
diff --git a/org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/RecordPatternTest.java b/org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/RecordPatternTest.java
index d18bdda60c6..d7ab328fdab 100644
--- a/org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/RecordPatternTest.java
+++ b/org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/RecordPatternTest.java
@@ -3952,4 +3952,148 @@ public static void main(String[] args) {
 				"s = switch on null\n" +
 				"s = default threw exception");
 	}
+	public void testIssue1804_0() {
+		runConformTest(new String[] { "X.java", """
+				public class X {
+					record Paper(int color) {}
+					record Box<T>(T a) {}
+					public static void main(String[] args) {
+						Box<?> b = new Box<>(null);
+						boolean res = b instanceof Box(Paper a);
+						if (res) {
+							System.out.println("res is true");
+						} else {
+							System.out.println("res is false");
+						}
+					}
+				}
+				""" }, "res is false");
+	}
+	public void testIssue1804_1() {
+		runConformTest(new String[] { "X.java", """
+				public class X {
+					record Paper(int color) {}
+					record Box<T>(T a) {}
+					public static void main(String[] args) {
+						Box<?> b = new Box<>(new Paper(0));
+						boolean res = b instanceof Box(Paper a);
+						if (res) {
+							System.out.println("res is true");
+						} else {
+							System.out.println("res is false");
+						}
+					}
+				}
+				""" }, "res is true");
+	}
+	public void testIssue1804_2() {
+		runConformTest(new String[] { "X.java", """
+				public class X {
+					record Paper(int color) {}
+					record Box<T>(T a) {}
+					public static void main(String[] args) {
+						Box<?> b = new Box<>(new Paper(0));
+						boolean res = b instanceof Box(Paper a) && a == null;
+						if (res) {
+							System.out.println("res is true");
+						} else {
+							System.out.println("res is false");
+						}
+					}
+				}
+				""" }, "res is false");
+	}
+	public void testIssue1804_3() {
+		runConformTest(new String[] { "X.java", """
+				public class X {
+					record Paper(int color) {}
+					record Box<T>(T a) {}
+					public static void main(String[] args) {
+						Box b = new Box<>(null);
+						System.out.println(b instanceof Box(Paper a));
+						System.out.println(b instanceof Box(Object a));
+					}
+				}
+				""" }, "false\ntrue");
+	}
+	public void testIssue1804_4() {
+		runConformTest(new String[] { "X.java", """
+				public class X {
+					record Paper(int color) {}
+					record Box<T>(T a) {}
+					public static void main(String argv[]) {
+						foo(null, null);
+					}
+					public static void foo(String abc, String def) {
+						Box<?> p = new Box<>(new Paper(0));
+						boolean b = false;
+						switch (p) {
+							case Box(Paper a) -> {
+								b = true;
+								break;
+							}
+							default -> {
+								b = false;
+								break;
+							}
+						}
+						System.out.println(b);
+					}
+				}
+				""" }, "true");
+	}
+	public void testIssue1804_5() {
+		runConformTest(new String[] { "X.java", """
+				public class X {
+					record Paper(int color) {}
+					record Box<T>(T a) {}
+					public static void main(String argv[]) {
+						foo(null, null);
+					}
+					public static void foo(String abc, String def) {
+						Box<?> p = new Box<>(null);
+						boolean b = false;
+						switch (p) {
+							case Box(Paper a) -> {
+								b = true;
+								break;
+							}
+							default -> {
+								b = false;
+								break;
+							}
+						}
+						System.out.println(b);
+					}
+				}
+				""" }, "false");
+	}
+	public void testIssue1804_6() {
+		runConformTest(new String[] { "X.java", """
+				public class X {
+					record Paper(int color) {}
+					record Box<T>(T a, T b) {}
+					public static void main(String argv[]) {
+						foo(null, null);
+					}
+					public static void foo(String abc, String def) {
+						Box<?> p = new Box<>(new Paper(0), new Paper(1));
+						boolean c = false;
+						switch (p) {
+							case Box(Paper a, Paper b) -> {
+								System.out.println(a.color);
+								System.out.println(b.color);
+								c = true;
+								break;
+							}
+							default -> {
+								c = false;
+								break;
+							}
+						}
+						System.out.println(c);
+					}
+				}
+				""" }, "0\n1\ntrue");
+	}
 }