diff --git a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java
index 454ab01c83f..d2f466698e7 100644
--- a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java
+++ b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java
@@ -1089,6 +1089,12 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
       runTest("compiler/testData/diagnostics/tests/phantomIntersections.kt");
     }
 
+    @Test
+    @TestMetadata("postfixIncSmartCast.kt")
+    public void testPostfixIncSmartCast() {
+      runTest("compiler/testData/diagnostics/tests/postfixIncSmartCast.kt");
+    }
+
     @Test
     @TestMetadata("prefixIncReturnType.kt")
     public void testPrefixIncReturnType() {
@@ -35518,6 +35524,12 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
         runTest("compiler/testData/diagnostics/tests/smartCasts/incDecToNull.kt");
       }
 
+      @Test
+      @TestMetadata("incrementAfterAssignment.kt")
+      public void testIncrementAfterAssignment() {
+        runTest("compiler/testData/diagnostics/tests/smartCasts/incrementAfterAssignment.kt");
+      }
+
       @Test
       @TestMetadata("kt10232.kt")
       public void testKt10232() {
diff --git a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java
index 38528dfa600..a7a7a332475 100644
--- a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java
+++ b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java
@@ -1089,6 +1089,12 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
       runTest("compiler/testData/diagnostics/tests/phantomIntersections.kt");
     }
 
+    @Test
+    @TestMetadata("postfixIncSmartCast.kt")
+    public void testPostfixIncSmartCast() {
+      runTest("compiler/testData/diagnostics/tests/postfixIncSmartCast.kt");
+    }
+
     @Test
     @TestMetadata("prefixIncReturnType.kt")
     public void testPrefixIncReturnType() {
@@ -35518,6 +35524,12 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
         runTest("compiler/testData/diagnostics/tests/smartCasts/incDecToNull.kt");
       }
 
+      @Test
+      @TestMetadata("incrementAfterAssignment.kt")
+      public void testIncrementAfterAssignment() {
+        runTest("compiler/testData/diagnostics/tests/smartCasts/incrementAfterAssignment.kt");
+      }
+
       @Test
       @TestMetadata("kt10232.kt")
       public void testKt10232() {
diff --git a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java
index 455c81bc9f1..e92e62a43d2 100644
--- a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java
+++ b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java
@@ -1089,6 +1089,12 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
       runTest("compiler/testData/diagnostics/tests/phantomIntersections.kt");
     }
 
+    @Test
+    @TestMetadata("postfixIncSmartCast.kt")
+    public void testPostfixIncSmartCast() {
+      runTest("compiler/testData/diagnostics/tests/postfixIncSmartCast.kt");
+    }
+
     @Test
     @TestMetadata("prefixIncReturnType.kt")
     public void testPrefixIncReturnType() {
@@ -33090,6 +33096,12 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
         runTest("compiler/testData/diagnostics/tests/smartCasts/incDecToNull.kt");
       }
 
+      @Test
+      @TestMetadata("incrementAfterAssignment.kt")
+      public void testIncrementAfterAssignment() {
+        runTest("compiler/testData/diagnostics/tests/smartCasts/incrementAfterAssignment.kt");
+      }
+
       @Test
       @TestMetadata("kt10232.kt")
       public void testKt10232() {
diff --git a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java
index 40db665ccfc..4750bbb9895 100644
--- a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java
+++ b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java
@@ -1089,6 +1089,12 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
       runTest("compiler/testData/diagnostics/tests/phantomIntersections.kt");
     }
 
+    @Test
+    @TestMetadata("postfixIncSmartCast.kt")
+    public void testPostfixIncSmartCast() {
+      runTest("compiler/testData/diagnostics/tests/postfixIncSmartCast.kt");
+    }
+
     @Test
     @TestMetadata("prefixIncReturnType.kt")
     public void testPrefixIncReturnType() {
@@ -33228,6 +33234,12 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
         runTest("compiler/testData/diagnostics/tests/smartCasts/incDecToNull.kt");
       }
 
+      @Test
+      @TestMetadata("incrementAfterAssignment.kt")
+      public void testIncrementAfterAssignment() {
+        runTest("compiler/testData/diagnostics/tests/smartCasts/incrementAfterAssignment.kt");
+      }
+
       @Test
       @TestMetadata("kt10232.kt")
       public void testKt10232() {
diff --git a/compiler/testData/diagnostics/tests/postfixIncSmartCast.fir.kt b/compiler/testData/diagnostics/tests/postfixIncSmartCast.fir.kt
new file mode 100644
index 00000000000..41f2f51b0ed
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/postfixIncSmartCast.fir.kt
@@ -0,0 +1,11 @@
+open class I {
+    operator fun inc(): ST = ST()
+}
+
+class ST : I()
+
+fun main() {
+    var local = I()
+    val x: ST = <!INITIALIZER_TYPE_MISMATCH!>local++<!>
+    val y: ST = local
+}
diff --git a/compiler/testData/diagnostics/tests/postfixIncSmartCast.kt b/compiler/testData/diagnostics/tests/postfixIncSmartCast.kt
new file mode 100644
index 00000000000..bad4e4a6e02
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/postfixIncSmartCast.kt
@@ -0,0 +1,11 @@
+open class I {
+    operator fun inc(): ST = ST()
+}
+
+class ST : I()
+
+fun main() {
+    var local = I()
+    val x: ST = <!TYPE_MISMATCH!>local++<!>
+    val y: ST = <!TYPE_MISMATCH!>local<!>
+}
diff --git a/compiler/testData/diagnostics/tests/smartCasts/incrementAfterAssignment.fir.kt b/compiler/testData/diagnostics/tests/smartCasts/incrementAfterAssignment.fir.kt
new file mode 100644
index 00000000000..6ebf323d99a
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/smartCasts/incrementAfterAssignment.fir.kt
@@ -0,0 +1,27 @@
+// WITH_STDLIB
+// SKIP_TEXT
+// ISSUE: KT-29559
+
+fun consume(i: Int) {}
+fun consume(c: Char) {}
+fun consume(a: Any?) {}
+
+fun test1() {
+    var a: Any
+
+    a = 1
+    consume(a)
+
+    a = 1
+    consume(a++)
+
+    a = 1
+    consume(++a)
+
+    a = 't'
+    consume(a++)
+
+    a = 't'
+    consume(++a)
+    consume(a++)
+}
diff --git a/compiler/testData/diagnostics/tests/smartCasts/incrementAfterAssignment.kt b/compiler/testData/diagnostics/tests/smartCasts/incrementAfterAssignment.kt
new file mode 100644
index 00000000000..458406ecdac
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/smartCasts/incrementAfterAssignment.kt
@@ -0,0 +1,27 @@
+// WITH_STDLIB
+// SKIP_TEXT
+// ISSUE: KT-29559
+
+fun consume(i: Int) {}
+fun consume(c: Char) {}
+fun consume(a: Any?) {}
+
+fun test1() {
+    var a: Any
+
+    a = 1
+    consume(<!DEBUG_INFO_SMARTCAST!>a<!>)
+
+    a = 1
+    consume(<!TYPE_MISMATCH!><!DEBUG_INFO_SMARTCAST!>a<!>++<!>)
+
+    a = 1
+    consume(++<!DEBUG_INFO_SMARTCAST!>a<!>)
+
+    a = 't'
+    consume(<!TYPE_MISMATCH!><!DEBUG_INFO_SMARTCAST!>a<!>++<!>)
+
+    a = 't'
+    consume(++<!DEBUG_INFO_SMARTCAST!>a<!>)
+    consume(<!DEBUG_INFO_SMARTCAST!><!DEBUG_INFO_SMARTCAST!>a<!>++<!>)
+}
diff --git a/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java b/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java
index 89ce284fa01..efd420fa867 100644
--- a/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java
+++ b/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java
@@ -1089,6 +1089,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
       runTest("compiler/testData/diagnostics/tests/phantomIntersections.kt");
     }
 
+    @Test
+    @TestMetadata("postfixIncSmartCast.kt")
+    public void testPostfixIncSmartCast() {
+      runTest("compiler/testData/diagnostics/tests/postfixIncSmartCast.kt");
+    }
+
     @Test
     @TestMetadata("prefixIncReturnType.kt")
     public void testPrefixIncReturnType() {
@@ -35518,6 +35524,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
         runTest("compiler/testData/diagnostics/tests/smartCasts/incDecToNull.kt");
       }
 
+      @Test
+      @TestMetadata("incrementAfterAssignment.kt")
+      public void testIncrementAfterAssignment() {
+        runTest("compiler/testData/diagnostics/tests/smartCasts/incrementAfterAssignment.kt");
+      }
+
       @Test
       @TestMetadata("kt10232.kt")
       public void testKt10232() {