[CALCITE-7542] RexCall.isAlwaysTrue()/isAlwaysFalse() incorrectly returns true for CAST(boolean AS non-boolean)

core/src/main/java/org/apache/calcite/rex/RexCall.java

@@ -228,8 +228,13 @@ private boolean digestWithType() {
       return operands.get(0).isAlwaysFalse();
     case IS_NOT_FALSE:
     case IS_TRUE:
-    case CAST:
       return operands.get(0).isAlwaysTrue();
+    case CAST:
+      // Only delegate to the operand if the result type is also BOOLEAN.
+      // CAST(TRUE AS INTEGER) has isAlwaysTrue() == false even though its
+      // operand is always true, because the result is an INTEGER, not a BOOLEAN.
+      return getType().getSqlTypeName() == SqlTypeName.BOOLEAN
+          && operands.get(0).isAlwaysTrue();
     case SEARCH:
       final Sarg<?> sarg = ((RexLiteral) operands.get(1)).getValueAs(Sarg.class);
       return requireNonNull(sarg, "sarg").isAll()
@@ -250,8 +255,11 @@ private boolean digestWithType() {
       return operands.get(0).isAlwaysTrue();
     case IS_NOT_FALSE:
     case IS_TRUE:
-    case CAST:
       return operands.get(0).isAlwaysFalse();
+    case CAST:
+      // Only delegate to the operand if the result type is also BOOLEAN.
+      return getType().getSqlTypeName() == SqlTypeName.BOOLEAN
+          && operands.get(0).isAlwaysFalse();
     case SEARCH:
       final Sarg<?> sarg = ((RexLiteral) operands.get(1)).getValueAs(Sarg.class);
       return requireNonNull(sarg, "sarg").isNone()

core/src/test/java/org/apache/calcite/rex/RexProgramTest.java

@@ -4130,6 +4130,55 @@ private void checkSarg(String message, Sarg sarg,
     checkSimplify(isTrue(like(ref, literal("%"))), "IS NOT NULL($0)");
   }
 
+  /** Unit tests for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-7542">[CALCITE-7542]
+   * RexCall.isAlwaysTrue()/isAlwaysFalse() incorrectly returns true
+   * for CAST(boolean AS non-boolean)</a>. */
+  @Test void testIsAlwaysTrueCastBooleanToInteger() {
+    // CAST(TRUE AS INTEGER) is not a boolean expression; isAlwaysTrue() must be false.
+    final RexNode castTrueToInt = abstractCast(trueLiteral, tInt());
+    assertThat("CAST(TRUE AS INTEGER).isAlwaysTrue()",
+        castTrueToInt.isAlwaysTrue(), is(false));
+    assertThat("CAST(TRUE AS INTEGER).isAlwaysFalse()",
+        castTrueToInt.isAlwaysFalse(), is(false));
+  }
+
+  @Test void testIsAlwaysFalseCastBooleanToInteger() {
+    // CAST(FALSE AS INTEGER) is not a boolean expression; isAlwaysFalse() must be false.
+    final RexNode castFalseToInt = abstractCast(falseLiteral, tInt());
+    assertThat("CAST(FALSE AS INTEGER).isAlwaysFalse()",
+        castFalseToInt.isAlwaysFalse(), is(false));
+    assertThat("CAST(FALSE AS INTEGER).isAlwaysTrue()",
+        castFalseToInt.isAlwaysTrue(), is(false));
+  }
+
+  @Test void testIsAlwaysTrueCastBooleanToBoolean() {
+    // CAST(TRUE AS BOOLEAN) preserves the always-true property.
+    final RexNode castTrueToBool = abstractCast(trueLiteral, tBool());
+    assertThat("CAST(TRUE AS BOOLEAN).isAlwaysTrue()",
+        castTrueToBool.isAlwaysTrue(), is(true));
+  }
+
+  @Test void testIsAlwaysFalseCastBooleanToBoolean() {
+    // CAST(FALSE AS BOOLEAN) preserves the always-false property.
+    final RexNode castFalseToBool = abstractCast(falseLiteral, tBool());
+    assertThat("CAST(FALSE AS BOOLEAN).isAlwaysFalse()",
+        castFalseToBool.isAlwaysFalse(), is(true));
+  }
+
+  @Test void testIsAlwaysTrueFalseCastNonBooleanCallToBoolean() {
+    // CAST(1 + 1 AS BOOLEAN): the inner operand is a non-literal, non-boolean
+    // RexCall. isAlwaysTrue()/isAlwaysFalse() must safely return false on the
+    // recursive call rather than crashing — the contract is "ask freely, get
+    // a safe false for non-boolean expressions," matching RexLiteral and the
+    // RexNode base class.
+    final RexNode castIntExprToBool = abstractCast(plus(literal(1), literal(1)), tBool());
+    assertThat("CAST(1 + 1 AS BOOLEAN).isAlwaysTrue()",
+        castIntExprToBool.isAlwaysTrue(), is(false));
+    assertThat("CAST(1 + 1 AS BOOLEAN).isAlwaysFalse()",
+        castIntExprToBool.isAlwaysFalse(), is(false));
+  }
+
   /** Unit tests for
    * <a href="https://issues.apache.org/jira/browse/CALCITE-2438">[CALCITE-2438]
    * RexCall#isAlwaysTrue returns incorrect result</a>. */