Fix comments

src/Functions/FunctionsConversion.h

@@ -2516,6 +2516,7 @@ protected:
     }
 
     bool useDefaultImplementationForNulls() const override { return false; }
+    /// CAST(Nothing, T) -> T
     bool useDefaultImplementationForNothing() const override { return false; }
     bool useDefaultImplementationForConstants() const override { return true; }
     bool useDefaultImplementationForLowCardinalityColumns() const override { return false; }

src/Functions/FunctionsMiscellaneous.h

@@ -51,6 +51,9 @@ public:
     }
 
     bool useDefaultImplementationForNulls() const override { return false; }
+    /// It's possible if expression_actions contains function that don't use
+    /// default implementation for Nothing.
+    /// Example: arrayMap(x -> CAST(x, 'UInt8'), []);
     bool useDefaultImplementationForNothing() const override { return false; }
 
 private:
@@ -119,6 +122,9 @@ public:
     String getName() const override { return "FunctionCapture"; }
 
     bool useDefaultImplementationForNulls() const override { return false; }
+    /// It's possible if expression_actions contains function that don't use
+    /// default implementation for Nothing and one of captured columns can be Nothing
+    /// Example: SELECT arrayMap(x -> [x, arrayElement(y, 0)], []), [] as y
     bool useDefaultImplementationForNothing() const override { return false; }
     bool useDefaultImplementationForLowCardinalityColumns() const override { return false; }
 
@@ -249,6 +255,7 @@ public:
 
     String getName() const override { return name; }
     bool useDefaultImplementationForNulls() const override { return false; }
+    /// See comment in ExecutableFunctionCapture.
     bool useDefaultImplementationForNothing() const override { return false; }
     bool useDefaultImplementationForLowCardinalityColumns() const override { return false; }
     DataTypePtr getReturnTypeImpl(const ColumnsWithTypeAndName &) const override { return return_type; }

src/Functions/IFunction.cpp

@@ -225,8 +225,9 @@ ColumnPtr IExecutableFunction::defaultImplementationForNothing(
             getName(),
             result_type->getName());
 
-    return ColumnConst::create(ColumnNothing::create(1), input_rows_count);
+    if (input_rows_count > 0)
-
+        throw Exception(ErrorCodes::ILLEGAL_COLUMN, "Cannot create non-empty column with type Nothing");
+    return ColumnNothing::create(0);
 }
 
 ColumnPtr IExecutableFunction::executeWithoutLowCardinalityColumns(

src/Functions/array/array.cpp

@@ -20,6 +20,7 @@ public:
     }
 
     bool useDefaultImplementationForNulls() const override { return false; }
+    /// array(..., Nothing, ...) -> Array(..., Nothing, ...)
     bool useDefaultImplementationForNothing() const override { return false; }
     bool useDefaultImplementationForConstants() const override { return true; }
 

src/Functions/assumeNotNull.cpp

@@ -7,6 +7,12 @@
 
 namespace DB
 {
+
+namespace ErrorCodes
+{
+    extern const int ILLEGAL_COLUMN;
+}
+
 namespace
 {
 
@@ -33,7 +39,6 @@ public:
 
     size_t getNumberOfArguments() const override { return 1; }
     bool useDefaultImplementationForNulls() const override { return false; }
-    bool useDefaultImplementationForNothing() const override { return false; }
     bool useDefaultImplementationForConstants() const override { return true; }
     ColumnNumbers getArgumentsThatDontImplyNullableReturnType(size_t /*number_of_arguments*/) const override { return {0}; }
 
@@ -46,6 +51,9 @@ public:
     {
         const ColumnPtr & col = arguments[0].column;
 
+        if (arguments[0].type->onlyNull() && !col->empty())
+            throw Exception(ErrorCodes::ILLEGAL_COLUMN, "Cannot create non-empty column with type Nothing");
+
         if (const auto * nullable_col = checkAndGetColumn<ColumnNullable>(*col))
             return nullable_col->getNestedColumnPtr();
         else

src/Functions/indexHint.cpp

@@ -39,8 +39,6 @@ public:
 
     bool useDefaultImplementationForNulls() const override { return false; }
 
-    bool useDefaultImplementationForNothing() const override { return false; }
-
     bool isSuitableForConstantFolding() const override { return false; }
 
     bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }

src/Functions/map.cpp

@@ -65,6 +65,7 @@ public:
     bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return true; }
 
     bool useDefaultImplementationForNulls() const override { return false; }
+    /// map(..., Nothing) -> Map(..., Nothing)
     bool useDefaultImplementationForNothing() const override { return false; }
     bool useDefaultImplementationForConstants() const override { return true; }
 

src/Functions/materialize.h

@@ -23,11 +23,6 @@ public:
         return false;
     }
 
-    bool useDefaultImplementationForNothing() const override
-    {
-        return false;
-    }
-
     /// Get the function name.
     String getName() const override
     {

src/Functions/tuple.cpp

@@ -52,6 +52,7 @@ public:
     bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }
 
     bool useDefaultImplementationForNulls() const override { return false; }
+    /// tuple(..., Nothing, ...) -> Tuple(..., Nothing, ...)
     bool useDefaultImplementationForNothing() const override { return false; }
     bool useDefaultImplementationForConstants() const override { return true; }
 

tests/queries/0_stateless/02294_nothing_arguments_in_functions.reference

@@ -4,32 +4,26 @@ Array(Nothing)
 Array(Nothing)
 []
 Array(Nothing)
-Array(Nothing)
-Array(Nothing)
 []
 Array(Nothing)
+Array(String)
 Array(Nothing)
 Array(Nothing)
-
+Array(Array(Nothing))
-Nothing
+Array(Array(Nothing))
-Const(Nothing)
+Array(Map(UInt8, Nothing))
-Nothing
+Array(Map(UInt8, Nothing))
-Const(Nothing)
+Array(Tuple(Nothing))
+Array(Tuple(UInt8, Nothing))
+Nothing
+Nothing
 Nothing
 Nothing
-Array(Nothing)
-Const(Array(Nothing))
 Array(Nothing)
 Array(Nothing)
 Map(UInt8, Nothing)
-Const(Map(UInt8, Nothing))
-Map(UInt8, Nothing)
 Map(UInt8, Nothing)
 Tuple(UInt8, Nothing)
-Const(Tuple(UInt8, Nothing))
-Tuple(UInt8, Nothing)
 Tuple(UInt8, Nothing)
 Nothing
-Const(Nothing)
-Nothing
 Nothing

tests/queries/0_stateless/02294_nothing_arguments_in_functions.sql

@@ -5,39 +5,36 @@ select toTypeName(arrayMap((x, y) -> x + y, [], []));
 select arrayMap((x, y) -> x + y, [], CAST([], 'Array(Int32)'));
 select toTypeName(arrayMap((x, y) -> x + y, [], CAST([], 'Array(Int32)')));
 
-select toTypeName(arrayMap(x -> 2 * x, [assumeNotNull(NULL)]));
-select toColumnTypeName(arrayMap(x -> 2 * x, [assumeNotNull(NULL)]));
-
 select arrayFilter(x -> 2 * x < 0, []);
 select toTypeName(arrayFilter(x -> 2 * x < 0, []));
-select toTypeName(arrayFilter(x -> 2 * x < 0, [assumeNotNull(NULL)]));
-select toColumnTypeName(arrayFilter(x -> 2 * x < 0, [assumeNotNull(NULL)]));
 
-select CAST(assumeNotNull(NULL), 'String');
+select toTypeName(arrayMap(x -> CAST(x, 'String'), []));
-select toTypeName(toInt32(assumeNotNull(NULL)));
+select toTypeName(arrayMap(x -> toInt32(x), []));
-select toColumnTypeName(toInt32(assumeNotNull(NULL)));
+select toColumnTypeName(arrayMap(x -> toInt32(x), []));
+
+select toTypeName(arrayMap(x -> [x], []));
+select toColumnTypeName(arrayMap(x -> [x], []));
+
+select toTypeName(arrayMap(x ->map(1, x), []));
+select toColumnTypeName(arrayMap(x -> map(1, x), []));
+
+select toTypeName(arrayMap(x ->tuple(x), []));
+select toColumnTypeName(arrayMap(x -> tuple(1, x), []));
+
+select toTypeName(toInt32(assumeNotNull(materialize(NULL))));
+select toColumnTypeName(toInt32(assumeNotNull(materialize(NULL))));
 
-select toTypeName(assumeNotNull(NULL));
-select toColumnTypeName(assumeNotNull(NULL));
 select toTypeName(assumeNotNull(materialize(NULL)));
 select toColumnTypeName(assumeNotNull(materialize(NULL)));
 
-select toTypeName([assumeNotNull(NULL)]);
-select toColumnTypeName([assumeNotNull(NULL)]);
 select toTypeName([assumeNotNull(materialize(NULL))]);
 select toColumnTypeName([assumeNotNull(materialize(NULL))]);
 
-select toTypeName(map(1, assumeNotNull(NULL)));
-select toColumnTypeName(map(1, assumeNotNull(NULL)));
 select toTypeName(map(1, assumeNotNull(materialize(NULL))));
 select toColumnTypeName(map(1, assumeNotNull(materialize(NULL))));
 
-select toTypeName(tuple(1, assumeNotNull(NULL)));
-select toColumnTypeName(tuple(1, assumeNotNull(NULL)));
 select toTypeName(tuple(1, assumeNotNull(materialize(NULL))));
 select toColumnTypeName(tuple(1, assumeNotNull(materialize(NULL))));
 
-select toTypeName(assumeNotNull(NULL) * 2);
-select toColumnTypeName(assumeNotNull(NULL) * 2);
 select toTypeName(assumeNotNull(materialize(NULL)) * 2);
 select toColumnTypeName(assumeNotNull(materialize(NULL)) * 2);

tests/queries/0_stateless/02294_nothing_arguments_in_functions_errors.reference

@@ -0,0 +1,3 @@
+OK
+OK
+OK

tests/queries/0_stateless/02294_nothing_arguments_in_functions_errors.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+
+CUR_DIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+# shellcheck source=../shell_config.sh
+. "$CUR_DIR"/../shell_config.sh
+
+$CLICKHOUSE_LOCAL -q "SELECT assumeNotNull(NULL)" 2>&1 | grep -q "ILLEGAL_COLUMN" && echo "OK" || echo "FAIL"
+$CLICKHOUSE_LOCAL -q "SELECT assumeNotNull(materialize(NULL))" 2>&1 | grep -q "ILLEGAL_TYPE_OF_ARGUMENT" && echo "OK" || echo "FAIL"
+$CLICKHOUSE_LOCAL -q "SELECT assumeNotNull(materialize(NULL)) from numbers(10)" 2>&1 | grep -q "ILLEGAL_TYPE_OF_ARGUMENT" && echo "OK" || echo "FAIL"
+