Fix compiler crash when const propagating a property of component-factory with its default value

We couldn't represent an empty component factory in the exrpession tree,
so add Expression::EmptyComponentFactory for that

internal/compiler/expression_tree.rs

@@ -737,6 +737,8 @@ pub enum Expression {
         lhs: Box<Expression>,
         rhs: Box<Expression>,
     },
+
+    EmptyComponentFactory,
 }
 
 impl Expression {
@@ -864,6 +866,7 @@ impl Expression {
             Expression::ComputeLayoutInfo(..) => crate::layout::layout_info_type(),
             Expression::SolveLayout(..) => Type::LayoutCache,
             Expression::MinMax { ty, .. } => ty.clone(),
+            Expression::EmptyComponentFactory => Type::ComponentFactory,
         }
     }
 
@@ -966,6 +969,7 @@ impl Expression {
                 visitor(lhs);
                 visitor(rhs);
             }
+            Expression::EmptyComponentFactory => {}
         }
     }
 
@@ -1070,6 +1074,7 @@ impl Expression {
                 visitor(lhs);
                 visitor(rhs);
             }
+            Expression::EmptyComponentFactory => {}
         }
     }
 
@@ -1148,6 +1153,7 @@ impl Expression {
             Expression::ComputeLayoutInfo(..) => false,
             Expression::SolveLayout(..) => false,
             Expression::MinMax { lhs, rhs, .. } => lhs.is_constant() && rhs.is_constant(),
+            Expression::EmptyComponentFactory => true,
         }
     }
 
@@ -1334,7 +1340,6 @@ impl Expression {
         match ty {
             Type::Invalid
             | Type::Callback { .. }
-            | Type::ComponentFactory
             | Type::Function { .. }
             | Type::InferredProperty
             | Type::InferredCallback
@@ -1379,6 +1384,7 @@ impl Expression {
             Type::Enumeration(enumeration) => {
                 Expression::EnumerationValue(enumeration.clone().default_value())
             }
+            Type::ComponentFactory => Expression::EmptyComponentFactory,
         }
     }
 
@@ -1781,5 +1787,6 @@ pub fn pretty_print(f: &mut dyn std::fmt::Write, expression: &Expression) -> std
             pretty_print(f, rhs)?;
             write!(f, ")")
         }
+        Expression::EmptyComponentFactory => write!(f, "<empty-component-factory>"),
     }
 }

internal/compiler/generator/cpp.rs

@@ -3096,6 +3096,7 @@ fn compile_expression(expr: &llr::Expression, ctx: &EvaluationContext) -> String
                 rhs_code = rhs_code
             )
         }
+        Expression::EmptyComponentFactory => panic!("component-factory not yet supported in C++"),
     }
 }
 

internal/compiler/generator/rust.rs

@@ -2395,6 +2395,7 @@ fn compile_expression(expr: &Expression, ctx: &EvaluationContext) -> TokenStream
                 }
             }
         }
+        Expression::EmptyComponentFactory => quote!(slint::ComponentFactory::default()),
     }
 }
 

internal/compiler/llr/expression.rs

@@ -187,6 +187,8 @@ pub enum Expression {
         lhs: Box<Expression>,
         rhs: Box<Expression>,
     },
+
+    EmptyComponentFactory,
 }
 
 impl Expression {
@@ -194,7 +196,6 @@ impl Expression {
         Some(match ty {
             Type::Invalid
             | Type::Callback { .. }
-            | Type::ComponentFactory
             | Type::Function { .. }
             | Type::Void
             | Type::InferredProperty
@@ -241,6 +242,7 @@ impl Expression {
             Type::Enumeration(enumeration) => {
                 Expression::EnumerationValue(enumeration.clone().default_value())
             }
+            Type::ComponentFactory => Expression::EmptyComponentFactory,
         })
     }
 
@@ -301,6 +303,7 @@ impl Expression {
                 Type::Array(super::lower_expression::grid_layout_cell_data_ty().into())
             }
             Self::MinMax { ty, .. } => ty.clone(),
+            Self::EmptyComponentFactory => Type::ComponentFactory,
         }
     }
 }
@@ -382,6 +385,7 @@ macro_rules! visit_impl {
                 $visitor(lhs);
                 $visitor(rhs);
             }
+            Expression::EmptyComponentFactory => {}
         }
     };
 }

internal/compiler/llr/lower_expression.rs

@@ -213,6 +213,7 @@ pub fn lower_expression(
             lhs: Box::new(lower_expression(lhs, ctx)),
             rhs: Box::new(lower_expression(rhs, ctx)),
         },
+        tree_Expression::EmptyComponentFactory => llr_Expression::EmptyComponentFactory,
     }
 }
 

internal/compiler/llr/optim_passes/inline_expressions.rs

@@ -51,6 +51,7 @@ fn expression_cost(exp: &Expression, ctx: &EvaluationContext) -> isize {
         Expression::BoxLayoutFunction { .. } => return isize::MAX,
         Expression::ComputeDialogLayoutCells { .. } => return isize::MAX,
         Expression::MinMax { .. } => 10,
+        Expression::EmptyComponentFactory => 10,
     };
 
     exp.visit(|e| cost = cost.saturating_add(expression_cost(e, ctx)));

internal/compiler/llr/pretty_print.rs

@@ -268,6 +268,7 @@ impl<'a, T> Display for DisplayExpression<'a, T> {
                 MinMaxOp::Min => write!(f, "min({}, {})", e(lhs), e(rhs)),
                 MinMaxOp::Max => write!(f, "max({}, {})", e(lhs), e(rhs)),
             },
+            Expression::EmptyComponentFactory => write!(f, "<empty-component-factory>",),
         }
     }
 }

internal/interpreter/eval.rs

@@ -394,6 +394,7 @@ pub fn eval_expression(expression: &Expression, local_context: &mut EvalLocalCon
                 MinMaxOp::Max => Value::Number(lhs.max(rhs)),
             }
         }
+        Expression::EmptyComponentFactory => Value::ComponentFactory(Default::default())
     }
 }
 

tests/cases/elements/component_container.slint

@@ -17,6 +17,11 @@ export component TestCase inherits Rectangle {
     in property<component-factory> c1 <=> cont1.component-factory;
     in property<component-factory> c2 <=> cont2.component-factory;
     out property<bool> outside-focus <=> outside.has-focus;
+
+
+    private property <component-factory> some-factory;
+    ComponentContainer { component-factory: some-factory; }
+    out property <bool> test: some-factory == some-factory;
 }
 
 /*