all: nested sum types (#6913)

vlib/v/ast/ast.v

@@ -365,7 +365,7 @@ pub:
 	is_arg          bool // fn args should not be autofreed
 pub mut:
 	typ             table.Type
-	sum_type_cast   table.Type
+	sum_type_casts  []table.Type // nested sum types require nested smart casting, for that a list of types is needed
 	pos             token.Position
 	is_used         bool
 	is_changed      bool // to detect mutable vars that are never changed
@@ -379,7 +379,7 @@ pub:
 	name           string
 	pos            token.Position
 	typ            table.Type
-	sum_type_cast table.Type
+	sum_type_casts []table.Type // nested sum types require nested smart casting, for that a list of types is needed
 }
 
 pub struct GlobalField {

vlib/v/checker/checker.v

@@ -1801,7 +1801,7 @@ pub fn (mut c Checker) selector_expr(mut selector_expr ast.SelectorExpr) table.T
 			if !prevent_sum_type_unwrapping_once {
 				scope := c.file.scope.innermost(selector_expr.pos.pos)
 				if scope_field := scope.find_struct_field(utyp, field_name) {
-					return scope_field.sum_type_cast
+					return scope_field.sum_type_casts.last()
 				}
 			}
 		}
@@ -3234,9 +3234,9 @@ pub fn (mut c Checker) ident(mut ident ast.Ident) table.Type {
 						c.error('undefined variable `$ident.name` (used before declaration)',
 							ident.pos)
 					}
-					is_sum_type_cast := obj.sum_type_cast != 0 && !c.prevent_sum_type_unwrapping_once
+					is_sum_type_cast := obj.sum_type_casts.len != 0 && !c.prevent_sum_type_unwrapping_once
 					c.prevent_sum_type_unwrapping_once = false
-					mut typ := if is_sum_type_cast { obj.sum_type_cast } else { obj.typ }
+					mut typ := if is_sum_type_cast { obj.sum_type_casts.last() } else { obj.typ }
 					if typ == 0 {
 						if mut obj.expr is ast.Ident {
 							if obj.expr.kind == .unresolved {
@@ -3561,37 +3561,47 @@ fn (mut c Checker) match_exprs(mut node ast.MatchExpr, type_sym table.TypeSymbol
 				mut scope := c.file.scope.innermost(branch.pos.pos)
 				match mut node.cond {
 					ast.SelectorExpr {
+						mut is_mut := false
+						mut sum_type_casts := []table.Type{}
 						expr_sym := c.table.get_type_symbol(node.cond.expr_type)
-						field := c.table.struct_find_field(expr_sym, node.cond.field_name) or {
+						if field := c.table.struct_find_field(expr_sym, node.cond.field_name) {
-							table.Field{}
+							is_mut = field.is_mut
+						}
+						if field := scope.find_struct_field(node.cond.expr_type, node.cond.field_name) {
+							sum_type_casts << field.sum_type_casts
 						}
-						is_mut := field.is_mut
 						is_root_mut := scope.is_selector_root_mutable(c.table, node.cond)
 						// smartcast either if the value is immutable or if the mut argument is explicitly given
 						if (!is_root_mut && !is_mut) || node.is_mut {
+							sum_type_casts << expr_type
 							scope.register_struct_field(ast.ScopeStructField{
 								struct_type: node.cond.expr_type
 								name: node.cond.field_name
 								typ: node.cond_type
-								sum_type_cast: expr_type
+								sum_type_casts: sum_type_casts
 								pos: node.cond.pos
 							})
 						}
 					}
 					ast.Ident {
 						mut is_mut := false
+						mut sum_type_casts := []table.Type{}
+						mut is_already_casted := false
 						if v := scope.find_var(node.cond.name) {
 							is_mut = v.is_mut
+							sum_type_casts << v.sum_type_casts
+							is_already_casted = v.pos.pos == node.cond.pos.pos
 						}
 						// smartcast either if the value is immutable or if the mut argument is explicitly given
-						if !is_mut || node.is_mut {
+						if (!is_mut || node.is_mut) && !is_already_casted {
+							sum_type_casts << expr_type
 							scope.register(node.var_name, ast.Var{
 								name: node.var_name
 								typ: node.cond_type
 								pos: node.cond.pos
 								is_used: true
 								is_mut: node.is_mut
-								sum_type_cast: expr_type
+								sum_type_casts: sum_type_casts
 							})
 						}
 					}
@@ -3823,38 +3833,46 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) table.Type {
 							mut is_mut := false
 							mut scope := c.file.scope.innermost(branch.body_pos.pos)
 							if mut infix.left is ast.Ident {
+								mut sum_type_casts := []table.Type{}
 								if v := scope.find_var(infix.left.name) {
 									is_mut = v.is_mut
+									sum_type_casts << v.sum_type_casts
 								}
 								// smartcast either if the value is immutable or if the mut argument is explicitly given
 								if (!is_mut || branch.is_mut_name) &&
 									left_sym.kind == .union_sum_type {
+									sum_type_casts << right_expr.typ
 									scope.register(branch.left_as_name, ast.Var{
 										name: branch.left_as_name
 										typ: infix.left_type
-										sum_type_cast: right_expr.typ
+										sum_type_casts: sum_type_casts
 										pos: infix.left.pos
 										is_used: true
 										is_mut: is_mut
 									})
 								}
 							} else if mut infix.left is ast.SelectorExpr {
+								mut sum_type_casts := []table.Type{}
 								expr_sym := c.table.get_type_symbol(infix.left.expr_type)
-								field := c.table.struct_find_field(expr_sym, infix.left.field_name) or {
+								if field := c.table.struct_find_field(expr_sym, infix.left.field_name) {
-									table.Field{}
-								}
 									is_mut = field.is_mut
+								}
+								if field := scope.find_struct_field(infix.left.expr_type,
+									infix.left.field_name) {
+									sum_type_casts << field.sum_type_casts
+								}
 								is_root_mut := scope.is_selector_root_mutable(c.table,
 									infix.left)
 								// smartcast either if the value is immutable or if the mut argument is explicitly given
 								if ((!is_root_mut && !is_mut) ||
 									branch.is_mut_name) &&
 									left_sym.kind == .union_sum_type {
+									sum_type_casts << right_expr.typ
 									scope.register_struct_field(ast.ScopeStructField{
 										struct_type: infix.left.expr_type
 										name: infix.left.field_name
 										typ: infix.left_type
-										sum_type_cast: right_expr.typ
+										sum_type_casts: sum_type_casts
 										pos: infix.left.pos
 									})
 								}

vlib/v/checker/tests/sum_type_assign_non_variant_err.out

@@ -0,0 +1,6 @@
+vlib/v/checker/tests/sum_type_assign_non_variant_err.vv:11:6: error: cannot assign to `w`: expected `Stmt`, not `IfExpr`
+    9 | fn main() {
+   10 |     mut w := Stmt{}
+   11 |     w = IfExpr{}
+      |         ~~~~~~~~
+   12 | }

vlib/v/checker/tests/sum_type_assign_non_variant_err.vv

@@ -0,0 +1,12 @@
+__type Expr = IfExpr | CallExpr | MatchExpr
+struct MatchExpr {}
+struct IfExpr {}
+struct CallExpr {}
+
+__type Stmt = Expr | AnotherThing
+struct AnotherThing {}
+
+fn main() {
+    mut w := Stmt{}
+	w = IfExpr{}
+}

vlib/v/gen/cgen.v

@@ -1301,7 +1301,7 @@ fn (mut g Gen) union_expr_with_cast(expr ast.Expr, got_type table.Type, expected
 				scope := g.file.scope.innermost(expr.position().pos)
 				if expr is ast.Ident {
 					if v := scope.find_var(expr.name) {
-						if v.sum_type_cast != 0 {
+						if v.sum_type_casts.len > 0 {
 							is_already_sum_type = true
 						}
 					}
@@ -2567,12 +2567,17 @@ fn (mut g Gen) expr(node ast.Expr) {
 						scope := g.file.scope.innermost(node.pos.pos)
 						if field := scope.find_struct_field(node.expr_type, node.field_name) {
 							// union sum type deref
+							for i, typ in field.sum_type_casts {
 								g.write('(*')
-							cast_sym := g.table.get_type_symbol(field.sum_type_cast)
+								cast_sym := g.table.get_type_symbol(typ)
+								if i != 0 {
+									sum_type_deref_field += ').'
+								}
 								if cast_sym.info is table.Aggregate as sym_info {
-								sum_type_deref_field = '_${sym_info.types[g.aggregate_type_idx]}'
+									sum_type_deref_field += '_${sym_info.types[g.aggregate_type_idx]}'
 								} else {
-								sum_type_deref_field = '_$field.sum_type_cast'
+									sum_type_deref_field += '_$typ'
+								}
 							}
 						}
 					}
@@ -3403,13 +3408,22 @@ fn (mut g Gen) ident(node ast.Ident) {
 		}
 		scope := g.file.scope.innermost(node.pos.pos)
 		if v := scope.find_var(node.name) {
-			if v.sum_type_cast != 0 {
+			if v.sum_type_casts.len > 0 {
 				if !prevent_sum_type_unwrapping_once {
-					sym := g.table.get_type_symbol(v.sum_type_cast)
+					for _ in v.sum_type_casts {
-					if sym.info is table.Aggregate as sym_info {
+						g.write('(*')
-						g.write('(*${name}._${sym_info.types[g.aggregate_type_idx]})')
+					}
+					for i, typ in v.sum_type_casts {
+						cast_sym := g.table.get_type_symbol(typ)
+						if i == 0 {
+							g.write(name)
+						}
+						if cast_sym.info is table.Aggregate as sym_info {
+							g.write('._${sym_info.types[g.aggregate_type_idx]}')
 						} else {
-						g.write('(*${name}._$v.sum_type_cast)')
+							g.write('._$typ')
+						}
+						g.write(')')
 					}
 					return
 				}
@@ -4645,7 +4659,7 @@ fn (mut g Gen) write_types(types []table.TypeSymbol) {
 				}
 				g.type_definitions.writeln('typedef struct {')
 				g.type_definitions.writeln('    union {')
-				for variant in g.table.get_union_sum_type_variants(it) {
+				for variant in it.variants {
 					g.type_definitions.writeln('        ${g.typ(variant.to_ptr())} _$variant.idx();')
 				}
 				g.type_definitions.writeln('    };')

vlib/v/table/atypes.v

@@ -853,18 +853,6 @@ pub:
 	variants []Type
 }
 
-pub fn (table &Table) get_union_sum_type_variants(sum_type UnionSumType) []Type {
-	mut variants := []Type{}
-	for variant in sum_type.variants {
-		sym := table.get_type_symbol(variant)
-		if sym.info is UnionSumType as sym_info {
-			variants << table.get_union_sum_type_variants(sym_info)
-		}
-		variants << variant
-	}
-	return variants
-}
-
 pub fn (table &Table) type_to_str(t Type) string {
 	sym := table.get_type_symbol(t)
 	mut res := sym.source_name

vlib/v/table/table.v

@@ -738,9 +738,6 @@ pub fn (table &Table) sumtype_has_variant(parent Type, variant Type) bool {
 			if v.idx() == variant.idx() {
 				return true
 			}
-			if table.sumtype_has_variant(v, variant) {
-				return true
-			}
 		}
 	}
 	return false

vlib/v/tests/union_sum_type_test.v

@@ -106,15 +106,49 @@ fn test_converting_down() {
 	assert res[1].name == 'three'
 }
 
+struct NodeWrapper {
+	node Node
+}
+
+fn test_nested_sumtype_selector() {
+	c := NodeWrapper{Node(Expr(IfExpr{pos: 1}))}
+	if c.node is Expr {
+		if c.node is IfExpr {
+			assert c.node.pos == 1
+		}
+		else {
+			assert false
+		}
+	}
+	else {
+		assert false
+	}
+}
+
+fn test_nested_sumtype_match_selector() {
+	c := NodeWrapper{Node(Expr(IfExpr{pos: 1}))}
+	match union c.node {
+		Expr {
+			match union c.node {
+				IfExpr {
+					assert c.node.pos == 1
+				}
+				else {
+					assert false
+				}
+			}
+		}
+		else {
+			assert false
+		}
+	}
+}
+
 fn test_nested_sumtype() {
-	mut a := Node{}
-	mut b := Node{}
-	a = StructDecl{pos: 1}
-	b = IfExpr{pos: 1}
 	c := Node(Expr(IfExpr{pos:1}))
 	if c is Expr {
 		if c is IfExpr {
-			assert true
+			assert c.pos == 1
 		}
 		else {
 			assert false
@@ -125,6 +159,25 @@ fn test_nested_sumtype() {
 	}
 }
 
+fn test_nested_sumtype_match() {
+	c := Node(Expr(IfExpr{pos: 1}))
+	match union c {
+		Expr {
+			match union c {
+				IfExpr {
+					assert c.pos == 1
+				}
+				else {
+					assert false
+				}
+			}
+		}
+		else {
+			assert false
+		}
+	}
+}
+
 __type Abc = int | string
 
 fn test_string_cast_to_sumtype() {