checker: add checking for comptime assign without comptime if checking (fix #23796) (#23848)

vlib/v/checker/assign.v

@@ -187,6 +187,11 @@ fn (mut c Checker) assign_stmt(mut node ast.AssignStmt) {
 				&& c.table.sym(left_type).kind in [.array, .map, .struct]
 		}
 		if c.comptime.comptime_for_field_var != '' && mut left is ast.ComptimeSelector {
+			if c.comptime.has_different_types && node.right[i].is_literal()
+				&& !c.comptime.inside_comptime_if {
+				c.error('mismatched types: check field type with \$if to avoid this problem',
+					node.right[i].pos())
+			}
 			left_type = c.comptime.comptime_for_field_type
 			c.expected_type = c.unwrap_generic(left_type)
 		}

vlib/v/checker/comptime.v

@@ -271,6 +271,8 @@ fn (mut c Checker) comptime_for(mut node ast.ComptimeFor) {
 					return
 				}
 			}
+			has_different_types := fields.len > 1
+				&& !fields.all(c.check_basic(it.typ, fields[0].typ))
 			for field in fields {
 				c.push_new_comptime_info()
 				c.comptime.inside_comptime_for = true
@@ -283,6 +285,7 @@ fn (mut c Checker) comptime_for(mut node ast.ComptimeFor) {
 				c.type_resolver.update_ct_type(node.val_var, c.field_data_type)
 				c.type_resolver.update_ct_type('${node.val_var}.typ', node.typ)
 				c.comptime.comptime_for_field_type = field.typ
+				c.comptime.has_different_types = has_different_types
 				c.stmts(mut node.stmts)
 
 				unwrapped_expr_type := c.unwrap_generic(field.typ)
@@ -809,6 +812,7 @@ fn (mut c Checker) comptime_if_cond(mut cond ast.Expr, pos token.Pos) ComptimeBr
 					} else if cond.left in [ast.Ident, ast.SelectorExpr, ast.TypeNode] {
 						// `$if method.type is string`
 						c.expr(mut cond.left)
+						c.comptime.inside_comptime_if = true
 						if mut cond.left is ast.SelectorExpr && cond.right is ast.ComptimeType {
 							comptime_type := cond.right as ast.ComptimeType
 							if c.comptime.is_comptime_selector_type(cond.left) {
@@ -1075,6 +1079,8 @@ fn (mut c Checker) push_new_comptime_info() {
 	c.type_resolver.info_stack << type_resolver.ResolverInfo{
 		saved_type_map:               c.type_resolver.type_map.clone()
 		inside_comptime_for:          c.comptime.inside_comptime_for
+		inside_comptime_if:           c.comptime.inside_comptime_if
+		has_different_types:          c.comptime.has_different_types
 		comptime_for_variant_var:     c.comptime.comptime_for_variant_var
 		comptime_for_field_var:       c.comptime.comptime_for_field_var
 		comptime_for_field_type:      c.comptime.comptime_for_field_type
@@ -1091,6 +1097,8 @@ fn (mut c Checker) pop_comptime_info() {
 	old := c.type_resolver.info_stack.pop()
 	c.type_resolver.type_map = old.saved_type_map.clone()
 	c.comptime.inside_comptime_for = old.inside_comptime_for
+	c.comptime.inside_comptime_if = old.inside_comptime_if
+	c.comptime.has_different_types = old.has_different_types
 	c.comptime.comptime_for_variant_var = old.comptime_for_variant_var
 	c.comptime.comptime_for_field_var = old.comptime_for_field_var
 	c.comptime.comptime_for_field_type = old.comptime_for_field_type

vlib/v/checker/if.v

@@ -53,6 +53,10 @@ fn (mut c Checker) if_expr(mut node ast.IfExpr) ast.Type {
 	mut skip_state := ComptimeBranchSkipState.unknown
 	mut found_branch := false // Whether a matching branch was found- skip the rest
 	mut is_comptime_type_is_expr := false // if `$if T is string`
+	last_in_comptime_if := c.comptime.inside_comptime_if
+	defer {
+		c.comptime.inside_comptime_if = last_in_comptime_if
+	}
 	for i in 0 .. node.branches.len {
 		mut branch := node.branches[i]
 		if branch.cond is ast.ParExpr && !c.pref.translated && !c.file.is_translated {

vlib/v/checker/tests/comptime_selector_assign.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/comptime_selector_assign.vv:18:24: error: mismatched types: check field type with $if to avoid this problem
+   16 |                 typ.$(field.name) = 2
+   17 |             }
+   18 |             typ.$(field.name) = 3
+      |                                 ^
+   19 |         }
+   20 |     }

vlib/v/checker/tests/comptime_selector_assign.vv

@@ -0,0 +1,31 @@
+import x.json2 { Any, raw_decode }
+
+struct Income {
+mut:
+	email string
+	code  int
+}
+
+pub fn structuring[T](res Any) T {
+	mut typ := T{}
+	res_map := res.as_map()
+
+	$for field in T.fields {
+		if field.name in res_map {
+			$if field.typ is int {
+				typ.$(field.name) = 2
+			}
+			typ.$(field.name) = 3
+		}
+	}
+	return typ
+}
+
+fn main() {
+	res := raw_decode('{
+        "email": ["sdvsdv", "sds"],
+        "code": 12
+    }')!.as_map()
+
+	structuring[Income](res)
+}

vlib/v/type_resolver/type_resolver.v

@@ -15,6 +15,9 @@ pub mut:
 	comptime_loop_id int
 	// $for
 	inside_comptime_for bool
+	// $if
+	inside_comptime_if  bool
+	has_different_types bool
 	// .variants
 	comptime_for_variant_var string
 	// .fields