gen: unwrap optional on if guard expr (#6903)

vlib/v/checker/checker.v

@@ -3219,7 +3219,14 @@ pub fn (mut c Checker) ident(mut ident ast.Ident) table.Type {
 								return table.void_type
 							}
 						}
-						typ = c.expr(obj.expr)
+						if mut obj.expr is ast.IfGuardExpr {
+							// new variable from if guard shouldn't have the optional flag for further use
+							// a temp variable will be generated which unwraps it
+							if_guard_var_type := c.expr(obj.expr.expr)
+							typ = if_guard_var_type.clear_flag(.optional)
+						} else {
+							typ = c.expr(obj.expr)
+						}
 					}
 					is_optional := typ.has_flag(.optional)
 					ident.kind = .variable

vlib/v/gen/cgen.v

@@ -3544,7 +3544,8 @@ fn (mut g Gen) if_expr(node ast.IfExpr) {
 					g.expr(branch.cond.expr)
 					g.writeln(', ${var_name}.ok) {')
 					if branch.cond.var_name != '_' {
-						g.writeln('\t${g.typ(branch.cond.expr_type)} $branch.cond.var_name = $var_name;')
+						base_type := g.base_type(branch.cond.expr_type)
+						g.writeln('\t$base_type $branch.cond.var_name = *($base_type*)${var_name}.data;')
 					}
 				}
 				else {

vlib/v/parser/if_match.v

@@ -106,15 +106,15 @@ fn (mut p Parser) if_expr(is_comptime bool) ast.IfExpr {
 			p.check(.decl_assign)
 			comments << p.eat_comments()
 			expr := p.expr(0)
-			p.scope.register(var_name, ast.Var{
-				name: var_name
-				expr: expr
-				pos: var_pos
-			})
 			cond = ast.IfGuardExpr{
 				var_name: var_name
 				expr: expr
 			}
+			p.scope.register(var_name, ast.Var{
+				name: var_name
+				expr: cond
+				pos: var_pos
+			})
 			prev_guard = true
 		} else {
 			prev_guard = false