goscript_types/check/

typexpr.rs

#![allow(dead_code)]
use super::super::constant;
use super::super::lookup;
use super::super::obj::EntityType;
use super::super::objects::{ObjKey, ScopeKey, TCObjects, TypeKey};
use super::super::operand::{Operand, OperandMode};
use super::super::scope::Scope;
use super::super::typ::{self, Type};
use super::check::{Checker, FilesContext, ObjContext};
use super::interface::MethodInfo;
use goscript_parser::ast::{self, Expr, FieldList, Node};
use goscript_parser::objects::{FuncTypeKey, IdentKey};
use goscript_parser::{Pos, Token};
use std::borrow::Borrow;
use std::collections::HashMap;

impl<'a> Checker<'a> {
    /// ident type-checks identifier ikey and initializes x with the value or type of ikey.
    /// If an error occurred, x.mode is set to invalid.
    /// For the meaning of def, see Checker.defined_type, below.
    /// If want_type is set, the identifier e is expected to denote a type.
    pub fn ident(
        &mut self,
        x: &mut Operand,
        ikey: IdentKey,
        def: Option<TypeKey>,
        want_type: bool,
        fctx: &mut FilesContext,
    ) {
        x.mode = OperandMode::Invalid;
        x.expr = Some(Expr::Ident(ikey));

        // Note that we cannot use check.lookup here because the returned scope
        // may be different from obj.parent(). See also Scope.lookup_parent doc.
        let name = &self.ast_ident(ikey).name;
        if let Some((skey, okey)) =
            Scope::lookup_parent(&self.octx.scope.unwrap(), name, self.octx.pos, self.tc_objs)
        {
            self.result.record_use(ikey, okey);

            // Type-check the object.
            // Only call Checker.obj_decl if the object doesn't have a type yet
            // (in which case we must actually determine it) or the object is a
            // TypeName and we also want a type (in which case we might detect
            // a cycle which needs to be reported). Otherwise we can skip the
            // call and avoid a possible cycle error in favor of the more
            // informative "not a type/value" error that this function's caller
            // will issue
            let lobj = self.lobj(okey);
            let pkg = lobj.pkg();
            let mut otype = lobj.typ();
            if otype.is_none() || (lobj.entity_type().is_type_name() && want_type) {
                self.obj_decl(okey, def, fctx);
                // type must have been assigned by Checker.obj_decl
                otype = self.lobj(okey).typ();
            }
            debug_assert!(otype.is_some());

            // The object may be dot-imported: If so, remove its package from
            // the map of unused dot imports for the respective file scope.
            // (This code is only needed for dot-imports. Without them,
            // we only have to mark variables, see Var case below).
            if pkg.is_some() && pkg != Some(self.pkg) {
                fctx.unused_dot_imports
                    .get_mut(&skey)
                    .unwrap()
                    .remove(&pkg.unwrap());
            }

            let lobj = self.lobj(okey);
            let invalid_type = self.invalid_type();
            match lobj.entity_type() {
                EntityType::PkgName(_, _) => {
                    let pos = self.ast_ident(ikey).pos;
                    let msg = format!("use of package {} not in selector", lobj.name());
                    self.error(pos, msg);
                    return;
                }
                EntityType::Const(_) => {
                    self.add_decl_dep(okey);
                    if otype == Some(invalid_type) {
                        return;
                    }
                    if okey == *self.tc_objs.universe().iota() {
                        if self.octx.iota.is_none() {
                            let pos = self.ast_ident(ikey).pos;
                            self.error_str(pos, "cannot use iota outside constant declaration");
                            return;
                        }
                        x.mode = OperandMode::Constant(self.octx.iota.clone().unwrap());
                    } else {
                        x.mode = OperandMode::Constant(self.lobj(okey).const_val().clone());
                    }
                }
                EntityType::TypeName => x.mode = OperandMode::TypeExpr,
                EntityType::Var(_) => {
                    // It's ok to mark non-local variables, but ignore variables
                    // from other packages to avoid potential race conditions with
                    // dot-imported variables.
                    if lobj.pkg() == Some(self.pkg) {
                        self.lobj_mut(okey)
                            .entity_type_mut()
                            .var_property_mut()
                            .used = true;
                    }
                    self.add_decl_dep(okey);
                    if otype == Some(invalid_type) {
                        return;
                    }
                    x.mode = OperandMode::Variable;
                }
                EntityType::Func(_) => {
                    self.add_decl_dep(okey);
                    x.mode = OperandMode::Value;
                }
                EntityType::Label(_) => unreachable!(),
                EntityType::Builtin(id) => x.mode = OperandMode::Builtin(*id),
                EntityType::Nil => x.mode = OperandMode::Value,
            }
            x.typ = otype;
        } else {
            let pos = self.ast_ident(ikey).pos;
            if name == "_" {
                self.error(pos, "cannot use _ as value or type".to_string());
            } else {
                self.error(pos, format!("undeclared name: {}", name));
            }
        }
    }

    /// type_expr type-checks the type expression e and returns its type, or Invalid Type.
    pub fn type_expr(&mut self, e: &Expr, fctx: &mut FilesContext) -> TypeKey {
        self.defined_type(e, None, fctx)
    }

    /// defined_type is like type_expr but also accepts a type name def.
    /// If def is_some(), e is the type specification for the defined type def, declared
    /// in a type declaration, and def.underlying will be set to the type of e before
    /// any components of e are type-checked.
    pub fn defined_type(
        &mut self,
        e: &Expr,
        def: Option<TypeKey>,
        fctx: &mut FilesContext,
    ) -> TypeKey {
        if self.config().trace_checker {
            let ed = self.new_dis(e);
            self.trace_begin(ed.pos(), &format!("{}", ed));
        }
        let t = self.type_internal(e, def, fctx);
        debug_assert!(typ::is_typed(t, self.tc_objs));
        self.result
            .record_type_and_value(e, OperandMode::TypeExpr, t);
        if self.config().trace_checker {
            let pos = e.pos(self.ast_objs);
            self.trace_end(pos, &format!("=> {}", self.new_dis(&t)));
        }
        t
    }

    /// indirect_type is like type_expr but it also breaks the (otherwise) infinite size of
    /// recursivetypes by introducing an indirection. It should be called for components of
    /// types that are not laid out in place in memory, such as pointer base types, slice or
    /// map element types, function parameter types, etc.
    pub fn indirect_type(&mut self, e: &Expr, fctx: &mut FilesContext) -> TypeKey {
        fctx.push(*self.tc_objs.universe().indir());
        let t = self.defined_type(e, None, fctx);
        fctx.pop();
        t
    }

    /// func_type type-checks a function or method type.
    pub fn func_type(
        &mut self,
        recv: Option<&FieldList>,
        ftype: FuncTypeKey,
        fctx: &mut FilesContext,
    ) -> TypeKey {
        let skey = self
            .tc_objs
            .new_scope(self.octx.scope, 0, 0, "function".to_string(), true);
        self.result.record_scope(&ftype, skey);

        let (recv_list, _) = self.collect_params(skey, recv, false, fctx);
        let ftype_val = &self.ast_objs.ftypes[ftype];
        let (p, r) = (ftype_val.params.clone(), ftype_val.results.clone());
        let (params, variadic) = self.collect_params(skey, Some(&p), true, fctx);
        let (results, _) = self.collect_params(skey, r.as_ref(), false, fctx);

        let mut recv_okey = None;
        if recv.is_some() {
            // recv parameter list present (may be empty)
            // spec: "The receiver is specified via an extra parameter section preceding the
            // method name. That parameter section must declare a single parameter, the receiver."
            let invalid_type = self.invalid_type();
            let recv_var = match recv_list.len() {
                x if x == 0 => {
                    let pos = recv.unwrap().pos(self.ast_objs);
                    self.error_str(pos, "method is missing receiver");
                    self.tc_objs
                        .new_param_var(0, None, "".to_string(), Some(invalid_type))
                }
                x if x > 1 => {
                    let pos = self.lobj(recv_list[recv_list.len() - 1]).pos();
                    self.error_str(pos, "method must have exactly one receiver");
                    recv_list[0] // continue with first receiver
                }
                x if x == 1 => recv_list[0],
                _ => unreachable!(),
            };
            recv_okey = Some(recv_var);

            // spec: "The receiver type must be of the form T or *T where T is a type name."
            // (ignore invalid types - error was reported before)
            let recv_var_val = self.lobj(recv_var);
            let recv_type = recv_var_val.typ().unwrap();
            let (t, _) = lookup::try_deref(recv_type, self.tc_objs);
            if t != invalid_type {
                let err_msg = if let Some(n) = self.otype(t).try_as_named() {
                    // spec: "The type denoted by T is called the receiver base type; it must not
                    // be a pointer or interface type and it must be declared in the same package
                    // as the method."
                    if self.lobj(n.obj().unwrap()).pkg() != Some(self.pkg) {
                        Some("type not defined in this package")
                    } else {
                        match self.otype(n.underlying()) {
                            typ::Type::Basic(b) => {
                                if b.typ() == typ::BasicType::UnsafePointer {
                                    Some("unsafe.Pointer")
                                } else {
                                    None
                                }
                            }
                            typ::Type::Pointer(_) | typ::Type::Interface(_) => {
                                Some("pointer or interface type")
                            }
                            _ => None,
                        }
                    }
                } else {
                    Some("basic or unnamed type")
                };
                if let Some(err) = err_msg {
                    let pos = recv_var_val.pos();
                    let td = self.new_dis(&recv_type);
                    self.error(pos, format!("invalid receiver {} ({})", td, err));
                    // ok to continue
                }
            }
        }

        let params_tuple = self.tc_objs.new_t_tuple(params);
        let results_tuple = self.tc_objs.new_t_tuple(results);
        self.tc_objs
            .new_t_signature(Some(skey), recv_okey, params_tuple, results_tuple, variadic)
    }

    /// type_internal drives type checking of types.
    /// Must only be called by defined_type.
    fn type_internal(
        &mut self,
        e: &Expr,
        def: Option<TypeKey>,
        fctx: &mut FilesContext,
    ) -> TypeKey {
        let set_underlying = |typ: Option<TypeKey>, tc_objs: &mut TCObjects| {
            if let Some(d) = def {
                tc_objs.types[d]
                    .try_as_named_mut()
                    .unwrap()
                    .set_underlying(typ.unwrap());
            }
        };
        let pos = e.pos(self.ast_objs);
        let result_t: Option<TypeKey> = match e {
            Expr::Bad(_) => None,
            Expr::Ident(i) => {
                let mut x = Operand::new();
                self.ident(&mut x, *i, def, true, fctx);
                match x.mode {
                    OperandMode::TypeExpr => {
                        set_underlying(x.typ, self.tc_objs);
                        x.typ
                    }
                    OperandMode::Invalid => None, // ignore - error reported before
                    OperandMode::NoValue => {
                        error_operand!(x, "{} used as type", self);
                        None
                    }
                    _ => {
                        error_operand!(x, "{} is not a type", self);
                        None
                    }
                }
            }
            Expr::Selector(s) => {
                let mut x = Operand::new();
                self.selector(&mut x, s, fctx);
                match x.mode {
                    OperandMode::TypeExpr => {
                        set_underlying(x.typ, self.tc_objs);
                        x.typ
                    }
                    OperandMode::Invalid => None, // ignore - error reported before
                    OperandMode::NoValue => {
                        error_operand!(x, "{} used as type", self);
                        None
                    }
                    _ => {
                        error_operand!(x, "{} is not a type", self);
                        None
                    }
                }
            }
            Expr::Paren(p) => Some(self.defined_type(&p.expr, def, fctx)),
            Expr::Array(a) => {
                if let Some(l) = &a.len {
                    let len = self.array_len(&l, fctx);
                    let elem = self.type_expr(&a.elt, fctx);
                    let t = self.tc_objs.new_t_array(elem, len);
                    set_underlying(Some(t), self.tc_objs);
                    Some(t)
                } else {
                    let elem = self.indirect_type(&a.elt, fctx);
                    let t = self.tc_objs.new_t_slice(elem);
                    set_underlying(Some(t), self.tc_objs);
                    Some(t)
                }
            }
            Expr::Struct(s) => {
                let t = self.struct_type(s, fctx);
                set_underlying(Some(t), self.tc_objs);
                Some(t)
            }
            Expr::Star(s) => {
                let base = self.indirect_type(&s.expr, fctx);
                let t = self.tc_objs.new_t_pointer(base);
                set_underlying(Some(t), self.tc_objs);
                Some(t)
            }
            Expr::Func(f) => {
                let t = self.func_type(None, *f, fctx);
                set_underlying(Some(t), self.tc_objs);
                Some(t)
            }
            Expr::Interface(_) => {
                let t = self.interface_type(e, def, fctx);
                set_underlying(Some(t), self.tc_objs);
                Some(t)
            }
            Expr::Map(m) => {
                let k = self.indirect_type(&m.key, fctx);
                let v = self.indirect_type(&m.val, fctx);
                let t = self.tc_objs.new_t_map(k, v);
                set_underlying(Some(t), self.tc_objs);

                let pos = m.key.pos(self.ast_objs);
                let f = move |checker: &mut Checker, _: &mut FilesContext| {
                    if !typ::comparable(k, checker.tc_objs) {
                        let td = checker.new_dis(&k);
                        checker.error(pos, format!("invalid map key type {}", td));
                    }
                };
                fctx.later(Box::new(f));

                Some(t)
            }
            Expr::Chan(chan) => {
                let dir = match chan.dir {
                    ast::ChanDir::Send => typ::ChanDir::SendOnly,
                    ast::ChanDir::Recv => typ::ChanDir::RecvOnly,
                    ast::ChanDir::SendRecv => typ::ChanDir::SendRecv,
                };
                let elem = self.indirect_type(&chan.val, fctx);
                let t = self.tc_objs.new_t_chan(dir, elem);
                set_underlying(Some(t), self.tc_objs);
                Some(t)
            }
            _ => {
                let ed = self.new_dis(e);
                self.error(pos, format!("{} is not a type", ed));
                None
            }
        };
        if let Some(t) = result_t {
            t
        } else {
            let invalid_type = self.invalid_type();
            set_underlying(Some(invalid_type), self.tc_objs);
            invalid_type
        }
    }

    /// type_or_nil type-checks the type expression (or nil value) e
    /// and returns the typ of e, or None.
    /// If e is neither a type nor nil, typOrNil returns Typ[Invalid].
    pub fn type_or_nil(&mut self, e: &Expr, fctx: &mut FilesContext) -> Option<TypeKey> {
        let mut x = Operand::new();
        self.raw_expr(&mut x, e, None, fctx);
        let invalid_type = self.invalid_type();
        match x.mode {
            OperandMode::Invalid => Some(invalid_type), // ignore - error reported before
            OperandMode::NoValue => {
                error_operand!(x, "{} used as type", self);
                Some(invalid_type)
            }
            OperandMode::TypeExpr => x.typ,
            _ => {
                if x.mode == OperandMode::Value && x.is_nil(self.tc_objs.universe()) {
                    None
                } else {
                    error_operand!(x, "{} is not a type", self);
                    Some(invalid_type)
                }
            }
        }
    }

    fn array_len(&mut self, e: &Expr, fctx: &mut FilesContext) -> Option<u64> {
        let mut x = Operand::new();
        self.expr(&mut x, e, fctx);
        if let OperandMode::Constant(v) = &x.mode {
            let t = x.typ.unwrap();
            if typ::is_untyped(t, self.tc_objs) || typ::is_integer(t, self.tc_objs) {
                let int = v.to_int();
                let int_type = self
                    .otype(self.basic_type(typ::BasicType::Int))
                    .try_as_basic()
                    .unwrap();
                if let constant::Value::Int(_) = int.borrow() {
                    if int.representable(int_type, None) {
                        let (n, exact) = int.int_as_u64();
                        if exact {
                            return Some(n);
                        } else {
                            error_operand!(x, "invalid array length {}", self);
                            return None;
                        }
                    }
                }
            }
            error_operand!(x, "array length {} must be integer", self);
        } else {
            if x.mode != OperandMode::Invalid {
                error_operand!(x, "array length {} must be constant", self);
            }
        }
        None
    }

    fn collect_params(
        &mut self,
        skey: ScopeKey,
        fl: Option<&FieldList>,
        variadic_ok: bool,
        fctx: &mut FilesContext,
    ) -> (Vec<ObjKey>, bool) {
        if let Some(l) = fl {
            let (mut named, mut anonymous, mut variadic) = (false, false, false);
            let mut params = Vec::new();
            for (i, fkey) in l.list.iter().enumerate() {
                let field = &self.ast_objs.fields[*fkey];
                let mut ftype = &field.typ;
                let field_names = field.names.clone();
                if let Expr::Ellipsis(elli) = ftype {
                    ftype = elli.elt.as_ref().unwrap();
                    if variadic_ok && i == l.list.len() - 1 && field_names.len() <= 1 {
                        variadic = true
                    } else {
                        self.soft_error(
                            elli.pos,
                            "can only use ... with final parameter in list".to_string(),
                        )
                        // ignore ... and continue
                    }
                }
                let ftype = &ftype.clone();
                let ty = self.indirect_type(ftype, fctx);
                // The parser ensures that f.Tag is nil and we don't
                // care if a constructed AST contains a non-nil tag.
                if field_names.len() > 0 {
                    for name in field_names.iter() {
                        let ident = &self.ast_objs.idents[*name];
                        if ident.name == "" {
                            self.invalid_ast(ident.pos, "anonymous parameter");
                            // ok to continue
                        }
                        let par_name = ident.name.clone();
                        let par = self.tc_objs.new_param_var(
                            ident.pos,
                            Some(self.pkg),
                            par_name,
                            Some(ty),
                        );
                        let scope_pos = self.scope(skey).pos();
                        self.declare(skey, Some(*name), par, scope_pos);
                        params.push(par);
                    }
                    named = true;
                } else {
                    // anonymous parameter
                    let par = self.tc_objs.new_param_var(
                        ftype.pos(self.ast_objs),
                        Some(self.pkg),
                        "".to_string(),
                        Some(ty),
                    );
                    self.result.record_implicit(fkey, par);
                    params.push(par);
                    anonymous = true;
                }
            }
            if named && anonymous {
                self.invalid_ast(
                    l.pos(self.ast_objs),
                    "list contains both named and anonymous parameters",
                )
                // ok to continue
            }
            // For a variadic function, change the last parameter's type from T to []T.
            // Since we type-checked T rather than ...T, we also need to retro-actively
            // record the type for ...T.
            if variadic {
                let last = params[params.len() - 1];
                let t = self.tc_objs.new_t_slice(self.lobj(last).typ().unwrap());
                self.lobj_mut(last).set_type(Some(t));
                let e = &self.ast_objs.fields[l.list[l.list.len() - 1]].typ;
                self.result
                    .record_type_and_value(e, OperandMode::TypeExpr, t);
            }
            (params, variadic)
        } else {
            (vec![], false)
        }
    }

    fn interface_type(
        &mut self,
        expr: &ast::Expr,
        def: Option<TypeKey>,
        fctx: &mut FilesContext,
    ) -> TypeKey {
        let iface = match expr {
            Expr::Interface(i) => i,
            _ => unreachable!(),
        };
        if iface.methods.list.len() == 0 {
            return self.tc_objs.new_t_empty_interface();
        }

        let itype = self.tc_objs.new_t_interface(vec![], vec![]);
        // collect embedded interfaces
        // Only needed for printing and API. Delay collection
        // to end of type-checking (for package-global interfaces)
        // when all types are complete. Local interfaces are handled
        // after each statement (as each statement processes delayed
        // functions).
        let context_clone = self.octx.clone();
        let expr_clone = expr.clone();
        let iface_clone = iface.clone();
        let f = move |checker: &mut Checker, fctx: &mut FilesContext| {
            if checker.config().trace_checker {
                let ed = checker.new_dis(&expr_clone);
                let msg = format!("-- delayed checking embedded interfaces of {}", ed);
                checker.trace_begin(iface_clone.interface, &msg);
            }
            //replace checker's ctx with context_clone
            let ctx_backup = std::mem::replace(&mut checker.octx, context_clone);

            let mut embeds = vec![];
            for fkey in iface_clone.methods.list.iter() {
                let field = &checker.ast_objs.fields[*fkey];
                if field.names.len() == 0 {
                    let texpr = field.typ.clone();
                    let ty = checker.indirect_type(&texpr, fctx);
                    // ty should be a named type denoting an interface
                    // (the parser will make sure it's a named type but
                    // constructed ASTs may be wrong).
                    if ty == checker.invalid_type() {
                        continue; // error reported before
                    }
                    match checker.otype(typ::underlying_type(ty, checker.tc_objs)) {
                        typ::Type::Interface(embed) => {
                            // Correct embedded interfaces must be complete
                            assert!(embed.all_methods().is_some());
                        }
                        _ => {
                            let pos = texpr.pos(checker.ast_objs);
                            let td = checker.new_dis(&ty);
                            checker.error(pos, format!("{} is not an interface", td));
                            continue;
                        }
                    }
                    // collect interface
                    embeds.push(ty);
                }
            }
            embeds.sort_by(compare_by_type_name!(checker.tc_objs));
            *checker.otype_interface_mut(itype).embeddeds_mut() = embeds;

            // restore ctx
            checker.octx = ctx_backup;
            // trace_end
            if checker.config().trace_checker {
                checker.trace_end(
                    iface_clone.interface,
                    "-- end of delayed checking embedded interfaces",
                )
            }
        };
        fctx.later(Box::new(f));

        // compute method set
        let (tname, path) = if let Some(d) = def {
            let t = *self.otype(d).try_as_named().unwrap().obj();
            (t, vec![t.unwrap()])
        } else {
            (None, vec![])
        };
        let info = self.info_from_type_lit(self.octx.scope.unwrap(), iface, tname, &path, fctx);
        if info.is_none() || info.as_ref().unwrap().as_ref().borrow().is_empty() {
            // we got an error or the empty interface - exit early
            self.otype_interface_mut(itype).set_empty_complete();
            return itype;
        }

        // use named receiver type if available (for better error messages)
        let recv_type = if let Some(d) = def { d } else { itype };

        // Correct receiver type for all methods explicitly declared
        // by this interface after we're done with type-checking at
        // this level. See comment below for details.
        let f = move |checker: &mut Checker, _: &mut FilesContext| {
            for m in checker.otype_interface(itype).methods().clone().iter() {
                let t = checker.lobj(*m).typ().unwrap();
                let o = checker.otype_signature(t).recv().unwrap();
                checker.lobj_mut(o).set_type(Some(recv_type));
            }
        };
        fctx.later(Box::new(f));

        // collect methods
        let info_ref = info.as_ref().unwrap().as_ref().borrow();
        let explicits = info_ref.explicits;
        let mut sig_fix: Vec<MethodInfo> = vec![];
        for (i, minfo) in info_ref.methods.iter().enumerate() {
            let fun = if minfo.func().is_none() {
                let name_key = self.ast_objs.fields[minfo.src().unwrap()].names[0];
                let ident = self.ast_ident(name_key);
                let name = ident.name.clone();
                let pos = ident.pos;
                // Don't type-check signature yet - use an
                // empty signature now and update it later.
                // But set up receiver since we know it and
                // its position, and because interface method
                // signatures don't get a receiver via regular
                // type-checking (there isn't a receiver in the
                // method's AST). Setting the receiver type is
                // also important for ptrRecv() (see methodset.go).
                //
                // Note: For embedded methods, the receiver type
                // should be the type of the interface that declared
                // the methods in the first place. Since we get the
                // methods here via methodInfo, which may be computed
                // before we have all relevant interface types, we use
                // the current interface's type (recvType). This may be
                // the type of the interface embedding the interface that
                // declared the methods. This doesn't matter for type-
                // checking (we only care about the receiver type for
                // the ptrRecv predicate, and it's never a pointer recv
                // for interfaces), but it matters for go/types clients
                // and for printing. We correct the receiver after type-
                // checking.

                let recv_key =
                    self.tc_objs
                        .new_var(pos, Some(self.pkg), "".to_string(), Some(recv_type));
                let empty_tuple = *self.tc_objs.universe().no_value_tuple();
                let sig_key = self.tc_objs.new_t_signature(
                    None,
                    Some(recv_key),
                    empty_tuple,
                    empty_tuple,
                    false,
                );
                let fun_key = self
                    .tc_objs
                    .new_func(pos, Some(self.pkg), name, Some(sig_key));
                minfo.set_func(fun_key);
                self.result.record_def(name_key, Some(fun_key));
                sig_fix.push(minfo.clone());
                fun_key
            } else {
                minfo.func().unwrap()
            };
            let itype_val = self.otype_interface_mut(itype);
            if i < explicits {
                itype_val.methods_mut().push(fun);
            }
            itype_val.all_methods_push(fun);
        }
        drop(info_ref);

        // fix signatures now that we have collected all methods
        let invalid_type = self.invalid_type();
        let saved_context = self.octx.clone();
        for minfo in sig_fix {
            // (possibly embedded) methods must be type-checked within their scope and
            // type-checking them must not affect the current context
            self.octx = ObjContext::new();
            self.octx.scope = minfo.scope();
            let ftype = self.ast_objs.fields[minfo.src().unwrap()].typ.clone();
            let ty = self.indirect_type(&ftype, fctx);
            if let Some(sig) = self.otype(ty).try_as_signature() {
                let sig_copy = *sig;
                // update signature, but keep recv that was set up before
                let old = self.otype_signature_mut(self.lobj(minfo.func().unwrap()).typ().unwrap());
                let recv = *old.recv(); // save recv
                *old = sig_copy;
                old.set_recv(recv); // restore recv
            } else {
                if ty != invalid_type {
                    let pos = ftype.pos(self.ast_objs);
                    let td = self.new_dis(&ty);
                    self.invalid_ast(pos, &format!("{} is not a method signature", td));
                }
            }
        }
        self.octx = saved_context;

        // sort methods
        let itype_val = self.otype_interface(itype);
        let mut methods = itype_val.methods().clone();
        methods.sort_by(compare_by_method_name!(self.tc_objs));
        *self.otype_interface_mut(itype).methods_mut() = methods;
        // sort all_methods
        let itype_val = self.otype_interface(itype);
        if itype_val.all_methods().is_none() {
            itype_val.set_empty_complete();
        } else {
            itype_val
                .all_methods_mut()
                .as_mut()
                .unwrap()
                .sort_by(compare_by_method_name!(self.tc_objs));
        }

        itype
    }

    fn tag(&self, t: &Option<Expr>) -> Option<String> {
        if let Some(e) = t {
            if let Expr::BasicLit(bl) = e {
                if let Token::STRING(data) = &bl.token {
                    return Some(data.as_str_str().1.clone());
                }
                self.invalid_ast(
                    e.pos(self.ast_objs),
                    &format!("incorrect tag syntax: {}", bl.token),
                )
            } else {
                unreachable!()
            }
        }
        None
    }

    fn declare_in_set(&self, set: &mut HashMap<String, ObjKey>, fld: ObjKey, pos: Pos) -> bool {
        if let Some(okey) = self.insert_obj_to_set(set, fld) {
            self.error(pos, format!("{} redeclared", self.lobj(fld).name()));
            self.report_alt_decl(okey);
            false
        } else {
            true
        }
    }

    fn add_field(
        &mut self,
        fields: &mut Vec<ObjKey>,
        tags: &mut Option<Vec<Option<String>>>,
        oset: &mut HashMap<String, ObjKey>,
        ty: TypeKey,
        tag: Option<String>,
        ikey: IdentKey,
        embedded: bool,
        pos: Pos,
    ) {
        if tag.is_some() && tags.is_none() {
            *tags = Some(vec![]);
        }
        if tags.is_some() {
            tags.as_mut().unwrap().push(tag);
        }
        let name = &self.ast_ident(ikey).name.clone();
        let fld = self
            .tc_objs
            .new_field(pos, Some(self.pkg), name.clone(), Some(ty), embedded);
        if name == "_" || self.declare_in_set(oset, fld, pos) {
            fields.push(fld);
            self.result.record_def(ikey, Some(fld));
        }
    }

    fn embedded_field_ident(e: &Expr) -> Option<IdentKey> {
        match e {
            Expr::Ident(i) => Some(*i),
            Expr::Star(s) => match s.expr {
                // *T is valid, but **T is not
                Expr::Star(_) => None,
                _ => Checker::embedded_field_ident(&s.expr),
            },
            Expr::Selector(s) => Some(s.sel),
            _ => None,
        }
    }

    fn struct_type(&mut self, st: &ast::StructType, fctx: &mut FilesContext) -> TypeKey {
        let fields = &st.fields.list;
        if fields.len() == 0 {
            return self.tc_objs.new_t_struct(vec![], None);
        }

        let mut field_objs: Vec<ObjKey> = vec![];
        let mut tags: Option<Vec<Option<String>>> = None;
        let mut oset: HashMap<String, ObjKey> = HashMap::new();
        for f in fields {
            let field = &self.ast_objs.fields[*f];
            let fnames = field.names.clone();
            let ftag = self.tag(&field.tag);
            let ftype = field.typ.clone();
            let ty = self.type_expr(&ftype, fctx);
            if fnames.len() > 0 {
                // named fields
                for name in fnames.iter() {
                    self.add_field(
                        &mut field_objs,
                        &mut tags,
                        &mut oset,
                        ty,
                        ftag.clone(),
                        *name,
                        false,
                        self.ast_ident(*name).pos,
                    );
                }
            } else {
                // embedded field
                // spec: "An embedded type must be specified as a type name T or as a pointer
                // to a non-interface type name *T, and T itself may not be a pointer type."
                let field = &self.ast_objs.fields[*f];
                let pos = field.typ.pos(self.ast_objs);
                let invalid_type = self.invalid_type();
                let mut add_invalid = |c: &mut Checker, ident: IdentKey| {
                    c.add_field(
                        &mut field_objs,
                        &mut tags,
                        &mut oset,
                        invalid_type,
                        None,
                        ident,
                        false,
                        pos,
                    );
                };
                if let Some(ident) = Checker::embedded_field_ident(&field.typ) {
                    let (t, is_ptr) = lookup::try_deref(ty, self.tc_objs);
                    // Because we have a name, typ must be of the form T or *T, where T is the name
                    // of a (named or alias) type, and t (= deref(typ)) must be the type of T.
                    let t = typ::underlying_type(t, self.tc_objs);
                    let type_val = self.otype(t);
                    match type_val {
                        typ::Type::Basic(_) if t == invalid_type => {
                            // error was reported before
                            add_invalid(self, ident);
                        }
                        typ::Type::Basic(b) if b.typ() == typ::BasicType::UnsafePointer => {
                            self.error_str(pos, "embedded field type cannot be unsafe.Pointer");
                            add_invalid(self, ident);
                        }
                        typ::Type::Pointer(_) => {
                            self.error_str(pos, "embedded field type cannot be a pointer");
                            add_invalid(self, ident);
                        }
                        typ::Type::Interface(_) if is_ptr => {
                            self.error_str(
                                pos,
                                "embedded field type cannot be a pointer to an interface",
                            );
                            add_invalid(self, ident);
                        }
                        _ => self.add_field(
                            &mut field_objs,
                            &mut tags,
                            &mut oset,
                            ty,
                            ftag.clone(),
                            ident,
                            true,
                            pos,
                        ),
                    }
                } else {
                    let ed = self.new_dis(&field.typ);
                    self.invalid_ast(pos, &format!("embedded field type {} has no name", ed));
                    let ident = self.ast_objs.idents.insert(ast::Ident::blank(pos));
                    add_invalid(self, ident);
                }
            }
        }

        self.tc_objs.new_t_struct(field_objs, tags)
    }
}