Infinite recursion (stack overflow) calling trait function on tuples

[xunilrj]

I managed to reproduce this problem with this minimal example on master.

script;

trait T1 {
    fn trait_fn() -> Self;
}

impl T1 for u64 {
    fn trait_fn() -> u64 {
        0
    }
}

impl<A> T1 for (A, ) 
where
    A: T1
{
    fn trait_fn() -> (A, ) {
        (A::trait_fn(), )
    }
}

fn f<T> () 
where
    T: T1
{
    T::trait_fn();
}

fn main() {
    let a = f::<(u64, )>();
}

The first interesting code in the stack is at sway-core/src/language/ty/expression/expression_variant.rs:784 (all the others frames in our codebase point to compiler derived clone()s)

(gdb) where
#0  0x00005555576de047 in alloc::slice::hack::{impl#0}::to_vec<sway_core::language::ty::expression::expression::TyExpression, alloc::alloc::Global> (s=..., 
    alloc=...) at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/alloc/src/slice.rs:124
#1  0x0000555557a16138 in alloc::slice::hack::to_vec<sway_core::language::ty::expression::expression::TyExpression, alloc::alloc::Global> (s=..., alloc=...)
    at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/alloc/src/slice.rs:111
#2  alloc::slice::{impl#0}::to_vec_in<sway_core::language::ty::expression::expression::TyExpression, alloc::alloc::Global> (self=..., alloc=...)
    at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/alloc/src/slice.rs:441
#3  alloc::vec::{impl#10}::clone<sway_core::language::ty::expression::expression::TyExpression, alloc::alloc::Global> (self=0x55555b4b29c0)
    at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/alloc/src/vec/mod.rs:2685
#4  0x0000555557ed22ca in sway_core::language::ty::expression::expression_variant::{impl#11}::clone (self=0x55555b4b29b8)
    at sway-core/src/language/ty/expression/expression_variant.rs:54
#5  0x0000555557b47f08 in sway_core::language::ty::expression::expression::{impl#13}::clone (self=0x55555b4b29b8)
    at sway-core/src/language/ty/expression/expression.rs:24
#6  0x0000555557d3f279 in sway_core::language::ty::ast_node::{impl#22}::clone (self=0x55555b4b29b0) at sway-core/src/language/ty/ast_node.rs:453
#7  0x0000555557d3f058 in sway_core::language::ty::ast_node::{impl#20}::clone (self=0x55555b4b29b0) at sway-core/src/language/ty/ast_node.rs:28
#8  0x0000555557bf582e in alloc::slice::hack::{impl#0}::to_vec<sway_core::language::ty::ast_node::TyAstNode, alloc::alloc::Global> (s=..., alloc=...)
    at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/alloc/src/slice.rs:146
#9  0x0000555557a1a8f8 in alloc::slice::hack::to_vec<sway_core::language::ty::ast_node::TyAstNode, alloc::alloc::Global> (s=..., alloc=...)
    at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/alloc/src/slice.rs:111
#10 alloc::slice::{impl#0}::to_vec_in<sway_core::language::ty::ast_node::TyAstNode, alloc::alloc::Global> (self=..., alloc=...)
--Type <RET> for more, q to quit, c to continue without paging--
    at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/alloc/src/slice.rs:441
#11 alloc::vec::{impl#10}::clone<sway_core::language::ty::ast_node::TyAstNode, alloc::alloc::Global> (self=0x55555b4b30b0)
    at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/alloc/src/vec/mod.rs:2685
#12 0x0000555557be59fa in sway_core::language::ty::code_block::{impl#8}::clone (self=0x55555b4b3088) at sway-core/src/language/ty/code_block.rs:13
#13 0x0000555557c5e8fb in sway_core::language::ty::declaration::function::{impl#19}::clone (self=0x55555b4b3040)
    at sway-core/src/language/ty/declaration/function.rs:30
#14 0x000055555797c6e1 in sway_core::decl_engine::ref::DeclRef<sway_core::decl_engine::id::DeclId<sway_core::language::ty::declaration::function::TyFunctionDecl>>::replace_decls_and_insert_new_with_parent<sway_core::language::ty::declaration::function::TyFunctionDecl> (self=0x7fffff8036b8, decl_mapping=0x7ffffff86b30, 
    handler=0x7fffff804168, ctx=0x7ffffff88290) at sway-core/src/decl_engine/ref.rs:171
#15 0x0000555557b4f76b in sway_core::language::ty::expression::expression_variant::{impl#4}::replace_decls_inner::{closure#0} (handler=0x7fffff804168)
    at sway-core/src/language/ty/expression/expression_variant.rs:784
#16 0x0000555557c6502d in sway_error::handler::Handler::scope<(), sway_core::language::ty::expression::expression_variant::{impl#4}::replace_decls_inner::{closure_env#0}> (self=0x7fffff805228, f=...) at sway-error/src/handler.rs:60
#17 0x0000555557ecdcb4 in sway_core::language::ty::expression::expression_variant::{impl#4}::replace_decls_inner (self=0x55555b327ae0, 
    decl_mapping=0x7ffffff86b30, handler=0x7fffff805228, ctx=0x7ffffff88290) at sway-core/src/language/ty/expression/expression_variant.rs:765
#18 0x0000555557b4e94d in sway_core::decl_engine::replace_decls::ReplaceDecls::replace_decls<sway_core::language::ty::expression::expression_variant::TyExpressionVariant> (self=0x55555b327ae0, decl_mapping=0x7ffffff86b30, handler=0x7fffff805228, ctx=0x7ffffff88290) at sway-core/src/decl_engine/replace_decls.rs:26
#19 0x0000555557b23cce in sway_core::language::ty::expression::expression::{impl#4}::replace_decls_inner (self=0x55555b327ae0, decl_mapping=0x7ffffff86b30, 
    handler=0x7fffff805228, ctx=0x7ffffff88290) at sway-core/src/language/ty/expression/expression.rs:69

[esdrubal]

So with #5515, ReplaceDecls, CollectTypesMetadata, HashWithEngines now have a mechanism that interrupts recursive visiting.

But we still have a recursion problem in the IR side of the compiler.