`stellar contract invoke` panics when contract function returns spec type `SC_SPEC_TYPE_VAL`

Start with the result-formatting path used by stellar contract invoke, focusing on handling ScType::Val and the SC_SPEC_TYPE_VAL contract return type. Reproduce the panic with the provided Bool(false) contract and invocation steps. Done means the command completes without panicking and displays the returned value, including false and other ScVal variants.

What version are you using?

stellar-cli 25.1.0

What did you do?

When a Soroban contract function has return type Val (which maps to SC_SPEC_TYPE_VAL in the contract spec), and the function returns Bool(false), calling the function via stellar contract invoke panics.

Minimal reproducing contract:

#![no_std]

use soroban_sdk::{contract, contractimpl, Env, Val};

#[contract]
pub struct BoolFalseContract;

#[contractimpl]
impl BoolFalseContract {
    pub fn retval(_env: Env) -> Val {
        Val::from_bool(false).into()
    }
}

Cargo.toml:

[package]
name = "bool_false_poc"
version = "0.1.0"
edition = "2021"
publish = false

[lib]
crate-type = ["cdylib"]

[dependencies]
soroban-sdk = "25.1.0"

[dev-dependencies]
soroban-sdk = { version = "25.1.0", features = ["testutils"] }

[profile.release]
opt-level = "z"
overflow-checks = true
debug = 0
strip = "symbols"
debug-assertions = false
panic = "abort"
codegen-units = 1
lto = true

Steps to reproduce:

# Build the contract
cargo build --release --target wasm32-unknown-unknown

# Deploy to local network
stellar contract deploy \
  --wasm target/wasm32-unknown-unknown/release/bool_false_poc.wasm \
  --source deployer --network local --alias bool-false-poc

# Invoke the function — this panics
stellar contract invoke --id bool-false-poc --source deployer --network local -- retval

What did you expect to see?

The CLI should successfully display the return value, e.g.:

false

What did you see instead?

The CLI panics with:

thread 'main' panicked at 'not yet implemented: Bool(false,) doesn't have a matching Val'

Notes

• The contract itself executes correctly — the issue is purely in the CLI's result formatting
• All non-Void ScVal variants are affected when the spec type is SC_SPEC_TYPE_VAL, not just Bool
• A fix would need to handle ScType::Val for all ScVal variants, likely by recursively inferring the concrete type from the value itself