[ICE] crash on multiply in sizeof()

[jyn514]

Expected behavior
RCC gives an error saying the array is too large.

Actual Behavior
RCC crashes with overflow.

Code

char h[][3U-3827228678929574271][3] = {{4,5,6}};
The application panicked (crashed).
Message:  attempt to multiply with overflow

Backtrace

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ BACKTRACE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
                          (6 post panic frames hidden)                          
 6: core::panicking::panic::ha556f2c3753f3759
    at src/libcore/panicking.rs:70
 7: <u64 as core::ops::arith::Mul>::mul::h5181c21b5c178bc2
    at /rustc/73528e339aae0f17a15ffa49a8ac608f50c6cf14/src/libcore/ops/arith.rs:318
 8: <u64 as core::ops::arith::Mul<&u64>>::mul::h1d1276c4c74de715
    at src/lib.rs:1
 9: rcc::arch::<impl rcc::data::types::Type>::sizeof::{{closure}}::hed6dc419ce36a058
    at src/arch/mod.rs:74
10: core::result::Result<T,E>::and_then::haa7997835743a121
    at /rustc/73528e339aae0f17a15ffa49a8ac608f50c6cf14/src/libcore/result.rs:691
11: rcc::arch::<impl rcc::data::types::Type>::sizeof::h82206b81eeb141c1
    at src/arch/mod.rs:74
12: rcc::arch::<impl rcc::data::types::Type>::sizeof::h82206b81eeb141c1
    at src/arch/mod.rs:74
13: rcc::ir::static_init::<impl rcc::ir::Compiler>::store_static::had90360549edd56e
    at src/ir/static_init.rs:77
14: rcc::ir::compile::haeb8251a574ff20c
    at src/ir/mod.rs:89
15: rcc::compile::h87633814d689a39f
    at src/lib.rs:98
16: rcc::real_main::h1dd2cb989e6fa0d8
    at src/main.rs:101
17: rcc::main::h396b827397690aa0
    at src/main.rs:169
                        (10 runtime init frames hidden)

[jyn514]

Instructions:

• In arch/mod.rs, change n * l to checked_mul. If overflow occurs, return an error.