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MIPS standard says:

Format: JALR rs (rd = 31 implied)
JALR rd, rs
Restrictions:

Register specifiers rs and rd must not be equal, because such an instruction does not have the same effect when reexecuted. The result of executing such an instruction is UNPREDICTABLE.

This restriction permits an exception handler to resume execution by re-executing the branch when an exception occurs in the branch delay slot. ))

However, now $ra can be used like other general purpose registers, which means that it is possible to generate legal instructions like jalr $ra (equivalent to jalr $ra, $ra).

Currently, the SPIM simulator covers up the problem, because it can execute jalr $ra in the way we expect instead of rejecting it.

See Ty::assignable_to.

See decaf-rs/typeck/src/type_pass.rs:74-80

Some rule functions have name starting with filed_def_, and maybe it should be field_def_.

有些函数的名字以 filed_def_ 开头，疑似笔误。

class Main {
    static void main() {
        class Main[] x = new class Main[10];
        x[g()].f();
    }

    static void f() {}

    static int g() {
        Print("123");
        return 1;
    }
}

x[g()] should be evaluated but it is not.