Function compile_while

core/src/compiler/top.rs:727–757

Compiles a `WHILE` loop and emits bytecode into `ctx`.

(
    ctx: &mut Context,
    symtable: &mut LocalSymtable<'_>,
    span: WhileSpan,
)

/// Compiles a `WHILE` loop and emits bytecode into `ctx`.
fn compile_while(
    ctx: &mut Context,
    symtable: &mut LocalSymtable<'_>,
    span: WhileSpan,
) -> Result<()> {
    let start_pc = ctx.codegen.next_pc();

    let (jump_end_pc, cond_reg, guard_pos) = {
        let guard_pos = span.expr.start_pos();
        let mut frozen = symtable.frozen();
        let mut scope = frozen.temp_scope();
        let reg = scope.alloc().map_err(|e| Error::from_syms(e, guard_pos))?;
        compile_expr_as_type(&mut ctx.codegen, &mut frozen, reg, span.expr, ExprType::Boolean)?;
        (ctx.codegen.emit(bytecode::make_nop(), guard_pos), reg, guard_pos)
    };

    for stmt in span.body {
        compile_stmt(ctx, symtable, stmt)?;
    }

    let start_target =
        u16::try_from(start_pc).map_err(|_| Error::TargetTooFar(guard_pos, start_pc))?;
    ctx.codegen.emit(bytecode::make_jump(start_target), guard_pos);

    let end_addr = ctx.codegen.next_pc();
    let end_target =
        u16::try_from(end_addr).map_err(|_| Error::TargetTooFar(guard_pos, end_addr))?;
    ctx.codegen.patch(jump_end_pc, bytecode::make_jump_if_false(cond_reg, end_target));

    Ok(())
}

/// Compiles a single `stmt` into the `ctx`.
fn compile_stmt(