crates/hir_ty/src/consteval.rs

   1 //! Constant evaluation details
   2
   3 use std::convert::TryInto;
   4
   5 use hir_def::{
   6     builtin_type::BuiltinUint,
   7     expr::{Expr, Literal},
   8     type_ref::ConstScalar,
   9 };
  10
  11 use crate::{Const, ConstData, ConstValue, Interner, TyKind};
  12
  13 /// Extension trait for [`Const`]
  14 pub trait ConstExt {
  15     /// Is a [`Const`] unknown?
  16     fn is_unknown(&self) -> bool;
  17 }
  18
  19 impl ConstExt for Const {
  20     fn is_unknown(&self) -> bool {
  21         match self.data(&Interner).value {
  22             // interned Unknown
  23             chalk_ir::ConstValue::Concrete(chalk_ir::ConcreteConst {
  24                 interned: ConstScalar::Unknown,
  25             }) => true,
  26
  27             // interned concrete anything else
  28             chalk_ir::ConstValue::Concrete(..) => false,
  29
  30             _ => {
  31                 tracing::error!(
  32                     "is_unknown was called on a non-concrete constant value! {:?}",
  33                     self
  34                 );
  35                 true
  36             }
  37         }
  38     }
  39 }
  40
  41 // FIXME: support more than just evaluating literals
  42 pub fn eval_usize(expr: &Expr) -> Option<u64> {
  43     match expr {
  44         Expr::Literal(Literal::Uint(v, None | Some(BuiltinUint::Usize))) => (*v).try_into().ok(),
  45         _ => None,
  46     }
  47 }
  48
  49 /// Interns a possibly-unknown target usize
  50 pub fn usize_const(value: Option<u64>) -> Const {
  51     ConstData {
  52         ty: TyKind::Scalar(chalk_ir::Scalar::Uint(chalk_ir::UintTy::Usize)).intern(&Interner),
  53         value: ConstValue::Concrete(chalk_ir::ConcreteConst {
  54             interned: value.map(ConstScalar::Usize).unwrap_or(ConstScalar::Unknown),
  55         }),
  56     }
  57     .intern(&Interner)
  58 }