Support negative, char & bool const generics

crates/hir-def/src/body.rs

@@ -238,7 +238,7 @@ pub struct Mark {
 }
 
 /// The body of an item (function, const etc.).
-#[derive(Debug, Eq, PartialEq)]
+#[derive(Debug, Default, Eq, PartialEq)]
 pub struct Body {
     pub exprs: Arena<Expr>,
     pub pats: Arena<Pat>,

crates/hir-def/src/body/lower.rs

@@ -1,7 +1,7 @@
 //! Transforms `ast::Expr` into an equivalent `hir_def::expr::Expr`
 //! representation.
 
-use std::{mem, sync::Arc};
+use std::{collections::HashMap, mem, sync::Arc};
 
 use either::Either;
 use hir_expand::{
@@ -10,8 +10,6 @@ use hir_expand::{
     name::{name, AsName, Name},
     ExpandError, HirFileId, InFile,
 };
-use la_arena::Arena;
-use profile::Count;
 use rustc_hash::FxHashMap;
 use syntax::{
     ast::{
@@ -28,8 +26,8 @@ use crate::{
     builtin_type::{BuiltinFloat, BuiltinInt, BuiltinUint},
     db::DefDatabase,
     expr::{
-        dummy_expr_id, Array, BindingAnnotation, Expr, ExprId, FloatTypeWrapper, Label, LabelId,
-        Literal, MatchArm, Pat, PatId, RecordFieldPat, RecordLitField, Statement,
+        Array, BindingAnnotation, Expr, ExprId, FloatTypeWrapper, Label, LabelId, Literal,
+        MatchArm, Pat, PatId, RecordFieldPat, RecordLitField, Statement,
     },
     intern::Interned,
     item_scope::BuiltinShadowMode,
@@ -82,24 +80,8 @@ pub(super) fn lower(
     params: Option<ast::ParamList>,
     body: Option<ast::Expr>,
 ) -> (Body, BodySourceMap) {
-    ExprCollector {
-        db,
-        source_map: BodySourceMap::default(),
-        body: Body {
-            exprs: Arena::default(),
-            pats: Arena::default(),
-            labels: Arena::default(),
-            params: Vec::new(),
-            body_expr: dummy_expr_id(),
-            block_scopes: Vec::new(),
-            _c: Count::new(),
-            or_pats: Default::default(),
-        },
-        expander,
-        name_to_pat_grouping: Default::default(),
-        is_lowering_inside_or_pat: false,
-    }
-    .collect(params, body)
+    let collector = ExprCollector::new(db, expander);
+    collector.collect(params, body)
 }
 
 struct ExprCollector<'a> {
@@ -112,7 +94,18 @@ struct ExprCollector<'a> {
     is_lowering_inside_or_pat: bool,
 }
 
-impl ExprCollector<'_> {
+impl<'a> ExprCollector<'a> {
+    pub(crate) fn new(db: &'a dyn DefDatabase, expander: Expander) -> Self {
+        Self {
+            db,
+            expander,
+            body: Body::default(),
+            source_map: BodySourceMap::default(),
+            name_to_pat_grouping: HashMap::default(),
+            is_lowering_inside_or_pat: false,
+        }
+    }
+
     fn collect(
         mut self,
         param_list: Option<ast::ParamList>,
@@ -197,7 +190,8 @@ impl ExprCollector<'_> {
     }
 
     fn collect_expr(&mut self, expr: ast::Expr) -> ExprId {
-        self.maybe_collect_expr(expr).unwrap_or_else(|| self.missing_expr())
+        let expr_id = self.maybe_collect_expr(expr).unwrap_or_else(|| self.missing_expr());
+        expr_id
     }
 
     /// Returns `None` if and only if the expression is `#[cfg]`d out.
@@ -689,7 +683,6 @@ impl ExprCollector<'_> {
         };
         let prev_def_map = mem::replace(&mut self.expander.def_map, def_map);
         let prev_local_module = mem::replace(&mut self.expander.module, module);
-
         let mut statements: Vec<_> =
             block.statements().filter_map(|s| self.collect_stmt(s)).collect();
         let tail = block.tail_expr().and_then(|e| self.maybe_collect_expr(e));

crates/hir-def/src/expr.rs

@@ -13,7 +13,7 @@
 //! See also a neighboring `body` module.
 
 use hir_expand::name::Name;
-use la_arena::{Idx, RawIdx};
+use la_arena::Idx;
 
 use crate::{
     builtin_type::{BuiltinFloat, BuiltinInt, BuiltinUint},
@@ -26,9 +26,6 @@ use crate::{
 pub use syntax::ast::{ArithOp, BinaryOp, CmpOp, LogicOp, Ordering, RangeOp, UnaryOp};
 
 pub type ExprId = Idx<Expr>;
-pub(crate) fn dummy_expr_id() -> ExprId {
-    ExprId::from_raw(RawIdx::from(!0))
-}
 
 pub type PatId = Idx<Pat>;
 

crates/hir-def/src/path/lower.rs

@@ -1,6 +1,9 @@
 //! Transforms syntax into `Path` objects, ideally with accounting for hygiene
 
-use crate::{intern::Interned, type_ref::ConstScalarOrPath};
+use crate::{
+    intern::Interned,
+    type_ref::{ConstScalar, ConstScalarOrPath},
+};
 
 use either::Either;
 use hir_expand::name::{name, AsName};
@@ -181,7 +184,10 @@ pub(super) fn lower_generic_args(
                 }
             }
             ast::GenericArg::ConstArg(arg) => {
-                let arg = ConstScalarOrPath::from_expr_opt(arg.expr());
+                let arg = arg.expr().map_or(
+                    ConstScalarOrPath::Scalar(ConstScalar::Unknown),
+                    ConstScalarOrPath::from_expr,
+                );
                 args.push(GenericArg::Const(arg))
             }
         }

crates/hir-def/src/type_ref.rs

@@ -5,10 +5,15 @@ use hir_expand::{
     name::{AsName, Name},
     AstId, InFile,
 };
-use std::{convert::TryInto, fmt::Write};
 use syntax::ast::{self, HasName};
 
-use crate::{body::LowerCtx, intern::Interned, path::Path};
+use crate::{
+    body::LowerCtx,
+    builtin_type::{BuiltinInt, BuiltinType, BuiltinUint},
+    expr::Literal,
+    intern::Interned,
+    path::Path,
+};
 
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 pub enum Mutability {
@@ -177,7 +182,10 @@ impl TypeRef {
                 // `hir_def::body::lower` to lower this into an `Expr` and then evaluate it at the
                 // `hir_ty` level, which would allow knowing the type of:
                 // let v: [u8; 2 + 2] = [0u8; 4];
-                let len = ConstScalarOrPath::from_expr_opt(inner.expr());
+                let len = inner.expr().map_or(
+                    ConstScalarOrPath::Scalar(ConstScalar::Unknown),
+                    ConstScalarOrPath::from_expr,
+                );
 
                 TypeRef::Array(Box::new(TypeRef::from_ast_opt(ctx, inner.ty())), len)
             }
@@ -386,39 +394,41 @@ impl std::fmt::Display for ConstScalarOrPath {
 }
 
 impl ConstScalarOrPath {
-    pub(crate) fn from_expr_opt(expr: Option<ast::Expr>) -> Self {
-        match expr {
-            Some(x) => Self::from_expr(x),
-            None => Self::Scalar(ConstScalar::Unknown),
-        }
-    }
-
     // FIXME: as per the comments on `TypeRef::Array`, this evaluation should not happen at this
     // parse stage.
-    fn from_expr(expr: ast::Expr) -> Self {
+    pub(crate) fn from_expr(expr: ast::Expr) -> Self {
         match expr {
             ast::Expr::PathExpr(p) => {
                 match p.path().and_then(|x| x.segment()).and_then(|x| x.name_ref()) {
                     Some(x) => Self::Path(x.as_name()),
                     None => Self::Scalar(ConstScalar::Unknown),
                 }
             }
-            ast::Expr::Literal(lit) => {
-                let lkind = lit.kind();
-                match lkind {
-                    ast::LiteralKind::IntNumber(num)
-                        if num.suffix() == None || num.suffix() == Some("usize") =>
-                    {
-                        Self::Scalar(
-                            num.value()
-                                .and_then(|v| v.try_into().ok())
-                                .map(ConstScalar::Usize)
-                                .unwrap_or(ConstScalar::Unknown),
-                        )
+            ast::Expr::PrefixExpr(prefix_expr) => match prefix_expr.op_kind() {
+                Some(ast::UnaryOp::Neg) => {
+                    let unsigned = prefix_expr
+                        .expr()
+                        .map_or(Self::Scalar(ConstScalar::Unknown), Self::from_expr);
+                    // Add sign
+                    match unsigned {
+                        Self::Scalar(ConstScalar::UInt(num)) => {
+                            Self::Scalar(ConstScalar::Int(-(num as i128)))
+                        }
+                        other => other,
                     }
-                    _ => Self::Scalar(ConstScalar::Unknown),
                 }
-            }
+                _ => prefix_expr.expr().map_or(Self::Scalar(ConstScalar::Unknown), Self::from_expr),
+            },
+            ast::Expr::Literal(literal) => Self::Scalar(match literal.kind() {
+                ast::LiteralKind::IntNumber(num) => {
+                    num.value().map(ConstScalar::UInt).unwrap_or(ConstScalar::Unknown)
+                }
+                ast::LiteralKind::Char(c) => {
+                    c.value().map(ConstScalar::Char).unwrap_or(ConstScalar::Unknown)
+                }
+                ast::LiteralKind::Bool(f) => ConstScalar::Bool(f),
+                _ => ConstScalar::Unknown,
+            }),
             _ => Self::Scalar(ConstScalar::Unknown),
         }
     }
@@ -427,9 +437,10 @@ impl ConstScalarOrPath {
 /// A concrete constant value
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum ConstScalar {
-    // for now, we only support the trivial case of constant evaluating the length of an array
-    // Note that this is u64 because the target usize may be bigger than our usize
-    Usize(u64),
+    Int(i128),
+    UInt(u128),
+    Bool(bool),
+    Char(char),
 
     /// Case of an unknown value that rustc might know but we don't
     // FIXME: this is a hack to get around chalk not being able to represent unevaluatable
@@ -439,21 +450,37 @@ pub enum ConstScalar {
     Unknown,
 }
 
-impl std::fmt::Display for ConstScalar {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
+impl ConstScalar {
+    pub fn builtin_type(&self) -> BuiltinType {
         match self {
-            ConstScalar::Usize(us) => us.fmt(f),
-            ConstScalar::Unknown => f.write_char('_'),
+            ConstScalar::UInt(_) | ConstScalar::Unknown => BuiltinType::Uint(BuiltinUint::U128),
+            ConstScalar::Int(_) => BuiltinType::Int(BuiltinInt::I128),
+            ConstScalar::Char(_) => BuiltinType::Char,
+            ConstScalar::Bool(_) => BuiltinType::Bool,
         }
     }
 }
 
-impl ConstScalar {
-    /// Gets a target usize out of the ConstScalar
-    pub fn as_usize(&self) -> Option<u64> {
+impl From<Literal> for ConstScalar {
+    fn from(literal: Literal) -> Self {
+        match literal {
+            Literal::Char(c) => Self::Char(c),
+            Literal::Bool(flag) => Self::Bool(flag),
+            Literal::Int(num, _) => Self::Int(num),
+            Literal::Uint(num, _) => Self::UInt(num),
+            _ => Self::Unknown,
+        }
+    }
+}
+
+impl std::fmt::Display for ConstScalar {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
         match self {
-            &ConstScalar::Usize(us) => Some(us),
-            _ => None,
+            ConstScalar::Int(num) => num.fmt(f),
+            ConstScalar::UInt(num) => num.fmt(f),
+            ConstScalar::Bool(flag) => flag.fmt(f),
+            ConstScalar::Char(c) => write!(f, "'{c}'"),
+            ConstScalar::Unknown => f.write_str("{unknown}"),
         }
     }
 }

crates/hir-ty/src/consteval.rs

@@ -347,17 +347,6 @@ pub fn eval_const(
     }
 }
 
-pub fn eval_usize(expr: Idx<Expr>, mut ctx: ConstEvalCtx<'_>) -> Option<u64> {
-    if let Ok(ce) = eval_const(expr, &mut ctx) {
-        match ce {
-            ComputedExpr::Literal(Literal::Int(x, _)) => return x.try_into().ok(),
-            ComputedExpr::Literal(Literal::Uint(x, _)) => return x.try_into().ok(),
-            _ => {}
-        }
-    }
-    None
-}
-
 pub(crate) fn path_to_const(
     db: &dyn HirDatabase,
     resolver: &Resolver,
@@ -406,19 +395,24 @@ pub fn unknown_const_as_generic(ty: Ty) -> GenericArg {
 }
 
 /// Interns a constant scalar with the given type
-pub fn intern_scalar_const(value: ConstScalar, ty: Ty) -> Const {
+pub fn intern_const_scalar_with_type(value: ConstScalar, ty: Ty) -> Const {
     ConstData { ty, value: ConstValue::Concrete(chalk_ir::ConcreteConst { interned: value }) }
         .intern(Interner)
 }
 
 /// Interns a possibly-unknown target usize
-pub fn usize_const(value: Option<u64>) -> Const {
-    intern_scalar_const(
-        value.map(ConstScalar::Usize).unwrap_or(ConstScalar::Unknown),
+pub fn usize_const(value: Option<u128>) -> Const {
+    intern_const_scalar_with_type(
+        value.map(ConstScalar::UInt).unwrap_or(ConstScalar::Unknown),
         TyBuilder::usize(),
     )
 }
 
+/// Interns a constant scalar with the default type
+pub fn intern_const_scalar(value: ConstScalar) -> Const {
+    intern_const_scalar_with_type(value, TyBuilder::builtin(value.builtin_type()))
+}
+
 pub(crate) fn const_eval_recover(
     _: &dyn HirDatabase,
     _: &[String],
@@ -463,15 +457,20 @@ pub(crate) fn eval_to_const<'a>(
         }
     }
     let body = ctx.body.clone();
-    let ctx = ConstEvalCtx {
+    let mut ctx = ConstEvalCtx {
         db: ctx.db,
         owner: ctx.owner,
         exprs: &body.exprs,
         pats: &body.pats,
         local_data: HashMap::default(),
         infer: &ctx.result,
     };
-    usize_const(eval_usize(expr, ctx))
+    let computed_expr = eval_const(expr, &mut ctx);
+    let const_scalar = match computed_expr {
+        Ok(ComputedExpr::Literal(literal)) => literal.into(),
+        _ => ConstScalar::Unknown,
+    };
+    intern_const_scalar_with_type(const_scalar, TyBuilder::usize())
 }
 
 #[cfg(test)]

crates/hir-ty/src/infer.rs

@@ -605,10 +605,10 @@ impl<'a> InferenceContext<'a> {
         let data = c.data(Interner);
         match data.value {
             ConstValue::Concrete(cc) => match cc.interned {
-                hir_def::type_ref::ConstScalar::Usize(_) => c,
                 hir_def::type_ref::ConstScalar::Unknown => {
                     self.table.new_const_var(data.ty.clone())
                 }
+                _ => c,
             },
             _ => c,
         }

crates/hir-ty/src/infer/expr.rs

@@ -729,7 +729,7 @@ impl<'a> InferenceContext<'a> {
                             let cur_elem_ty = self.infer_expr_inner(expr, &expected);
                             coerce.coerce(self, Some(expr), &cur_elem_ty);
                         }
-                        consteval::usize_const(Some(items.len() as u64))
+                        consteval::usize_const(Some(items.len() as u128))
                     }
                     &Array::Repeat { initializer, repeat } => {
                         self.infer_expr_coerce(initializer, &Expectation::has_type(elem_ty));
@@ -766,7 +766,7 @@ impl<'a> InferenceContext<'a> {
                 Literal::ByteString(bs) => {
                     let byte_type = TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(Interner);
 
-                    let len = consteval::usize_const(Some(bs.len() as u64));
+                    let len = consteval::usize_const(Some(bs.len() as u128));
 
                     let array_type = TyKind::Array(byte_type, len).intern(Interner);
                     TyKind::Ref(Mutability::Not, static_lifetime(), array_type).intern(Interner)