Refactor parsing/lowering of consts

For use in parsing array types

Author: nathanwhit

chalk-integration/src/lowering.rs

@@ -1460,6 +1460,36 @@ impl LowerTy for Ty {
     }
 }
 
+trait LowerConst {
+    fn lower(&self, env: &Env) -> LowerResult<chalk_ir::Const<ChalkIr>>;
+}
+
+impl LowerConst for Const {
+    fn lower(&self, env: &Env) -> LowerResult<chalk_ir::Const<ChalkIr>> {
+        let interner = env.interner();
+        match self {
+            Const::Id(name) => {
+                let parameter = env.lookup_generic_arg(name)?;
+                parameter
+                    .constant(interner)
+                    .ok_or_else(|| RustIrError::IncorrectParameterKind {
+                        identifier: name.clone(),
+                        expected: Kind::Const,
+                        actual: parameter.kind(),
+                    })
+                    .map(|c| c.clone())
+            }
+            Const::Value(value) => Ok(chalk_ir::ConstData {
+                ty: get_type_of_u32(),
+                value: chalk_ir::ConstValue::Concrete(chalk_ir::ConcreteConst {
+                    interned: value.clone(),
+                }),
+            }
+            .intern(interner)),
+        }
+    }
+}
+
 trait LowerGenericArg {
     fn lower(&self, env: &Env) -> LowerResult<chalk_ir::GenericArg<ChalkIr>>;
 }
@@ -1471,14 +1501,7 @@ impl LowerGenericArg for GenericArg {
             GenericArg::Ty(ref t) => Ok(t.lower(env)?.cast(interner)),
             GenericArg::Lifetime(ref l) => Ok(l.lower(env)?.cast(interner)),
             GenericArg::Id(name) => env.lookup_generic_arg(&name),
-            GenericArg::ConstValue(value) => Ok(chalk_ir::ConstData {
-                ty: get_type_of_u32(),
-                value: chalk_ir::ConstValue::Concrete(chalk_ir::ConcreteConst {
-                    interned: value.clone(),
-                }),
-            }
-            .intern(interner)
-            .cast(interner)),
+            GenericArg::Const(c) => Ok(c.lower(env)?.cast(interner)),
         }
     }
 }

chalk-parse/src/ast.rs

@@ -109,7 +109,13 @@ pub enum GenericArg {
     Ty(Ty),
     Lifetime(Lifetime),
     Id(Identifier),
-    ConstValue(u32),
+    Const(Const),
+}
+
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub enum Const {
+    Id(Identifier),
+    Value(u32),
 }
 
 #[derive(Clone, PartialEq, Eq, Debug)]
@@ -214,7 +220,7 @@ pub enum Ty {
     },
     Array {
         ty: Box<Ty>,
-        len: Box<GenericArg>,
+        len: Const,
     },
     Raw {
         mutability: Mutability,

chalk-parse/src/parser.lalrpop

@@ -239,7 +239,7 @@ TyWithoutId: Ty = {
     "&" <l: Lifetime> "mut" <t:Ty> => Ty::Ref{ mutability: Mutability::Mut, lifetime: l, ty: Box::new(t) },
     "&" <l: Lifetime> <t:Ty> => Ty::Ref{ mutability: Mutability::Not, lifetime: l, ty: Box::new(t) },
     "[" <t:Ty> "]" => Ty::Slice { ty: Box::new(t) }, 
-    "[" <t:Ty> ";" <len:GenericArg> "]" => Ty::Array { ty: Box::new(t), len: Box::new(len) },
+    "[" <t:Ty> ";" <len:Const> "]" => Ty::Array { ty: Box::new(t), len },
 };
 
 ScalarType: ScalarType = {
@@ -281,11 +281,20 @@ Lifetime: Lifetime = {
     <n:LifetimeId> => Lifetime::Id { name: n },
 };
 
+ConstWithoutId: Const = {
+    ConstValue => Const::Value(<>),
+};
+
+Const : Const = {
+    Id => Const::Id(<>),
+    ConstWithoutId,
+};
+
 GenericArg: GenericArg = {
     TyWithoutId => GenericArg::Ty(<>),
     Lifetime => GenericArg::Lifetime(<>),
     Id => GenericArg::Id(<>),
-    ConstValue => GenericArg::ConstValue(<>),
+    ConstWithoutId => GenericArg::Const(<>),
 };
 
 ProjectionTy: ProjectionTy = {