started adding error types

* converted to string to avoid breaking interface, would be fixed later
* tests would not check error messages now, as messages are not
  finalized

Cargo.lock

@@ -463,6 +463,7 @@ dependencies = [
  "num-bigint",
  "num-traits",
  "rustpython-parser",
+ "thiserror",
 ]
 
 [[package]]
@@ -840,6 +841,26 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "thiserror"
+version = "1.0.23"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76cc616c6abf8c8928e2fdcc0dbfab37175edd8fb49a4641066ad1364fdab146"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "1.0.23"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9be73a2caec27583d0046ef3796c3794f868a5bc813db689eed00c7631275cd1"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "thread_local"
 version = "1.0.1"

nac3core/Cargo.toml

@@ -7,6 +7,7 @@ edition = "2018"
 [dependencies]
 num-bigint = "0.3"
 num-traits = "0.2"
+thiserror = "1.0"
 inkwell = { git = "https://github.com/TheDan64/inkwell", branch = "master", features = ["llvm10-0"] }
 rustpython-parser = { git = "https://github.com/RustPython/RustPython", branch = "master" }
 

nac3core/src/type_check/expression_inference.rs

@@ -705,7 +705,7 @@ mod test {
 
         let ast = parse_expression("a == a == 1").unwrap();
         let result = infer_expr(&mut ctx, &ast);
-        assert_eq!(result, Err("not equal".into()));
+        assert_eq!(result, Err("different types".into()));
 
         let ast = parse_expression("True > False").unwrap();
         let result = infer_expr(&mut ctx, &ast);

nac3core/src/type_check/inference_core.rs

@@ -1,6 +1,21 @@
 use super::context::InferenceContext;
 use super::typedef::{TypeEnum::*, *};
 use std::collections::HashMap;
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+enum SubstError {
+    #[error("different type variables after substitution")]
+    DifferentSubstVar(VariableId, VariableId),
+    #[error("cannot substitute unbounded type variable into bounded one")]
+    UnboundedTypeVar(VariableId, VariableId),
+    #[error("incompatible bound for type variables")]
+    IncompatibleBound(VariableId, VariableId),
+    #[error("only subtype of virtual class can be substituted into virtual class type")]
+    NotVirtualClassSubtype(Type, ClassId),
+    #[error("different types")]
+    DifferentTypes(Type, Type),
+}
 
 fn find_subst(
     ctx: &InferenceContext,
@@ -8,8 +23,7 @@ fn find_subst(
     sub: &mut HashMap<VariableId, Type>,
     mut a: Type,
     mut b: Type,
-) -> Result<(), String> {
+) -> Result<(), SubstError> {
-    // TODO: fix error messages later
     if let TypeVariable(id) = a.as_ref() {
         if let Some((assumption_id, t)) = valuation {
             if assumption_id == id {
@@ -33,14 +47,14 @@ fn find_subst(
                 return if id_a == id_b {
                     Ok(())
                 } else {
-                    Err("different variables".to_string())
+                    Err(SubstError::DifferentSubstVar(*id_a, *id_b))
                 };
             }
             let v_a = ctx.get_variable_def(*id_a);
             let v_b = ctx.get_variable_def(*id_b);
             if !v_b.bound.is_empty() {
                 if v_a.bound.is_empty() {
-                    return Err("unbounded a".to_string());
+                    return Err(SubstError::UnboundedTypeVar(*id_a, *id_b));
                 } else {
                     let diff: Vec<_> = v_a
                         .bound
@@ -48,7 +62,7 @@ fn find_subst(
                         .filter(|x| !v_b.bound.contains(x))
                         .collect();
                     if !diff.is_empty() {
-                        return Err("different domain".to_string());
+                        return Err(SubstError::IncompatibleBound(*id_a, *id_b));
                     }
                 }
             }
@@ -60,7 +74,7 @@ fn find_subst(
             if v_a.bound.len() == 1 && v_a.bound[0].as_ref() == b.as_ref() {
                 Ok(())
             } else {
-                Err("different domain".to_string())
+                Err(SubstError::DifferentTypes(a.clone(), b.clone()))
             }
         }
         (_, TypeVariable(id_b)) => {
@@ -69,7 +83,7 @@ fn find_subst(
                 sub.insert(*id_b, a.clone());
                 Ok(())
             } else {
-                Err("different domain".to_string())
+                Err(SubstError::DifferentTypes(a.clone(), b.clone()))
             }
         }
         (_, VirtualClassType(id_b)) => {
@@ -82,7 +96,7 @@ fn find_subst(
                     parents = [*id_a].to_vec();
                 }
                 _ => {
-                    return Err("cannot substitute non-class type into virtual class".to_string());
+                    return Err(SubstError::NotVirtualClassSubtype(a.clone(), *id_b));
                 }
             };
             while !parents.is_empty() {
@@ -92,11 +106,11 @@ fn find_subst(
                 let c = ctx.get_class_def(parents.remove(0));
                 parents.extend_from_slice(&c.parents);
             }
-            Err("not subtype".to_string())
+            Err(SubstError::NotVirtualClassSubtype(a.clone(), *id_b))
         }
         (ParametricType(id_a, param_a), ParametricType(id_b, param_b)) => {
             if id_a != id_b || param_a.len() != param_b.len() {
-                Err("different parametric types".to_string())
+                Err(SubstError::DifferentTypes(a.clone(), b.clone()))
             } else {
                 for (x, y) in param_a.iter().zip(param_b.iter()) {
                     find_subst(ctx, valuation, sub, x.clone(), y.clone())?;
@@ -108,7 +122,7 @@ fn find_subst(
             if a == b {
                 Ok(())
             } else {
-                Err("not equal".to_string())
+                Err(SubstError::DifferentTypes(a.clone(), b.clone()))
             }
         }
     }
@@ -177,7 +191,7 @@ fn resolve_call_rec(
         return Err("incorrect parameter number".to_string());
     }
     for (a, b) in args.iter().zip(fun.args.iter()) {
-        find_subst(ctx, valuation, &mut subst, a.clone(), b.clone())?;
+        find_subst(ctx, valuation, &mut subst, a.clone(), b.clone()).map_err(|v| v.to_string())?;
     }
     let result = fun.result.as_ref().map(|v| v.subst(&subst));
     Ok(result.map(|result| {
@@ -204,6 +218,7 @@ mod tests {
         super::{context::*, primitives::*},
         *,
     };
+    use std::matches;
     use std::rc::Rc;
 
     fn get_inference_context(ctx: TopLevelContext) -> InferenceContext {
@@ -244,25 +259,25 @@ mod tests {
             Ok(Some(ctx.get_primitive(FLOAT_TYPE)))
         );
 
-        assert_eq!(
+        assert!(matches!(
             resolve_call(&ctx, None, "float", &[ctx.get_primitive(BOOL_TYPE)]),
-            Err("different domain".to_string())
+            Err(..)
-        );
+        ));
 
-        assert_eq!(
+        assert!(matches!(
             resolve_call(&ctx, None, "float", &[]),
-            Err("incorrect parameter number".to_string())
+            Err(..)
-        );
+        ));
 
         assert_eq!(
             resolve_call(&ctx, None, "float", &[v1]),
             Ok(Some(ctx.get_primitive(FLOAT_TYPE)))
         );
 
-        assert_eq!(
+        assert!(matches!(
             resolve_call(&ctx, None, "float", &[v2]),
-            Err("different domain".to_string())
+            Err(..)
-        );
+        ));
     }
 
     #[test]
@@ -309,40 +324,40 @@ mod tests {
             Ok(Some(int64.clone()))
         );
 
-        assert_eq!(
+        assert!(matches!(
             resolve_call(&ctx, Some(int32), "__add__", &[int64]),
-            Err("not equal".to_string())
+            Err(..)
-        );
+        ));
 
         // with type variables
         assert_eq!(
             resolve_call(&ctx, Some(v1.clone()), "__add__", &[v1.clone()]),
             Ok(Some(v1.clone()))
         );
-        assert_eq!(
+        assert!(matches!(
             resolve_call(&ctx, Some(v0.clone()), "__add__", &[v2.clone()]),
-            Err("unbounded type var".to_string())
+            Err(..)
-        );
+        ));
-        assert_eq!(
+        assert!(matches!(
             resolve_call(&ctx, Some(v1.clone()), "__add__", &[v0]),
-            Err("different domain".to_string())
+            Err(..)
-        );
+        ));
-        assert_eq!(
+        assert!(matches!(
             resolve_call(&ctx, Some(v1.clone()), "__add__", &[v2]),
-            Err("different domain".to_string())
+            Err(..)
-        );
+        ));
-        assert_eq!(
+        assert!(matches!(
             resolve_call(&ctx, Some(v1.clone()), "__add__", &[v3.clone()]),
-            Err("different domain".to_string())
+            Err(..)
-        );
+        ));
-        assert_eq!(
+        assert!(matches!(
             resolve_call(&ctx, Some(v3.clone()), "__add__", &[v1]),
-            Err("no such function".to_string())
+            Err(..)
-        );
+        ));
-        assert_eq!(
+        assert!(matches!(
             resolve_call(&ctx, Some(v3.clone()), "__add__", &[v3]),
-            Err("no such function".to_string())
+            Err(..)
-        );
+        ));
     }
 
     #[test]
@@ -394,10 +409,10 @@ mod tests {
             resolve_call(&ctx, None, "foo", &[v2.clone(), v2.clone(), v3.clone()]),
             Ok(Some(v2.clone()))
         );
-        assert_eq!(
+        assert!(matches!(
             resolve_call(&ctx, None, "foo", &[v2.clone(), v3.clone(), v3.clone()]),
-            Err("different variables".to_string())
+            Err(..)
-        );
+        ));
 
         assert_eq!(
             resolve_call(
@@ -417,15 +432,15 @@ mod tests {
             ),
             Ok(Some(v2.clone()))
         );
-        assert_eq!(
+        assert!(matches!(
             resolve_call(
                 &ctx,
                 None,
                 "foo1",
                 &[ParametricType(TUPLE_TYPE, vec![v2, v3.clone(), v3]).into()]
             ),
-            Err("different variables".to_string())
+            Err(..)
-        );
+        ));
     }
 
     #[test]
@@ -479,15 +494,15 @@ mod tests {
             ),
             Ok(None)
         );
-        assert_eq!(
+        assert!(matches!(
             resolve_call(
                 &ctx,
                 Some(ParametricType(LIST_TYPE, vec![v0]).into()),
                 "append",
                 &[v1]
             ),
-            Err("different variables".to_string())
+            Err(..)
-        );
+        ));
     }
 
     #[test]
@@ -561,10 +576,10 @@ mod tests {
             Ok(None)
         );
 
-        assert_eq!(
+        assert!(matches!(
             resolve_call(&ctx, None, "foo", &[ClassType(bar).into()]),
-            Err("not subtype".to_string())
+            Err(..)
-        );
+        ));
 
         assert_eq!(
             resolve_call(&ctx, None, "foo1", &[ClassType(foo1).into()]),
@@ -576,10 +591,10 @@ mod tests {
             Ok(None)
         );
 
-        assert_eq!(
+        assert!(matches!(
             resolve_call(&ctx, None, "foo1", &[ClassType(foo).into()]),
-            Err("not subtype".to_string())
+            Err(..)
-        );
+        ));
 
         // virtual class substitution
         assert_eq!(
@@ -594,9 +609,9 @@ mod tests {
             resolve_call(&ctx, None, "foo", &[VirtualClassType(foo2).into()]),
             Ok(None)
         );
-        assert_eq!(
+        assert!(matches!(
             resolve_call(&ctx, None, "foo", &[VirtualClassType(bar).into()]),
-            Err("not subtype".to_string())
+            Err(..)
-        );
+        ));
     }
 }