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tests: add tests for variance inference and subtyping

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This commit is contained in:
Louis Heredero
2026-06-20 16:48:19 +02:00
parent 9467187313
commit 48a20b4aa0
4 changed files with 628 additions and 5 deletions
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10
midas/checker/types.py
View File

@@ -1,7 +1,7 @@
from __future__ import annotations
from dataclasses import dataclass, field
from enum import Enum, auto
from enum import StrEnum
from typing import Optional, assert_never
import midas.ast.midas as m
@@ -103,10 +103,10 @@ class ExtensionType:
return f"{self.base} & {self.extension}"
class Variance(Enum):
INVARIANT = auto()
COVARIANT = auto()
CONTRAVARIANT = auto()
class Variance(StrEnum):
INVARIANT = "INVARIANT"
COVARIANT = "COVARIANT"
CONTRAVARIANT = "CONTRAVARIANT"
@dataclass(frozen=True, kw_only=True)

59
tests/cases/checker/07_variance.midas Normal file
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@@ -0,0 +1,59 @@
// T is invariant (unused)
type Unused[T] = object
// T is covariant
type Covariant[T] = object
// T is contravariant
type Contravariant[T] = object
// T is invariant
type Invariant[T] = object
extend Covariant[T] {
def foo: fn() -> T
}
extend Contravariant[T] {
def foo: fn(T, /) -> None
}
extend Invariant[T] {
def foo: fn(T, /) -> T
}
// T is covariant
type Coco[T] = object
extend Coco[T] {
def foo: fn() -> Covariant[T]
}
// T is contravariant
type Cocontra[T] = object
extend Cocontra[T] {
def foo: fn() -> Contravariant[T]
}
// T is contravariant
type Contraco[T] = object
extend Contraco[T] {
def foo: fn(Covariant[T], /) -> None
}
// T is covariant
type Contracontra[T] = object
extend Contracontra[T] {
def foo: fn(Contravariant[T], /) -> None
}
type T1[T] = object
type T2[T] = object
extend T1[T] {
def foo: fn() -> T2[T]
}
extend T2[T] {
def foo: fn() -> T1[T]
}

52
tests/cases/checker/07_variance.py Normal file
View File

@@ -0,0 +1,52 @@
from _ import (
T1,
T2,
Coco,
Cocontra,
Contraco,
Contracontra,
Contravariant,
Covariant,
Invariant,
Unused,
)
unused: Unused
covariant: Covariant
contravariant: Contravariant
invariant: Invariant
coco: Coco
cocontra: Cocontra
contraco: Contraco
contracontra: Contracontra
t1: T1
t2: T2
# Dummy print to prudce judgements for the expressions
print(
unused,
covariant,
contravariant,
invariant,
coco,
cocontra,
contraco,
contracontra,
t1,
t2,
)
cov1: Covariant[float]
cov2: Covariant[int]
cov1 = cov2 # Ok because int <: float => Covariant[int] <: Covariant[float]
cov2 = cov1 # Invalid
contra1: Contravariant[float]
contra2: Contravariant[int]
contra1 = contra2 # Invalid
contra2 = contra1 # Ok because int <: float => Covariant[float] <: Covariant[int]
inv1: Invariant[float]
inv2: Invariant[int]
inv1 = inv2 # Invalid
inv2 = inv1 # Invalid

512
tests/cases/checker/07_variance.py.ref.json Normal file
View File

@@ -0,0 +1,512 @@
{
"diagnostics": [
{
"type": "Error",
"location": {
"start": [
28,
4
],
"end": [
28,
13
]
},
"message": "Too many positional arguments"
},
{
"type": "Error",
"location": {
"start": [
42,
0
],
"end": [
42,
11
]
},
"message": "Cannot assign Covariant[float] to variable 'cov2' of type Covariant[int]"
},
{
"type": "Error",
"location": {
"start": [
46,
0
],
"end": [
46,
17
]
},
"message": "Cannot assign Contravariant[int] to variable 'contra1' of type Contravariant[float]"
},
{
"type": "Error",
"location": {
"start": [
51,
0
],
"end": [
51,
11
]
},
"message": "Cannot assign Invariant[int] to variable 'inv1' of type Invariant[float]"
},
{
"type": "Error",
"location": {
"start": [
52,
0
],
"end": [
52,
11
]
},
"message": "Cannot assign Invariant[float] to variable 'inv2' of type Invariant[int]"
}
],
"judgments": [
{
"location": {
"from": "L26:0",
"to": "L26:5"
},
"expr": {
"_type": "VariableExpr",
"name": "print"
},
"type": {
"pos_args": [
{
"pos": 0,
"name": "object",
"type": {},
"required": true
}
],
"args": [],
"kw_args": [],
"returns": {}
}
},
{
"location": {
"from": "L27:4",
"to": "L27:10"
},
"expr": {
"_type": "VariableExpr",
"name": "unused"
},
"type": {
"name": "Unused",
"params": [
{
"name": "T",
"bound": null,
"variance": "INVARIANT"
}
],
"body": {
"name": "object"
}
}
},
{
"location": {
"from": "L28:4",
"to": "L28:13"
},
"expr": {
"_type": "VariableExpr",
"name": "covariant"
},
"type": {
"name": "Covariant",
"params": [
{
"name": "T",
"bound": null,
"variance": "COVARIANT"
}
],
"body": {
"name": "object"
}
}
},
{
"location": {
"from": "L29:4",
"to": "L29:17"
},
"expr": {
"_type": "VariableExpr",
"name": "contravariant"
},
"type": {
"name": "Contravariant",
"params": [
{
"name": "T",
"bound": null,
"variance": "CONTRAVARIANT"
}
],
"body": {
"name": "object"
}
}
},
{
"location": {
"from": "L30:4",
"to": "L30:13"
},
"expr": {
"_type": "VariableExpr",
"name": "invariant"
},
"type": {
"name": "Invariant",
"params": [
{
"name": "T",
"bound": null,
"variance": "INVARIANT"
}
],
"body": {
"name": "object"
}
}
},
{
"location": {
"from": "L31:4",
"to": "L31:8"
},
"expr": {
"_type": "VariableExpr",
"name": "coco"
},
"type": {
"name": "Coco",
"params": [
{
"name": "T",
"bound": null,
"variance": "COVARIANT"
}
],
"body": {
"name": "object"
}
}
},
{
"location": {
"from": "L32:4",
"to": "L32:12"
},
"expr": {
"_type": "VariableExpr",
"name": "cocontra"
},
"type": {
"name": "Cocontra",
"params": [
{
"name": "T",
"bound": null,
"variance": "CONTRAVARIANT"
}
],
"body": {
"name": "object"
}
}
},
{
"location": {
"from": "L33:4",
"to": "L33:12"
},
"expr": {
"_type": "VariableExpr",
"name": "contraco"
},
"type": {
"name": "Contraco",
"params": [
{
"name": "T",
"bound": null,
"variance": "CONTRAVARIANT"
}
],
"body": {
"name": "object"
}
}
},
{
"location": {
"from": "L34:4",
"to": "L34:16"
},
"expr": {
"_type": "VariableExpr",
"name": "contracontra"
},
"type": {
"name": "Contracontra",
"params": [
{
"name": "T",
"bound": null,
"variance": "COVARIANT"
}
],
"body": {
"name": "object"
}
}
},
{
"location": {
"from": "L35:4",
"to": "L35:6"
},
"expr": {
"_type": "VariableExpr",
"name": "t1"
},
"type": {
"name": "T1",
"params": [
{
"name": "T",
"bound": null,
"variance": "INVARIANT"
}
],
"body": {
"name": "object"
}
}
},
{
"location": {
"from": "L36:4",
"to": "L36:6"
},
"expr": {
"_type": "VariableExpr",
"name": "t2"
},
"type": {
"name": "T2",
"params": [
{
"name": "T",
"bound": null,
"variance": "INVARIANT"
}
],
"body": {
"name": "object"
}
}
},
{
"location": {
"from": "L26:0",
"to": "L37:1"
},
"expr": {
"_type": "CallExpr",
"callee": {
"_type": "VariableExpr",
"name": "print"
},
"arguments": [
{
"_type": "VariableExpr",
"name": "unused"
},
{
"_type": "VariableExpr",
"name": "covariant"
},
{
"_type": "VariableExpr",
"name": "contravariant"
},
{
"_type": "VariableExpr",
"name": "invariant"
},
{
"_type": "VariableExpr",
"name": "coco"
},
{
"_type": "VariableExpr",
"name": "cocontra"
},
{
"_type": "VariableExpr",
"name": "contraco"
},
{
"_type": "VariableExpr",
"name": "contracontra"
},
{
"_type": "VariableExpr",
"name": "t1"
},
{
"_type": "VariableExpr",
"name": "t2"
}
],
"keywords": {}
},
"type": {}
},
{
"location": {
"from": "L41:7",
"to": "L41:11"
},
"expr": {
"_type": "VariableExpr",
"name": "cov2"
},
"type": {
"name": "Covariant",
"args": [
{
"name": "int"
}
],
"body": {
"name": "object"
}
}
},
{
"location": {
"from": "L42:7",
"to": "L42:11"
},
"expr": {
"_type": "VariableExpr",
"name": "cov1"
},
"type": {
"name": "Covariant",
"args": [
{
"name": "float"
}
],
"body": {
"name": "object"
}
}
},
{
"location": {
"from": "L46:10",
"to": "L46:17"
},
"expr": {
"_type": "VariableExpr",
"name": "contra2"
},
"type": {
"name": "Contravariant",
"args": [
{
"name": "int"
}
],
"body": {
"name": "object"
}
}
},
{
"location": {
"from": "L47:10",
"to": "L47:17"
},
"expr": {
"_type": "VariableExpr",
"name": "contra1"
},
"type": {
"name": "Contravariant",
"args": [
{
"name": "float"
}
],
"body": {
"name": "object"
}
}
},
{
"location": {
"from": "L51:7",
"to": "L51:11"
},
"expr": {
"_type": "VariableExpr",
"name": "inv2"
},
"type": {
"name": "Invariant",
"args": [
{
"name": "int"
}
],
"body": {
"name": "object"
}
}
},
{
"location": {
"from": "L52:7",
"to": "L52:11"
},
"expr": {
"_type": "VariableExpr",
"name": "inv1"
},
"type": {
"name": "Invariant",
"args": [
{
"name": "float"
}
],
"body": {
"name": "object"
}
}
}
]
}