Mark overridable external properties as const (#1864)

docs/modules/release-notes/pages/0.33.adoc

@@ -69,6 +69,19 @@ A `Class` value typechecked against `Class<T>` must be a subclass of `T`.
 
 If `T` does not resolve to a class type (i.e. it is a union type, nullable type, string literal type, parameterized type, or `nothing`), the type check will always fail.
 
+=== Standard library `external` module properties are now marked `const`
+
+Previously, module properties in `pkl:math` and `pkl:release` could be overriden by amending the module.
+Doing this makes little sense—these value are constants and overriding them by amending their module would be odd.
+
+This is a breaking change for code that looks like this:
+[source,pkl]
+----
+bogusMath = (import("pkl:math")) {
+  minInt = -1
+}
+----
+
 === XXX
 
 == Bug Fixes [small]#🐜#

stdlib/math.pkl

@@ -22,63 +22,63 @@
 module pkl.math
 
 /// The minimum [Int] value: `-9223372036854775808`.
-external minInt: Int
+external const minInt: Int
 
 /// The minimum [Int8] value: -128.
-external minInt8: Int8
+external const minInt8: Int8
 
 /// The minimum [Int16] value: -32768.
-external minInt16: Int16
+external const minInt16: Int16
 
 /// The minimum [Int32] value: -2147483648.
-external minInt32: Int32
+external const minInt32: Int32
 
 /// The maximum [Int] value: `9223372036854775807`.
-external maxInt: Int
+external const maxInt: Int
 
 /// The maximum [Int8] value: 127.
-external maxInt8: Int8
+external const maxInt8: Int8
 
 /// The maximum [Int16] value: 32767.
-external maxInt16: Int16
+external const maxInt16: Int16
 
 /// The maximum [Int32] value: 2147483647.
-external maxInt32: Int32
+external const maxInt32: Int32
 
 /// The maximum [UInt] value: 9223372036854775807.
 ///
 /// Note that [maxUInt] is equal to [maxInt],
 /// not `maxInt * 2 + 1` as one might expect.
 /// That is, [UInt] has half the range of [Int].
-external maxUInt: UInt
+external const maxUInt: UInt
 
 /// The maximum [UInt8] value: 255.
-external maxUInt8: UInt8
+external const maxUInt8: UInt8
 
 /// The maximum [UInt16] value: 65535.
-external maxUInt16: UInt16
+external const maxUInt16: UInt16
 
 /// The maximum [UInt32] value: 4294967295.
-external maxUInt32: UInt32
+external const maxUInt32: UInt32
 
 /// The minimum finite [Float] value: `-1.7976931348623157e308`.
 ///
 /// Operations whose value is less than [minFiniteFloat] return -[Infinity].
-external minFiniteFloat: Float
+external const minFiniteFloat: Float
 
 /// The maximum finite [Float] value: `1.7976931348623157e308`.
 ///
 /// Operations whose value is greater than [maxFiniteFloat] return [Infinity].
-external maxFiniteFloat: Float
+external const maxFiniteFloat: Float
 
 /// The minimum positive [Float] value that is greater than zero: `4.9e-324`.
-external minPositiveFloat: Float
+external const minPositiveFloat: Float
 
 /// The number [e](https://en.wikipedia.org/wiki/E_(mathematical_constant)).
-external e: Float
+external const e: Float
 
 /// The number [π](https://en.wikipedia.org/wiki/Pi).
-external pi: Float
+external const pi: Float
 
 /// Returns e [raised to the power](https://en.wikipedia.org/wiki/Exponential_function) of
 /// [exponent].

stdlib/release.pkl

@@ -21,7 +21,7 @@ module pkl.release
 import "pkl:semver"
 
 /// The Pkl release that the current program runs on.
-external current: Release
+external const current: Release
 
 /// A Pkl release.
 class Release {