Test and document supercalls using the same method/property name (#943)

docs/modules/language-reference/pages/index.adoc

@@ -2036,6 +2036,29 @@ greeting2 = greetPigeon(parrot)  // <4>
 <3> Call instance method on `pigeon`.
 <4> Call module method (on `this`).
 
+Like other object-oriented languages, methods defined on extended classes and modules may be overridden.
+The parent type's method may be called via the `super` keyword.
+
+[source%parsed,{pkl}]
+----
+open class Bird {
+  name: String
+  function canEat(food: String): Boolean = food == "seeds"
+}
+
+class InsectivorousBird extends Bird {
+  function canEat(food: String): Boolean = super.canEat(food) || food == "insects" // <1>
+}
+
+swallow = new InsectivorousBird { name = "Swallow" }
+
+canEatSeeds = swallow.canEat("seeds") // <2>
+canEatMeat = swallow.canEat("insects")  // <3>
+----
+<1> Call parent class instance method (on `this`).
+<2> result: `true`
+<3> result: `true`
+
 NOTE: Methods do not support named parameters or default parameter values.
 The xref:blog:ROOT:class-as-a-function.adoc[Class-as-a-function] pattern may be a suitable replacement.
 

pkl-core/src/test/files/LanguageSnippetTests/input/classes/supercalls.pkl

@@ -1,18 +1,24 @@
 open class One {
   prefix = ""
   function say(msg) = prefix + msg
+  function sameMethod() = 1
+  sameProp = "a"
 }
 
 open class Two extends One {
   pigeon = super.say("Pigeon")
   function barnOwl() = super.say("Barn Owl")
   function say2(msg) = super.say(msg) + super.say(msg)
+  function sameMethod() = 2 + super.sameMethod()
+  sameProp = super.sameProp + "b"
 }
 
 class Three extends Two {
   pigeonBarnOwl = super.pigeon + super.barnOwl()
   function barnOwlPigeon() = super.barnOwl() + super.pigeon
   parrot = super.say("Parrot")
+  function sameMethod() = 3 + super.sameMethod()
+  sameProp = super.sameProp + "c"
 }
 
 local two = new Two {}
@@ -36,3 +42,5 @@ res9 = two2.say2("Parrot")
 res10 = three2.pigeonBarnOwl
 res11 = three2.barnOwlPigeon()
 res12 = three2.parrot
+res13 = three2.sameMethod()
+res14 = three2.sameProp

pkl-core/src/test/files/LanguageSnippetTests/input/modules/supercalls1.pkl

@@ -2,3 +2,5 @@ open module supercalls1
 
 prefix = ""
 function say(msg) = prefix + msg
+function sameMethod() = 1
+sameProp = "a"

pkl-core/src/test/files/LanguageSnippetTests/input/modules/supercalls2.pkl

@@ -5,3 +5,5 @@ extends "supercalls1.pkl"
 hidden pigeon = super.say("Pigeon")
 function barnOwl() = super.say("Barn Owl")
 function say2(msg) = super.say(msg) + super.say(msg)
+function sameMethod() = 2 + super.sameMethod()
+sameProp = super.sameProp + "b"

pkl-core/src/test/files/LanguageSnippetTests/input/modules/supercalls3.pkl

@@ -8,6 +8,8 @@ hidden pigeonBarnOwl = super.pigeon + super.barnOwl()
 function barnOwlPigeon() = super.barnOwl() + super.pigeon
 hidden parrot = super.say("Parrot")
 function other() = super.other()
+function sameMethod() = 3 + super.sameMethod()
+sameProp = super.sameProp + "c"
 
 prefix = "Oh "
 
@@ -18,3 +20,4 @@ res4 = pigeonBarnOwl
 res5 = barnOwlPigeon()
 res6 = parrot
 res7 = test.catch(() -> other())
+res8 = sameMethod()

pkl-core/src/test/files/LanguageSnippetTests/output/classes/supercalls.pcf

@@ -10,3 +10,5 @@ res9 = "Oh ParrotOh Parrot"
 res10 = "Oh PigeonOh Barn Owl"
 res11 = "Oh Barn OwlOh Pigeon"
 res12 = "Oh Parrot"
+res13 = 6
+res14 = "abc"

pkl-core/src/test/files/LanguageSnippetTests/output/modules/supercalls1.pcf

@@ -1 +1,2 @@
 prefix = ""
+sameProp = "a"

pkl-core/src/test/files/LanguageSnippetTests/output/modules/supercalls2.pcf

@@ -1 +1,2 @@
 prefix = ""
+sameProp = "ab"

pkl-core/src/test/files/LanguageSnippetTests/output/modules/supercalls3.pcf

@@ -1,4 +1,5 @@
 prefix = "Oh "
+sameProp = "abc"
 res1 = "Oh Pigeon"
 res2 = "Oh Barn Owl"
 res3 = "Oh ParrotOh Parrot"
@@ -6,3 +7,4 @@ res4 = "Oh PigeonOh Barn Owl"
 res5 = "Oh Barn OwlOh Pigeon"
 res6 = "Oh Parrot"
 res7 = "Cannot find method `other` in module `supercalls2`."
+res8 = 6