Intersection Type (#1603)

Author: markwpearce

docs/intersection-types.md

@@ -0,0 +1,86 @@
+# Intersection Types
+
+BrighterScript Intersection Types are a way to define a type that combines the members of multiple types. They are similar to Intersection Types found in other languages, such as [TypeScript](https://www.typescriptlang.org/docs/handbook/2/objects.html#intersection-types).
+
+## Syntax
+
+Intersection types can be declared with the following syntax: `<type> and <type>`. For example, the parameter to the function below could be meets both the interfaces `HasId` and `HasUrl`:
+
+```BrighterScript
+interface HasId
+    id as string
+end interface
+
+interface HasUrl
+    url as string
+end interface
+
+function getUrlWithQueryId(value as HasId and HasUrl) as string
+    return value.url + "?id=" + value.id
+end function
+```
+
+Any number of inner types, including classes or interfaces, could be part of an intersection:
+
+```BrighterScript
+interface HasId
+    id as string
+end interface
+
+interface HasUrl
+    url as string
+end interface
+
+interface HasSize
+    width as integer
+    height as integer
+end interface
+
+
+function getUrlWithQuerySize(response as HasId and HasUrl and HasSize) as string
+    return value.url + "?id=" + value.id + "&w=" + value.width.toStr().trim() + "&h=" + value.height.toStr().trim()
+end function
+```
+
+## Members and Validation
+
+A diagnostic error will be raised when a member is accessed that is not a member of any of the types of a union. Note also that if a member is not the same type in each of the types in the union, it will itself be considered an intersection.
+
+```BrighterScript
+sub testIntersection(value as {id as string} and {id as integer})
+    ' This is an error - "value.id" is of type "string AND integer"
+    printInteger(value.id)
+end sub
+
+sub printInteger(x as integer)
+    print x
+end sub
+```
+
+## Transpilation
+
+Since Brightscript does not have intersection types natively, intersection types will be transpiled as `dynamic`.
+
+```BrighterScript
+
+interface HasRadius
+    radius as float
+end interface
+
+interface Point
+    x as float
+    y as float
+end interface
+
+function getCircleDetails(circle as HasRadius and Point) as string
+    return "Circle: radius=" + circle.radius.toStr() + ", center=" + circle.x.toStr() + "," + circle.y.toStr()
+end function
+```
+
+transpiles to
+
+```BrightScript
+function getCircleDetails(circle as dynamic) as string
+    return "Circle: radius=" + circle.radius.ToStr() + ", center=" + circle.x.toStr() + "," + circle.y.toStr()
+end function
+```

docs/readme.md

@@ -1,9 +1,11 @@
 # BrighterScript
+
 BrighterScript is a superset of Roku's BrightScript language. Its goal is to provide new functionality and enhanced syntax support to enhance the Roku channel developer experience.
 
 See the following pages for more information:
 
 ## [Annotations](annotations.md)
+
 ```brighterscript
 'mostly useful for plugins that change code based on annotations
 @logOnException()
@@ -13,12 +15,14 @@ end
 ```
 
 ## [Callfunc Operator](callfunc-operator.md)
+
 ```brighterscript
 'instead of `node.callfunc("someMethod", 1, 2, 3)`, you can do this:
 node@.someMethod(1, 2, 3)
 ```
 
 ## [Classes](classes.md)
+
 ```brighterscript
 class Movie
     public title as string
@@ -33,6 +37,7 @@ end class
 ```
 
 ## [Constants](constants.md)
+
 ```brighterscript
 const API_URL = "https://api.acme.com/v1/"
 sub main()
@@ -41,6 +46,7 @@ end sub
 ```
 
 ## [Enums](enums.md)
+
 ```brighterscript
 enum RemoteButton
     up = "up"
@@ -51,6 +57,7 @@ end enum
 ```
 
 ## [Exceptions](exceptions.md)
+
 ```brighterscript
 try
     somethingDangerous()
@@ -59,7 +66,40 @@ catch 'look, no exception variable!
 end try
 ```
 
+## [Imports](imports.md)
+
+```brighterscript
+import "pkg:/source/util.bs"
+sub main()
+    print util_toUpper("hello world")
+end sub
+```
+
+## [Interfaces](interfaces.md)
+
+```brighterscript
+interface IMyComponent
+   top as roSGNodeMyComponent
+
+   isSelected as boolean
+   selectedIndex as integer
+
+   data as {id as string, isEpisode as boolean}
+end interface
+```
+
+## [Intersection Types](intersection-types.md)
+
+```brighterscript
+type MyClassAA = MyClass and roAssociativeArray
+
+sub addData(klass as MyClass and roAssociativeArray, data as roAssociativeArray)
+    return klass.append(data)
+end sub
+```
+
 ## [Namespaces](namespaces.md)
+
 ```brighterscript
 namespace util
     function toUpper(value as string)
@@ -72,28 +112,24 @@ sub main()
 end sub
 ```
 
-## [Imports](imports.md)
-```brighterscript
-import "pkg:/source/util.bs"
-sub main()
-    print util_toUpper("hello world")
-end sub
-```
-
 ## [Null-coalescing operator](null-coalescing-operator.md)
+
 ```brighterscript
 userSettings = getSettingsFromRegistry() ?? {}
 ```
 
 ## [Plugins](plugins.md)
+
 Plugins can be used to manipulate code at any point during the program lifecycle.
 
 ## [Regular Expression Literals](regex-literals.md)
+
 ```brighterscript
 print /hello world/ig
 ```
 
 ## [Source Literals](source-literals.md)
+
 ```brighterscript
 print SOURCE_FILE_PATH
 print SOURCE_LINE_NUM
@@ -103,7 +139,9 @@ print SOURCE_LOCATION
 print PKG_PATH
 print PKG_LOCATION
 ```
+
 ## [Template Strings (Template Literals)](template-strings.md)
+
 ```brighterscript
 name = `John Smith`
 
@@ -114,16 +152,19 @@ second line text`
 ```
 
 ## [Ternary (Conditional) Operator](ternary-operator.md)
+
 ```brighterscript
 authStatus = user <> invalid ? "logged in" : "not logged in"
 ```
 
 ## [Typecasts](typecasts.md)
+
 ```BrighterScript
 nodeId = (node as roSgNode).id
 ```
 
 ## [Typed Arrays](typed-arrays.md)
+
 ```brighterscript
 function getY(translation as float[]) as float
     yValue = -1
@@ -135,6 +176,7 @@ end function
 ```
 
 ## [Type Statements](type-statements.md)
+
 ```brighterscript
 type number = integer or float or double
 
@@ -144,11 +186,13 @@ end function
 ```
 
 ## [Union Types](union-types.md)
+
 ```brighterscript
 sub logData(data as string or number)
     print data.toStr()
 end sub
 ```
 
 ## [Variable Shadowing](variable-shadowing.md)
+
 Name resolution rules for various types of shadowing.

src/CrossScopeValidator.ts

@@ -11,7 +11,7 @@ import type { ReferenceType } from './types/ReferenceType';
 import { getAllRequiredSymbolNames } from './types/ReferenceType';
 import type { TypeChainEntry, TypeChainProcessResult } from './interfaces';
 import { BscTypeKind } from './types/BscTypeKind';
-import { getAllTypesFromUnionType } from './types/helpers';
+import { getAllTypesFromCompoundType } from './types/helpers';
 import type { BscType } from './types/BscType';
 import type { BscFile } from './files/BscFile';
 import type { ClassStatement, ConstStatement, EnumMemberStatement, EnumStatement, InterfaceStatement, NamespaceStatement } from './parser/Statement';
@@ -222,7 +222,7 @@ export class CrossScopeValidator {
         }
 
         if (isUnionType(symbol.typeChain[0].type) && symbol.typeChain[0].data.isInstance) {
-            const allUnifiedTypes = getAllTypesFromUnionType(symbol.typeChain[0].type);
+            const allUnifiedTypes = getAllTypesFromCompoundType(symbol.typeChain[0].type);
             for (const unifiedType of allUnifiedTypes) {
                 unnamespacedNameLowers.push(joinTypeChainForKey(symbol.typeChain, unifiedType));
             }