Use '__this__' property in contextual type to indicate type of 'this'

ahejlsberg · ahejlsberg · commit f6a3a3fc3dc5 · 2017-02-14T12:04:39.000-08:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -11189,6 +11189,19 @@ namespace ts {
                         return getTypeOfSymbol(thisParameter);
                     }
                 }
+                if (isObjectLiteralMethod(func)) {
+                    // For methods in an object literal, look for a '__this__' property in the contextual
+                    // type for the object literal. If one exists, remove 'undefined' from the type of that
+                    // property and report it as the contextual type for 'this' in the method.
+                    const objectLiteral = <ObjectLiteralExpression>func.parent;
+                    const type = getApparentTypeOfContextualType(objectLiteral);
+                    if (type) {
+                        const propertyType = getTypeOfPropertyOfContextualType(type, "___this__");
+                        if (propertyType) {
+                            return getNonNullableType(propertyType);
+                        }
+                    }
+                }
             }
             return undefined;
         }

Original file line number	Diff line number	Diff line change
`@@ -11189,6 +11189,19 @@ namespace ts {`
`11189`	`11189`	`return getTypeOfSymbol(thisParameter);`
`11190`	`11190`	`}`
`11191`	`11191`	`}`
	`11192`	`+ if (isObjectLiteralMethod(func)) {`
	`11193`	`+ // For methods in an object literal, look for a '__this__' property in the contextual`
	`11194`	`+ // type for the object literal. If one exists, remove 'undefined' from the type of that`
	`11195`	`+ // property and report it as the contextual type for 'this' in the method.`
	`11196`	`+ const objectLiteral = <ObjectLiteralExpression>func.parent;`
	`11197`	`+ const type = getApparentTypeOfContextualType(objectLiteral);`
	`11198`	`+ if (type) {`
	`11199`	`+ const propertyType = getTypeOfPropertyOfContextualType(type, "___this__");`
	`11200`	`+ if (propertyType) {`
	`11201`	`+ return getNonNullableType(propertyType);`
	`11202`	`+ }`
	`11203`	`+ }`
	`11204`	`+ }`
`11192`	`11205`	`}`
`11193`	`11206`	`return undefined;`
`11194`	`11207`	`}`