Add comment providing context on the change

ahejlsberg · ahejlsberg · commit d2923460e967 · 2019-05-13T16:34:09.000-07:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -20387,6 +20387,7 @@ namespace ts {
 
         function isValidPropertyAccessForCompletions(node: PropertyAccessExpression | ImportTypeNode | QualifiedName, type: Type, property: Symbol): boolean {
             return isValidPropertyAccessWithType(node, node.kind === SyntaxKind.PropertyAccessExpression && node.expression.kind === SyntaxKind.SuperKeyword, property.escapedName, type);
+            // Previously we validated the 'this' type of methods but this adversely affected performance. See #31377 for more context.
         }
 
         function isValidPropertyAccessWithType(

Original file line number	Diff line number	Diff line change
`@@ -20387,6 +20387,7 @@ namespace ts {`
`20387`	`20387`
`20388`	`20388`	`function isValidPropertyAccessForCompletions(node: PropertyAccessExpression \| ImportTypeNode \| QualifiedName, type: Type, property: Symbol): boolean {`
`20389`	`20389`	`return isValidPropertyAccessWithType(node, node.kind === SyntaxKind.PropertyAccessExpression && node.expression.kind === SyntaxKind.SuperKeyword, property.escapedName, type);`
	`20390`	`+ // Previously we validated the 'this' type of methods but this adversely affected performance. See #31377 for more context.`
`20390`	`20391`	`}`
`20391`	`20392`
`20392`	`20393`	`function isValidPropertyAccessWithType(`