From 8694c5d6bd6edefda2e07f32e42eadf3f172f14f Mon Sep 17 00:00:00 2001
From: Andy Hanson <anhans@microsoft.com>
Date: Mon, 11 Dec 2017 07:40:01 -0800
Subject: [PATCH] Don't add completion for method if the `this` parameter
 doesn't match

---
 src/compiler/checker.ts                       | 25 +++++++++++++++----
 src/compiler/types.ts                         |  2 ++
 src/services/completions.ts                   |  6 ++---
 .../completionsMethodWithThisParameter.ts     | 15 +++++++++++
 4 files changed, 39 insertions(+), 9 deletions(-)
 create mode 100644 tests/cases/fourslash/completionsMethodWithThisParameter.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 4cc0bb7953184..006c0d960f572 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -185,7 +185,11 @@ namespace ts {
             },
             isValidPropertyAccess: (node, propertyName) => {
                 node = getParseTreeNode(node, isPropertyAccessOrQualifiedName);
-                return node ? isValidPropertyAccess(node, escapeLeadingUnderscores(propertyName)) : false;
+                return !!node && isValidPropertyAccess(node, escapeLeadingUnderscores(propertyName));
+            },
+            isValidPropertyAccessForCompletions: (node, type, property) => {
+                node = getParseTreeNode(node, isPropertyAccessExpression);
+                return !!node && isValidPropertyAccessForCompletions(node, type, property);
             },
             getSignatureFromDeclaration: declaration => {
                 declaration = getParseTreeNode(declaration, isFunctionLike);
@@ -16006,13 +16010,24 @@ namespace ts {
         }
 
         function isValidPropertyAccess(node: PropertyAccessExpression | QualifiedName, propertyName: __String): boolean {
-            const left = node.kind === SyntaxKind.PropertyAccessExpression
-                ? (<PropertyAccessExpression>node).expression
-                : (<QualifiedName>node).left;
-
+            const left = node.kind === SyntaxKind.PropertyAccessExpression ? node.expression : node.left;
             return isValidPropertyAccessWithType(node, left, propertyName, getWidenedType(checkExpression(left)));
         }
 
+        function isValidPropertyAccessForCompletions(node: PropertyAccessExpression, type: Type, property: Symbol): boolean {
+            return isValidPropertyAccessWithType(node, node.expression, property.escapedName, type)
+                && (!(property.flags & ts.SymbolFlags.Method) || isValidMethodAccess(property, type));
+        }
+        function isValidMethodAccess(method: Symbol, type: Type) {
+            const propType = getTypeOfFuncClassEnumModule(method);
+            const signatures = getSignaturesOfType(propType, SignatureKind.Call);
+            Debug.assert(signatures.length !== 0);
+            return signatures.some(sig => {
+                const thisType = getThisTypeOfSignature(sig);
+                return !thisType || isTypeAssignableTo(type, thisType);
+            });
+        }
+
         function isValidPropertyAccessWithType(
             node: PropertyAccessExpression | QualifiedName,
             left: LeftHandSideExpression | QualifiedName,
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index db53db2aecbe2..aec03264fafec 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -2753,6 +2753,8 @@ namespace ts {
 
         getConstantValue(node: EnumMember | PropertyAccessExpression | ElementAccessExpression): string | number | undefined;
         isValidPropertyAccess(node: PropertyAccessExpression | QualifiedName, propertyName: string): boolean;
+        /** Exclude accesses to private properties or methods with a `this` parameter that `type` doesn't satisfy. */
+        /* @internal */ isValidPropertyAccessForCompletions(node: PropertyAccessExpression, type: Type, property: Symbol): boolean;
         /** Follow all aliases to get the original symbol. */
         getAliasedSymbol(symbol: Symbol): Symbol;
         /** Follow a *single* alias to get the immediately aliased symbol. */
diff --git a/src/services/completions.ts b/src/services/completions.ts
index d893f4852e4f8..bb6a7df6b6842 100644
--- a/src/services/completions.ts
+++ b/src/services/completions.ts
@@ -918,9 +918,8 @@ namespace ts.Completions {
                 symbols.push(...getPropertiesForCompletion(type, typeChecker, /*isForAccess*/ true));
             }
             else {
-                // Filter private properties
                 for (const symbol of type.getApparentProperties()) {
-                    if (typeChecker.isValidPropertyAccess(<PropertyAccessExpression>(node.parent), symbol.name)) {
+                    if (typeChecker.isValidPropertyAccessForCompletions(<PropertyAccessExpression>(node.parent), type, symbol)) {
                         symbols.push(symbol);
                     }
                 }
@@ -2119,8 +2118,7 @@ namespace ts.Completions {
 
     /**
      * Gets all properties on a type, but if that type is a union of several types,
-     * tries to only include those types which declare properties, not methods.
-     * This ensures that we don't try providing completions for all the methods on e.g. Array.
+     * excludes array-like types or callable/constructable types.
      */
     function getPropertiesForCompletion(type: Type, checker: TypeChecker, isForAccess: boolean): Symbol[] {
         if (!(type.flags & TypeFlags.Union)) {
diff --git a/tests/cases/fourslash/completionsMethodWithThisParameter.ts b/tests/cases/fourslash/completionsMethodWithThisParameter.ts
new file mode 100644
index 0000000000000..b455ba4f5b80f
--- /dev/null
+++ b/tests/cases/fourslash/completionsMethodWithThisParameter.ts
@@ -0,0 +1,15 @@
+/// <reference path='fourslash.ts'/>
+
+////class A<T> {
+////    value: T; // Make the type parameter actually matter
+////    ms(this: A<string>) {}
+////    mo(this: A<{}>) {}
+////}
+////
+////const s = new A<string>();
+////const n = new A<number>();
+////s./*s*/;
+////n./*n*/;
+
+verify.completionsAt("s", ["value", "ms", "mo"]);
+verify.completionsAt("n", ["value", "mo"]);
\ No newline at end of file