Merge pull request #853 from Microsoft/objectLiteralCompletion

Fix crash when getting member completion for an object literal

src/compiler/checker.ts

@@ -4508,8 +4508,21 @@ module ts {
             }
             else {
                 error(node, Diagnostics.Supplied_parameters_do_not_match_any_signature_of_call_target);
-                return resolveErrorCall(node);
             }
+
+            // No signature was applicable. We have already reported the errors for the invalid signature.
+            // If this is a type resolution session, e.g. Language Service, try to get better information that anySignature.
+            // Pick the first candidate that matches the arity. This way we can get a contextual type for cases like:
+            //  declare function f(a: { xa: number; xb: number; });
+            //  f({ |
+            if (!fullTypeCheck) {
+                for (var i = 0, n = candidates.length; i < n; i++) {
+                    if (signatureHasCorrectArity(node, candidates[i])) {
+                        return candidates[i];
+                    }
+                }
+            }
+
             return resolveErrorCall(node);
 
             // The candidate list orders groups in reverse, but within a group signatures are kept in declaration order

src/compiler/types.ts

@@ -1204,7 +1204,8 @@ module ts {
         }
 
         public static toString(parts: SymbolDisplayPart[]) {
-            return parts.map(p => p.text).join("");
+            var result = map(parts, p => p.text);
+            return result ? result.join("") : "";
         }
     }
 

src/services/services.ts

@@ -2162,9 +2162,16 @@ module ts {
             }
 
             // TODO: this is a hack for now, we need a proper walking mechanism to verify that we have the correct node
-            var mappedNode = getTouchingToken(sourceFile, TypeScript.end(node) - 1);
-            if (isPunctuation(mappedNode.kind)) {
-                mappedNode = mappedNode.parent;
+            var precedingToken = findTokenOnLeftOfPosition(sourceFile, TypeScript.end(node));
+            var mappedNode: Node;
+            if (!precedingToken) {
+                mappedNode = sourceFile;
+            }
+            else if (isPunctuation(precedingToken.kind)) {
+                mappedNode = precedingToken.parent;
+            }
+            else {
+                mappedNode = precedingToken;
             }
 
             Debug.assert(mappedNode, "Could not map a Fidelity node to an AST node");

tests/cases/fourslash/completionListInObjectLiteralThatIsParameterOfFunctionCall.ts

@@ -0,0 +1,11 @@
+/// <reference path='fourslash.ts'/>
+
+////function f(a: { xa: number; xb: number; }) { }
+////var xc;
+////f({
+////    /**/
+
+goTo.marker()
+verify.memberListContains('xa');
+verify.memberListContains('xb');
+verify.memberListCount(2);