Only add unique inferences to candidate arrays

ahejlsberg · ahejlsberg · commit f59229bf2209 · 2018-09-26T06:54:37.000-07:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -1,6 +1,3 @@
-
-
-
 /* @internal */
 namespace ts {
     const ambientModuleSymbolRegex = /^".+"$/;
@@ -13553,10 +13550,10 @@ namespace ts {
                                 // We make contravariant inferences only if we are in a pure contravariant position,
                                 // i.e. only if we have not descended into a bivariant position.
                                 if (contravariant && !bivariant) {
-                                    inference.contraCandidates = append(inference.contraCandidates, candidate);
+                                    inference.contraCandidates = appendIfUnique(inference.contraCandidates, candidate);
                                 }
                                 else {
-                                    inference.candidates = append(inference.candidates, candidate);
+                                    inference.candidates = appendIfUnique(inference.candidates, candidate);
                                 }
                             }
                             if (!(priority & InferencePriority.ReturnType) && target.flags & TypeFlags.TypeParameter && !isTypeParameterAtTopLevel(originalTarget, <TypeParameter>target)) {

Original file line number	Diff line number	Diff line change
`@@ -1,6 +1,3 @@`
`1`		`-`
`2`		`-`
`3`		`-`
`4`	`1`	`/* @internal */`
`5`	`2`	`namespace ts {`
`6`	`3`	`const ambientModuleSymbolRegex = /^".+"$/;`
`@@ -13553,10 +13550,10 @@ namespace ts {`
`13553`	`13550`	`// We make contravariant inferences only if we are in a pure contravariant position,`
`13554`	`13551`	`// i.e. only if we have not descended into a bivariant position.`
`13555`	`13552`	`if (contravariant && !bivariant) {`
`13556`		`- inference.contraCandidates = append(inference.contraCandidates, candidate);`
	`13553`	`+ inference.contraCandidates = appendIfUnique(inference.contraCandidates, candidate);`
`13557`	`13554`	`}`
`13558`	`13555`	`else {`
`13559`		`- inference.candidates = append(inference.candidates, candidate);`
	`13556`	`+ inference.candidates = appendIfUnique(inference.candidates, candidate);`
`13560`	`13557`	`}`
`13561`	`13558`	`}`
`13562`	`13559`	`if (!(priority & InferencePriority.ReturnType) && target.flags & TypeFlags.TypeParameter && !isTypeParameterAtTopLevel(originalTarget, <TypeParameter>target)) {`