For React Component class, we fill in missing type parameter and instantiate the constructor signature with the new type arguments.

Kanchalai Tanglertsampan · Yui T · commit 1e806cea01a0 · 2017-05-03T15:15:47.000-07:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -13438,7 +13438,18 @@ namespace ts {
                 }
             }
 
-            return getUnionType(map(signatures, getReturnTypeOfSignature), /*subtypeReduction*/ true);
+            const instantiatedSignatures = [];
+            for (const signature of signatures) {
+                if (signature.typeParameters) {
+                    const typeArguments = fillMissingTypeArguments(/*typeArguments*/ undefined, signature.typeParameters, /*minTypeArgumentCount*/ 0);
+                    instantiatedSignatures.push(getSignatureInstantiation(signature, typeArguments));
+                }
+                else {
+                    instantiatedSignatures.push(signature);
+                }
+            }
+
+            return getUnionType(map(instantiatedSignatures, getReturnTypeOfSignature), /*subtypeReduction*/ true);
         }
 
         /**

Original file line number	Diff line number	Diff line change
`@@ -13438,7 +13438,18 @@ namespace ts {`
`13438`	`13438`	`}`
`13439`	`13439`	`}`
`13440`	`13440`
`13441`		`- return getUnionType(map(signatures, getReturnTypeOfSignature), /subtypeReduction/ true);`
	`13441`	`+ const instantiatedSignatures = [];`
	`13442`	`+ for (const signature of signatures) {`
	`13443`	`+ if (signature.typeParameters) {`
	`13444`	`+ const typeArguments = fillMissingTypeArguments(/typeArguments/ undefined, signature.typeParameters, /minTypeArgumentCount/ 0);`
	`13445`	`+ instantiatedSignatures.push(getSignatureInstantiation(signature, typeArguments));`
	`13446`	`+ }`
	`13447`	`+ else {`
	`13448`	`+ instantiatedSignatures.push(signature);`
	`13449`	`+ }`
	`13450`	`+ }`
	`13451`	`+`
	`13452`	`+ return getUnionType(map(instantiatedSignatures, getReturnTypeOfSignature), /subtypeReduction/ true);`
`13442`	`13453`	`}`
`13443`	`13454`
`13444`	`13455`	`/**`