Stop analyzing loop branches when declared type is seen

ahejlsberg · ahejlsberg · commit c9a3ea6fe0fd · 2016-05-11T12:49:42.000-07:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -7780,16 +7780,15 @@ namespace ts {
                     if (cache[key]) {
                         return cache[key];
                     }
-                    // If the type at a particular antecedent path is the declared type and the
-                    // reference is known to always be assigned (i.e. when declared and initial types
-                    // are the same), there is no reason to process more antecedents since the only
-                    // possible outcome is subtypes that will be removed in the final union type anyway.
-                    if (type === declaredType && declaredType === initialType) {
-                        return cache[key] = type;
-                    }
                     if (!contains(antecedentTypes, type)) {
                         antecedentTypes.push(type);
                     }
+                    // If the type at a particular antecedent path is the declared type there is no
+                    // reason to process more antecedents since the only possible outcome is subtypes
+                    // that will be removed in the final union type anyway.
+                    if (type === declaredType) {
+                        break;
+                    }
                 }
                 return cache[key] = getUnionType(antecedentTypes);
             }

Original file line number	Diff line number	Diff line change
`@@ -7780,16 +7780,15 @@ namespace ts {`
`7780`	`7780`	`if (cache[key]) {`
`7781`	`7781`	`return cache[key];`
`7782`	`7782`	`}`
`7783`		`- // If the type at a particular antecedent path is the declared type and the`
`7784`		`- // reference is known to always be assigned (i.e. when declared and initial types`
`7785`		`- // are the same), there is no reason to process more antecedents since the only`
`7786`		`- // possible outcome is subtypes that will be removed in the final union type anyway.`
`7787`		`- if (type === declaredType && declaredType === initialType) {`
`7788`		`- return cache[key] = type;`
`7789`		`- }`
`7790`	`7783`	`if (!contains(antecedentTypes, type)) {`
`7791`	`7784`	`antecedentTypes.push(type);`
`7792`	`7785`	`}`
	`7786`	`+ // If the type at a particular antecedent path is the declared type there is no`
	`7787`	`+ // reason to process more antecedents since the only possible outcome is subtypes`
	`7788`	`+ // that will be removed in the final union type anyway.`
	`7789`	`+ if (type === declaredType) {`
	`7790`	`+ break;`
	`7791`	`+ }`
`7793`	`7792`	`}`
`7794`	`7793`	`return cache[key] = getUnionType(antecedentTypes);`
`7795`	`7794`	`}`