Add missing check in getTypeAtSwitchClause

ahejlsberg · ahejlsberg · commit c80f532e01a9 · 2018-10-08T09:59:47.000-07:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -14972,9 +14972,12 @@ namespace ts {
             }
 
             function getTypeAtSwitchClause(flow: FlowSwitchClause): FlowType {
+                const expr = flow.switchStatement.expression;
+                if (containsMatchingReferenceDiscriminant(reference, expr)) {
+                    return declaredType;
+                }
                 const flowType = getTypeAtFlowNode(flow.antecedent);
                 let type = getTypeFromFlowType(flowType);
-                const expr = flow.switchStatement.expression;
                 if (isMatchingReference(reference, expr)) {
                     type = narrowTypeBySwitchOnDiscriminant(type, flow.switchStatement, flow.clauseStart, flow.clauseEnd);
                 }

Original file line number	Diff line number	Diff line change
`@@ -14972,9 +14972,12 @@ namespace ts {`
`14972`	`14972`	`}`
`14973`	`14973`
`14974`	`14974`	`function getTypeAtSwitchClause(flow: FlowSwitchClause): FlowType {`
	`14975`	`+ const expr = flow.switchStatement.expression;`
	`14976`	`+ if (containsMatchingReferenceDiscriminant(reference, expr)) {`
	`14977`	`+ return declaredType;`
	`14978`	`+ }`
`14975`	`14979`	`const flowType = getTypeAtFlowNode(flow.antecedent);`
`14976`	`14980`	`let type = getTypeFromFlowType(flowType);`
`14977`		`- const expr = flow.switchStatement.expression;`
`14978`	`14981`	`if (isMatchingReference(reference, expr)) {`
`14979`	`14982`	`type = narrowTypeBySwitchOnDiscriminant(type, flow.switchStatement, flow.clauseStart, flow.clauseEnd);`
`14980`	`14983`	`}`