Cherry-pick PR #47136 into release-4.5 (#47379)

Component commits: e61702c Fix extract type crash Co-authored-by: Andrew Branch <andrew@wheream.io>
microsoft · Jan 12, 2022 · 0854a93 · 0854a93
1 parent a5ebd53
commit 0854a93
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diff --git a/src/services/refactors/extractType.ts b/src/services/refactors/extractType.ts
@@ -145,8 +145,8 @@ namespace ts.refactor {
             if (isTypeReferenceNode(node)) {
                 if (isIdentifier(node.typeName)) {
                     const symbol = checker.resolveName(node.typeName.text, node.typeName, SymbolFlags.TypeParameter, /* excludeGlobals */ true);
-                    if (symbol?.declarations) {
-                        const declaration = cast(first(symbol.declarations), isTypeParameterDeclaration);
+                    const declaration = tryCast(symbol?.declarations?.[0], isTypeParameterDeclaration);
+                    if (declaration) {
                         if (rangeContainsSkipTrivia(statement, declaration, file) && !rangeContainsSkipTrivia(selection, declaration, file)) {
                             pushIfUnique(result, declaration);
                         }

diff --git a/tests/cases/fourslash/extractTypeUnresolvedAlias.ts b/tests/cases/fourslash/extractTypeUnresolvedAlias.ts
@@ -0,0 +1,10 @@
+/// <reference path="fourslash.ts" />
+
+//// import {Renderer} from '';
+//// 
+//// export class X {
+////   constructor(renderer: /**/[|Renderer|]) {}
+//// }
+
+goTo.selectRange(test.ranges()[0]);
+verify.refactorAvailable("Extract type", "Extract to type alias");