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Recognize unresolved type-only default imports during alias lookup #64896

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f965789
Preserve type-only aliases when module resolution fails
Andarist Oct 21, 2026
dcd66eb
Add baseline coverage for type-only import reexports
Andarist Oct 21, 2026
1181940
Compute type-only alias markers before propagating them
Andarist Oct 21, 2026
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15 changes: 8 additions & 7 deletions tsc/internal/checker/checker.go
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Expand Up @@ -2200,6 +2200,8 @@ func isPropertyImmediatelyReferencedWithinDeclaration(declaration *ast.Node, usa
func (c *Checker) getTypeOnlyAliasDeclaration(symbol *ast.Symbol) *ast.Node {
if symbol.Flags()&ast.SymbolFlagsAlias != 0 {
c.resolveAlias(symbol)
// Alias resolution may fail before recording the declaration's type-only marker.
c.markSymbolOfAliasDeclarationIfTypeOnly(core.FirstOrNil(symbol.Declarations()), nil)
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return c.aliasSymbolLinks.Get(symbol).typeOnlyDeclaration
}
return nil
Expand All @@ -2209,12 +2211,10 @@ func (c *Checker) getTypeOnlyAliasDeclaration(symbol *ast.Symbol) *ast.Node {
// the symbol for the given meaning
func (c *Checker) getTypeOnlyAliasDeclarationEx(symbol *ast.Symbol, meaning ast.SymbolFlags) *ast.Node {
for symbol.Flags()&ast.SymbolFlagsAlias != 0 && symbol.Flags()&meaning == 0 {
resolved := c.resolveAlias(symbol)
links := c.aliasSymbolLinks.Get(symbol)
if links.typeOnlyDeclaration != nil {
return links.typeOnlyDeclaration
if declaration := c.getTypeOnlyAliasDeclaration(symbol); declaration != nil {
return declaration
}
symbol = resolved
symbol = c.resolveAlias(symbol)
}
return nil
}
Expand Down Expand Up @@ -16700,9 +16700,10 @@ func (c *Checker) resolveAlias(symbol *ast.Symbol) *ast.Symbol {

func (c *Checker) resolveIndirectionAlias(source *ast.Symbol, target *ast.Symbol) *ast.Symbol {
result := c.getMergedSymbol(c.resolveAlias(target))
if targetLinks := c.aliasSymbolLinks.Get(target); targetLinks.typeOnlyDeclaration != nil {
// Compute the target's type-only marker before propagating it, even if alias resolution failed.
if typeOnlyDeclaration := c.getTypeOnlyAliasDeclaration(target); typeOnlyDeclaration != nil {
if sourceLinks := c.aliasSymbolLinks.Get(source); sourceLinks.typeOnlyDeclaration == nil {
sourceLinks.typeOnlyDeclaration = targetLinks.typeOnlyDeclaration
sourceLinks.typeOnlyDeclaration = typeOnlyDeclaration
}
}
return result
Expand Down
40 changes: 40 additions & 0 deletions .../reference/compiler/decoratorMetadataTypeOnlyUnresolvedImport(module=commonjs).errors.txt
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@@ -0,0 +1,40 @@
decoratorMetadataTypeOnlyUnresolvedImport.ts(1,22): error TS2307: Cannot find module './missing-default' or its corresponding type declarations.
decoratorMetadataTypeOnlyUnresolvedImport.ts(2,26): error TS2307: Cannot find module './missing-named' or its corresponding type declarations.
decoratorMetadataTypeOnlyUnresolvedImport.ts(3,37): error TS2307: Cannot find module './missing-default-specifier' or its corresponding type declarations.
decoratorMetadataTypeOnlyUnresolvedImport.ts(13,11): error TS1361: 'Foo' cannot be used as a value because it was imported using 'import type'.
decoratorMetadataTypeOnlyUnresolvedImport.ts(14,11): error TS1361: 'Bar' cannot be used as a value because it was imported using 'import type'.
decoratorMetadataTypeOnlyUnresolvedImport.ts(15,11): error TS1361: 'Baz' cannot be used as a value because it was imported using 'import type'.


==== decoratorMetadataTypeOnlyUnresolvedImport.ts (6 errors) ====
import type Foo from "./missing-default";
~~~~~~~~~~~~~~~~~~~
!!! error TS2307: Cannot find module './missing-default' or its corresponding type declarations.
import { type Bar } from "./missing-named";
~~~~~~~~~~~~~~~~~
!!! error TS2307: Cannot find module './missing-named' or its corresponding type declarations.
import type { default as Baz } from "./missing-default-specifier";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
!!! error TS2307: Cannot find module './missing-default-specifier' or its corresponding type declarations.

function dec(_target: unknown, _key: unknown) {}

class C {
@dec a!: Foo;
@dec b!: Bar;
@dec c!: Baz;
}

const x = Foo;
~~~
!!! error TS1361: 'Foo' cannot be used as a value because it was imported using 'import type'.
!!! related TS1376 decoratorMetadataTypeOnlyUnresolvedImport.ts:1:8: 'Foo' was imported here.
const y = Bar;
~~~
!!! error TS1361: 'Bar' cannot be used as a value because it was imported using 'import type'.
!!! related TS1376 decoratorMetadataTypeOnlyUnresolvedImport.ts:2:10: 'Bar' was imported here.
const z = Baz;
~~~
!!! error TS1361: 'Baz' cannot be used as a value because it was imported using 'import type'.
!!! related TS1376 decoratorMetadataTypeOnlyUnresolvedImport.ts:3:15: 'Baz' was imported here.

50 changes: 50 additions & 0 deletions ...aselines/reference/compiler/decoratorMetadataTypeOnlyUnresolvedImport(module=commonjs).js
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@@ -0,0 +1,50 @@
//// [tests/cases/compiler/decoratorMetadataTypeOnlyUnresolvedImport.ts] ////

//// [decoratorMetadataTypeOnlyUnresolvedImport.ts]
import type Foo from "./missing-default";
import { type Bar } from "./missing-named";
import type { default as Baz } from "./missing-default-specifier";

function dec(_target: unknown, _key: unknown) {}

class C {
@dec a!: Foo;
@dec b!: Bar;
@dec c!: Baz;
}

const x = Foo;
const y = Bar;
const z = Baz;


//// [decoratorMetadataTypeOnlyUnresolvedImport.js]
"use strict";
var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {
var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;
if (typeof Reflect === "object" && typeof Reflect.decorate === "function") r = Reflect.decorate(decorators, target, key, desc);
else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
return c > 3 && r && Object.defineProperty(target, key, r), r;
};
var __metadata = (this && this.__metadata) || function (k, v) {
if (typeof Reflect === "object" && typeof Reflect.metadata === "function") return Reflect.metadata(k, v);
};
Object.defineProperty(exports, "__esModule", { value: true });
function dec(_target, _key) { }
class C {
}
__decorate([
dec,
__metadata("design:type", Object)
], C.prototype, "a", void 0);
__decorate([
dec,
__metadata("design:type", Object)
], C.prototype, "b", void 0);
__decorate([
dec,
__metadata("design:type", Object)
], C.prototype, "c", void 0);
const x = Foo;
const y = Bar;
const z = Baz;
48 changes: 48 additions & 0 deletions ...nes/reference/compiler/decoratorMetadataTypeOnlyUnresolvedImport(module=commonjs).symbols
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//// [tests/cases/compiler/decoratorMetadataTypeOnlyUnresolvedImport.ts] ////

=== decoratorMetadataTypeOnlyUnresolvedImport.ts ===
import type Foo from "./missing-default";
>Foo : Symbol(Foo, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 0, 6))

import { type Bar } from "./missing-named";
>Bar : Symbol(Bar, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 1, 8))

import type { default as Baz } from "./missing-default-specifier";
>Baz : Symbol(Baz, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 2, 13))

function dec(_target: unknown, _key: unknown) {}
>dec : Symbol(dec, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 2, 66))
>_target : Symbol(_target, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 4, 13))
>_key : Symbol(_key, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 4, 30))

class C {
>C : Symbol(C, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 4, 48))

@dec a!: Foo;
>dec : Symbol(dec, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 2, 66))
>a : Symbol(C.a, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 6, 9))
>Foo : Symbol(Foo, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 0, 6))

@dec b!: Bar;
>dec : Symbol(dec, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 2, 66))
>b : Symbol(C.b, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 7, 17))
>Bar : Symbol(Bar, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 1, 8))

@dec c!: Baz;
>dec : Symbol(dec, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 2, 66))
>c : Symbol(C.c, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 8, 17))
>Baz : Symbol(Baz, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 2, 13))
}

const x = Foo;
>x : Symbol(x, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 12, 5))
>Foo : Symbol(Foo, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 0, 6))

const y = Bar;
>y : Symbol(y, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 13, 5))
>Bar : Symbol(Bar, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 1, 8))

const z = Baz;
>z : Symbol(z, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 14, 5))
>Baz : Symbol(Baz, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 2, 13))

46 changes: 46 additions & 0 deletions ...lines/reference/compiler/decoratorMetadataTypeOnlyUnresolvedImport(module=commonjs).types
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//// [tests/cases/compiler/decoratorMetadataTypeOnlyUnresolvedImport.ts] ////

=== decoratorMetadataTypeOnlyUnresolvedImport.ts ===
import type Foo from "./missing-default";
>Foo : any

import { type Bar } from "./missing-named";
>Bar : any

import type { default as Baz } from "./missing-default-specifier";
>default : any
>Baz : any

function dec(_target: unknown, _key: unknown) {}
>dec : (_target: unknown, _key: unknown) => void
>_target : unknown
>_key : unknown

class C {
>C : C

@dec a!: Foo;
>dec : (_target: unknown, _key: unknown) => void
>a : Foo

@dec b!: Bar;
>dec : (_target: unknown, _key: unknown) => void
>b : Bar

@dec c!: Baz;
>dec : (_target: unknown, _key: unknown) => void
>c : Baz
}

const x = Foo;
>x : any
>Foo : any

const y = Bar;
>y : any
>Bar : any

const z = Baz;
>z : any
>Baz : any

40 changes: 40 additions & 0 deletions ...es/reference/compiler/decoratorMetadataTypeOnlyUnresolvedImport(module=esnext).errors.txt
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@@ -0,0 +1,40 @@
decoratorMetadataTypeOnlyUnresolvedImport.ts(1,22): error TS2307: Cannot find module './missing-default' or its corresponding type declarations.
decoratorMetadataTypeOnlyUnresolvedImport.ts(2,26): error TS2307: Cannot find module './missing-named' or its corresponding type declarations.
decoratorMetadataTypeOnlyUnresolvedImport.ts(3,37): error TS2307: Cannot find module './missing-default-specifier' or its corresponding type declarations.
decoratorMetadataTypeOnlyUnresolvedImport.ts(13,11): error TS1361: 'Foo' cannot be used as a value because it was imported using 'import type'.
decoratorMetadataTypeOnlyUnresolvedImport.ts(14,11): error TS1361: 'Bar' cannot be used as a value because it was imported using 'import type'.
decoratorMetadataTypeOnlyUnresolvedImport.ts(15,11): error TS1361: 'Baz' cannot be used as a value because it was imported using 'import type'.


==== decoratorMetadataTypeOnlyUnresolvedImport.ts (6 errors) ====
import type Foo from "./missing-default";
~~~~~~~~~~~~~~~~~~~
!!! error TS2307: Cannot find module './missing-default' or its corresponding type declarations.
import { type Bar } from "./missing-named";
~~~~~~~~~~~~~~~~~
!!! error TS2307: Cannot find module './missing-named' or its corresponding type declarations.
import type { default as Baz } from "./missing-default-specifier";
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
!!! error TS2307: Cannot find module './missing-default-specifier' or its corresponding type declarations.

function dec(_target: unknown, _key: unknown) {}

class C {
@dec a!: Foo;
@dec b!: Bar;
@dec c!: Baz;
}

const x = Foo;
~~~
!!! error TS1361: 'Foo' cannot be used as a value because it was imported using 'import type'.
!!! related TS1376 decoratorMetadataTypeOnlyUnresolvedImport.ts:1:8: 'Foo' was imported here.
const y = Bar;
~~~
!!! error TS1361: 'Bar' cannot be used as a value because it was imported using 'import type'.
!!! related TS1376 decoratorMetadataTypeOnlyUnresolvedImport.ts:2:10: 'Bar' was imported here.
const z = Baz;
~~~
!!! error TS1361: 'Baz' cannot be used as a value because it was imported using 'import type'.
!!! related TS1376 decoratorMetadataTypeOnlyUnresolvedImport.ts:3:15: 'Baz' was imported here.

49 changes: 49 additions & 0 deletions .../baselines/reference/compiler/decoratorMetadataTypeOnlyUnresolvedImport(module=esnext).js
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//// [tests/cases/compiler/decoratorMetadataTypeOnlyUnresolvedImport.ts] ////

//// [decoratorMetadataTypeOnlyUnresolvedImport.ts]
import type Foo from "./missing-default";
import { type Bar } from "./missing-named";
import type { default as Baz } from "./missing-default-specifier";

function dec(_target: unknown, _key: unknown) {}

class C {
@dec a!: Foo;
@dec b!: Bar;
@dec c!: Baz;
}

const x = Foo;
const y = Bar;
const z = Baz;


//// [decoratorMetadataTypeOnlyUnresolvedImport.js]
var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {
var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;
if (typeof Reflect === "object" && typeof Reflect.decorate === "function") r = Reflect.decorate(decorators, target, key, desc);
else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
return c > 3 && r && Object.defineProperty(target, key, r), r;
};
var __metadata = (this && this.__metadata) || function (k, v) {
if (typeof Reflect === "object" && typeof Reflect.metadata === "function") return Reflect.metadata(k, v);
};
function dec(_target, _key) { }
class C {
}
__decorate([
dec,
__metadata("design:type", Object)
], C.prototype, "a", void 0);
__decorate([
dec,
__metadata("design:type", Object)
], C.prototype, "b", void 0);
__decorate([
dec,
__metadata("design:type", Object)
], C.prototype, "c", void 0);
const x = Foo;
const y = Bar;
const z = Baz;
export {};
48 changes: 48 additions & 0 deletions ...lines/reference/compiler/decoratorMetadataTypeOnlyUnresolvedImport(module=esnext).symbols
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@@ -0,0 +1,48 @@
//// [tests/cases/compiler/decoratorMetadataTypeOnlyUnresolvedImport.ts] ////

=== decoratorMetadataTypeOnlyUnresolvedImport.ts ===
import type Foo from "./missing-default";
>Foo : Symbol(Foo, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 0, 6))

import { type Bar } from "./missing-named";
>Bar : Symbol(Bar, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 1, 8))

import type { default as Baz } from "./missing-default-specifier";
>Baz : Symbol(Baz, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 2, 13))

function dec(_target: unknown, _key: unknown) {}
>dec : Symbol(dec, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 2, 66))
>_target : Symbol(_target, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 4, 13))
>_key : Symbol(_key, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 4, 30))

class C {
>C : Symbol(C, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 4, 48))

@dec a!: Foo;
>dec : Symbol(dec, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 2, 66))
>a : Symbol(C.a, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 6, 9))
>Foo : Symbol(Foo, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 0, 6))

@dec b!: Bar;
>dec : Symbol(dec, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 2, 66))
>b : Symbol(C.b, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 7, 17))
>Bar : Symbol(Bar, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 1, 8))

@dec c!: Baz;
>dec : Symbol(dec, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 2, 66))
>c : Symbol(C.c, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 8, 17))
>Baz : Symbol(Baz, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 2, 13))
}

const x = Foo;
>x : Symbol(x, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 12, 5))
>Foo : Symbol(Foo, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 0, 6))

const y = Bar;
>y : Symbol(y, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 13, 5))
>Bar : Symbol(Bar, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 1, 8))

const z = Baz;
>z : Symbol(z, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 14, 5))
>Baz : Symbol(Baz, Decl(decoratorMetadataTypeOnlyUnresolvedImport.ts, 2, 13))

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