fix(ivy): support emitting a reference to interface declarations (#34849)

In #34021 the ngtsc compiler gained the ability to emit type parameter
constraints, which would generate imports for any type reference that
is used within the constraint. However, the `AbsoluteModuleStrategy`
reference emitter strategy did not consider interface declarations as a
valid declaration it can generate an import for, throwing an error
instead.

This commit fixes the issue by including interface declarations in the
logic that determines whether something is a declaration.

Fixes #34837

PR Close #34849

packages/compiler-cli/src/ngtsc/annotations/src/util.ts

@@ -190,7 +190,8 @@ export function toR3Reference(
     valueRef: Reference, typeRef: Reference, valueContext: ts.SourceFile,
     typeContext: ts.SourceFile, refEmitter: ReferenceEmitter): R3Reference {
   const value = refEmitter.emit(valueRef, valueContext);
-  const type = refEmitter.emit(typeRef, typeContext, ImportFlags.ForceNewImport);
+  const type = refEmitter.emit(
+      typeRef, typeContext, ImportFlags.ForceNewImport | ImportFlags.AllowTypeImports);
   if (value === null || type === null) {
     throw new Error(`Could not refer to ${ts.SyntaxKind[valueRef.node.kind]}`);
   }

packages/compiler-cli/src/ngtsc/imports/src/emitter.ts

@@ -12,7 +12,7 @@ import {UnifiedModulesHost} from '../../core/api';
 import {LogicalFileSystem, LogicalProjectPath, PathSegment, absoluteFromSourceFile, dirname, relative} from '../../file_system';
 import {stripExtension} from '../../file_system/src/util';
 import {ReflectionHost} from '../../reflection';
-import {getSourceFile, isDeclaration, nodeNameForError} from '../../util/src/typescript';
+import {getSourceFile, isDeclaration, isTypeDeclaration, nodeNameForError} from '../../util/src/typescript';
 
 import {findExportedNameOfNode} from './find_export';
 import {Reference} from './references';
@@ -40,6 +40,15 @@ export enum ImportFlags {
    * into TypeScript and type-checked (such as in template type-checking).
    */
   NoAliasing = 0x02,
+
+  /**
+   * Indicates that an import to a type-only declaration is allowed.
+   *
+   * For references that occur in type-positions, the referred declaration may be a type-only
+   * declaration that is not retained during emit. Including this flag allows to emit references to
+   * type-only declarations as used in e.g. template type-checking.
+   */
+  AllowTypeImports = 0x04,
 }
 
 /**
@@ -61,7 +70,7 @@ export interface ReferenceEmitStrategy {
    *
    * @param ref the `Reference` for which to generate an expression
    * @param context the source file in which the `Expression` must be valid
-   * @param importMode a flag which controls whether imports should be generated or not
+   * @param importFlags a flag which controls whether imports should be generated or not
    * @returns an `Expression` which refers to the `Reference`, or `null` if none can be generated
    */
   emit(ref: Reference, context: ts.SourceFile, importFlags: ImportFlags): Expression|null;
@@ -133,14 +142,18 @@ export class AbsoluteModuleStrategy implements ReferenceEmitStrategy {
       protected program: ts.Program, protected checker: ts.TypeChecker,
       protected moduleResolver: ModuleResolver, private reflectionHost: ReflectionHost) {}
 
-  emit(ref: Reference<ts.Node>, context: ts.SourceFile): Expression|null {
+  emit(ref: Reference<ts.Node>, context: ts.SourceFile, importFlags: ImportFlags): Expression|null {
     if (ref.bestGuessOwningModule === null) {
       // There is no module name available for this Reference, meaning it was arrived at via a
       // relative path.
       return null;
     } else if (!isDeclaration(ref.node)) {
       // It's not possible to import something which isn't a declaration.
-      throw new Error('Debug assert: importing a Reference to non-declaration?');
+      throw new Error(
+          `Debug assert: unable to import a Reference to non-declaration of type ${ts.SyntaxKind[ref.node.kind]}.`);
+    } else if ((importFlags & ImportFlags.AllowTypeImports) === 0 && isTypeDeclaration(ref.node)) {
+      throw new Error(
+          `Importing a type-only declaration of type ${ts.SyntaxKind[ref.node.kind]} in a value position is not allowed.`);
     }
 
     // Try to find the exported name of the declaration, if one is available.

packages/compiler-cli/src/ngtsc/imports/test/emitter_spec.ts

@@ -8,18 +8,128 @@
 import {ExternalExpr} from '@angular/compiler';
 import * as ts from 'typescript';
 
-import {LogicalFileSystem, absoluteFrom} from '../../file_system';
-import {runInEachFileSystem} from '../../file_system/testing';
+import {LogicalFileSystem, absoluteFrom as _} from '../../file_system';
+import {TestFile, runInEachFileSystem} from '../../file_system/testing';
 import {Declaration, TypeScriptReflectionHost} from '../../reflection';
 import {getDeclaration, makeProgram} from '../../testing';
-import {LogicalProjectStrategy} from '../src/emitter';
+import {AbsoluteModuleStrategy, ImportFlags, LogicalProjectStrategy} from '../src/emitter';
 import {Reference} from '../src/references';
+import {ModuleResolver} from '../src/resolver';
 
 runInEachFileSystem(() => {
-  describe('LogicalProjectStrategy', () => {
-    let _: typeof absoluteFrom;
-    beforeEach(() => _ = absoluteFrom);
+  describe('AbsoluteModuleStrategy', () => {
+    function makeStrategy(files: TestFile[]) {
+      const {program, host} = makeProgram(files);
+      const checker = program.getTypeChecker();
+      const moduleResolver = new ModuleResolver(
+          program, program.getCompilerOptions(), host, /* moduleResolutionCache */ null);
+      const strategy = new AbsoluteModuleStrategy(
+          program, checker, moduleResolver, new TypeScriptReflectionHost(checker));
 
+      return {strategy, program};
+    }
+
+    it('should not generate an import for a reference without owning module', () => {
+      const {strategy, program} = makeStrategy([
+        {
+          name: _('/node_modules/external.d.ts'),
+          contents: `export declare class Foo {}`,
+        },
+        {
+          name: _('/context.ts'),
+          contents: 'export class Context {}',
+        },
+      ]);
+      const decl =
+          getDeclaration(program, _('/node_modules/external.d.ts'), 'Foo', ts.isClassDeclaration);
+      const context = program.getSourceFile(_('/context.ts')) !;
+
+      const reference = new Reference(decl);
+      const emitted = strategy.emit(reference, context, ImportFlags.None);
+      expect(emitted).toBeNull();
+    });
+
+    it('should generate an import using the exported name of the declaration', () => {
+      const {strategy, program} = makeStrategy([
+        {
+          name: _('/node_modules/external.d.ts'),
+          contents: `
+            declare class Foo {}
+            export {Foo as Bar};
+          `,
+        },
+        {
+          name: _('/context.ts'),
+          contents: 'export class Context {}',
+        },
+      ]);
+      const decl =
+          getDeclaration(program, _('/node_modules/external.d.ts'), 'Foo', ts.isClassDeclaration);
+      const context = program.getSourceFile(_('/context.ts')) !;
+
+      const reference = new Reference(decl, {
+        specifier: 'external',
+        resolutionContext: context.fileName,
+      });
+      const emitted = strategy.emit(reference, context, ImportFlags.None);
+      if (!(emitted instanceof ExternalExpr)) {
+        return fail('Reference should be emitted as ExternalExpr');
+      }
+      expect(emitted.value.name).toEqual('Bar');
+      expect(emitted.value.moduleName).toEqual('external');
+    });
+
+    it('should throw when generating an import to a type-only declaration when not allowed', () => {
+      const {strategy, program} = makeStrategy([
+        {
+          name: _('/node_modules/external.d.ts'),
+          contents: `export declare interface Foo {}`,
+        },
+        {
+          name: _('/context.ts'),
+          contents: 'export class Context {}',
+        },
+      ]);
+      const decl = getDeclaration(
+          program, _('/node_modules/external.d.ts'), 'Foo', ts.isInterfaceDeclaration);
+      const context = program.getSourceFile(_('/context.ts')) !;
+
+      const reference = new Reference(decl, {
+        specifier: 'external',
+        resolutionContext: context.fileName,
+      });
+      expect(() => strategy.emit(reference, context, ImportFlags.None))
+          .toThrowError(
+              'Importing a type-only declaration of type InterfaceDeclaration in a value position is not allowed.');
+    });
+
+    it('should generate an import to a type-only declaration when allowed', () => {
+      const {strategy, program} = makeStrategy([
+        {
+          name: _('/node_modules/external.d.ts'),
+          contents: `export declare interface Foo {}`,
+        },
+        {
+          name: _('/context.ts'),
+          contents: 'export class Context {}',
+        },
+      ]);
+      const decl = getDeclaration(
+          program, _('/node_modules/external.d.ts'), 'Foo', ts.isInterfaceDeclaration);
+      const context = program.getSourceFile(_('/context.ts')) !;
+
+      const reference =
+          new Reference(decl, {specifier: 'external', resolutionContext: context.fileName});
+      const emitted = strategy.emit(reference, context, ImportFlags.AllowTypeImports);
+      if (!(emitted instanceof ExternalExpr)) {
+        return fail('Reference should be emitted as ExternalExpr');
+      }
+      expect(emitted.value.name).toEqual('Foo');
+      expect(emitted.value.moduleName).toEqual('external');
+    });
+  });
+
+  describe('LogicalProjectStrategy', () => {
     it('should enumerate exports with the ReflectionHost', () => {
       // Use a modified ReflectionHost that prefixes all export names that it enumerates.
       class TestHost extends TypeScriptReflectionHost {

packages/compiler-cli/src/ngtsc/testing/src/utils.ts

@@ -76,7 +76,9 @@ export function getDeclaration<T extends ts.Declaration>(
             chosenDecl = decl;
           }
         });
-      } else if (ts.isClassDeclaration(node) || ts.isFunctionDeclaration(node)) {
+      } else if (
+          ts.isClassDeclaration(node) || ts.isFunctionDeclaration(node) ||
+          ts.isInterfaceDeclaration(node)) {
         if (node.name !== undefined && node.name.text === name) {
           chosenDecl = node;
         }

packages/compiler-cli/src/ngtsc/typecheck/src/environment.ts

@@ -222,7 +222,8 @@ export class Environment {
    * This may involve importing the node into the file if it's not declared there already.
    */
   referenceType(ref: Reference): ts.TypeNode {
-    const ngExpr = this.refEmitter.emit(ref, this.contextFile, ImportFlags.NoAliasing);
+    const ngExpr = this.refEmitter.emit(
+        ref, this.contextFile, ImportFlags.NoAliasing | ImportFlags.AllowTypeImports);
 
     // Create an `ExpressionType` from the `Expression` and translate it via `translateType`.
     // TODO(alxhub): support references to types with generic arguments in a clean way.

packages/compiler-cli/src/ngtsc/typecheck/test/type_parameter_emitter_spec.ts

@@ -162,5 +162,53 @@ runInEachFileSystem(() => {
           .toThrowError('A type reference to emit must be imported from an absolute module');
     });
 
+    it('can emit references to interfaces', () => {
+      const additionalFiles: TestFile[] = [{
+        name: absoluteFrom('/node_modules/types/index.d.ts'),
+        contents: `export declare interface MyInterface {}`,
+      }];
+      const emitter = createEmitter(
+          `
+          import {MyInterface} from 'types';
+
+          export class TestClass<T extends MyInterface> {}`,
+          additionalFiles);
+
+      expect(emitter.canEmit()).toBe(true);
+      expect(emit(emitter)).toEqual('<T extends test.MyInterface>');
+    });
+
+    it('can emit references to enums', () => {
+      const additionalFiles: TestFile[] = [{
+        name: absoluteFrom('/node_modules/types/index.d.ts'),
+        contents: `export declare enum MyEnum {}`,
+      }];
+      const emitter = createEmitter(
+          `
+          import {MyEnum} from 'types';
+
+          export class TestClass<T extends MyEnum> {}`,
+          additionalFiles);
+
+      expect(emitter.canEmit()).toBe(true);
+      expect(emit(emitter)).toEqual('<T extends test.MyEnum>');
+    });
+
+    it('can emit references to type aliases', () => {
+      const additionalFiles: TestFile[] = [{
+        name: absoluteFrom('/node_modules/types/index.d.ts'),
+        contents: `export declare type MyType = string;`,
+      }];
+      const emitter = createEmitter(
+          `
+          import {MyType} from 'types';
+
+          export class TestClass<T extends MyType> {}`,
+          additionalFiles);
+
+      expect(emitter.canEmit()).toBe(true);
+      expect(emit(emitter)).toEqual('<T extends test.MyType>');
+    });
+
   });
 });

packages/compiler-cli/src/ngtsc/util/src/typescript.ts

@@ -67,9 +67,19 @@ export function identifierOfNode(decl: ts.Node & {name?: ts.Node}): ts.Identifie
 }
 
 export function isDeclaration(node: ts.Node): node is ts.Declaration {
-  return ts.isEnumDeclaration(node) || ts.isClassDeclaration(node) ||
-      ts.isFunctionDeclaration(node) || ts.isVariableDeclaration(node) ||
-      ts.isTypeAliasDeclaration(node);
+  return isValueDeclaration(node) || isTypeDeclaration(node);
+}
+
+export function isValueDeclaration(node: ts.Node): node is ts.ClassDeclaration|
+    ts.FunctionDeclaration|ts.VariableDeclaration {
+  return ts.isClassDeclaration(node) || ts.isFunctionDeclaration(node) ||
+      ts.isVariableDeclaration(node);
+}
+
+export function isTypeDeclaration(node: ts.Node): node is ts.EnumDeclaration|
+    ts.TypeAliasDeclaration|ts.InterfaceDeclaration {
+  return ts.isEnumDeclaration(node) || ts.isTypeAliasDeclaration(node) ||
+      ts.isInterfaceDeclaration(node);
 }
 
 export function isExported(node: ts.Declaration): boolean {