perf(ivy): template type-check the entire program in 1 file if possible (#29698)

The template type-checking engine previously would assemble a type-checking
program by inserting Type Check Blocks (TCBs) into existing user files. This
approach proved expensive, as TypeScript has to re-parse and re-type-check
those files when processing the type-checking program.

Instead, a far more performant approach is to augment the program with a
single type-checking file, into which all TCBs are generated. Additionally,
type constructors are also inlined into this file.

This is not always possible - both TCBs and type constructors can sometimes
require inlining into user code, particularly if bound generic type
parameters are present, so the approach taken is actually a hybrid. These
operations are inlined if necessary, but are otherwise generated in a single
file.

It is critically important that the original program also include an empty
version of the type-checking file, otherwise the shape of the two programs
will be different and TypeScript will throw away all the old program
information. This leads to a painfully slow type checking pass, on the same
order as the original program creation. A shim to generate this file in the
original program is therefore added.

Testing strategy: this commit is largely a refactor with no externally
observable behavioral differences, and thus no tests are needed.

PR Close #29698

packages/compiler-cli/src/ngtsc/shims/index.ts

@@ -11,3 +11,4 @@
 export {FactoryGenerator, FactoryInfo, generatedFactoryTransform} from './src/factory_generator';
 export {GeneratedShimsHostWrapper, ShimGenerator} from './src/host';
 export {SummaryGenerator} from './src/summary_generator';
+export {TypeCheckShimGenerator} from './src/typecheck_shim';

packages/compiler-cli/src/ngtsc/shims/src/typecheck_shim.ts

@@ -0,0 +1,33 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import * as ts from 'typescript';
+
+import {AbsoluteFsPath} from '../../path';
+
+import {ShimGenerator} from './host';
+
+/**
+ * A `ShimGenerator` which adds a type-checking file to the `ts.Program`.
+ *
+ * This is a requirement for performant template type-checking, as TypeScript will only reuse
+ * information in the main program when creating the type-checking program if the set of files in
+ * each are exactly the same. Thus, the main program also needs the synthetic type-checking file.
+ */
+export class TypeCheckShimGenerator implements ShimGenerator {
+  constructor(private typeCheckFile: AbsoluteFsPath) {}
+
+  recognize(fileName: AbsoluteFsPath): boolean { return fileName === this.typeCheckFile; }
+
+  generate(genFileName: AbsoluteFsPath, readFile: (fileName: string) => ts.SourceFile | null):
+      ts.SourceFile|null {
+    return ts.createSourceFile(
+        genFileName, 'export const USED_FOR_NG_TYPE_CHECKING = true;', ts.ScriptTarget.Latest, true,
+        ts.ScriptKind.TS);
+  }
+}