refactor(ivy): correctly type class declarations in ngtsc/ngcc (#29209)

Previously, several `ngtsc` and `ngcc` APIs dealing with class
declaration nodes used inconsistent types. For example, some methods of
the `DecoratorHandler` interface expected a `ts.Declaration` argument,
but actual `DecoratorHandler` implementations specified a stricter
`ts.ClassDeclaration` type.

As a result, the stricter methods would operate under the incorrect
assumption that their arguments were of type `ts.ClassDeclaration`,
while the actual arguments might be of different types (e.g. `ngcc`
would call them with `ts.FunctionDeclaration` or
`ts.VariableDeclaration` arguments, when compiling ES5 code).

Additionally, since we need those class declarations to be referenced in
other parts of the program, `ngtsc`/`ngcc` had to either repeatedly
check for `ts.isIdentifier(node.name)` or assume there was a `name`
identifier and use `node.name!`. While this assumption happens to be
true in the current implementation, working around type-checking is
error-prone (e.g. the assumption might stop being true in the future).

This commit fixes this by introducing a new type to be used for such
class declarations (`ts.Declaration & {name: ts.Identifier}`) and using
it consistently throughput the code.

PR Close #29209

packages/compiler-cli/src/ngtsc/imports/BUILD.bazel

@@ -11,6 +11,7 @@ ts_library(
         "//packages:types",
         "//packages/compiler",
         "//packages/compiler-cli/src/ngtsc/path",
+        "//packages/compiler-cli/src/ngtsc/reflection",
         "//packages/compiler-cli/src/ngtsc/util",
         "@npm//@types/node",
         "@npm//typescript",

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

@@ -9,6 +9,7 @@
 import {Expression, ExternalExpr} from '@angular/compiler';
 import * as ts from 'typescript';
 
+import {ClassDeclaration} from '../../reflection';
 import {FileToModuleHost, ReferenceEmitStrategy} from './emitter';
 import {ImportMode, Reference} from './references';
 
@@ -18,20 +19,16 @@ const CHARS_TO_ESCAPE = /[^a-zA-Z0-9/_]/g;
 export class AliasGenerator {
   constructor(private fileToModuleHost: FileToModuleHost) {}
 
-  aliasSymbolName(decl: ts.Declaration, context: ts.SourceFile): string {
-    if (!ts.isClassDeclaration(decl)) {
-      throw new Error(`Attempt to write an alias to something which isn't a class`);
-    }
-
+  aliasSymbolName(decl: ClassDeclaration, context: ts.SourceFile): string {
     // The declared module is used to get the name of the alias.
     const declModule =
         this.fileToModuleHost.fileNameToModuleName(decl.getSourceFile().fileName, context.fileName);
 
     const replaced = declModule.replace(CHARS_TO_ESCAPE, '_').replace(/\//g, '$');
-    return 'ɵng$' + replaced + '$$' + decl.name !.text;
+    return 'ɵng$' + replaced + '$$' + decl.name.text;
   }
 
-  aliasTo(decl: ts.Declaration, via: ts.SourceFile): Expression {
+  aliasTo(decl: ClassDeclaration, via: ts.SourceFile): Expression {
     const name = this.aliasSymbolName(decl, via);
     // viaModule is the module it'll actually be imported from.
     const moduleName = this.fileToModuleHost.fileNameToModuleName(via.fileName, via.fileName);