refactor(compiler-cli): move the expression expression type checker (#16562)

The expression type checker moved from the language service
to the compiler-cli in preparation to using it to check
template expressions.

packages/compiler/src/ast_path.ts

@@ -0,0 +1,48 @@
+/**
+ * @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
+ */
+
+/**
+ * A path is an ordered set of elements. Typically a path is to  a
+ * particular offset in a source file. The head of the list is the top
+ * most node. The tail is the node that contains the offset directly.
+ *
+ * For example, the expresion `a + b + c` might have an ast that looks
+ * like:
+ *     +
+ *    / \
+ *   a   +
+ *      / \
+ *     b   c
+ *
+ * The path to the node at offset 9 would be `['+' at 1-10, '+' at 7-10,
+ * 'c' at 9-10]` and the path the node at offset 1 would be
+ * `['+' at 1-10, 'a' at 1-2]`.
+ */
+export class AstPath<T> {
+  constructor(private path: T[], public position: number = -1) {}
+
+  get empty(): boolean { return !this.path || !this.path.length; }
+  get head(): T|undefined { return this.path[0]; }
+  get tail(): T|undefined { return this.path[this.path.length - 1]; }
+
+  parentOf(node: T|undefined): T|undefined {
+    return node && this.path[this.path.indexOf(node) - 1];
+  }
+  childOf(node: T): T|undefined { return this.path[this.path.indexOf(node) + 1]; }
+
+  first<N extends T>(ctor: {new (...args: any[]): N}): N|undefined {
+    for (let i = this.path.length - 1; i >= 0; i--) {
+      let item = this.path[i];
+      if (item instanceof ctor) return <N>item;
+    }
+  }
+
+  push(node: T) { this.path.push(node); }
+
+  pop(): T { return this.path.pop() !; }
+}