feat(compiler): support a non-null postfix assert (#16672)

Template expressions can now use a post-fix `!` operator
that asserts the target of the operator is not null. This is
similar to the TypeScript non-null assert operator. Expressions
generated in factories will be generated with the non-null assert
operator.

Closes: #10855

packages/compiler/src/expression_parser/ast.ts

@@ -166,6 +166,13 @@ export class PrefixNot extends AST {
   }
 }
 
+export class NonNullAssert extends AST {
+  constructor(span: ParseSpan, public expression: AST) { super(span); }
+  visit(visitor: AstVisitor, context: any = null): any {
+    return visitor.visitNonNullAssert(this, context);
+  }
+}
+
 export class MethodCall extends AST {
   constructor(span: ParseSpan, public receiver: AST, public name: string, public args: any[]) {
     super(span);
@@ -222,6 +229,7 @@ export interface AstVisitor {
   visitMethodCall(ast: MethodCall, context: any): any;
   visitPipe(ast: BindingPipe, context: any): any;
   visitPrefixNot(ast: PrefixNot, context: any): any;
+  visitNonNullAssert(ast: NonNullAssert, context: any): any;
   visitPropertyRead(ast: PropertyRead, context: any): any;
   visitPropertyWrite(ast: PropertyWrite, context: any): any;
   visitQuote(ast: Quote, context: any): any;
@@ -230,7 +238,7 @@ export interface AstVisitor {
   visit?(ast: AST, context?: any): any;
 }
 
-export class NullAstVisitor {
+export class NullAstVisitor implements AstVisitor {
   visitBinary(ast: Binary, context: any): any {}
   visitChain(ast: Chain, context: any): any {}
   visitConditional(ast: Conditional, context: any): any {}
@@ -245,6 +253,7 @@ export class NullAstVisitor {
   visitMethodCall(ast: MethodCall, context: any): any {}
   visitPipe(ast: BindingPipe, context: any): any {}
   visitPrefixNot(ast: PrefixNot, context: any): any {}
+  visitNonNullAssert(ast: NonNullAssert, context: any): any {}
   visitPropertyRead(ast: PropertyRead, context: any): any {}
   visitPropertyWrite(ast: PropertyWrite, context: any): any {}
   visitQuote(ast: Quote, context: any): any {}
@@ -303,6 +312,10 @@ export class RecursiveAstVisitor implements AstVisitor {
     ast.expression.visit(this);
     return null;
   }
+  visitNonNullAssert(ast: NonNullAssert, context: any): any {
+    ast.expression.visit(this);
+    return null;
+  }
   visitPropertyRead(ast: PropertyRead, context: any): any {
     ast.receiver.visit(this);
     return null;
@@ -379,6 +392,10 @@ export class AstTransformer implements AstVisitor {
     return new PrefixNot(ast.span, ast.expression.visit(this));
   }
 
+  visitNonNullAssert(ast: NonNullAssert, context: any): AST {
+    return new NonNullAssert(ast.span, ast.expression.visit(this));
+  }
+
   visitConditional(ast: Conditional, context: any): AST {
     return new Conditional(
         ast.span, ast.condition.visit(this), ast.trueExp.visit(this), ast.falseExp.visit(this));
@@ -461,6 +478,7 @@ export function visitAstChildren(ast: AST, visitor: AstVisitor, context?: any) {
       visitAll(ast.args);
     },
     visitPrefixNot(ast) { visit(ast.expression); },
+    visitNonNullAssert(ast) { visit(ast.expression); },
     visitPropertyRead(ast) { visit(ast.receiver); },
     visitPropertyWrite(ast) {
       visit(ast.receiver);

packages/compiler/src/expression_parser/parser.ts

@@ -10,7 +10,8 @@ import * as chars from '../chars';
 import {CompilerInjectable} from '../injectable';
 import {DEFAULT_INTERPOLATION_CONFIG, InterpolationConfig} from '../ml_parser/interpolation_config';
 import {escapeRegExp} from '../util';
-import {AST, ASTWithSource, AstVisitor, Binary, BindingPipe, Chain, Conditional, EmptyExpr, FunctionCall, ImplicitReceiver, Interpolation, KeyedRead, KeyedWrite, LiteralArray, LiteralMap, LiteralPrimitive, MethodCall, ParseSpan, ParserError, PrefixNot, PropertyRead, PropertyWrite, Quote, SafeMethodCall, SafePropertyRead, TemplateBinding} from './ast';
+
+import {AST, ASTWithSource, AstVisitor, Binary, BindingPipe, Chain, Conditional, EmptyExpr, FunctionCall, ImplicitReceiver, Interpolation, KeyedRead, KeyedWrite, LiteralArray, LiteralMap, LiteralPrimitive, MethodCall, NonNullAssert, ParseSpan, ParserError, PrefixNot, PropertyRead, PropertyWrite, Quote, SafeMethodCall, SafePropertyRead, TemplateBinding} from './ast';
 import {EOF, Lexer, Token, TokenType, isIdentifier, isQuote} from './lexer';
 
 
@@ -523,6 +524,9 @@ export class _ParseAST {
         this.expectCharacter(chars.$RPAREN);
         result = new FunctionCall(this.span(result.span.start), result, args);
 
+      } else if (this.optionalOperator('!')) {
+        result = new NonNullAssert(this.span(result.span.start), result);
+
       } else {
         return result;
       }
@@ -811,6 +815,8 @@ class SimpleExpressionChecker implements AstVisitor {
 
   visitPrefixNot(ast: PrefixNot, context: any) {}
 
+  visitNonNullAssert(ast: NonNullAssert, context: any) {}
+
   visitConditional(ast: Conditional, context: any) {}
 
   visitPipe(ast: BindingPipe, context: any) { this.errors.push('pipes'); }