Prior to this change, the unary + and - operators would be parsed as `x - 0`
and `0 - x` respectively. The runtime semantics of these expressions are
equivalent, however they may introduce inaccurate template type checking
errors as the literal type is lost, for example:
```ts
@Component({
  template: `<button [disabled]="isAdjacent(-1)"></button>`
})
export class Example {
  isAdjacent(direction: -1 | 1): boolean { return false; }
}
```
would incorrectly report a type-check error:
> error TS2345: Argument of type 'number' is not assignable to parameter
  of type '-1 | 1'.
Additionally, the translated expression for the unary + operator would be
considered as arithmetic expression with an incompatible left-hand side:
> error TS2362: The left-hand side of an arithmetic operation must be of
  type 'any', 'number', 'bigint' or an enum type.
To resolve this issues, the implicit transformation should be avoided.
This commit adds a new unary AST node to represent these expressions,
allowing for more accurate type-checking.
Fixes #20845
Fixes #36178
PR Close #37918
		
	
			
		
			
				
	
	
		
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			172 lines
		
	
	
		
			5.1 KiB
		
	
	
	
		
			TypeScript
		
	
	
	
	
	
| /**
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|  * @license
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|  * Copyright Google LLC All Rights Reserved.
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|  *
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|  * Use of this source code is governed by an MIT-style license that can be
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|  * found in the LICENSE file at https://angular.io/license
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|  */
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| 
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| import {AbsoluteSourceSpan} from '@angular/compiler';
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| import * as e from '../../../src/expression_parser/ast';
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| import * as t from '../../../src/template_parser/template_ast';
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| import {unparse} from '../../expression_parser/utils/unparser';
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| 
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| type HumanizedExpressionSource = [string, AbsoluteSourceSpan];
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| class ExpressionSourceHumanizer extends e.RecursiveAstVisitor implements t.TemplateAstVisitor {
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|   result: HumanizedExpressionSource[] = [];
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| 
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|   private recordAst(ast: e.AST) {
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|     this.result.push([unparse(ast), ast.sourceSpan]);
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|   }
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| 
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|   // This method is defined to reconcile the type of ExpressionSourceHumanizer
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|   // since both RecursiveAstVisitor and TemplateAstVisitor define the visit()
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|   // method in their interfaces.
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|   visit(node: e.AST|t.TemplateAst, context?: any) {
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|     node.visit(this, context);
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|   }
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| 
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|   visitASTWithSource(ast: e.ASTWithSource) {
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|     this.recordAst(ast);
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|     this.visitAll([ast.ast], null);
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|   }
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|   visitUnary(ast: e.Unary) {
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|     this.recordAst(ast);
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|     super.visitUnary(ast, null);
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|   }
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|   visitBinary(ast: e.Binary) {
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|     this.recordAst(ast);
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|     super.visitBinary(ast, null);
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|   }
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|   visitChain(ast: e.Chain) {
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|     this.recordAst(ast);
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|     super.visitChain(ast, null);
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|   }
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|   visitConditional(ast: e.Conditional) {
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|     this.recordAst(ast);
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|     super.visitConditional(ast, null);
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|   }
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|   visitFunctionCall(ast: e.FunctionCall) {
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|     this.recordAst(ast);
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|     super.visitFunctionCall(ast, null);
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|   }
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|   visitImplicitReceiver(ast: e.ImplicitReceiver) {
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|     this.recordAst(ast);
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|     super.visitImplicitReceiver(ast, null);
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|   }
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|   visitInterpolation(ast: e.Interpolation) {
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|     this.recordAst(ast);
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|     super.visitInterpolation(ast, null);
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|   }
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|   visitKeyedRead(ast: e.KeyedRead) {
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|     this.recordAst(ast);
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|     super.visitKeyedRead(ast, null);
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|   }
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|   visitKeyedWrite(ast: e.KeyedWrite) {
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|     this.recordAst(ast);
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|     super.visitKeyedWrite(ast, null);
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|   }
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|   visitLiteralPrimitive(ast: e.LiteralPrimitive) {
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|     this.recordAst(ast);
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|     super.visitLiteralPrimitive(ast, null);
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|   }
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|   visitLiteralArray(ast: e.LiteralArray) {
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|     this.recordAst(ast);
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|     super.visitLiteralArray(ast, null);
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|   }
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|   visitLiteralMap(ast: e.LiteralMap) {
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|     this.recordAst(ast);
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|     super.visitLiteralMap(ast, null);
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|   }
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|   visitMethodCall(ast: e.MethodCall) {
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|     this.recordAst(ast);
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|     super.visitMethodCall(ast, null);
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|   }
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|   visitNonNullAssert(ast: e.NonNullAssert) {
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|     this.recordAst(ast);
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|     super.visitNonNullAssert(ast, null);
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|   }
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|   visitPipe(ast: e.BindingPipe) {
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|     this.recordAst(ast);
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|     super.visitPipe(ast, null);
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|   }
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|   visitPrefixNot(ast: e.PrefixNot) {
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|     this.recordAst(ast);
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|     super.visitPrefixNot(ast, null);
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|   }
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|   visitPropertyRead(ast: e.PropertyRead) {
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|     this.recordAst(ast);
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|     super.visitPropertyRead(ast, null);
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|   }
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|   visitPropertyWrite(ast: e.PropertyWrite) {
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|     this.recordAst(ast);
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|     super.visitPropertyWrite(ast, null);
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|   }
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|   visitSafeMethodCall(ast: e.SafeMethodCall) {
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|     this.recordAst(ast);
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|     super.visitSafeMethodCall(ast, null);
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|   }
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|   visitSafePropertyRead(ast: e.SafePropertyRead) {
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|     this.recordAst(ast);
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|     super.visitSafePropertyRead(ast, null);
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|   }
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|   visitQuote(ast: e.Quote) {
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|     this.recordAst(ast);
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|     super.visitQuote(ast, null);
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|   }
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| 
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|   visitNgContent(ast: t.NgContentAst) {}
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|   visitEmbeddedTemplate(ast: t.EmbeddedTemplateAst) {
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|     t.templateVisitAll(this, ast.attrs);
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|     t.templateVisitAll(this, ast.children);
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|     t.templateVisitAll(this, ast.directives);
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|     t.templateVisitAll(this, ast.outputs);
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|     t.templateVisitAll(this, ast.providers);
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|     t.templateVisitAll(this, ast.references);
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|     t.templateVisitAll(this, ast.variables);
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|   }
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|   visitElement(ast: t.ElementAst) {
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|     t.templateVisitAll(this, ast.attrs);
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|     t.templateVisitAll(this, ast.children);
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|     t.templateVisitAll(this, ast.directives);
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|     t.templateVisitAll(this, ast.inputs);
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|     t.templateVisitAll(this, ast.outputs);
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|     t.templateVisitAll(this, ast.providers);
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|     t.templateVisitAll(this, ast.references);
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|   }
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|   visitReference(ast: t.ReferenceAst) {}
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|   visitVariable(ast: t.VariableAst) {}
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|   visitEvent(ast: t.BoundEventAst) {
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|     ast.handler.visit(this);
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|   }
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|   visitElementProperty(ast: t.BoundElementPropertyAst) {
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|     ast.value.visit(this);
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|   }
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|   visitAttr(ast: t.AttrAst) {}
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|   visitBoundText(ast: t.BoundTextAst) {
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|     ast.value.visit(this);
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|   }
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|   visitText(ast: t.TextAst) {}
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|   visitDirective(ast: t.DirectiveAst) {
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|     t.templateVisitAll(this, ast.hostEvents);
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|     t.templateVisitAll(this, ast.hostProperties);
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|     t.templateVisitAll(this, ast.inputs);
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|   }
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|   visitDirectiveProperty(ast: t.BoundDirectivePropertyAst) {
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|     ast.value.visit(this);
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|   }
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| }
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| 
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| /**
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|  * Humanizes expression AST source spans in a template by returning an array of tuples
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|  *   [unparsed AST, AST source span]
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|  * for each expression in the template.
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|  * @param templateAsts template AST to humanize
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|  */
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| export function humanizeExpressionSource(templateAsts: t.TemplateAst[]):
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|     HumanizedExpressionSource[] {
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|   const humanizer = new ExpressionSourceHumanizer();
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|   t.templateVisitAll(humanizer, templateAsts);
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|   return humanizer.result;
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| }
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