Commit Graph

1015 Commits

Author SHA1 Message Date
Trotyl 8d613c1d42 feat(compiler): allow trailing comma in array literal (#22277)
Allows `[1, 2, ]` syntax in angular expressions.

closes #20773

PR Close #22277
2020-12-02 14:57:05 -08:00
Charles Lyding 318255a5f8 build: support building with TypeScript 4.1 (#39571)
TypeScript 4.1 is now used to build and test within the repository.

PR Close #39571
2020-11-25 11:10:01 -08:00
Krzysztof Grzybek 94e790d4ee fix(compiler): report better error on interpolation in an expression (#30300)
Compiler results in weird error message when encounters interpolation inside
existing expression context, e.g. *ngIf="name {{ name }}"

PR Close #30300
2020-11-25 10:53:19 -08:00
JoostK e75244ec00 feat(compiler-cli): support for partial compilation of components (#39707)
This commit implements partial compilation of components, together with
linking the partial declaration into its full AOT output.

This commit does not yet enable accurate source maps into external
templates. This requires additional work to account for escape sequences
which is non-trivial. Inline templates that were represented using a
string or template literal are transplated into the partial declaration
output, so their source maps should be accurate. Note, however, that
the accuracy of source maps is not currently verified in tests; this is
also left as future work.

The golden files of partial compilation output have been updated to
reflect the generated code for components. Please note that the current
output should not yet be considered stable.

PR Close #39707
2020-11-24 13:05:49 -08:00
JoostK 6c7eb351d4 refactor(compiler-cli): extract compilation utilities for partial compilation of components (#39707)
This commit is a precursor to supporting the partial compilation of
components, which leverages some of the compilation infrastructure that
is in place for directives.

PR Close #39707
2020-11-24 13:05:43 -08:00
Bjarki 2ae3fa009e refactor(compiler): remove unnecessary trustConstantScript function (#39554)
Script tags, inline event handlers and other script contexts are
forbidden or stripped from Angular templates by the compiler. In the
context of Trusted Types, this leaves no sinks that require use of a
TrustedScript. This means that trustConstantScript is never used, and
can be removed.

PR Close #39554
2020-11-23 08:29:09 -08:00
Bjarki 4916870dff fix(compiler): only promote Trusted Types to constants when necessary (#39554)
Previously all constant values of security-sensitive attributes and
properties were promoted to Trusted Types. While this is not inherently
bad, it is also not optimal.

Use the newly added Trusted Types schema to restrict promotion to
constants that are in a Trusted Types-relevant context.

PR Close #39554
2020-11-23 08:29:08 -08:00
Bjarki c8a99ef458 fix(compiler): disallow i18n of security-sensitive attributes (#39554)
To minimize security risk (XSS in particular) in the i18n pipeline,
disallow i18n translation of attributes that are Trusted Types sinks.
Add integration tests to ensure that such sinks cannot be translated.

PR Close #39554
2020-11-23 08:29:06 -08:00
Bjarki bb70a9bda4 feat(compiler): support error reporting in I18nMetaVisitor (#39554)
Make it possible to report errors from the I18nMetaVisitor parser.

PR Close #39554
2020-11-23 08:29:05 -08:00
Bjarki 358c50e226 feat(compiler): add schema for Trusted Types sinks (#39554)
Create a schema with an associated function to classify Trusted Types
sinks.

Piggyback a typo fix.

PR Close #39554
2020-11-23 08:29:04 -08:00
Marcono1234 3e1e5a15ba docs: update links to use HTTPS as protocol (#39718)
PR Close #39718
2020-11-20 12:52:16 -08:00
Pete Bacon Darwin 969ad329de refactor(compiler): tidy up interpolation splitting (#39717)
When parsing for i18n messages, interpolated strings are
split into `Text` and `Placeholder` pieces.  The method that
does this `_visitTextWithInterpolation()` was becoming too
complex. This commit refactors that method along with some
associated functions that it uses.

PR Close #39717
2020-11-20 08:35:56 -08:00
Pete Bacon Darwin 0462a616c3 fix(compiler): ensure that placeholders have the correct sourceSpan (#39717)
When the `preserveWhitespaces` is not true, the template parser will
process the parsed AST nodes to remove excess whitespace. Since the
generated `goog.getMsg()` statements rely upon the AST nodes after
this whitespace is removed, the i18n extraction must make a second pass.

Previously this resulted in innacurrate source-spans for the i18n text and
placeholder nodes that were extracted in the second pass.

This commit fixes this by reusing the source-spans from the first pass
when extracting the nodes in the second pass.

Fixes #39671

PR Close #39717
2020-11-20 08:35:55 -08:00
cexbrayat 066126ae2f fix(core): remove duplicated noop function (#39761)
The codebase currently contains several `noop` functions,
and they can end up in the bundle of an application.
A recent commit 6fbe21941d tipped us off
as it introduced several `noop` occurrences in the golden symbol files.
After investigating with @petebacondarwin,
we decided to remove the duplicated functions.

This probably shaves only a few bytes,
but this commit removes the duplicated functions,
by always using the one in `core/src/utils/noop`.

PR Close #39761
2020-11-19 12:14:12 -08:00
Alex Rickabaugh 3613e7c4e5 test(compiler-cli): move testing utils to separate package (#39594)
ngtsc has a robust suite of testing utilities, designed for in-memory
testing of a TypeScript compiler. Previously these utilities lived in the
`test` directory for the compiler-cli package.

This commit moves those utilities to an `ngtsc/testing` package, enabling
them to be depended on separately and opening the door for using them from
the upcoming language server testing infrastructure.

As part of this refactoring, the `fake_core` package (a lightweight API
replacement for @angular/core) is expanded to include functionality needed
for Language Service test use cases.

PR Close #39594
2020-11-17 11:59:56 -08:00
JoostK d281ea820b perf(compiler): use raw bytes to represent utf-8 encoded strings (#39694)
The result of utf-8 encoding a string was represented in a string, where
each individual character represented a single byte according to its
character code. All usages of this data were interested in the byte
itself, so this required conversion from a character back to its code.
This commit simply stores the individual bytes in array to avoid the
conversion. This yields a ~10% performance improvement for i18n message
ID computation.

PR Close #39694
2020-11-17 10:09:28 -08:00
JoostK 604b4e46c8 perf(compiler): optimize computation of i18n message ids (#39694)
Message ID computation makes extensive use of big integer
multiplications in order to translate the message's fingerprint into
a numerical representation. In large compilations with heavy use of i18n
this was showing up high in profiler sessions.

There are two factors contributing to the bottleneck:

1. a suboptimal big integer representation using strings, which requires
repeated allocation and conversion from a character to numeric digits
and back.
2. repeated computation of the necessary base-256 exponents and their
multiplication factors.

The first bottleneck is addressed using a representation that uses an
array of individual digits. This avoids repeated conversion and
allocation overhead is also greatly reduced, as adding two big integers
can now be done in-place with virtually no memory allocations.

The second point is addressed by a memoized exponentiation pool to
optimize the multiplication of a base-256 exponent.

As an additional optimization are the two 32-bit words now converted to
decimal per word, instead of going through an intermediate byte buffer
and doing the decimal conversion per byte.

The results of these optimizations depend a lot on the number of i18n
messages for which a message should be computed. Benchmarks have shown
that computing message IDs is now ~6x faster for 1,000 messages, ~14x
faster for 10,000 messages, and ~24x faster for 100,000 messages.

PR Close #39694
2020-11-17 10:09:28 -08:00
Misko Hevery 1ac68e3f2b refactor(core): Remove circular dependency on `render3` JIT and ViewEngine (#39621)
JIT needs to identify which type is `ChangeDetectorRef`. It was doing so
by importing `ChangeDetectorRef` and than comparing the types. This creates
circular dependency as well as prevents tree shaking. The new solution is
to brand the class with `__ChangeDetectorRef__` so that it can be identified
without creating circular dependency.

PR Close #39621
2020-11-16 09:12:46 -08:00
Andrew Scott 8a1c98c5e8 refactor(compiler-cli): add keySpan to reference nodes (#39616)
Similar to #39613, #39609, and #38898, we should store the `keySpan` for
Reference nodes so that we can accurately map from a template node to a
span in the original file. This is most notably an issue at the moment
for directive references `#ref="exportAs"`. The current behavior for the
language service when requesting information for the reference
is that it will return a text span that results in
highlighting the entire source when it should only highlight "ref" (test
added for this case as well).

PR Close #39616
2020-11-12 15:12:53 -08:00
Andrew Scott c33326c538 refactor(compiler-cli): add keySpan to parsed events (#39609)
Though we currently have the knowledge of where the `key` for an
event binding appears during parsing, we do not propagate this
information to the output AST. This means that once we produce the
template AST, we have no way of mapping a template position to the key
span alone. The best we can currently do is map back to the
`sourceSpan`. This presents problems downstream, specifically for the
language service, where we cannot provide correct information about a
position in a template because the AST is not granular enough.

This is essentially identical to the change from #38898, but for event
bindings rather than input bindings.

PR Close #39609
2020-11-12 15:09:17 -08:00
Andrew Scott 21651d362d refactor(compiler-cli): add keySpan to text attributes (#39613)
Similar to #39609 and #38898, though we currently have the knowledge of where the key for an
attribute appears during parsing, we do not propagate this
information to the output AST. This means that once we produce the
template AST, we have no way of mapping a template position to the key
span alone. The best we can currently do is map back to the
sourceSpan. This presents problems downstream, specifically for the
language service, where we cannot provide correct information about a
position in a template because the AST is not granular enough.

PR Close #39613
2020-11-12 14:19:00 -08:00
Pete Bacon Darwin 1f956184c4 fix(compiler): skipping leading whitespace should not break placeholder source-spans (#39486)
Tokenized text node may have leading whitespace skipped from their
source-span. But the source-span is used to compute where there are
interpolated blocks, resulting in placeholder nodes whose source-spans
are offset by the amount of skipped characters.

This fix uses the `fullStart` location of text source-spans for computing
the source-span of placeholders, so that they are accurate.

Fixes #39195

PR Close #39486
2020-11-06 09:01:37 -08:00
Pete Bacon Darwin 43d8e9aad2 refactor(compiler): capture `fullStart` locations when tokenizing (#39486)
This commit ensures that when leading whitespace is skipped by
the tokenizer, the original start location (before skipping) is captured
in the `fullStart` property of the token's source-span.

PR Close #39486
2020-11-06 09:01:37 -08:00
Pete Bacon Darwin 8d90c1ad97 refactor(compiler): store the `fullStart` location on `ParseSourceSpan`s (#39486)
The lexer is able to skip leading trivia in the `start` location of tokens.
This makes the source-span more friendly since things like elements
appear to begin at the start of the opening tag, rather than at the
start of any leading whitespace, which could include newlines.

But some tooling requires the full source-span to be available, such
as when tokenizing a text span into an Angular expression.

This commit simply adds the `fullStart` location to the `ParseSourceSpan`
class, and ensures that places where such spans are cloned, this
property flows through too.

PR Close #39486
2020-11-06 09:01:37 -08:00
Pete Bacon Darwin 3f4fe45277 fix(compiler): ensure that i18n message-parts have the correct source-span (#39486)
In an i18n message, two placeholders next to each other must have
an "empty" message-part to separate them. Previously, the source-span
for this message-part was pointing to the wrong original location.
This caused problems in the generated source-maps and lead to extracted
i18n messages from being rendered incorrectly.

PR Close #39486
2020-11-06 09:01:37 -08:00
JoostK 306a1307c7 refactor(compiler-cli): rename `$ngDeclareDirective`/`$ngDeclareComponent` to use `ɵɵ` prefix (#39518)
For consistency with other generated code, the partial declaration
functions are renamed to use the `ɵɵ` prefix which indicates that it is
generated API.

This commit also removes the declaration from the public API golden
file, as it's not yet considered stable at this point. Once the linker
is finalized will these declaration function be included into the golden
file.

PR Close #39518
2020-11-04 10:44:37 -08:00
JoostK 8c0a92bb45 feat(compiler-cli): partial compilation of directives (#39518)
This commit implements partial code generation for directives, which
will be transformed by the linker plugin to fully AOT compiled code in
follow-up work.

PR Close #39518
2020-11-04 10:44:37 -08:00
Kristiyan Kostadinov cbc0907bfd fix(compiler): preserve this.$event and this.$any accesses in expressions (#39323)
Currently expressions `$event.foo()` and `this.$event.foo()`, as well as `$any(foo)` and
`this.$any(foo)`, are treated as the same expression by the compiler, because `this` is considered
the same implicit receiver as when the receiver is omitted. This introduces the following issues:

1. Any time something called `$any` is used, it'll be stripped away, leaving only the first parameter.
2. If something called `$event` is used anywhere in a template, it'll be preserved as `$event`,
rather than being rewritten to `ctx.$event`, causing the value to undefined at runtime. This
applies to listener, property and text bindings.

These changes resolve the first issue and part of the second one by preserving anything that
is accessed through `this`, even if it's one of the "special" ones like `$any` or `$event`.
Furthermore, these changes only expose the `$event` global variable inside event listeners,
whereas previously it was available everywhere.

Fixes #30278.

PR Close #39323
2020-10-30 10:49:15 -07:00
ayazhafiz 3241d922fc refactor(compiler): parse bindings "by hand" rather than via regex (#39375)
To support recovery of malformed binding property names like `([a)`,
`[a`, or `()`, the binding parser needs to be more permissive w.r.t. the
kinds of bindings it can detect. This is difficult to do maintainably
with a regex, but is trivial with a "hand-rolled" string parser. This
commit refactors render3's binding attribute parsing to use this method
for multi-delimited bindings (namely via the `()`, `[]`, and `[()]`)
syntax, making the way recovery of malformed bindings in a future patch.

Note that we can keep using a regex for prefix-only binding syntax
(e.g. `bind-`, `ref-`) because validation of the binding is complete
once we have matched the prefix, and the only thing left to do is check
that the binding identifier is non-empty, which is trivial.

Part of #38596

PR Close #39375
2020-10-30 09:40:56 -07:00
Kristiyan Kostadinov fe343d8d96 refactor(compiler): clean up i18n attribute generation logic (#39498)
This is follow-up from [an earlier discussion](https://github.com/angular/angular/pull/39408#discussion_r511908358).
After some testing, it looks like the type of `Element.attributes` was correct in specifying that it
only has `TextAttribute` instances. This means that the extra checks that filter out `BoundAttribute`
instances from the array isn't necessary. There is another loop a bit further down that actually
extracts the bound i18n attributes.

PR Close #39498
2020-10-29 16:07:50 -07:00
ayazhafiz e3365724f2 feat(compiler): recover expression parsing in more malformed pipe cases (#39437)
This commit handles the following cases:
- incomplete pipes in a pipe chain
- incomplete arguments in a pipe chain
- incomplete arguments provided to a pipe
- nested pipes

The idea is to unconditionally recover on the presence of a pipe, which
should be okay because expression parsing can be independently between
pipes.

PR Close #39437
2020-10-29 12:38:40 -07:00
Bjarki f54662e931 fix(core): mark Trusted Types as declarations (#39471)
Angular-internal type definitions for Trusted Types were added in #39211.
When compiled using the Closure compiler with certain optimization
flags, identifiers from these type definitions (such as createPolicy)
are currently uglified and renamed to shorter strings. This causes
Angular applications compiled in this way to fail to create a Trusted
Types policy, and fall bock to using strings.

To fix this, mark the internal Trusted Types definitions as declarations
using the "declare" keyword. Also convert types to interfaces, for
the reasons explained in https://ncjamieson.com/prefer-interfaces/

PR Close #39471
2020-10-29 11:58:48 -07:00
Alan Agius dd0ba3f4ab docs: rename `ng xi18n` to `ng extract-i18n` (#39337)
In Angular CLI version 11, xi18n has been changed from `ng xi18n` to `ng extract-i18n`.

PR Close #39337
2020-10-28 14:42:27 -07:00
ayazhafiz 19b88cef71 fix(compiler): do not throw away render3 AST on errors (#39413)
Currently render3's `parseTemplate` throws away the parsed AST and
returns an empty list of HTML nodes if HTML->R3 translation failed. This
is not preferrable in some contexts like that of a language service,
where we would like a well-formed AST even if it is has errors.

PR Close #39413
2020-10-27 13:37:19 -07:00
Kristiyan Kostadinov 58408d6a60 fix(compiler): treat i18n attributes with no bindings as static attributes (#39408)
Currently `i18n` attributes are treated the same no matter if they have data bindings or not. This
both generates more code since they have to go through the `ɵɵi18nAttributes` instruction and
prevents the translated attributes from being injected using the `@Attribute` decorator.

These changes makes it so that static translated attributes are treated in the same way as regular
static attributes and all other `i18n` attributes go through the old code path.

Fixes #38231.

PR Close #39408
2020-10-27 13:31:29 -07:00
pmartijena 421efbf69b docs: fix grammatical errors and typos (#38868)
Fixed run on sentences, grammatical errors, and made "ivy" "Ivy" everywhere for consistency.
PR Close #38868
2020-10-27 13:18:01 -07:00
Andrew Kushnir 9186ad84ae refactor(core): remove unused i18n placeholder for projection (#39172)
Runtime i18n logic doesn't distinguish `<ng-content>` tag placeholders and regular element tag
placeholders in i18n messages, so there is no need to have a special marker for projection-based
placeholders and element markers can be used instead.

PR Close #39172
2020-10-27 10:39:37 -07:00
ayazhafiz 3f00c6150b test(compiler): Demonstrate recoverable parsing of unterminated pipes (#39113)
There is no actionable change in this commit other than to pretty-print
EOF tokens. Actual parsing of unterminated pipes is already supported,
this just adds a test for it.

Part of #38596

PR Close #39113
2020-10-22 13:41:51 -07:00
ayazhafiz e44e10bb81 feat(compiler): support recovery of malformed property writes (#39103)
This feature is trivial to support since
89c5255b8c has landed.

PR Close #39103
2020-10-22 13:36:50 -07:00
Bjarki 765fa337e3 fix(compiler): use Trusted Types policy in JIT compiler (#39210)
The JIT compiler uses the Function constructor to compile arbitrary
strings into executable code at runtime, which causes Trusted Types
violations. To address this, JitEvaluator is instead made to use the
Trusted Types compatible Function constructor introduced by Angular's
Trusted Types policy for JIT.

PR Close #39210
2020-10-16 08:13:14 -07:00
Bjarki 6570292672 feat(core): create a Trusted Types policy for JIT compiler (#39210)
Introduce a Trusted Types policy for use by Angular's JIT compiler named
angular#unsafe-jit. As the compiler turns arbitrary untrusted strings
into executable code at runtime, using Angular's main Trusted Types
policy does not seem appropriate, unless it can be ensured that the
provided strings are indeed trusted. Until then, this JIT policy can be
allowed by applications that rely on the JIT compiler but want to
enforce Trusted Types, knowing that a compromise of the JIT compiler can
lead to arbitrary script execution. In particular, this is required for
enabling Trusted Types in Angular unit tests, since they make use of the
JIT compiler.

Also export the internal Trusted Types definitions from the core package
so that they can be used in the compiler package.

PR Close #39210
2020-10-16 08:13:14 -07:00
Bjarki 6e18d2dacc fix(compiler): promote constants in templates to Trusted Types (#39211)
Angular treats constant values of attributes and properties in templates
as secure. This means that these values are not sanitized, and are
instead passed directly to the corresponding setAttribute or setProperty
function. In cases where the given attribute or property is
security-sensitive, this causes a Trusted Types violation.

To address this, functions for promoting constant strings to each of the
three Trusted Types are introduced to Angular's private codegen API. The
compiler is updated to wrap constant strings with calls to these
functions as appropriate when constructing the `consts` array. This is
only done for security-sensitive attributes and properties, as
classified by Angular's dom_security_schema.

PR Close #39211
2020-10-15 09:08:01 -07:00
crisbeto 7f689a291a fix(compiler): incorrectly encapsulating @import containing colons and semicolons (#38716)
At a high level, the current shadow DOM shim logic works by escaping the content of a CSS rule
(e.g. `div {color: red;}` becomes `div {%BLOCK%}`), using a regex to parse out things like the
selector and the rule body, and then re-adding the content after the selector has been modified.
The problem is that the regex has to be very broad in order capture all of the different use cases,
which can cause it to match strings suffixed with a semi-colon in some places where it shouldn't,
like this URL from Google Fonts `https://fonts.googleapis.com/css2?family=Roboto:wght@400;500&display=swap`.
Most of the time this is fine, because the logic that escapes the rule content to `%BLOCK%` will
have converted it to something that won't be matched by the regex. However, it breaks down for rules
like `@import` which don't have a body, but can still have quoted content with characters that can
match the regex.

These changes resolve the issue by making a second pass over the escaped string and replacing all
of the remaining quoted content with `%QUOTED%` before parsing it with the regex. Once everything
has been processed, we make a final pass where we restore the quoted content.

In a previous iteration of this PR, I went with a shorter approach which narrowed down the
regex so that it doesn't capture rules without a body. It fixed the issue, but it also ended
up breaking some of the more contrived unit test cases. I decided not to pursue it further, because
we would've ended up with a very long and brittle regex that likely would've broken in even weirder
ways.

Fixes #38587.

PR Close #38716
2020-10-09 08:33:04 -07:00
Kristiyan Kostadinov 4a1c12c773 feat(core): remove ViewEncapsulation.Native (#38882)
Removes `ViewEncapsulation.Native` which has been deprecated for several major versions.

BREAKING CHANGES:
* `ViewEncapsulation.Native` has been removed. Use `ViewEncapsulation.ShadowDom` instead. Existing
usages will be updated automatically by `ng update`.

PR Close #38882
2020-10-08 11:56:03 -07:00
JoostK 0a16e60afa fix(compiler-cli): type checking of expressions within ICUs (#39072)
Expressions within ICU expressions in templates were not previously
type-checked, as they were skipped while traversing the elements
within a template. This commit enables type checking of these
expressions by actually visiting the expressions.

BREAKING CHANGE:
Expressions within ICUs are now type-checked again, fixing a regression
in Ivy. This may cause compilation failures if errors are found in
expressions that appear within an ICU. Please correct these expressions
to resolve the type-check errors.

Fixes #39064

PR Close #39072
2020-10-08 11:55:27 -07:00
JoostK 4b06ef75aa refactor(compiler): associate accurate source spans with ICU expressions (#39072)
Prior to this change, expressions within ICUs would have a source span
corresponding with the whole ICU. This commit narrows down the source
spans of these expressions to the exact location in the source file, as
a prerequisite for reporting type check errors within these expressions.

PR Close #39072
2020-10-08 11:55:27 -07:00
Alex Rickabaugh 72755eadd2 refactor(compiler): add getEntitiesInTemplateScope to template binder (#39048)
The template binding API in @angular/compiler exposes information about a
template that is synthesized from the template structure and its scope
(associated directives and pipes).

This commit introduces a new API, `getEntitiesInTemplateScope`, which
accepts a `Template` object (or `null` to indicate the root template) and
returns all `Reference` and `Variable` nodes that are visible at that level
of the template, including those declared in parent templates.

This API is needed by the template type-checker to support autocompletion
APIs for the Language Service.

PR Close #39048
2020-10-06 13:55:00 -07:00
ayazhafiz 57f8dd2978 test(compiler): add tests for parsing of malformed property reads (#38998)
The expression parser already has support for recovering on malformed
property reads, but did not have tests describing the recovered ast in
such cases. This commit adds tests to demonstrate such cases; in
particular, the recovered ast is a full PropertyRead but with an empty
property name. This is likely the most preferred option, as it does not
constrain consumers of the AST to what the property name should look
like. Furthermore, we cannot mark the property name as empty in any
other way (e.g. an EmptyExpr) because the property name, as of present,
is a string field rather than an AST itself.

Note that tokens past a malformed property read are not preserved in the
AST (for example in `foo.1234`, `1234` is not preserved in the AST).
This is because the extra tokens do not belong to the singular
expression created by the property read, and there is not a meaningful
way to interpret a secondary expression in a single parsed expression.

Part of #38596

PR Close #38998
2020-10-05 14:24:46 -07:00
ayazhafiz 89c5255b8c refactor(compiler): iteratively parse interpolations (#38977)
This patch refactors the interpolation parser to do so iteratively
rather than using a regex. Doing so prepares us for supporting granular
recovery on poorly-formed interpolations, for example when an
interpolation does not terminate (`{{ 1 + 2`) or is not terminated
properly (`{{ 1 + 2 {{ 2 + 3 }}`).

Part of #38596

PR Close #38977
2020-10-02 15:13:23 -07:00
ayazhafiz 3bbbf39b58 feat(compiler): Recover on malformed keyed reads and keyed writes (#39004)
This patch adds support for recovering well-formed (and near-complete)
ASTs for semantically malformed keyed reads and keyed writes. See the
added tests for details on the types of semantics we can now recover;
in particular, notice that some assumptions are made about the form of
a keyed read/write intended by a user. For example, in the malformed
expression `a[1 + = 2`, we assume that the user meant to write a binary
expression for the key of `a`, and assign that key the value `2`. In
particular, we now parse this as `a[1 + <empty expression>] = 2`. There
are some different interpretations that can be made here, but I think
this is reasonable.

The actual changes in the parser code are fairly minimal (a nice
surprise!); the biggest addition is a `writeContext` that marks whether
the `=` operator can serve as a recovery point after error detection.

Part of #38596

PR Close #39004
2020-10-02 11:37:03 -07:00