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fix(codegen): don't over-parenthesize TSTypeAssertion operand#23004

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fix/codegen-type-assertion-operand
Jun 6, 2026
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fix(codegen): don't over-parenthesize TSTypeAssertion operand#23004
graphite-app[bot] merged 1 commit into
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fix/codegen-type-assertion-operand

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@Boshen

@Boshen Boshen commented Jun 6, 2026

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What

The operand of an angle-bracket assertion <T>x is a UnaryExpression (TS grammar: < Type > UnaryExpression), but codegen printed it at Precedence::Member. That wrapped every unary operand in redundant parentheses.

It now prints the operand at Precedence::Exponentiation — exactly what UnaryExpression::gen_expr uses for its own argument — so a UnaryExpression operand stays bare while looser operands (binary, conditional, **) are still wrapped.

Examples

Input Before After
<T>-x <T>(-x) <T>-x
<T>typeof x <T>(typeof x) <T>typeof x
<T><U>x <T>(<U>x) <T><U>x
<T>x() <T>(x()) <T>x()

Operands that genuinely require parentheses keep them:

Input Output
<T>(b + c) <T>(b + c)
<T>(d ** e) <T>(d ** e)
<T>(h ? i : j) <T>(h ? i : j)

Follow-up to #23002.

@github-actions github-actions Bot added the A-codegen Area - Code Generation label Jun 6, 2026
@Boshen Boshen added the 0-merge Merge with Graphite Merge Queue label Jun 6, 2026

Boshen commented Jun 6, 2026

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## What

The operand of an angle-bracket assertion `<T>x` is a `UnaryExpression` (TS grammar: `< Type > UnaryExpression`), but codegen printed it at `Precedence::Member`. That wrapped **every** unary operand in redundant parentheses.

It now prints the operand at `Precedence::Exponentiation` — exactly what `UnaryExpression::gen_expr` uses for its own argument — so a `UnaryExpression` operand stays bare while looser operands (binary, conditional, `**`) are still wrapped.

## Examples

| Input | Before | After |
| --- | --- | --- |
| `<T>-x` | `<T>(-x)` | `<T>-x` |
| `<T>typeof x` | `<T>(typeof x)` | `<T>typeof x` |
| `<T><U>x` | `<T>(<U>x)` | `<T><U>x` |
| `<T>x()` | `<T>(x())` | `<T>x()` |

Operands that genuinely require parentheses keep them:

| Input | Output |
| --- | --- |
| `<T>(b + c)` | `<T>(b + c)` |
| `<T>(d ** e)` | `<T>(d ** e)` |
| `<T>(h ? i : j)` | `<T>(h ? i : j)` |

Follow-up to #23002.
@graphite-app graphite-app Bot force-pushed the fix/codegen-type-assertion-operand branch from 0d2c1bd to 294c473 Compare June 6, 2026 07:51
@codspeed-hq

codspeed-hq Bot commented Jun 6, 2026

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Merging this PR will not alter performance

✅ 52 untouched benchmarks
⏩ 14 skipped benchmarks1


Comparing fix/codegen-type-assertion-operand (0d2c1bd) with main (1295882)2

Open in CodSpeed

Footnotes

  1. 14 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports.

  2. No successful run was found on main (786d96f) during the generation of this report, so 1295882 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report.

@graphite-app graphite-app Bot merged commit 294c473 into main Jun 6, 2026
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@graphite-app graphite-app Bot removed the 0-merge Merge with Graphite Merge Queue label Jun 6, 2026
@graphite-app graphite-app Bot deleted the fix/codegen-type-assertion-operand branch June 6, 2026 07:55
Boshen added a commit that referenced this pull request Jun 8, 2026
### 💥 BREAKING CHANGES

- ee4dc73 ast: [**BREAKING**] Add `#[non_exhaustive]` to AST nodes
(#23046) (overlookmotel)
- 4c35362 ast: [**BREAKING**] Add
`AstBuilder::template_element_escape_raw` and
`template_element_escape_raw_with_lone_surrogates` methods (#23047)
(overlookmotel)

### 🚀 Features

- b846ab2 react_compiler: Integrate the Rust port of the React Compiler
(#22942) (Boshen)
- 5b8dd68 parser: Report TS1255 for invalid class definite assertions
(#22917) (camc314)
- 85efabf semantic: Make building the class table optional, off by
default (#22862) (Boshen)

### 🐛 Bug Fixes

- 556acdc codegen: Parenthesize TS-cast assignment targets (#23112)
(Boshen)
- 37169ff codegen: Don't emit space between postfix `--` and `>` when
minifying (#23036) (Boshen)
- a4b1bf7 codegen: Drop redundant whitespace in minified TypeScript
output (#23038) (Boshen)
- cf53285 parser: Report reserved type-declaration names in the parser
(#23035) (Boshen)
- 4e44969 ast: Fix UB in `escape_template_element_raw` (#23052)
(overlookmotel)
- c543154 parser: Report comma operator in JSX expression in the parser
(#23030) (Boshen)
- 325c94f codegen: Tighten conditional-type and constructor-type
whitespace when minifying (#23033) (Boshen)
- 95dd3a2 parser: Report `import type` alias to a non-external reference
in the parser (#23032) (Boshen)
- 90180b8 codegen: Drop space after `:` in function return type when
minifying (#23028) (Boshen)
- 6da876e parser: Report `abstract` private class field in the parser
(#23029) (Boshen)
- 28467ce codegen: Don't emit space before a postfix update operand when
minifying (#23027) (Boshen)
- cb29926 codegen: Drop redundant space after `export default` when
minifying (#23024) (Boshen)
- 62965ae codegen: Drop redundant space after `else` when minifying
(#23025) (Boshen)
- 989230a parser: Report compound assignment to non-simple target in the
parser (#23022) (Boshen)
- 06f367c parser: Report `super.#field` private access in the parser
(#23014) (Boshen)
- 184edef codegen: Print space before `const`/`declare` enum modifier
(#23013) (Boshen)
- 4d722e0 parser: Report duplicate switch `default` clause in the parser
(#23012) (Boshen)
- 597ed85 codegen: Parenthesize `let`/`async` for-of head target
(#23008) (Boshen)
- 8b631bf codegen: Remove stray space before mapped type value colon
(#23010) (Boshen)
- c08407e codegen: Don't over-parenthesize `in` inside an arrow in a
for-init (#23009) (Boshen)
- 600cd6f codegen: Parenthesize lower-precedence
`TSInstantiationExpression` operand (#23007) (Boshen)
- 187e1a5 codegen: Don't leak space after comment-only JSX expression
container (#23006) (Boshen)
- 294c473 codegen: Don't over-parenthesize `TSTypeAssertion` operand
(#23004) (Boshen)
- 786d96f codegen: Give `TSTypeAssertion` unary precedence (#23002)
(Boshen)
- 1295882 parser: Report `new.target` and `import.meta` syntax errors in
the parser (#23003) (Boshen)
- d727b6b codegen: Parenthesize `await` expression as base of `**`
(#23001) (Boshen)
- 67dfa08 codegen: Keep parentheses around `new` callees containing a
call (#22997) (Boshen)
- 17e7cf3 parser: Disallow unerasable `as`/`satisfies` assertions
(#22986) (Boshen)
- beb46d3 parser: Commit to module goal on decorated exports (#22941)
(Boshen)
- 49e63f7 isolated-declarations: Require annotations for satisfies
initializers (#22898) (camc314)
- 8c93601 isolated-declarations: Allow unknown enum initializer in
non-const enum (#22900) (camc314)

### ⚡ Performance

- 7d89909 parser: Peek instead of lookahead for yield disambiguation
(#23071) (Boshen)
- bf872f0 parser: Skip arrow lookahead for a parenthesized literal
(#23070) (Boshen)
- d19fc54 parser: Guard type-argument speculation behind an angle-token
check (#23069) (Boshen)
- 8eb5507 parser: Skip redundant member-rest re-scan on call entry
(#23068) (Boshen)
- 883dfc1 parser: Skip parse_call_expression_rest when no call follows
(#23063) (Boshen)
- b171153 parser: Peek before the await-using lookahead (#23059)
(Boshen)
- 56f21bd parser: Use peek_token for the TS `asserts` type predicate
(#23058) (Boshen)
- 68805ac parser: Use peek_token instead of checkpoint/rewind for
single-token decisions (#23056) (Boshen)
- 1f9d8eb ast: `AstBuilder::template_element_escape_raw` avoid
allocation if no escape required (#23053) (overlookmotel)
- 502b04d semantic: Move cold function redeclaration handling into
`#[cold]` function (#22973) (overlookmotel)

### 📚 Documentation

- 275d318 napi/minifier: Point `target` to oxc docs (#23102) (camc314)

Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>
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