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perf(packages/codegen): remove redundant printSpaceBeforeIdentifier and last updates in printParams (#27652)

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Perf optimization.

When printing function params, use `writeNoLast` over `write` where it's provably safe to do so.
This commit is contained in:
overlookmotel committed 2026-10-13 12:30:39 +00:00
1 parent e533278327
commit 2ab6b63df5
1 file changed
+23 -13
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packages/codegen/src-js/print/function.ts
+23 -13
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@@ -1,13 +1,12 @@
// Functions.
import { typeAssertIs } from "../asserts.ts";
import { debugAssert, typeAssertIs } from "../asserts.ts";
import { printBindingPattern } from "./binding_pattern.ts";
import { CAT_CLOSE_BRACKET, CAT_IDENT, CAT_OTHER, CAT_START_OF_STMT } from "./categories.ts";
import {
debugAssertLastFresh,
markMapStart,
write,
writeIdent,
writeNoLast,
writeWithMap,
writeWithMapEnd,
@@ -163,6 +162,9 @@ export function printParenParams(params: ESTree.ParamPattern[], state: State): v
* @param state - Printer state
*/
function printParams(params: ESTree.ParamPattern[], state: State): void {
debugAssertLastFresh(state);
debugAssert(state.last === CAT_OTHER && state.lastCharWritten === "(");
const { length } = params;
for (let i = 0; i < length; i++) {
if (i > 0) write(state, ", ", CAT_OTHER);
@@ -177,7 +179,10 @@ function printParams(params: ESTree.ParamPattern[], state: State): void {
if (TS && paramType === "Identifier") {
typeAssertIs<ESTree.BindingIdentifier>(param);
if (param.name === "this") {
writeIdent(state, "this");
// `printTypeAnnotation` prints `: ` first. On next turn of loop, `, ` is written.
// Or if this is last param, we return to caller, who immediately writes `)` or `) =>`.
// In any of these cases, nothing reads `last`, so writing it is redundant.
writeNoLast(state, "this");
if (param.typeAnnotation != null) printTypeAnnotation(param.typeAnnotation, state);
continue;
}
@@ -192,20 +197,25 @@ function printParams(params: ESTree.ParamPattern[], state: State): void {
if (TS && paramType === "TSParameterProperty") {
typeAssertIs<ESTree.TSParameterProperty>(param);
// * At start of function, last char written was `(`.
// * On each turn of loop after the first, `, ` is written.
// * `printDecorators` prints a trailing ` `.
// * The 3 conditions below all print something ending with ` `.
// So in all cases, `last` is `CAT_OTHER`. Therefore there's no need to rewrite `last` as `CAT_OTHER`
// in the 3 conditions below. Set `lastIsStale = false` after so no error in `printBindingPattern`.
debugAssertLastFresh(state);
debugAssert(state.last === CAT_OTHER);
if (param.accessibility != null) {
printSpaceBeforeIdentifier(state);
writeNoLast(state, param.accessibility);
write(state, " ", CAT_OTHER);
writeNoLast(state, " ");
}
if (param.override) {
printSpaceBeforeIdentifier(state);
write(state, "override ", CAT_OTHER);
}
if (param.readonly) {
printSpaceBeforeIdentifier(state);
write(state, "readonly ", CAT_OTHER);
}
if (param.override) writeNoLast(state, "override ");
if (param.readonly) writeNoLast(state, "readonly ");
if (DEBUG) state.lastIsStale = false;
printBindingPattern(param.parameter, state);
} else {