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Merge pull request microsoft#23956 from Kingwl/emit-var-at-top
emit temporary vars at the top of the scope
2 parents 7271ec1 + ad5a4c7 commit f7311ef

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307 files changed

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‎src/compiler/core.ts

Lines changed: 15 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -951,6 +951,21 @@ namespace ts {
951951
return to;
952952
}
953953

954+
/**
955+
* Appends a range of value to begin of an array, returning the array.
956+
*
957+
* @param to The array to which `value` is to be appended. If `to` is `undefined`, a new array
958+
* is created if `value` was appended.
959+
* @param from The values to append to the array. If `from` is `undefined`, nothing is
960+
* appended. If an element of `from` is `undefined`, that element is not appended.
961+
*/
962+
export function prependRange<T>(to: T[], from: ReadonlyArray<T> | undefined): T[] | undefined {
963+
if (from === undefined || from.length === 0) return to;
964+
if (to === undefined) return from.slice();
965+
to.unshift(...from);
966+
return to;
967+
}
968+
954969
/**
955970
* @return Whether the value was added.
956971
*/

‎src/compiler/transformers/es2015.ts

Lines changed: 11 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -529,7 +529,7 @@ namespace ts {
529529
createVariableStatement(/*modifiers*/ undefined,
530530
createVariableDeclarationList(taggedTemplateStringDeclarations)));
531531
}
532-
addRange(statements, endLexicalEnvironment());
532+
prependRange(statements, endLexicalEnvironment());
533533
exitSubtree(ancestorFacts, HierarchyFacts.None, HierarchyFacts.None);
534534
return updateSourceFileNode(
535535
node,
@@ -836,7 +836,7 @@ namespace ts {
836836
setEmitFlags(statement, EmitFlags.NoComments | EmitFlags.NoTokenSourceMaps);
837837
statements.push(statement);
838838

839-
addRange(statements, endLexicalEnvironment());
839+
prependRange(statements, endLexicalEnvironment());
840840

841841
const block = createBlock(setTextRange(createNodeArray(statements), /*location*/ node.members), /*multiLine*/ true);
842842
setEmitFlags(block, EmitFlags.NoComments);
@@ -979,7 +979,7 @@ namespace ts {
979979
);
980980
}
981981

982-
addRange(statements, endLexicalEnvironment());
982+
prependRange(statements, endLexicalEnvironment());
983983

984984
if (constructor) {
985985
prependCaptureNewTargetIfNeeded(statements, constructor, /*copyOnWrite*/ false);
@@ -1894,7 +1894,7 @@ namespace ts {
18941894
}
18951895

18961896
const lexicalEnvironment = context.endLexicalEnvironment();
1897-
addRange(statements, lexicalEnvironment);
1897+
prependRange(statements, lexicalEnvironment);
18981898

18991899
prependCaptureNewTargetIfNeeded(statements, node, /*copyOnWrite*/ false);
19001900

@@ -2712,7 +2712,7 @@ namespace ts {
27122712
if (loopOutParameters.length) {
27132713
copyOutParameters(loopOutParameters, CopyDirection.ToOutParameter, statements);
27142714
}
2715-
addRange(statements, lexicalEnvironment);
2715+
prependRange(statements, lexicalEnvironment);
27162716
loopBody = createBlock(statements, /*multiline*/ true);
27172717
}
27182718

@@ -3309,10 +3309,12 @@ namespace ts {
33093309
// expression, but we will restore them later to preserve comments and source maps.
33103310
const body = cast(cast(skipOuterExpressions(node.expression), isArrowFunction).body, isBlock);
33113311

3312-
// The class statements are the statements generated by visiting the first statement of the
3312+
// The class statements are the statements generated by visiting the first statement with initializer of the
33133313
// body (1), while all other statements are added to remainingStatements (2)
3314-
const classStatements = visitNodes(body.statements, visitor, isStatement, 0, 1);
3315-
const remainingStatements = visitNodes(body.statements, visitor, isStatement, 1, body.statements.length - 1);
3314+
const isVariableStatementWithInitializer = (stmt: Statement) => isVariableStatement(stmt) && !!firstOrUndefined(stmt.declarationList.declarations).initializer;
3315+
const bodyStatements = visitNodes(body.statements, visitor, isStatement);
3316+
const classStatements = filter(bodyStatements, isVariableStatementWithInitializer);
3317+
const remainingStatements = filter(bodyStatements, stmt => !isVariableStatementWithInitializer(stmt));
33163318
const varStatement = cast(firstOrUndefined(classStatements), isVariableStatement);
33173319

33183320
// We know there is only one variable declaration here as we verified this in an
@@ -3324,6 +3326,7 @@ namespace ts {
33243326
// we see as an assignment, for example:
33253327
//
33263328
// (function () {
3329+
// var C_1;
33273330
// var C = C_1 = (function () {
33283331
// function C() {
33293332
// }
@@ -3332,7 +3335,6 @@ namespace ts {
33323335
// }());
33333336
// C = C_1 = __decorate([dec], C);
33343337
// return C;
3335-
// var C_1;
33363338
// }())
33373339
//
33383340
const aliasAssignment = tryCast(initializer, isAssignmentExpression);

‎src/compiler/transformers/es2017.ts

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -412,7 +412,7 @@ namespace ts {
412412
)
413413
);
414414

415-
addRange(statements, endLexicalEnvironment());
415+
prependRange(statements, endLexicalEnvironment());
416416

417417
const block = createBlock(statements, /*multiLine*/ true);
418418
setTextRange(block, node.body);
@@ -443,7 +443,7 @@ namespace ts {
443443
const declarations = endLexicalEnvironment();
444444
if (some(declarations)) {
445445
const block = convertToFunctionBody(expression);
446-
result = updateBlock(block, setTextRange(createNodeArray(concatenate(block.statements, declarations)), block.statements));
446+
result = updateBlock(block, setTextRange(createNodeArray(concatenate(declarations, block.statements)), block.statements));
447447
}
448448
else {
449449
result = expression;

‎src/compiler/transformers/esnext.ts

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -663,7 +663,7 @@ namespace ts {
663663
)
664664
);
665665

666-
addRange(statements, endLexicalEnvironment());
666+
prependRange(statements, endLexicalEnvironment());
667667
const block = updateBlock(node.body, statements);
668668

669669
// Minor optimization, emit `_super` helper to capture `super` access in an arrow.
@@ -692,11 +692,11 @@ namespace ts {
692692
statementOffset = addPrologue(statements, body.statements, /*ensureUseStrict*/ false, visitor);
693693
}
694694
addRange(statements, appendObjectRestAssignmentsIfNeeded(/*statements*/ undefined, node));
695-
const trailingStatements = endLexicalEnvironment();
696-
if (statementOffset > 0 || some(statements) || some(trailingStatements)) {
695+
const leadingStatements = endLexicalEnvironment();
696+
if (statementOffset > 0 || some(statements) || some(leadingStatements)) {
697697
const block = convertToFunctionBody(body, /*multiLine*/ true);
698+
prependRange(statements, leadingStatements);
698699
addRange(statements, block.statements.slice(statementOffset));
699-
addRange(statements, trailingStatements);
700700
return updateBlock(block, setTextRange(createNodeArray(statements), block.statements));
701701
}
702702
return body;

‎src/compiler/transformers/generators.ts

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -586,7 +586,7 @@ namespace ts {
586586
transformAndEmitStatements(body.statements, statementOffset);
587587

588588
const buildResult = build();
589-
addRange(statements, endLexicalEnvironment());
589+
prependRange(statements, endLexicalEnvironment());
590590
statements.push(createReturn(buildResult));
591591

592592
// Restore previous generator state

‎src/compiler/transformers/module/module.ts

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -97,7 +97,7 @@ namespace ts {
9797
append(statements, visitNode(currentModuleInfo.externalHelpersImportDeclaration, sourceElementVisitor, isStatement));
9898
addRange(statements, visitNodes(node.statements, sourceElementVisitor, isStatement, statementOffset));
9999
addExportEqualsIfNeeded(statements, /*emitAsReturn*/ false);
100-
addRange(statements, endLexicalEnvironment());
100+
prependRange(statements, endLexicalEnvironment());
101101

102102
const updated = updateSourceFileNode(node, setTextRange(createNodeArray(statements), node.statements));
103103
if (currentModuleInfo.hasExportStarsToExportValues && !compilerOptions.importHelpers) {
@@ -426,7 +426,7 @@ namespace ts {
426426

427427
// End the lexical environment for the module body
428428
// and merge any new lexical declarations.
429-
addRange(statements, endLexicalEnvironment());
429+
prependRange(statements, endLexicalEnvironment());
430430

431431
const body = createBlock(statements, /*multiLine*/ true);
432432
if (currentModuleInfo.hasExportStarsToExportValues && !compilerOptions.importHelpers) {

‎src/compiler/transformers/module/system.ts

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -257,7 +257,7 @@ namespace ts {
257257
// We emit hoisted variables early to align roughly with our previous emit output.
258258
// Two key differences in this approach are:
259259
// - Temporary variables will appear at the top rather than at the bottom of the file
260-
addRange(statements, endLexicalEnvironment());
260+
prependRange(statements, endLexicalEnvironment());
261261

262262
const exportStarFunction = addExportStarIfNeeded(statements);
263263
const moduleObject = createObjectLiteral([

‎src/compiler/transformers/ts.ts

Lines changed: 5 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -669,7 +669,7 @@ namespace ts {
669669
setEmitFlags(statement, EmitFlags.NoComments | EmitFlags.NoTokenSourceMaps);
670670
statements.push(statement);
671671

672-
addRange(statements, context.endLexicalEnvironment());
672+
prependRange(statements, context.endLexicalEnvironment());
673673

674674
const iife = createImmediatelyInvokedArrowFunction(statements);
675675
setEmitFlags(iife, EmitFlags.TypeScriptClassWrapper);
@@ -2685,8 +2685,9 @@ namespace ts {
26852685

26862686
const statements: Statement[] = [];
26872687
startLexicalEnvironment();
2688-
addRange(statements, map(node.members, transformEnumMember));
2689-
addRange(statements, endLexicalEnvironment());
2688+
const members = map(node.members, transformEnumMember);
2689+
prependRange(statements, endLexicalEnvironment());
2690+
addRange(statements, members);
26902691

26912692
currentNamespaceContainerName = savedCurrentNamespaceLocalName;
26922693
return createBlock(
@@ -3000,7 +3001,7 @@ namespace ts {
30003001
statementsLocation = moveRangePos(moduleBlock.statements, -1);
30013002
}
30023003

3003-
addRange(statements, endLexicalEnvironment());
3004+
prependRange(statements, endLexicalEnvironment());
30043005
currentNamespaceContainerName = savedCurrentNamespaceContainerName;
30053006
currentNamespace = savedCurrentNamespace;
30063007
currentScopeFirstDeclarationsOfName = savedCurrentScopeFirstDeclarationsOfName;

‎src/compiler/visitor.ts

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -145,7 +145,7 @@ namespace ts {
145145
statements = setTextRange(createNodeArray([createStatement(createLiteral("use strict")), ...statements]), statements);
146146
}
147147
const declarations = context.endLexicalEnvironment();
148-
return setTextRange(createNodeArray(concatenate(statements, declarations)), statements);
148+
return setTextRange(createNodeArray(concatenate(declarations, statements)), statements);
149149
}
150150

151151
/**
@@ -1468,8 +1468,8 @@ namespace ts {
14681468
}
14691469

14701470
return isNodeArray(statements)
1471-
? setTextRange(createNodeArray(concatenate(statements, declarations)), statements)
1472-
: addRange(statements, declarations);
1471+
? setTextRange(createNodeArray(concatenate(declarations, statements)), statements)
1472+
: prependRange(statements, declarations);
14731473
}
14741474

14751475
/**

‎tests/baselines/reference/ES5For-of30.js

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,11 +7,11 @@ for ([a = 1, b = ""] of tuple) {
77
}
88

99
//// [ES5For-of30.js]
10+
var _a, _b, _c;
1011
var a, b;
1112
var tuple = [2, "3"];
1213
for (var _i = 0, tuple_1 = tuple; _i < tuple_1.length; _i++) {
1314
_a = tuple_1[_i], _b = _a[0], a = _b === void 0 ? 1 : _b, _c = _a[1], b = _c === void 0 ? "" : _c;
1415
a;
1516
b;
1617
}
17-
var _a, _b, _c;

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