Hoisted declarations should occur after prologue directives (#24386)

src/compiler/core.ts

@@ -1006,21 +1006,6 @@ namespace ts {
         return to;
     }
 
-    /**
-     * Appends a range of value to begin of an array, returning the array.
-     *
-     * @param to The array to which `value` is to be appended. If `to` is `undefined`, a new array
-     * is created if `value` was appended.
-     * @param from The values to append to the array. If `from` is `undefined`, nothing is
-     * appended. If an element of `from` is `undefined`, that element is not appended.
-     */
-    export function prependRange<T>(to: T[], from: ReadonlyArray<T> | undefined): T[] | undefined {
-        if (from === undefined || from.length === 0) return to;
-        if (to === undefined) return from.slice();
-        to.unshift(...from);
-        return to;
-    }
-
     /**
      * @return Whether the value was added.
      */

src/compiler/transformers/es2015.ts

@@ -529,7 +529,7 @@ namespace ts {
                     createVariableStatement(/*modifiers*/ undefined,
                         createVariableDeclarationList(taggedTemplateStringDeclarations)));
             }
-            prependRange(statements, endLexicalEnvironment());
+            prependStatements(statements, endLexicalEnvironment());
             exitSubtree(ancestorFacts, HierarchyFacts.None, HierarchyFacts.None);
             return updateSourceFileNode(
                 node,
@@ -837,7 +837,7 @@ namespace ts {
             setEmitFlags(statement, EmitFlags.NoComments | EmitFlags.NoTokenSourceMaps);
             statements.push(statement);
 
-            prependRange(statements, endLexicalEnvironment());
+            prependStatements(statements, endLexicalEnvironment());
 
             const block = createBlock(setTextRange(createNodeArray(statements), /*location*/ node.members), /*multiLine*/ true);
             setEmitFlags(block, EmitFlags.NoComments);
@@ -980,7 +980,7 @@ namespace ts {
                 );
             }
 
-            prependRange(statements, endLexicalEnvironment());
+            prependStatements(statements, endLexicalEnvironment());
 
             if (constructor) {
                 prependCaptureNewTargetIfNeeded(statements, constructor, /*copyOnWrite*/ false);
@@ -1896,7 +1896,7 @@ namespace ts {
             }
 
             const lexicalEnvironment = context.endLexicalEnvironment();
-            prependRange(statements, lexicalEnvironment);
+            prependStatements(statements, lexicalEnvironment);
 
             prependCaptureNewTargetIfNeeded(statements, node, /*copyOnWrite*/ false);
 
@@ -2712,7 +2712,7 @@ namespace ts {
                 if (loopOutParameters.length) {
                     copyOutParameters(loopOutParameters, CopyDirection.ToOutParameter, statements);
                 }
-                prependRange(statements, lexicalEnvironment);
+                prependStatements(statements, lexicalEnvironment);
                 loopBody = createBlock(statements, /*multiline*/ true);
             }
 

src/compiler/transformers/es2017.ts

@@ -413,7 +413,7 @@ namespace ts {
                     )
                 );
 
-                prependRange(statements, endLexicalEnvironment());
+                prependStatements(statements, endLexicalEnvironment());
 
                 const block = createBlock(statements, /*multiLine*/ true);
                 setTextRange(block, node.body);

src/compiler/transformers/esnext.ts

@@ -663,7 +663,7 @@ namespace ts {
                 )
             );
 
-            prependRange(statements, endLexicalEnvironment());
+            prependStatements(statements, endLexicalEnvironment());
             const block = updateBlock(node.body!, statements);
 
             // Minor optimization, emit `_super` helper to capture `super` access in an arrow.
@@ -695,7 +695,7 @@ namespace ts {
             const leadingStatements = endLexicalEnvironment();
             if (statementOffset > 0 || some(statements) || some(leadingStatements)) {
                 const block = convertToFunctionBody(body, /*multiLine*/ true);
-                prependRange(statements, leadingStatements);
+                prependStatements(statements, leadingStatements);
                 addRange(statements, block.statements.slice(statementOffset));
                 return updateBlock(block, setTextRange(createNodeArray(statements), block.statements));
             }

src/compiler/transformers/generators.ts

@@ -587,7 +587,7 @@ namespace ts {
             transformAndEmitStatements(body.statements, statementOffset);
 
             const buildResult = build();
-            prependRange(statements, endLexicalEnvironment());
+            prependStatements(statements, endLexicalEnvironment());
             statements.push(createReturn(buildResult));
 
             // Restore previous generator state

src/compiler/transformers/module/module.ts

@@ -97,7 +97,7 @@ namespace ts {
             append(statements, visitNode(currentModuleInfo.externalHelpersImportDeclaration, sourceElementVisitor, isStatement));
             addRange(statements, visitNodes(node.statements, sourceElementVisitor, isStatement, statementOffset));
             addExportEqualsIfNeeded(statements, /*emitAsReturn*/ false);
-            prependRange(statements, endLexicalEnvironment());
+            prependStatements(statements, endLexicalEnvironment());
 
             const updated = updateSourceFileNode(node, setTextRange(createNodeArray(statements), node.statements));
             if (currentModuleInfo.hasExportStarsToExportValues && !compilerOptions.importHelpers) {
@@ -426,7 +426,7 @@ namespace ts {
 
             // End the lexical environment for the module body
             // and merge any new lexical declarations.
-            prependRange(statements, endLexicalEnvironment());
+            prependStatements(statements, endLexicalEnvironment());
 
             const body = createBlock(statements, /*multiLine*/ true);
             if (currentModuleInfo.hasExportStarsToExportValues && !compilerOptions.importHelpers) {

src/compiler/transformers/module/system.ts

@@ -257,7 +257,7 @@ namespace ts {
             // We emit hoisted variables early to align roughly with our previous emit output.
             // Two key differences in this approach are:
             // - Temporary variables will appear at the top rather than at the bottom of the file
-            prependRange(statements, endLexicalEnvironment());
+            prependStatements(statements, endLexicalEnvironment());
 
             const exportStarFunction = addExportStarIfNeeded(statements)!; // TODO: GH#18217
             const moduleObject = createObjectLiteral([

src/compiler/transformers/ts.ts

@@ -669,7 +669,7 @@ namespace ts {
                 setEmitFlags(statement, EmitFlags.NoComments | EmitFlags.NoTokenSourceMaps);
                 statements.push(statement);
 
-                prependRange(statements, context.endLexicalEnvironment());
+                prependStatements(statements, context.endLexicalEnvironment());
 
                 const iife = createImmediatelyInvokedArrowFunction(statements);
                 setEmitFlags(iife, EmitFlags.TypeScriptClassWrapper);
@@ -2693,7 +2693,7 @@ namespace ts {
             const statements: Statement[] = [];
             startLexicalEnvironment();
             const members = map(node.members, transformEnumMember);
-            prependRange(statements, endLexicalEnvironment());
+            prependStatements(statements, endLexicalEnvironment());
             addRange(statements, members);
 
             currentNamespaceContainerName = savedCurrentNamespaceLocalName;
@@ -3008,7 +3008,7 @@ namespace ts {
                 statementsLocation = moveRangePos(moduleBlock.statements, -1);
             }
 
-            prependRange(statements, endLexicalEnvironment());
+            prependStatements(statements, endLexicalEnvironment());
             currentNamespaceContainerName = savedCurrentNamespaceContainerName;
             currentNamespace = savedCurrentNamespace;
             currentScopeFirstDeclarationsOfName = savedCurrentScopeFirstDeclarationsOfName;

src/compiler/utilities.ts

@@ -254,6 +254,25 @@ namespace ts {
         return !nodeIsMissing(node);
     }
 
+    /**
+     * Appends a range of value to begin of an array, returning the array.
+     *
+     * @param to The array to which `value` is to be appended. If `to` is `undefined`, a new array
+     * is created if `value` was appended.
+     * @param from The values to append to the array. If `from` is `undefined`, nothing is
+     * appended. If an element of `from` is `undefined`, that element is not appended.
+     */
+    export function prependStatements<T extends Statement>(to: T[], from: ReadonlyArray<T> | undefined): T[] | undefined {
+        if (from === undefined || from.length === 0) return to;
+        if (to === undefined) return from.slice();
+        const prologue = to.length && isPrologueDirective(to[0]) && to.shift();
+        to.unshift(...from);
+        if (prologue) {
+            to.unshift(prologue);
+        }
+        return to;
+    }
+
     /**
      * Determine if the given comment is a triple-slash
      *

src/compiler/visitor.ts

@@ -1469,7 +1469,7 @@ namespace ts {
 
         return isNodeArray(statements)
             ? setTextRange(createNodeArray(concatenate(declarations, statements)), statements)
-            : prependRange(statements, declarations);
+            : prependStatements(statements, declarations);
     }
 
     /**