From dd1ef88d016dc40a145eafc0a1169e7f0a4a9ebe Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Tue, 6 Apr 2021 17:07:35 -0700
Subject: [PATCH] Use control flow to type CommonJS exports (#42751)

* Allow redeclaring CommonJS alias with initial undefined

This allows us to read our own output, plus the times when people
manually write exactly the same pattern.

Fixes #40555

* Use control flow to type commonjs exports

1. Could probably use a *lot* more tests.
2. getTypeOfAlias redoes some work from resolveAlias because it needs to
not resolve the alias completely, just to its export.

* fix lint, improve jsdoc

* Add tests, improve+fix control flow

1. Update the module.exports test to match the exports ones.
2. Add a test of evolving commonjs type.
3. Add a test of assignment as last statement.

(1) exposed a bug that required a better synthetic reference. (3)
exposed a bug that was most easily fixed by giving source files a
`endFlowNode` like functions and setting it in the binder.

* fix lint
---
 src/compiler/binder.ts                        |  1 +
 src/compiler/checker.ts                       | 45 +++++++++---
 src/compiler/types.ts                         |  1 +
 .../moduleExportDuplicateAlias.errors.txt     | 20 +++---
 .../reference/moduleExportDuplicateAlias.js   | 20 +++++-
 .../moduleExportDuplicateAlias.symbols        | 33 +++++++--
 .../moduleExportDuplicateAlias.types          | 31 +++++++--
 .../reference/moduleExportDuplicateAlias2.js  | 32 +++++++++
 .../moduleExportDuplicateAlias2.symbols       | 44 ++++++++++++
 .../moduleExportDuplicateAlias2.types         | 50 ++++++++++++++
 .../reference/moduleExportDuplicateAlias3.js  | 39 +++++++++++
 .../moduleExportDuplicateAlias3.symbols       | 57 ++++++++++++++++
 .../moduleExportDuplicateAlias3.types         | 68 +++++++++++++++++++
 .../salsa/moduleExportDuplicateAlias.ts       |  9 ++-
 .../salsa/moduleExportDuplicateAlias2.ts      | 14 ++++
 .../salsa/moduleExportDuplicateAlias3.ts      | 17 +++++
 16 files changed, 450 insertions(+), 31 deletions(-)
 create mode 100644 tests/baselines/reference/moduleExportDuplicateAlias2.js
 create mode 100644 tests/baselines/reference/moduleExportDuplicateAlias2.symbols
 create mode 100644 tests/baselines/reference/moduleExportDuplicateAlias2.types
 create mode 100644 tests/baselines/reference/moduleExportDuplicateAlias3.js
 create mode 100644 tests/baselines/reference/moduleExportDuplicateAlias3.symbols
 create mode 100644 tests/baselines/reference/moduleExportDuplicateAlias3.types
 create mode 100644 tests/cases/conformance/salsa/moduleExportDuplicateAlias2.ts
 create mode 100644 tests/cases/conformance/salsa/moduleExportDuplicateAlias3.ts

diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index c6a2b14afdf..7038d1121dd 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -683,6 +683,7 @@ namespace ts {
                 }
                 if (node.kind === SyntaxKind.SourceFile) {
                     node.flags |= emitFlags;
+                    (node as SourceFile).endFlowNode = currentFlow;
                 }
 
                 if (currentReturnTarget) {
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 6d85af03e53..2d5db22a565 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -2473,7 +2473,7 @@ namespace ts {
         }
 
         function getDeclarationOfAliasSymbol(symbol: Symbol): Declaration | undefined {
-            return symbol.declarations?.find(isAliasSymbolDeclaration);
+            return symbol.declarations && findLast<Declaration>(symbol.declarations, isAliasSymbolDeclaration);
         }
 
         /**
@@ -8449,6 +8449,23 @@ namespace ts {
             };
         }
 
+        /** Create a synthetic property access flow node after the last statement of the file */
+        function getFlowTypeFromCommonJSExport(symbol: Symbol) {
+            const file = getSourceFileOfNode(symbol.declarations![0]);
+            const accessName = unescapeLeadingUnderscores(symbol.escapedName);
+            const areAllModuleExports = symbol.declarations!.every(d => isInJSFile(d) && isAccessExpression(d) && isModuleExportsAccessExpression(d.expression));
+            const reference = areAllModuleExports
+                ? factory.createPropertyAccessExpression(factory.createPropertyAccessExpression(factory.createIdentifier("module"), factory.createIdentifier("exports")), accessName)
+                : factory.createPropertyAccessExpression(factory.createIdentifier("exports"), accessName);
+            if (areAllModuleExports) {
+                setParent((reference.expression as PropertyAccessExpression).expression, reference.expression);
+            }
+            setParent(reference.expression, reference);
+            setParent(reference, file);
+            reference.flowNode = file.endFlowNode;
+            return getFlowTypeOfReference(reference, autoType, undefinedType);
+        }
+
         function getFlowTypeInConstructor(symbol: Symbol, constructor: ConstructorDeclaration) {
             const accessName = startsWith(symbol.escapedName as string, "__#")
                 ? factory.createPrivateIdentifier((symbol.escapedName as string).split("@")[1])
@@ -9186,14 +9203,15 @@ namespace ts {
             const links = getSymbolLinks(symbol);
             if (!links.type) {
                 const targetSymbol = resolveAlias(symbol);
-
+                const exportSymbol = symbol.declarations && getTargetOfAliasDeclaration(getDeclarationOfAliasSymbol(symbol)!, /*dontResolveAlias*/ true);
                 // It only makes sense to get the type of a value symbol. If the result of resolving
                 // the alias is not a value, then it has no type. To get the type associated with a
                 // type symbol, call getDeclaredTypeOfSymbol.
                 // This check is important because without it, a call to getTypeOfSymbol could end
                 // up recursively calling getTypeOfAlias, causing a stack overflow.
-                links.type = targetSymbol.flags & SymbolFlags.Value
-                    ? getTypeOfSymbol(targetSymbol)
+                links.type = exportSymbol?.declarations && isDuplicatedCommonJSExport(exportSymbol.declarations) && symbol.declarations!.length ? getFlowTypeFromCommonJSExport(exportSymbol)
+                    : isDuplicatedCommonJSExport(symbol.declarations) ? autoType
+                    : targetSymbol.flags & SymbolFlags.Value ? getTypeOfSymbol(targetSymbol)
                     : errorType;
             }
             return links.type;
@@ -27133,7 +27151,10 @@ namespace ts {
             // accessor, or optional method.
             const assignmentKind = getAssignmentTargetKind(node);
             if (assignmentKind === AssignmentKind.Definite ||
-                prop && !(prop.flags & (SymbolFlags.Variable | SymbolFlags.Property | SymbolFlags.Accessor)) && !(prop.flags & SymbolFlags.Method && propType.flags & TypeFlags.Union)) {
+                prop &&
+                !(prop.flags & (SymbolFlags.Variable | SymbolFlags.Property | SymbolFlags.Accessor))
+                && !(prop.flags & SymbolFlags.Method && propType.flags & TypeFlags.Union)
+                && !isDuplicatedCommonJSExport(prop.declarations)) {
                 return propType;
             }
             if (propType === autoType) {
@@ -38154,9 +38175,11 @@ namespace ts {
                             return;
                         }
                         if (exportedDeclarationsCount > 1) {
-                            for (const declaration of declarations!) {
-                                if (isNotOverload(declaration)) {
-                                    diagnostics.add(createDiagnosticForNode(declaration, Diagnostics.Cannot_redeclare_exported_variable_0, unescapeLeadingUnderscores(id)));
+                            if (!isDuplicatedCommonJSExport(declarations)) {
+                                for (const declaration of declarations!) {
+                                    if (isNotOverload(declaration)) {
+                                        diagnostics.add(createDiagnosticForNode(declaration, Diagnostics.Cannot_redeclare_exported_variable_0, unescapeLeadingUnderscores(id)));
+                                    }
                                 }
                             }
                         }
@@ -38166,6 +38189,12 @@ namespace ts {
             }
         }
 
+        function isDuplicatedCommonJSExport(declarations: Declaration[] | undefined) {
+            return declarations
+                && declarations.length > 1
+                && declarations.every(d => isInJSFile(d) && isAccessExpression(d) && (isExportsIdentifier(d.expression) || isModuleExportsAccessExpression(d.expression)));
+        }
+
         function checkSourceElement(node: Node | undefined): void {
             if (node) {
                 const saveCurrentNode = currentNode;
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index defe381d481..8709515aa5a 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -3545,6 +3545,7 @@ namespace ts {
         /* @internal */ localJsxFragmentFactory?: EntityName;
 
         /* @internal */ exportedModulesFromDeclarationEmit?: ExportedModulesFromDeclarationEmit;
+        /* @internal */ endFlowNode?: FlowNode;
     }
 
     /* @internal */
diff --git a/tests/baselines/reference/moduleExportDuplicateAlias.errors.txt b/tests/baselines/reference/moduleExportDuplicateAlias.errors.txt
index d216af6f764..e744496c41f 100644
--- a/tests/baselines/reference/moduleExportDuplicateAlias.errors.txt
+++ b/tests/baselines/reference/moduleExportDuplicateAlias.errors.txt
@@ -1,16 +1,16 @@
-tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias.js(1,1): error TS2323: Cannot redeclare exported variable 'apply'.
-tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias.js(3,1): error TS2322: Type '() => void' is not assignable to type 'undefined'.
-tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias.js(3,1): error TS2323: Cannot redeclare exported variable 'apply'.
+tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias.js(3,1): error TS2722: Cannot invoke an object which is possibly 'undefined'.
 
 
-==== tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias.js (3 errors) ====
+==== tests/cases/conformance/salsa/test.js (0 errors) ====
+    const { apply } = require('./moduleExportAliasDuplicateAlias')
+    apply()
+    
+==== tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias.js (1 errors) ====
     exports.apply = undefined;
-    ~~~~~~~~~~~~~
-!!! error TS2323: Cannot redeclare exported variable 'apply'.
     function a() { }
+    exports.apply()
+    ~~~~~~~~~~~~~
+!!! error TS2722: Cannot invoke an object which is possibly 'undefined'.
     exports.apply = a;
-    ~~~~~~~~~~~~~
-!!! error TS2322: Type '() => void' is not assignable to type 'undefined'.
-    ~~~~~~~~~~~~~
-!!! error TS2323: Cannot redeclare exported variable 'apply'.
+    exports.apply()
     
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleExportDuplicateAlias.js b/tests/baselines/reference/moduleExportDuplicateAlias.js
index 305b19fd68b..f90ff20d565 100644
--- a/tests/baselines/reference/moduleExportDuplicateAlias.js
+++ b/tests/baselines/reference/moduleExportDuplicateAlias.js
@@ -1,14 +1,32 @@
+//// [tests/cases/conformance/salsa/moduleExportDuplicateAlias.ts] ////
+
 //// [moduleExportAliasDuplicateAlias.js]
 exports.apply = undefined;
 function a() { }
+exports.apply()
 exports.apply = a;
+exports.apply()
+
+//// [test.js]
+const { apply } = require('./moduleExportAliasDuplicateAlias')
+apply()
 
 
 //// [moduleExportAliasDuplicateAlias.js]
+"use strict";
 exports.apply = undefined;
 function a() { }
+exports.apply();
 exports.apply = a;
+exports.apply();
+//// [test.js]
+"use strict";
+var apply = require('./moduleExportAliasDuplicateAlias').apply;
+apply();
 
 
 //// [moduleExportAliasDuplicateAlias.d.ts]
-export { undefined as apply };
+export { a as apply };
+declare function a(): void;
+//// [test.d.ts]
+export {};
diff --git a/tests/baselines/reference/moduleExportDuplicateAlias.symbols b/tests/baselines/reference/moduleExportDuplicateAlias.symbols
index 5c9bfaae375..f8907d2abb8 100644
--- a/tests/baselines/reference/moduleExportDuplicateAlias.symbols
+++ b/tests/baselines/reference/moduleExportDuplicateAlias.symbols
@@ -1,16 +1,35 @@
+=== tests/cases/conformance/salsa/test.js ===
+const { apply } = require('./moduleExportAliasDuplicateAlias')
+>apply : Symbol(apply, Decl(test.js, 0, 7))
+>require : Symbol(require)
+>'./moduleExportAliasDuplicateAlias' : Symbol("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias", Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+
+apply()
+>apply : Symbol(apply, Decl(test.js, 0, 7))
+
 === tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias.js ===
 exports.apply = undefined;
->exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16))
->exports : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16))
->apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16))
->undefined : Symbol(apply)
+>exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 2, 15))
+>exports : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 2, 15))
+>apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 2, 15))
+>undefined : Symbol(undefined)
 
 function a() { }
 >a : Symbol(a, Decl(moduleExportAliasDuplicateAlias.js, 0, 26))
 
+exports.apply()
+>exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 2, 15))
+>exports : Symbol("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias", Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+>apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 2, 15))
+
 exports.apply = a;
->exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16))
->exports : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16))
->apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16))
+>exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 2, 15))
+>exports : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 2, 15))
+>apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 2, 15))
 >a : Symbol(a, Decl(moduleExportAliasDuplicateAlias.js, 0, 26))
 
+exports.apply()
+>exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 2, 15))
+>exports : Symbol("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias", Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+>apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 2, 15))
+
diff --git a/tests/baselines/reference/moduleExportDuplicateAlias.types b/tests/baselines/reference/moduleExportDuplicateAlias.types
index 1c924ac41e6..1ea6ae6082f 100644
--- a/tests/baselines/reference/moduleExportDuplicateAlias.types
+++ b/tests/baselines/reference/moduleExportDuplicateAlias.types
@@ -1,18 +1,41 @@
+=== tests/cases/conformance/salsa/test.js ===
+const { apply } = require('./moduleExportAliasDuplicateAlias')
+>apply : () => void
+>require('./moduleExportAliasDuplicateAlias') : typeof import("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias")
+>require : any
+>'./moduleExportAliasDuplicateAlias' : "./moduleExportAliasDuplicateAlias"
+
+apply()
+>apply() : void
+>apply : () => void
+
 === tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias.js ===
 exports.apply = undefined;
 >exports.apply = undefined : undefined
->exports.apply : undefined
+>exports.apply : any
 >exports : typeof import("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias")
->apply : undefined
+>apply : any
 >undefined : undefined
 
 function a() { }
 >a : () => void
 
-exports.apply = a;
->exports.apply = a : () => void
+exports.apply()
+>exports.apply() : any
 >exports.apply : undefined
 >exports : typeof import("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias")
 >apply : undefined
+
+exports.apply = a;
+>exports.apply = a : () => void
+>exports.apply : any
+>exports : typeof import("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias")
+>apply : any
 >a : () => void
 
+exports.apply()
+>exports.apply() : void
+>exports.apply : () => void
+>exports : typeof import("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias")
+>apply : () => void
+
diff --git a/tests/baselines/reference/moduleExportDuplicateAlias2.js b/tests/baselines/reference/moduleExportDuplicateAlias2.js
new file mode 100644
index 00000000000..89059dcd4f7
--- /dev/null
+++ b/tests/baselines/reference/moduleExportDuplicateAlias2.js
@@ -0,0 +1,32 @@
+//// [tests/cases/conformance/salsa/moduleExportDuplicateAlias2.ts] ////
+
+//// [moduleExportAliasDuplicateAlias.js]
+module.exports.apply = undefined;
+function a() { }
+module.exports.apply = a;
+module.exports.apply = a;
+module.exports.apply()
+
+//// [test.js]
+const { apply } = require('./moduleExportAliasDuplicateAlias')
+apply()
+
+
+//// [moduleExportAliasDuplicateAlias.js]
+"use strict";
+module.exports.apply = undefined;
+function a() { }
+module.exports.apply = a;
+module.exports.apply = a;
+module.exports.apply();
+//// [test.js]
+"use strict";
+var apply = require('./moduleExportAliasDuplicateAlias').apply;
+apply();
+
+
+//// [moduleExportAliasDuplicateAlias.d.ts]
+export { a as apply };
+declare function a(): void;
+//// [test.d.ts]
+export {};
diff --git a/tests/baselines/reference/moduleExportDuplicateAlias2.symbols b/tests/baselines/reference/moduleExportDuplicateAlias2.symbols
new file mode 100644
index 00000000000..0419db925b9
--- /dev/null
+++ b/tests/baselines/reference/moduleExportDuplicateAlias2.symbols
@@ -0,0 +1,44 @@
+=== tests/cases/conformance/salsa/test.js ===
+const { apply } = require('./moduleExportAliasDuplicateAlias')
+>apply : Symbol(apply, Decl(test.js, 0, 7))
+>require : Symbol(require)
+>'./moduleExportAliasDuplicateAlias' : Symbol("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias", Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+
+apply()
+>apply : Symbol(apply, Decl(test.js, 0, 7))
+
+=== tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias.js ===
+module.exports.apply = undefined;
+>module.exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16), Decl(moduleExportAliasDuplicateAlias.js, 2, 25))
+>module.exports : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16), Decl(moduleExportAliasDuplicateAlias.js, 2, 25))
+>module : Symbol(module, Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+>exports : Symbol(module.exports, Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+>apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16), Decl(moduleExportAliasDuplicateAlias.js, 2, 25))
+>undefined : Symbol(undefined)
+
+function a() { }
+>a : Symbol(a, Decl(moduleExportAliasDuplicateAlias.js, 0, 33))
+
+module.exports.apply = a;
+>module.exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16), Decl(moduleExportAliasDuplicateAlias.js, 2, 25))
+>module.exports : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16), Decl(moduleExportAliasDuplicateAlias.js, 2, 25))
+>module : Symbol(module, Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+>exports : Symbol(module.exports, Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+>apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16), Decl(moduleExportAliasDuplicateAlias.js, 2, 25))
+>a : Symbol(a, Decl(moduleExportAliasDuplicateAlias.js, 0, 33))
+
+module.exports.apply = a;
+>module.exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16), Decl(moduleExportAliasDuplicateAlias.js, 2, 25))
+>module.exports : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16), Decl(moduleExportAliasDuplicateAlias.js, 2, 25))
+>module : Symbol(module, Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+>exports : Symbol(module.exports, Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+>apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16), Decl(moduleExportAliasDuplicateAlias.js, 2, 25))
+>a : Symbol(a, Decl(moduleExportAliasDuplicateAlias.js, 0, 33))
+
+module.exports.apply()
+>module.exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16), Decl(moduleExportAliasDuplicateAlias.js, 2, 25))
+>module.exports : Symbol(module.exports, Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+>module : Symbol(module, Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+>exports : Symbol(module.exports, Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+>apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 1, 16), Decl(moduleExportAliasDuplicateAlias.js, 2, 25))
+
diff --git a/tests/baselines/reference/moduleExportDuplicateAlias2.types b/tests/baselines/reference/moduleExportDuplicateAlias2.types
new file mode 100644
index 00000000000..26d810b48b7
--- /dev/null
+++ b/tests/baselines/reference/moduleExportDuplicateAlias2.types
@@ -0,0 +1,50 @@
+=== tests/cases/conformance/salsa/test.js ===
+const { apply } = require('./moduleExportAliasDuplicateAlias')
+>apply : () => void
+>require('./moduleExportAliasDuplicateAlias') : typeof import("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias")
+>require : any
+>'./moduleExportAliasDuplicateAlias' : "./moduleExportAliasDuplicateAlias"
+
+apply()
+>apply() : void
+>apply : () => void
+
+=== tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias.js ===
+module.exports.apply = undefined;
+>module.exports.apply = undefined : undefined
+>module.exports.apply : any
+>module.exports : typeof module.exports
+>module : { exports: typeof module.exports; }
+>exports : typeof module.exports
+>apply : any
+>undefined : undefined
+
+function a() { }
+>a : () => void
+
+module.exports.apply = a;
+>module.exports.apply = a : () => void
+>module.exports.apply : any
+>module.exports : typeof module.exports
+>module : { exports: typeof module.exports; }
+>exports : typeof module.exports
+>apply : any
+>a : () => void
+
+module.exports.apply = a;
+>module.exports.apply = a : () => void
+>module.exports.apply : any
+>module.exports : typeof module.exports
+>module : { exports: typeof module.exports; }
+>exports : typeof module.exports
+>apply : any
+>a : () => void
+
+module.exports.apply()
+>module.exports.apply() : void
+>module.exports.apply : () => void
+>module.exports : typeof module.exports
+>module : { exports: typeof module.exports; }
+>exports : typeof module.exports
+>apply : () => void
+
diff --git a/tests/baselines/reference/moduleExportDuplicateAlias3.js b/tests/baselines/reference/moduleExportDuplicateAlias3.js
new file mode 100644
index 00000000000..666744dc4cd
--- /dev/null
+++ b/tests/baselines/reference/moduleExportDuplicateAlias3.js
@@ -0,0 +1,39 @@
+//// [tests/cases/conformance/salsa/moduleExportDuplicateAlias3.ts] ////
+
+//// [moduleExportAliasDuplicateAlias.js]
+exports.apply = undefined;
+exports.apply = undefined;
+function a() { }
+exports.apply = a;
+exports.apply()
+exports.apply = 'ok'
+var OK = exports.apply.toUpperCase()
+exports.apply = 1
+
+//// [test.js]
+const { apply } = require('./moduleExportAliasDuplicateAlias')
+const result = apply.toFixed()
+
+
+//// [moduleExportAliasDuplicateAlias.js]
+"use strict";
+exports.apply = undefined;
+exports.apply = undefined;
+function a() { }
+exports.apply = a;
+exports.apply();
+exports.apply = 'ok';
+var OK = exports.apply.toUpperCase();
+exports.apply = 1;
+//// [test.js]
+"use strict";
+var apply = require('./moduleExportAliasDuplicateAlias').apply;
+var result = apply.toFixed();
+
+
+//// [moduleExportAliasDuplicateAlias.d.ts]
+export var apply: string | number | typeof a | undefined;
+export { a as apply };
+declare function a(): void;
+//// [test.d.ts]
+export {};
diff --git a/tests/baselines/reference/moduleExportDuplicateAlias3.symbols b/tests/baselines/reference/moduleExportDuplicateAlias3.symbols
new file mode 100644
index 00000000000..8c8d2642287
--- /dev/null
+++ b/tests/baselines/reference/moduleExportDuplicateAlias3.symbols
@@ -0,0 +1,57 @@
+=== tests/cases/conformance/salsa/test.js ===
+const { apply } = require('./moduleExportAliasDuplicateAlias')
+>apply : Symbol(apply, Decl(test.js, 0, 7))
+>require : Symbol(require)
+>'./moduleExportAliasDuplicateAlias' : Symbol("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias", Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+
+const result = apply.toFixed()
+>result : Symbol(result, Decl(test.js, 1, 5))
+>apply.toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+>apply : Symbol(apply, Decl(test.js, 0, 7))
+>toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
+
+=== tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias.js ===
+exports.apply = undefined;
+>exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>exports : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>undefined : Symbol(undefined)
+
+exports.apply = undefined;
+>exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>exports : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>undefined : Symbol(undefined)
+
+function a() { }
+>a : Symbol(a, Decl(moduleExportAliasDuplicateAlias.js, 1, 26))
+
+exports.apply = a;
+>exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>exports : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>a : Symbol(a, Decl(moduleExportAliasDuplicateAlias.js, 1, 26))
+
+exports.apply()
+>exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>exports : Symbol("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias", Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+>apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+
+exports.apply = 'ok'
+>exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>exports : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+
+var OK = exports.apply.toUpperCase()
+>OK : Symbol(OK, Decl(moduleExportAliasDuplicateAlias.js, 6, 3))
+>exports.apply.toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+>exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>exports : Symbol("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias", Decl(moduleExportAliasDuplicateAlias.js, 0, 0))
+>apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>toUpperCase : Symbol(String.toUpperCase, Decl(lib.es5.d.ts, --, --))
+
+exports.apply = 1
+>exports.apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>exports : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+>apply : Symbol(apply, Decl(moduleExportAliasDuplicateAlias.js, 0, 0), Decl(moduleExportAliasDuplicateAlias.js, 0, 26), Decl(moduleExportAliasDuplicateAlias.js, 2, 16), Decl(moduleExportAliasDuplicateAlias.js, 4, 15), Decl(moduleExportAliasDuplicateAlias.js, 6, 36))
+
diff --git a/tests/baselines/reference/moduleExportDuplicateAlias3.types b/tests/baselines/reference/moduleExportDuplicateAlias3.types
new file mode 100644
index 00000000000..e0c71bdfd46
--- /dev/null
+++ b/tests/baselines/reference/moduleExportDuplicateAlias3.types
@@ -0,0 +1,68 @@
+=== tests/cases/conformance/salsa/test.js ===
+const { apply } = require('./moduleExportAliasDuplicateAlias')
+>apply : number
+>require('./moduleExportAliasDuplicateAlias') : typeof import("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias")
+>require : any
+>'./moduleExportAliasDuplicateAlias' : "./moduleExportAliasDuplicateAlias"
+
+const result = apply.toFixed()
+>result : string
+>apply.toFixed() : string
+>apply.toFixed : (fractionDigits?: number | undefined) => string
+>apply : number
+>toFixed : (fractionDigits?: number | undefined) => string
+
+=== tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias.js ===
+exports.apply = undefined;
+>exports.apply = undefined : undefined
+>exports.apply : string | number | (() => void) | undefined
+>exports : typeof import("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias")
+>apply : string | number | (() => void) | undefined
+>undefined : undefined
+
+exports.apply = undefined;
+>exports.apply = undefined : undefined
+>exports.apply : string | number | (() => void) | undefined
+>exports : typeof import("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias")
+>apply : string | number | (() => void) | undefined
+>undefined : undefined
+
+function a() { }
+>a : () => void
+
+exports.apply = a;
+>exports.apply = a : () => void
+>exports.apply : string | number | (() => void) | undefined
+>exports : typeof import("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias")
+>apply : string | number | (() => void) | undefined
+>a : () => void
+
+exports.apply()
+>exports.apply() : void
+>exports.apply : () => void
+>exports : typeof import("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias")
+>apply : () => void
+
+exports.apply = 'ok'
+>exports.apply = 'ok' : "ok"
+>exports.apply : string | number | (() => void) | undefined
+>exports : typeof import("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias")
+>apply : string | number | (() => void) | undefined
+>'ok' : "ok"
+
+var OK = exports.apply.toUpperCase()
+>OK : string
+>exports.apply.toUpperCase() : string
+>exports.apply.toUpperCase : () => string
+>exports.apply : string
+>exports : typeof import("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias")
+>apply : string
+>toUpperCase : () => string
+
+exports.apply = 1
+>exports.apply = 1 : 1
+>exports.apply : string | number | (() => void) | undefined
+>exports : typeof import("tests/cases/conformance/salsa/moduleExportAliasDuplicateAlias")
+>apply : string | number | (() => void) | undefined
+>1 : 1
+
diff --git a/tests/cases/conformance/salsa/moduleExportDuplicateAlias.ts b/tests/cases/conformance/salsa/moduleExportDuplicateAlias.ts
index 32e1a8a1ac7..b46f0e2445c 100644
--- a/tests/cases/conformance/salsa/moduleExportDuplicateAlias.ts
+++ b/tests/cases/conformance/salsa/moduleExportDuplicateAlias.ts
@@ -1,7 +1,14 @@
 // @checkJs: true
+// @strict: true
 // @declaration: true
-// @filename: moduleExportAliasDuplicateAlias.js
 // @outdir: out
+// @filename: moduleExportAliasDuplicateAlias.js
 exports.apply = undefined;
 function a() { }
+exports.apply()
 exports.apply = a;
+exports.apply()
+
+// @filename: test.js
+const { apply } = require('./moduleExportAliasDuplicateAlias')
+apply()
diff --git a/tests/cases/conformance/salsa/moduleExportDuplicateAlias2.ts b/tests/cases/conformance/salsa/moduleExportDuplicateAlias2.ts
new file mode 100644
index 00000000000..27f724d97be
--- /dev/null
+++ b/tests/cases/conformance/salsa/moduleExportDuplicateAlias2.ts
@@ -0,0 +1,14 @@
+// @checkJs: true
+// @strict: true
+// @declaration: true
+// @outdir: out
+// @filename: moduleExportAliasDuplicateAlias.js
+module.exports.apply = undefined;
+function a() { }
+module.exports.apply = a;
+module.exports.apply = a;
+module.exports.apply()
+
+// @filename: test.js
+const { apply } = require('./moduleExportAliasDuplicateAlias')
+apply()
diff --git a/tests/cases/conformance/salsa/moduleExportDuplicateAlias3.ts b/tests/cases/conformance/salsa/moduleExportDuplicateAlias3.ts
new file mode 100644
index 00000000000..7f78af66e31
--- /dev/null
+++ b/tests/cases/conformance/salsa/moduleExportDuplicateAlias3.ts
@@ -0,0 +1,17 @@
+// @checkJs: true
+// @strict: true
+// @declaration: true
+// @filename: moduleExportAliasDuplicateAlias.js
+// @outdir: out
+exports.apply = undefined;
+exports.apply = undefined;
+function a() { }
+exports.apply = a;
+exports.apply()
+exports.apply = 'ok'
+var OK = exports.apply.toUpperCase()
+exports.apply = 1
+
+// @filename: test.js
+const { apply } = require('./moduleExportAliasDuplicateAlias')
+const result = apply.toFixed()