diff --git a/src/compiler/declarationEmitter.ts b/src/compiler/declarationEmitter.ts
index 9534b22f47a..76c3175dcd5 100644
--- a/src/compiler/declarationEmitter.ts
+++ b/src/compiler/declarationEmitter.ts
@@ -69,22 +69,16 @@ namespace ts {
             if (!compilerOptions.noResolve) {
                 let addedGlobalFileReference = false;
                 forEach(root.referencedFiles, fileReference => {
-                    if (isJavaScript(fileReference.fileName)) {
-                        reportedDeclarationError = true;
-                        diagnostics.push(createFileDiagnostic(root, fileReference.pos, fileReference.end - fileReference.pos, Diagnostics.js_file_cannot_be_referenced_in_ts_file_when_emitting_declarations));
-                    }
-                    else {
-                        let referencedFile = tryResolveScriptReference(host, root, fileReference);
+                    let referencedFile = tryResolveScriptReference(host, root, fileReference);
 
-                        // All the references that are not going to be part of same file
-                        if (referencedFile && ((referencedFile.flags & NodeFlags.DeclarationFile) || // This is a declare file reference
-                            shouldEmitToOwnFile(referencedFile, compilerOptions) || // This is referenced file is emitting its own js file
-                            !addedGlobalFileReference)) { // Or the global out file corresponding to this reference was not added
+                    // All the references that are not going to be part of same file
+                    if (referencedFile && ((referencedFile.flags & NodeFlags.DeclarationFile) || // This is a declare file reference
+                        shouldEmitToOwnFile(referencedFile, compilerOptions) || // This is referenced file is emitting its own js file
+                        !addedGlobalFileReference)) { // Or the global out file corresponding to this reference was not added
 
-                            writeReferencePath(referencedFile);
-                            if (!isExternalModuleOrDeclarationFile(referencedFile)) {
-                                addedGlobalFileReference = true;
-                            }
+                        writeReferencePath(referencedFile);
+                        if (!isExternalModuleOrDeclarationFile(referencedFile)) {
+                            addedGlobalFileReference = true;
                         }
                     }
                 });
@@ -111,24 +105,18 @@ namespace ts {
             // Emit references corresponding to this file
             let emittedReferencedFiles: SourceFile[] = [];
             forEach(host.getSourceFiles(), sourceFile => {
-                if (!isExternalModuleOrDeclarationFile(sourceFile) && !isJavaScript(sourceFile.fileName)) {
+                if (!isExternalModuleOrDeclarationFile(sourceFile)) {
                     // Check what references need to be added
                     if (!compilerOptions.noResolve) {
                         forEach(sourceFile.referencedFiles, fileReference => {
-                            if (isJavaScript(fileReference.fileName)) {
-                                reportedDeclarationError = true;
-                                diagnostics.push(createFileDiagnostic(sourceFile, fileReference.pos, fileReference.end - fileReference.pos, Diagnostics.js_file_cannot_be_referenced_in_ts_file_when_emitting_declarations));
-                            }
-                            else {
-                                let referencedFile = tryResolveScriptReference(host, sourceFile, fileReference);
+                            let referencedFile = tryResolveScriptReference(host, sourceFile, fileReference);
 
-                                // If the reference file is a declaration file or an external module, emit that reference
-                                if (referencedFile && (isExternalModuleOrDeclarationFile(referencedFile) &&
-                                    !contains(emittedReferencedFiles, referencedFile))) { // If the file reference was not already emitted
+                            // If the reference file is a declaration file or an external module, emit that reference
+                            if (referencedFile && (isExternalModuleOrDeclarationFile(referencedFile) &&
+                                !contains(emittedReferencedFiles, referencedFile))) { // If the file reference was not already emitted
 
-                                    writeReferencePath(referencedFile);
-                                    emittedReferencedFiles.push(referencedFile);
-                                }
+                                writeReferencePath(referencedFile);
+                                emittedReferencedFiles.push(referencedFile);
                             }
                         });
                     }
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 00e13ba634c..d1beacfeaa9 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -2465,10 +2465,6 @@
         "category": "Error",
         "code": 8017
     },
-    ".js file cannot be referenced in .ts file when emitting declarations.": {
-        "category": "Error",
-        "code": 8018
-    },
 
     "Only identifiers/qualified-names with optional type arguments are currently supported in a class 'extends' clauses.": {
         "category": "Error",
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index ea2fd36889f..ff60a5927bd 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -342,7 +342,6 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, Promi
                 emitFile(getEmitFileNames(targetSourceFile, host), targetSourceFile);
             }
             else if (!isDeclarationFile(targetSourceFile) &&
-                !isJavaScript(targetSourceFile.fileName) &&
                 (compilerOptions.outFile || compilerOptions.out)) {
                 emitFile(getBundledEmitFileNames(compilerOptions));
             }
@@ -462,7 +461,7 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, Promi
             }
             else {
                 forEach(host.getSourceFiles(), sourceFile => {
-                    if (!isJavaScript(sourceFile.fileName) && !isExternalModuleOrDeclarationFile(sourceFile)) {
+                    if (!isExternalModuleOrDeclarationFile(sourceFile)) {
                         emitSourceFile(sourceFile);
                     }
                 });
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index f8a1af6f5cf..f4dd2c02c8d 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -1769,7 +1769,7 @@ namespace ts {
     }
 
     export function getEmitFileNames(sourceFile: SourceFile, host: EmitHost) {
-        if (!isDeclarationFile(sourceFile) && !isJavaScript(sourceFile.fileName)) {
+        if (!isDeclarationFile(sourceFile)) {
             let options = host.getCompilerOptions();
             let jsFilePath: string;
             if (shouldEmitToOwnFile(sourceFile, options)) {
@@ -1835,12 +1835,12 @@ namespace ts {
     }
 
     export function shouldEmitToOwnFile(sourceFile: SourceFile, compilerOptions: CompilerOptions): boolean {
-        if (!isDeclarationFile(sourceFile) && !isJavaScript(sourceFile.fileName)) {
+        if (!isDeclarationFile(sourceFile)) {
             if ((isExternalModule(sourceFile) || !(compilerOptions.outFile || compilerOptions.out))) {
                 // 1. in-browser single file compilation scenario
                 // 2. non supported extension file
                 return compilerOptions.isolatedModules ||
-                    forEach(supportedTypeScriptExtensions, extension => fileExtensionIs(sourceFile.fileName, extension));
+                    forEach(getSupportedExtensions(compilerOptions), extension => fileExtensionIs(sourceFile.fileName, extension));
             }
             return false;
         }
diff --git a/tests/baselines/reference/jsFileCompilationAmbientVarDeclarationSyntax.errors.txt b/tests/baselines/reference/jsFileCompilationAmbientVarDeclarationSyntax.errors.txt
index a210385d996..b0732afea72 100644
--- a/tests/baselines/reference/jsFileCompilationAmbientVarDeclarationSyntax.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationAmbientVarDeclarationSyntax.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,1): error TS8009: 'declare' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     declare var v;
     ~~~~~~~
diff --git a/tests/baselines/reference/jsFileCompilationDecoratorSyntax.errors.txt b/tests/baselines/reference/jsFileCompilationDecoratorSyntax.errors.txt
index 6017ddc7a11..b7fec2eefc6 100644
--- a/tests/baselines/reference/jsFileCompilationDecoratorSyntax.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationDecoratorSyntax.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,1): error TS8017: 'decorators' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     @internal class C { }
     ~~~~~~~~~
diff --git a/tests/baselines/reference/jsFileCompilationEmitBlockedCorrectly.errors.txt b/tests/baselines/reference/jsFileCompilationEmitBlockedCorrectly.errors.txt
index eb9e11e574b..5861e73f49b 100644
--- a/tests/baselines/reference/jsFileCompilationEmitBlockedCorrectly.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationEmitBlockedCorrectly.errors.txt
@@ -1,7 +1,9 @@
 error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
+error TS5056: Cannot write file 'tests/cases/compiler/a.js' since one or more input files would emit into it.
 
 
 !!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
+!!! error TS5056: Cannot write file 'tests/cases/compiler/a.js' since one or more input files would emit into it.
 ==== tests/cases/compiler/a.ts (0 errors) ====
     class c {
     }
diff --git a/tests/baselines/reference/jsFileCompilationEmitDeclarations.js b/tests/baselines/reference/jsFileCompilationEmitDeclarations.js
index 4c9f6802fd9..c6711e4e85f 100644
--- a/tests/baselines/reference/jsFileCompilationEmitDeclarations.js
+++ b/tests/baselines/reference/jsFileCompilationEmitDeclarations.js
@@ -15,8 +15,11 @@ var c = (function () {
     }
     return c;
 })();
+function foo() {
+}
 
 
 //// [out.d.ts]
 declare class c {
 }
+declare function foo(): void;
diff --git a/tests/baselines/reference/jsFileCompilationEmitTrippleSlashReference.js b/tests/baselines/reference/jsFileCompilationEmitTrippleSlashReference.js
index 33077f3038f..04f36213b1b 100644
--- a/tests/baselines/reference/jsFileCompilationEmitTrippleSlashReference.js
+++ b/tests/baselines/reference/jsFileCompilationEmitTrippleSlashReference.js
@@ -19,8 +19,15 @@ var c = (function () {
     }
     return c;
 })();
+function bar() {
+}
+/// <reference path="c.js"/>
+function foo() {
+}
 
 
 //// [out.d.ts]
 declare class c {
 }
+declare function bar(): void;
+declare function foo(): void;
diff --git a/tests/baselines/reference/jsFileCompilationEnumSyntax.errors.txt b/tests/baselines/reference/jsFileCompilationEnumSyntax.errors.txt
index 6b9d97e55bb..e9fd9cc31b7 100644
--- a/tests/baselines/reference/jsFileCompilationEnumSyntax.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationEnumSyntax.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,6): error TS8015: 'enum declarations' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     enum E { }
          ~
diff --git a/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithNoOut.errors.txt b/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithNoOut.errors.txt
index 1d6ddb3ed30..9be6b3f1ccd 100644
--- a/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithNoOut.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithNoOut.errors.txt
@@ -1,14 +1,13 @@
-tests/cases/compiler/b.ts(1,1): error TS8018: .js file cannot be referenced in .ts file when emitting declarations.
+error TS5055: Cannot write file 'tests/cases/compiler/c.js' which is one of the input files.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/c.js' which is one of the input files.
 ==== tests/cases/compiler/a.ts (0 errors) ====
     class c {
     }
     
-==== tests/cases/compiler/b.ts (1 errors) ====
+==== tests/cases/compiler/b.ts (0 errors) ====
     /// <reference path="c.js"/>
-    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS8018: .js file cannot be referenced in .ts file when emitting declarations.
     // error on above reference path when emitting declarations
     function foo() {
     }
diff --git a/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithNoOut.js b/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithNoOut.js
index 6bd76de881b..07d6fb812c0 100644
--- a/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithNoOut.js
+++ b/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithNoOut.js
@@ -30,3 +30,8 @@ function foo() {
 //// [a.d.ts]
 declare class c {
 }
+//// [c.d.ts]
+declare function bar(): void;
+//// [b.d.ts]
+/// <reference path="c.d.ts" />
+declare function foo(): void;
diff --git a/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithOut.errors.txt b/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithOut.errors.txt
deleted file mode 100644
index a658130e10a..00000000000
--- a/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithOut.errors.txt
+++ /dev/null
@@ -1,18 +0,0 @@
-tests/cases/compiler/b.ts(1,1): error TS8018: .js file cannot be referenced in .ts file when emitting declarations.
-
-
-==== tests/cases/compiler/a.ts (0 errors) ====
-    class c {
-    }
-    
-==== tests/cases/compiler/b.ts (1 errors) ====
-    /// <reference path="c.js"/>
-    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS8018: .js file cannot be referenced in .ts file when emitting declarations.
-    // error on above reference when emitting declarations
-    function foo() {
-    }
-    
-==== tests/cases/compiler/c.js (0 errors) ====
-    function bar() {
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithOut.js b/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithOut.js
index 99dd961db4c..0d1939d7208 100644
--- a/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithOut.js
+++ b/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithOut.js
@@ -20,7 +20,16 @@ var c = (function () {
     }
     return c;
 })();
+function bar() {
+}
 /// <reference path="c.js"/>
 // error on above reference when emitting declarations
 function foo() {
 }
+
+
+//// [out.d.ts]
+declare class c {
+}
+declare function bar(): void;
+declare function foo(): void;
diff --git a/tests/baselines/reference/jsFileCompilationNoErrorWithoutDeclarationsWithJsFileReferenceWithNoOut.symbols b/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithOut.symbols
similarity index 77%
rename from tests/baselines/reference/jsFileCompilationNoErrorWithoutDeclarationsWithJsFileReferenceWithNoOut.symbols
rename to tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithOut.symbols
index 06b80b144a4..544fe53f425 100644
--- a/tests/baselines/reference/jsFileCompilationNoErrorWithoutDeclarationsWithJsFileReferenceWithNoOut.symbols
+++ b/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithOut.symbols
@@ -5,7 +5,7 @@ class c {
 
 === tests/cases/compiler/b.ts ===
 /// <reference path="c.js"/>
-// no error on above reference path since not emitting declarations
+// error on above reference when emitting declarations
 function foo() {
 >foo : Symbol(foo, Decl(b.ts, 0, 0))
 }
diff --git a/tests/baselines/reference/jsFileCompilationNoErrorWithoutDeclarationsWithJsFileReferenceWithNoOut.types b/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithOut.types
similarity index 72%
rename from tests/baselines/reference/jsFileCompilationNoErrorWithoutDeclarationsWithJsFileReferenceWithNoOut.types
rename to tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithOut.types
index ea9b48061c3..8aafb9f61d0 100644
--- a/tests/baselines/reference/jsFileCompilationNoErrorWithoutDeclarationsWithJsFileReferenceWithNoOut.types
+++ b/tests/baselines/reference/jsFileCompilationErrorOnDeclarationsWithJsFileReferenceWithOut.types
@@ -5,7 +5,7 @@ class c {
 
 === tests/cases/compiler/b.ts ===
 /// <reference path="c.js"/>
-// no error on above reference path since not emitting declarations
+// error on above reference when emitting declarations
 function foo() {
 >foo : () => void
 }
diff --git a/tests/baselines/reference/jsFileCompilationExportAssignmentSyntax.errors.txt b/tests/baselines/reference/jsFileCompilationExportAssignmentSyntax.errors.txt
index a349e2bca13..27371222dce 100644
--- a/tests/baselines/reference/jsFileCompilationExportAssignmentSyntax.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationExportAssignmentSyntax.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,1): error TS8003: 'export=' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     export = b;
     ~~~~~~~~~~~
diff --git a/tests/baselines/reference/jsFileCompilationHeritageClauseSyntaxOfClass.errors.txt b/tests/baselines/reference/jsFileCompilationHeritageClauseSyntaxOfClass.errors.txt
index df014047b35..c7d080404a2 100644
--- a/tests/baselines/reference/jsFileCompilationHeritageClauseSyntaxOfClass.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationHeritageClauseSyntaxOfClass.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,9): error TS8005: 'implements clauses' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     class C implements D { }
             ~~~~~~~~~~~~
diff --git a/tests/baselines/reference/jsFileCompilationImportEqualsSyntax.errors.txt b/tests/baselines/reference/jsFileCompilationImportEqualsSyntax.errors.txt
index e53bf2ac860..36ab7aab188 100644
--- a/tests/baselines/reference/jsFileCompilationImportEqualsSyntax.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationImportEqualsSyntax.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,1): error TS8002: 'import ... =' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     import a = b;
     ~~~~~~~~~~~~~
diff --git a/tests/baselines/reference/jsFileCompilationInterfaceSyntax.errors.txt b/tests/baselines/reference/jsFileCompilationInterfaceSyntax.errors.txt
index c46c3c05b3f..3089aeecb49 100644
--- a/tests/baselines/reference/jsFileCompilationInterfaceSyntax.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationInterfaceSyntax.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,11): error TS8006: 'interface declarations' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     interface I { }
               ~
diff --git a/tests/baselines/reference/jsFileCompilationModuleSyntax.errors.txt b/tests/baselines/reference/jsFileCompilationModuleSyntax.errors.txt
index 8748064cc96..d85819b8588 100644
--- a/tests/baselines/reference/jsFileCompilationModuleSyntax.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationModuleSyntax.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,8): error TS8007: 'module declarations' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     module M { }
            ~
diff --git a/tests/baselines/reference/jsFileCompilationNoErrorWithoutDeclarationsWithJsFileReferenceWithNoOut.errors.txt b/tests/baselines/reference/jsFileCompilationNoErrorWithoutDeclarationsWithJsFileReferenceWithNoOut.errors.txt
new file mode 100644
index 00000000000..06bfd61c7ab
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationNoErrorWithoutDeclarationsWithJsFileReferenceWithNoOut.errors.txt
@@ -0,0 +1,17 @@
+error TS5055: Cannot write file 'tests/cases/compiler/c.js' which is one of the input files.
+
+
+!!! error TS5055: Cannot write file 'tests/cases/compiler/c.js' which is one of the input files.
+==== tests/cases/compiler/a.ts (0 errors) ====
+    class c {
+    }
+    
+==== tests/cases/compiler/b.ts (0 errors) ====
+    /// <reference path="c.js"/>
+    // no error on above reference path since not emitting declarations
+    function foo() {
+    }
+    
+==== tests/cases/compiler/c.js (0 errors) ====
+    function bar() {
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilationNoErrorWithoutDeclarationsWithJsFileReferenceWithOut.js b/tests/baselines/reference/jsFileCompilationNoErrorWithoutDeclarationsWithJsFileReferenceWithOut.js
index 55412253441..fae4936b6c9 100644
--- a/tests/baselines/reference/jsFileCompilationNoErrorWithoutDeclarationsWithJsFileReferenceWithOut.js
+++ b/tests/baselines/reference/jsFileCompilationNoErrorWithoutDeclarationsWithJsFileReferenceWithOut.js
@@ -20,6 +20,8 @@ var c = (function () {
     }
     return c;
 })();
+function bar() {
+}
 /// <reference path="c.js"/>
 //no  error on above reference since not emitting declarations
 function foo() {
diff --git a/tests/baselines/reference/jsFileCompilationOptionalParameter.errors.txt b/tests/baselines/reference/jsFileCompilationOptionalParameter.errors.txt
index 68b131d39f9..6d9e3c5919d 100644
--- a/tests/baselines/reference/jsFileCompilationOptionalParameter.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationOptionalParameter.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,13): error TS8009: '?' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     function F(p?) { }
                 ~
diff --git a/tests/baselines/reference/jsFileCompilationPropertySyntaxOfClass.errors.txt b/tests/baselines/reference/jsFileCompilationPropertySyntaxOfClass.errors.txt
index 0ecf6f3c666..5a35e68bcec 100644
--- a/tests/baselines/reference/jsFileCompilationPropertySyntaxOfClass.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationPropertySyntaxOfClass.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,11): error TS8014: 'property declarations' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     class C { v }
               ~
diff --git a/tests/baselines/reference/jsFileCompilationPublicMethodSyntaxOfClass.errors.txt b/tests/baselines/reference/jsFileCompilationPublicMethodSyntaxOfClass.errors.txt
index 907775c7be6..a6d47e5fbe3 100644
--- a/tests/baselines/reference/jsFileCompilationPublicMethodSyntaxOfClass.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationPublicMethodSyntaxOfClass.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(2,5): error TS8009: 'public' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     class C {
         public foo() {
diff --git a/tests/baselines/reference/jsFileCompilationPublicParameterModifier.errors.txt b/tests/baselines/reference/jsFileCompilationPublicParameterModifier.errors.txt
index e5072278f4c..fa3e0e34a77 100644
--- a/tests/baselines/reference/jsFileCompilationPublicParameterModifier.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationPublicParameterModifier.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,23): error TS8012: 'parameter modifiers' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     class C { constructor(public x) { }}
                           ~~~~~~
diff --git a/tests/baselines/reference/jsFileCompilationRestParameter.js b/tests/baselines/reference/jsFileCompilationRestParameter.js
index d28299c543a..bcba97af024 100644
--- a/tests/baselines/reference/jsFileCompilationRestParameter.js
+++ b/tests/baselines/reference/jsFileCompilationRestParameter.js
@@ -2,3 +2,4 @@
 function foo(...a) { }
 
 //// [b.js]
+function foo(...a) { }
diff --git a/tests/baselines/reference/jsFileCompilationReturnTypeSyntaxOfFunction.errors.txt b/tests/baselines/reference/jsFileCompilationReturnTypeSyntaxOfFunction.errors.txt
index 50746dcfc82..8b83a9d1f90 100644
--- a/tests/baselines/reference/jsFileCompilationReturnTypeSyntaxOfFunction.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationReturnTypeSyntaxOfFunction.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,15): error TS8010: 'types' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     function F(): number { }
                   ~~~~~~
diff --git a/tests/baselines/reference/jsFileCompilationSyntaxError.errors.txt b/tests/baselines/reference/jsFileCompilationSyntaxError.errors.txt
index 1ca6e251788..b06375e8a6a 100644
--- a/tests/baselines/reference/jsFileCompilationSyntaxError.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationSyntaxError.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(3,6): error TS1223: 'type' tag already specified.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     /**
       * @type {number}
diff --git a/tests/baselines/reference/jsFileCompilationTypeAliasSyntax.errors.txt b/tests/baselines/reference/jsFileCompilationTypeAliasSyntax.errors.txt
index 6af5751ea85..a0724e452b7 100644
--- a/tests/baselines/reference/jsFileCompilationTypeAliasSyntax.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationTypeAliasSyntax.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,1): error TS8008: 'type aliases' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     type a = b;
     ~~~~~~~~~~~
diff --git a/tests/baselines/reference/jsFileCompilationTypeArgumentSyntaxOfCall.errors.txt b/tests/baselines/reference/jsFileCompilationTypeArgumentSyntaxOfCall.errors.txt
index cade211aa63..acefc2ff569 100644
--- a/tests/baselines/reference/jsFileCompilationTypeArgumentSyntaxOfCall.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationTypeArgumentSyntaxOfCall.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,5): error TS8011: 'type arguments' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     Foo<number>();
         ~~~~~~
diff --git a/tests/baselines/reference/jsFileCompilationTypeAssertions.errors.txt b/tests/baselines/reference/jsFileCompilationTypeAssertions.errors.txt
index 6d4ef23dcc6..669e83688cc 100644
--- a/tests/baselines/reference/jsFileCompilationTypeAssertions.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationTypeAssertions.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,27): error TS17002: Expected corresponding JSX closing tag for 'string'.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     var v = <string>undefined;
                               
diff --git a/tests/baselines/reference/jsFileCompilationTypeOfParameter.errors.txt b/tests/baselines/reference/jsFileCompilationTypeOfParameter.errors.txt
index ae3fd23c6ef..69fa6251942 100644
--- a/tests/baselines/reference/jsFileCompilationTypeOfParameter.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationTypeOfParameter.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,15): error TS8010: 'types' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     function F(a: number) { }
                   ~~~~~~
diff --git a/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfClass.errors.txt b/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfClass.errors.txt
index 708ff378137..f279896c4ed 100644
--- a/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfClass.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfClass.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,9): error TS8004: 'type parameter declarations' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     class C<T> { }
             ~
diff --git a/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfFunction.errors.txt b/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfFunction.errors.txt
index 391e8f476da..9b056bcae50 100644
--- a/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfFunction.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfFunction.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,12): error TS8004: 'type parameter declarations' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     function F<T>() { }
                ~
diff --git a/tests/baselines/reference/jsFileCompilationTypeSyntaxOfVar.errors.txt b/tests/baselines/reference/jsFileCompilationTypeSyntaxOfVar.errors.txt
index a4486a5d49d..080cb580bf2 100644
--- a/tests/baselines/reference/jsFileCompilationTypeSyntaxOfVar.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationTypeSyntaxOfVar.errors.txt
@@ -1,6 +1,8 @@
+error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 tests/cases/compiler/a.js(1,8): error TS8010: 'types' can only be used in a .ts file.
 
 
+!!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     var v: () => number;
            ~~~~~~~~~~~~
diff --git a/tests/baselines/reference/jsFileCompilationWithJsEmitPathSameAsInput.errors.txt b/tests/baselines/reference/jsFileCompilationWithJsEmitPathSameAsInput.errors.txt
index 09e07a67bf3..134c95dee15 100644
--- a/tests/baselines/reference/jsFileCompilationWithJsEmitPathSameAsInput.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationWithJsEmitPathSameAsInput.errors.txt
@@ -1,7 +1,9 @@
 error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
+error TS5056: Cannot write file 'tests/cases/compiler/a.js' since one or more input files would emit into it.
 
 
 !!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
+!!! error TS5056: Cannot write file 'tests/cases/compiler/a.js' since one or more input files would emit into it.
 ==== tests/cases/compiler/a.ts (0 errors) ====
     class c {
     }
diff --git a/tests/baselines/reference/jsFileCompilationWithOut.js b/tests/baselines/reference/jsFileCompilationWithOut.js
index 7bab7b973ab..32d0261061f 100644
--- a/tests/baselines/reference/jsFileCompilationWithOut.js
+++ b/tests/baselines/reference/jsFileCompilationWithOut.js
@@ -15,3 +15,5 @@ var c = (function () {
     }
     return c;
 })();
+function foo() {
+}
diff --git a/tests/baselines/reference/jsFileCompilationWithoutOut.errors.txt b/tests/baselines/reference/jsFileCompilationWithoutOut.errors.txt
new file mode 100644
index 00000000000..3531296e019
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationWithoutOut.errors.txt
@@ -0,0 +1,12 @@
+error TS5055: Cannot write file 'tests/cases/compiler/b.js' which is one of the input files.
+
+
+!!! error TS5055: Cannot write file 'tests/cases/compiler/b.js' which is one of the input files.
+==== tests/cases/compiler/a.ts (0 errors) ====
+    class c {
+    }
+    
+==== tests/cases/compiler/b.js (0 errors) ====
+    function foo() {
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilationWithoutOut.symbols b/tests/baselines/reference/jsFileCompilationWithoutOut.symbols
deleted file mode 100644
index 5260b8d6cf3..00000000000
--- a/tests/baselines/reference/jsFileCompilationWithoutOut.symbols
+++ /dev/null
@@ -1,10 +0,0 @@
-=== tests/cases/compiler/a.ts ===
-class c {
->c : Symbol(c, Decl(a.ts, 0, 0))
-}
-
-=== tests/cases/compiler/b.js ===
-function foo() {
->foo : Symbol(foo, Decl(b.js, 0, 0))
-}
-
diff --git a/tests/baselines/reference/jsFileCompilationWithoutOut.types b/tests/baselines/reference/jsFileCompilationWithoutOut.types
deleted file mode 100644
index dce83eeb8eb..00000000000
--- a/tests/baselines/reference/jsFileCompilationWithoutOut.types
+++ /dev/null
@@ -1,10 +0,0 @@
-=== tests/cases/compiler/a.ts ===
-class c {
->c : c
-}
-
-=== tests/cases/compiler/b.js ===
-function foo() {
->foo : () => void
-}
-
diff --git a/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/amd/test.d.ts b/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/amd/test.d.ts
index 4c0b8989316..bbae04a30bf 100644
--- a/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/amd/test.d.ts
+++ b/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/amd/test.d.ts
@@ -1 +1,2 @@
 declare var test: number;
+declare var test2: number;
diff --git a/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/amd/test.js b/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/amd/test.js
index e757934f20c..f2115703462 100644
--- a/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/amd/test.js
+++ b/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/amd/test.js
@@ -1 +1,2 @@
 var test = 10;
+var test2 = 10; // Should get compiled
diff --git a/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/node/test.d.ts b/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/node/test.d.ts
index 4c0b8989316..bbae04a30bf 100644
--- a/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/node/test.d.ts
+++ b/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/node/test.d.ts
@@ -1 +1,2 @@
 declare var test: number;
+declare var test2: number;
diff --git a/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/node/test.js b/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/node/test.js
index e757934f20c..f2115703462 100644
--- a/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/node/test.js
+++ b/tests/baselines/reference/project/jsFileCompilationDifferentNamesNotSpecifiedWithJsExtensions/node/test.js
@@ -1 +1,2 @@
 var test = 10;
+var test2 = 10; // Should get compiled
diff --git a/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/amd/test.d.ts b/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/amd/test.d.ts
index 4c0b8989316..bbae04a30bf 100644
--- a/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/amd/test.d.ts
+++ b/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/amd/test.d.ts
@@ -1 +1,2 @@
 declare var test: number;
+declare var test2: number;
diff --git a/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/amd/test.js b/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/amd/test.js
index e757934f20c..f2115703462 100644
--- a/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/amd/test.js
+++ b/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/amd/test.js
@@ -1 +1,2 @@
 var test = 10;
+var test2 = 10; // Should get compiled
diff --git a/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/node/test.d.ts b/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/node/test.d.ts
index 4c0b8989316..bbae04a30bf 100644
--- a/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/node/test.d.ts
+++ b/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/node/test.d.ts
@@ -1 +1,2 @@
 declare var test: number;
+declare var test2: number;
diff --git a/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/node/test.js b/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/node/test.js
index e757934f20c..f2115703462 100644
--- a/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/node/test.js
+++ b/tests/baselines/reference/project/jsFileCompilationDifferentNamesSpecifiedWithJsExtensions/node/test.js
@@ -1 +1,2 @@
 var test = 10;
+var test2 = 10; // Should get compiled