diff --git a/src/compiler/sys.ts b/src/compiler/sys.ts
index 3b2eef73860f2..bdd6d4852e853 100644
--- a/src/compiler/sys.ts
+++ b/src/compiler/sys.ts
@@ -301,7 +301,7 @@ namespace ts {
                     if ((eventName === "change" || eventName === "rename")) {
                         const callbacks = fileWatcherCallbacks.get(fileName);
                         if (callbacks) {
-                            for (const fileCallback of fileWatcherCallbacks.get(fileName)) {
+                            for (const fileCallback of callbacks) {
                                 fileCallback(fileName);
                            }
                         }
diff --git a/src/compiler/transformers/module/module.ts b/src/compiler/transformers/module/module.ts
index 284dbe852d180..4003e8ce78bd2 100644
--- a/src/compiler/transformers/module/module.ts
+++ b/src/compiler/transformers/module/module.ts
@@ -581,7 +581,7 @@ namespace ts {
         function addExportMemberAssignments(statements: Statement[], name: Identifier): void {
             const specifiers = !exportEquals && exportSpecifiers && exportSpecifiers.get(name.text);
             if (specifiers) {
-                for (const specifier of exportSpecifiers.get(name.text)) {
+                for (const specifier of specifiers) {
                     statements.push(
                         startOnNewLine(
                             createStatement(
@@ -672,7 +672,7 @@ namespace ts {
                 if (specifiers) {
                     const sourceFileId = getOriginalNodeId(currentSourceFile);
                     const bindingNameExportSpecifiers = getOrUpdate(bindingNameExportSpecifiersForFileMap, sourceFileId, () => new StringMap());
-                    bindingNameExportSpecifiers.set(name.text, exportSpecifiers.get(name.text));
+                    bindingNameExportSpecifiers.set(name.text, specifiers);
                     addExportMemberAssignments(resultStatements, name);
                 }
             }
@@ -926,7 +926,7 @@ namespace ts {
                         setEmitFlags(transformedUnaryExpression, EmitFlags.NoSubstitution);
                     }
                     let nestedExportAssignment: BinaryExpression;
-                    for (const specifier of bindingNameExportSpecifiersMap.get(operand.text)) {
+                    for (const specifier of bindingNameExportSpecifiers) {
                         nestedExportAssignment = nestedExportAssignment ?
                             createExportAssignment(specifier.name, nestedExportAssignment) :
                             createExportAssignment(specifier.name, transformedUnaryExpression || node);
diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index 96f97e6489b40..53385ca5da3a9 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -700,7 +700,8 @@ namespace FourSlash {
             const uniqueItems = new ts.StringMap<string>();
             for (const item of completions.entries) {
                 if (!ts.setIfNotSet(uniqueItems, item.name, item.kind)) {
-                    assert.equal(item.kind, uniqueItems.get(item.name), `Items should have the same kind, got ${item.kind} and ${uniqueItems.get(item.name)}`);
+                    const uniqueItem = uniqueItems.get(item.name);
+                    assert.equal(item.kind, uniqueItem, `Items should have the same kind, got ${item.kind} and ${uniqueItem}`);
                 }
             }
         }
diff --git a/src/harness/harness.ts b/src/harness/harness.ts
index 13265b0d5475a..443ebb454d1e1 100644
--- a/src/harness/harness.ts
+++ b/src/harness/harness.ts
@@ -933,10 +933,9 @@ namespace Harness {
                 return undefined;
             }
 
-            if (!libFileNameSourceFileMap.get(fileName)) {
-                libFileNameSourceFileMap.set(fileName, createSourceFileAndAssertInvariants(fileName, IO.readFile(libFolder + fileName), ts.ScriptTarget.Latest));
-            }
-            return libFileNameSourceFileMap.get(fileName);
+            const sourceFile = libFileNameSourceFileMap.get(fileName);
+            return sourceFile || ts.setAndReturn(libFileNameSourceFileMap, fileName,
+                createSourceFileAndAssertInvariants(fileName, IO.readFile(libFolder + fileName), ts.ScriptTarget.Latest));
         }
 
         export function getDefaultLibFileName(options: ts.CompilerOptions): string {
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index ff5d54afc3075..4cf0caed51b94 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -1238,40 +1238,43 @@ namespace ts.server {
                 // close existing project and later we'll open a set of configured projects for these files
                 this.closeExternalProject(proj.projectFileName, /*suppressRefresh*/ true);
             }
-            else if (this.externalProjectToConfiguredProjectMap.get(proj.projectFileName)) {
-                // this project used to include config files
-                if (!tsConfigFiles) {
-                    // config files were removed from the project - close existing external project which in turn will close configured projects
-                    this.closeExternalProject(proj.projectFileName, /*suppressRefresh*/ true);
-                }
-                else {
-                    // project previously had some config files - compare them with new set of files and close all configured projects that correspond to unused files
-                    const oldConfigFiles = this.externalProjectToConfiguredProjectMap.get(proj.projectFileName);
-                    let iNew = 0;
-                    let iOld = 0;
-                    while (iNew < tsConfigFiles.length && iOld < oldConfigFiles.length) {
-                        const newConfig = tsConfigFiles[iNew];
-                        const oldConfig = oldConfigFiles[iOld];
-                        if (oldConfig < newConfig) {
-                            this.closeConfiguredProject(oldConfig);
-                            iOld++;
-                        }
-                        else if (oldConfig > newConfig) {
-                            iNew++;
+            else  {
+                const oldConfigFiles = this.externalProjectToConfiguredProjectMap.get(proj.projectFileName);
+                if (oldConfigFiles) {
+                    // this project used to include config files
+                    if (!tsConfigFiles) {
+                        // config files were removed from the project - close existing external project which in turn will close configured projects
+                        this.closeExternalProject(proj.projectFileName, /*suppressRefresh*/ true);
+                    }
+                    else {
+                        // project previously had some config files - compare them with new set of files and close all configured projects that correspond to unused files
+                        let iNew = 0;
+                        let iOld = 0;
+                        while (iNew < tsConfigFiles.length && iOld < oldConfigFiles.length) {
+                            const newConfig = tsConfigFiles[iNew];
+                            const oldConfig = oldConfigFiles[iOld];
+                            if (oldConfig < newConfig) {
+                                this.closeConfiguredProject(oldConfig);
+                                iOld++;
+                            }
+                            else if (oldConfig > newConfig) {
+                                iNew++;
+                            }
+                            else {
+                                // record existing config files so avoid extra add-refs
+                                (exisingConfigFiles || (exisingConfigFiles = [])).push(oldConfig);
+                                iOld++;
+                                iNew++;
+                            }
                         }
-                        else {
-                            // record existing config files so avoid extra add-refs
-                            (exisingConfigFiles || (exisingConfigFiles = [])).push(oldConfig);
-                            iOld++;
-                            iNew++;
+                        for (let i = iOld; i < oldConfigFiles.length; i++) {
+                            // projects for all remaining old config files should be closed
+                            this.closeConfiguredProject(oldConfigFiles[i]);
                         }
                     }
-                    for (let i = iOld; i < oldConfigFiles.length; i++) {
-                        // projects for all remaining old config files should be closed
-                        this.closeConfiguredProject(oldConfigFiles[i]);
-                    }
                 }
             }
+
             if (tsConfigFiles) {
                 // store the list of tsconfig files that belong to the external project
                 this.externalProjectToConfiguredProjectMap.set(proj.projectFileName, tsConfigFiles);