diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index 6957be484f35a..dc0ff55b89aa0 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -1478,6 +1478,14 @@ namespace ts {
                 // It's acceptable for multiple 'this' assignments of the same identifier to occur
                 declareSymbol(container.symbol.members, container.symbol, node, SymbolFlags.Property, SymbolFlags.PropertyExcludes & ~SymbolFlags.Property);
             }
+            else if (container.kind === SyntaxKind.Constructor && isInJavaScriptFile(node)) {
+                // this.foo assignment in a JavaScript class
+                // Bind this property to the containing class
+                const saveContainer = container;
+                container = container.parent;
+                bindPropertyOrMethodOrAccessor(node, SymbolFlags.Property, SymbolFlags.None);
+                container = saveContainer;
+            }
         }
 
         function bindPrototypePropertyAssignment(node: BinaryExpression) {
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 27b0839720559..49efcc7dc0b61 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -2937,6 +2937,14 @@ namespace ts {
                 }
                 // Handle module.exports = expr
                 if (declaration.kind === SyntaxKind.BinaryExpression) {
+                    // Use JS Doc type if present on parent expression statement
+                    if (declaration.flags & NodeFlags.JavaScriptFile) {
+                        const typeTag = getJSDocTypeTag(declaration.parent);
+                        if (typeTag && typeTag.typeExpression) {
+                            return links.type = getTypeFromTypeNode(typeTag.typeExpression.type);
+                        }
+                    }
+
                     return links.type = getUnionType(map(symbol.declarations, (decl: BinaryExpression) => checkExpressionCached(decl.right)));
                 }
                 if (declaration.kind === SyntaxKind.PropertyAccessExpression) {
@@ -8037,6 +8045,11 @@ namespace ts {
             const binaryExpression = <BinaryExpression>node.parent;
             const operator = binaryExpression.operatorToken.kind;
             if (operator >= SyntaxKind.FirstAssignment && operator <= SyntaxKind.LastAssignment) {
+                // Don't do this for special property assignments to avoid circularity
+                if (getSpecialPropertyAssignmentKind(binaryExpression) !== SpecialPropertyAssignmentKind.None) {
+                    return undefined;
+                }
+
                 // In an assignment expression, the right operand is contextually typed by the type of the left operand.
                 if (node === binaryExpression.right) {
                     return checkExpression(binaryExpression.left);
diff --git a/tests/cases/fourslash/javaScriptClass1.ts b/tests/cases/fourslash/javaScriptClass1.ts
new file mode 100644
index 0000000000000..19f7a39b6150d
--- /dev/null
+++ b/tests/cases/fourslash/javaScriptClass1.ts
@@ -0,0 +1,31 @@
+///<reference path="fourslash.ts" />
+
+// Classes have their shape inferred from assignments
+// to properties of 'this' in the constructor
+
+// @allowNonTsExtensions: true
+// @Filename: Foo.js
+//// class Foo {
+////    constructor() {
+////        this.bar = 'world';
+////        this.thing = () => 0;
+////        this.union = 'foo';
+////        this.union = 100;
+////    }
+//// }
+//// var x = new Foo();
+//// x/**/
+
+
+goTo.marker();
+edit.insert('.');
+verify.completionListContains("bar", /*displayText*/ undefined, /*documentation*/ undefined, "property");
+verify.completionListContains("thing", /*displayText*/ undefined, /*documentation*/ undefined, "property");
+verify.completionListContains("union", /*displayText*/ undefined, /*documentation*/ undefined, "property");
+
+edit.insert('bar.');
+verify.completionListContains("substr", /*displayText*/ undefined, /*documentation*/ undefined, "method");
+edit.backspace('bar.'.length);
+
+edit.insert('union.');
+verify.completionListContains("toString", /*displayText*/ undefined, /*documentation*/ undefined, "method");
\ No newline at end of file
diff --git a/tests/cases/fourslash/javaScriptClass2.ts b/tests/cases/fourslash/javaScriptClass2.ts
new file mode 100644
index 0000000000000..d6daa320c5a87
--- /dev/null
+++ b/tests/cases/fourslash/javaScriptClass2.ts
@@ -0,0 +1,22 @@
+///<reference path="fourslash.ts" />
+
+// In an inferred class, we can rename successfully
+
+// @allowNonTsExtensions: true
+// @Filename: Foo.js
+//// class Foo {
+////    constructor() {
+////        this.[|union|] = 'foo';
+////        this./*1*/[|union|] = 100;
+////    }
+////    method() { return this./*2*/[|union|]; }
+//// }
+//// var x = new Foo();
+//// x./*3*/[|union|];
+
+goTo.marker('1');
+verify.renameLocations(/*findInStrings*/false, /*findInComments*/false);
+goTo.marker('2');
+verify.renameLocations(/*findInStrings*/false, /*findInComments*/false);
+goTo.marker('3');
+verify.renameLocations(/*findInStrings*/false, /*findInComments*/false);
diff --git a/tests/cases/fourslash/javaScriptClass3.ts b/tests/cases/fourslash/javaScriptClass3.ts
new file mode 100644
index 0000000000000..47004d53b044f
--- /dev/null
+++ b/tests/cases/fourslash/javaScriptClass3.ts
@@ -0,0 +1,24 @@
+///<reference path="fourslash.ts" />
+
+// In an inferred class, we can to-to-def successfully
+
+// @allowNonTsExtensions: true
+// @Filename: Foo.js
+//// class Foo {
+////    constructor() {
+////        /*dst1*/this.alpha = 10;
+////        /*dst2*/this.beta = 'gamma';
+////    }
+////    method() { return this.alpha; }
+//// }
+//// var x = new Foo();
+//// x.alpha/*src1*/;
+//// x.beta/*src2*/;
+
+goTo.marker('src1');
+goTo.definition();
+verify.caretAtMarker('dst1');
+
+goTo.marker('src2');
+goTo.definition();
+verify.caretAtMarker('dst2');
diff --git a/tests/cases/fourslash/javaScriptClass4.ts b/tests/cases/fourslash/javaScriptClass4.ts
new file mode 100644
index 0000000000000..1148d5f320eb2
--- /dev/null
+++ b/tests/cases/fourslash/javaScriptClass4.ts
@@ -0,0 +1,22 @@
+///<reference path="fourslash.ts" />
+
+// Classes have their shape inferred from assignments
+// to properties of 'this' in the constructor
+
+// @allowNonTsExtensions: true
+// @Filename: Foo.js
+//// class Foo {
+////    constructor() {
+////        /**
+////          * @type {string}
+////        */
+////        this.baz = null;
+////    }
+//// }
+//// var x = new Foo();
+//// x/**/
+
+goTo.marker();
+edit.insert('.baz.');
+verify.completionListContains("substr", /*displayText*/ undefined, /*documentation*/ undefined, "method");
+