Non-nullable types

src/compiler/commandLineParser.ts

@@ -331,6 +331,11 @@ namespace ts {
             name: "noImplicitUseStrict",
             type: "boolean",
             description: Diagnostics.Do_not_emit_use_strict_directives_in_module_output
+        },
+        {
+            name: "strictNullChecks",
+            type: "boolean",
+            description: Diagnostics.Enable_strict_null_checks
         }
     ];
 

src/compiler/core.ts

@@ -242,8 +242,14 @@ namespace ts {
             const count = array.length;
             if (count > 0) {
                 let pos = 0;
-                let result = arguments.length <= 2 ? array[pos] : initial;
-                pos++;
+                let result: T | U;
+                if (arguments.length <= 2) {
+                    result = array[pos];
+                    pos++;
+                }
+                else {
+                    result = initial;
+                }
                 while (pos < count) {
                     result = f(<U>result, array[pos]);
                     pos++;
@@ -260,8 +266,14 @@ namespace ts {
         if (array) {
             let pos = array.length - 1;
             if (pos >= 0) {
-                let result = arguments.length <= 2 ? array[pos] : initial;
-                pos--;
+                let result: T | U;
+                if (arguments.length <= 2) {
+                    result = array[pos];
+                    pos--;
+                }
+                else {
+                    result = initial;
+                }
                 while (pos >= 0) {
                     result = f(<U>result, array[pos]);
                     pos--;

src/compiler/declarationEmitter.ts

@@ -367,6 +367,8 @@ namespace ts {
                 case SyntaxKind.BooleanKeyword:
                 case SyntaxKind.SymbolKeyword:
                 case SyntaxKind.VoidKeyword:
+                case SyntaxKind.UndefinedKeyword:
+                case SyntaxKind.NullKeyword:
                 case SyntaxKind.ThisType:
                 case SyntaxKind.StringLiteralType:
                     return writeTextOfNode(currentText, type);

src/compiler/diagnosticMessages.json

@@ -1103,6 +1103,10 @@
         "category": "Error",
         "code": 2365
     },
+    "Function lacks ending return statement and return type does not include 'undefined'.": {
+        "category": "Error",
+        "code": 2366
+    },
     "Type parameter name cannot be '{0}'": {
         "category": "Error",
         "code": 2368
@@ -1423,6 +1427,10 @@
         "category": "Error",
         "code": 2453
     },
+    "Variable '{0}' is used before being assigned.": {
+        "category": "Error",
+        "code": 2454
+    },
     "Type argument candidate '{1}' is not a valid type argument because it is not a supertype of candidate '{0}'.": {
         "category": "Error",
         "code": 2455
@@ -1719,6 +1727,10 @@
         "category": "Error",
         "code": 2530
     },
+    "Object is possibly 'null' or 'undefined'.": {
+        "category": "Error",
+        "code": 2531
+    },
     "JSX element attributes type '{0}' may not be a union type.": {
         "category": "Error",
         "code": 2600
@@ -2604,6 +2616,11 @@
         "category": "Message",
         "code": 6112
     },
+    "Enable strict null checks.": {
+        "category": "Message",
+        "code": 6113
+    },
+
     "Variable '{0}' implicitly has an '{1}' type.": {
         "category": "Error",
         "code": 7005

src/compiler/emitter.ts

@@ -1533,6 +1533,7 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
                     case SyntaxKind.JsxSpreadAttribute:
                     case SyntaxKind.JsxExpression:
                     case SyntaxKind.NewExpression:
+                    case SyntaxKind.NonNullExpression:
                     case SyntaxKind.ParenthesizedExpression:
                     case SyntaxKind.PostfixUnaryExpression:
                     case SyntaxKind.PrefixUnaryExpression:
@@ -2077,8 +2078,10 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
             function parenthesizeForAccess(expr: Expression): LeftHandSideExpression {
                 // When diagnosing whether the expression needs parentheses, the decision should be based
                 // on the innermost expression in a chain of nested type assertions.
-                while (expr.kind === SyntaxKind.TypeAssertionExpression || expr.kind === SyntaxKind.AsExpression) {
-                    expr = (<AssertionExpression>expr).expression;
+                while (expr.kind === SyntaxKind.TypeAssertionExpression ||
+                    expr.kind === SyntaxKind.AsExpression ||
+                    expr.kind === SyntaxKind.NonNullExpression) {
+                    expr = (<AssertionExpression | NonNullExpression>expr).expression;
                 }
 
                 // isLeftHandSideExpression is almost the correct criterion for when it is not necessary
@@ -2343,8 +2346,11 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
             }
 
             function skipParentheses(node: Expression): Expression {
-                while (node.kind === SyntaxKind.ParenthesizedExpression || node.kind === SyntaxKind.TypeAssertionExpression || node.kind === SyntaxKind.AsExpression) {
-                    node = (<ParenthesizedExpression | AssertionExpression>node).expression;
+                while (node.kind === SyntaxKind.ParenthesizedExpression ||
+                    node.kind === SyntaxKind.TypeAssertionExpression ||
+                    node.kind === SyntaxKind.AsExpression ||
+                    node.kind === SyntaxKind.NonNullExpression) {
+                    node = (<ParenthesizedExpression | AssertionExpression | NonNullExpression>node).expression;
                 }
                 return node;
             }
@@ -2518,13 +2524,17 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
                 // not the user. If we didn't want them, the emitter would not have put them
                 // there.
                 if (!nodeIsSynthesized(node) && node.parent.kind !== SyntaxKind.ArrowFunction) {
-                    if (node.expression.kind === SyntaxKind.TypeAssertionExpression || node.expression.kind === SyntaxKind.AsExpression) {
-                        let operand = (<TypeAssertion>node.expression).expression;
+                    if (node.expression.kind === SyntaxKind.TypeAssertionExpression ||
+                        node.expression.kind === SyntaxKind.AsExpression ||
+                        node.expression.kind === SyntaxKind.NonNullExpression) {
+                        let operand = (<TypeAssertion | NonNullExpression>node.expression).expression;
 
                         // Make sure we consider all nested cast expressions, e.g.:
                         // (<any><number><any>-A).x;
-                        while (operand.kind === SyntaxKind.TypeAssertionExpression || operand.kind === SyntaxKind.AsExpression) {
-                            operand = (<TypeAssertion>operand).expression;
+                        while (operand.kind === SyntaxKind.TypeAssertionExpression ||
+                            operand.kind === SyntaxKind.AsExpression ||
+                            operand.kind === SyntaxKind.NonNullExpression) {
+                            operand = (<TypeAssertion | NonNullExpression>operand).expression;
                         }
 
                         // We have an expression of the form: (<Type>SubExpr)
@@ -7928,9 +7938,9 @@ const _super = (function (geti, seti) {
                     case SyntaxKind.TaggedTemplateExpression:
                         return emitTaggedTemplateExpression(<TaggedTemplateExpression>node);
                     case SyntaxKind.TypeAssertionExpression:
-                        return emit((<TypeAssertion>node).expression);
                     case SyntaxKind.AsExpression:
-                        return emit((<AsExpression>node).expression);
+                    case SyntaxKind.NonNullExpression:
+                        return emit((<AssertionExpression | NonNullExpression>node).expression);
                     case SyntaxKind.ParenthesizedExpression:
                         return emitParenExpression(<ParenthesizedExpression>node);
                     case SyntaxKind.FunctionDeclaration:

src/compiler/parser.ts

@@ -177,6 +177,8 @@ namespace ts {
             case SyntaxKind.AsExpression:
                 return visitNode(cbNode, (<AsExpression>node).expression) ||
                     visitNode(cbNode, (<AsExpression>node).type);
+            case SyntaxKind.NonNullExpression:
+                return visitNode(cbNode, (<NonNullExpression>node).expression);
             case SyntaxKind.ConditionalExpression:
                 return visitNode(cbNode, (<ConditionalExpression>node).condition) ||
                     visitNode(cbNode, (<ConditionalExpression>node).questionToken) ||
@@ -2361,12 +2363,14 @@ namespace ts {
                 case SyntaxKind.NumberKeyword:
                 case SyntaxKind.BooleanKeyword:
                 case SyntaxKind.SymbolKeyword:
+                case SyntaxKind.UndefinedKeyword:
                     // If these are followed by a dot, then parse these out as a dotted type reference instead.
                     const node = tryParse(parseKeywordAndNoDot);
                     return node || parseTypeReference();
                 case SyntaxKind.StringLiteral:
                     return parseStringLiteralTypeNode();
                 case SyntaxKind.VoidKeyword:
+                case SyntaxKind.NullKeyword:
                     return parseTokenNode<TypeNode>();
                 case SyntaxKind.ThisKeyword: {
                     const thisKeyword = parseThisTypeNode();
@@ -2398,6 +2402,8 @@ namespace ts {
                 case SyntaxKind.BooleanKeyword:
                 case SyntaxKind.SymbolKeyword:
                 case SyntaxKind.VoidKeyword:
+                case SyntaxKind.UndefinedKeyword:
+                case SyntaxKind.NullKeyword:
                 case SyntaxKind.ThisKeyword:
                 case SyntaxKind.TypeOfKeyword:
                 case SyntaxKind.OpenBraceToken:
@@ -3724,6 +3730,14 @@ namespace ts {
                     continue;
                 }
 
+                if (token === SyntaxKind.ExclamationToken && !scanner.hasPrecedingLineBreak()) {
+                    nextToken();
+                    const nonNullExpression = <NonNullExpression>createNode(SyntaxKind.NonNullExpression, expression.pos);
+                    nonNullExpression.expression = expression;
+                    expression = finishNode(nonNullExpression);
+                    continue;
+                }
+
                 // when in the [Decorator] context, we do not parse ElementAccess as it could be part of a ComputedPropertyName
                 if (!inDecoratorContext() && parseOptional(SyntaxKind.OpenBracketToken)) {
                     const indexedAccess = <ElementAccessExpression>createNode(SyntaxKind.ElementAccessExpression, expression.pos);

src/compiler/scanner.ts

@@ -114,6 +114,7 @@ namespace ts {
         "try": SyntaxKind.TryKeyword,
         "type": SyntaxKind.TypeKeyword,
         "typeof": SyntaxKind.TypeOfKeyword,
+        "undefined": SyntaxKind.UndefinedKeyword,
         "var": SyntaxKind.VarKeyword,
         "void": SyntaxKind.VoidKeyword,
         "while": SyntaxKind.WhileKeyword,

src/compiler/types.ts

@@ -171,6 +171,7 @@ namespace ts {
         StringKeyword,
         SymbolKeyword,
         TypeKeyword,
+        UndefinedKeyword,
         FromKeyword,
         GlobalKeyword,
         OfKeyword, // LastKeyword and LastToken
@@ -240,6 +241,7 @@ namespace ts {
         OmittedExpression,
         ExpressionWithTypeArguments,
         AsExpression,
+        NonNullExpression,
 
         // Misc
         TemplateSpan,
@@ -475,6 +477,11 @@ namespace ts {
         originalKeywordKind?: SyntaxKind;              // Original syntaxKind which get set so that we can report an error later
     }
 
+    // Transient identifier node (marked by id === -1)
+    export interface TransientIdentifier extends Identifier {
+        resolvedSymbol: Symbol;
+    }
+
     // @kind(SyntaxKind.QualifiedName)
     export interface QualifiedName extends Node {
         // Must have same layout as PropertyAccess
@@ -968,6 +975,8 @@ namespace ts {
         name: Identifier;
     }
 
+    export type IdentifierOrPropertyAccess = Identifier | PropertyAccessExpression;
+
     // @kind(SyntaxKind.ElementAccessExpression)
     export interface ElementAccessExpression extends MemberExpression {
         expression: LeftHandSideExpression;
@@ -1012,6 +1021,11 @@ namespace ts {
 
     export type AssertionExpression = TypeAssertion | AsExpression;
 
+    // @kind(SyntaxKind.NonNullExpression)
+    export interface NonNullExpression extends LeftHandSideExpression {
+        expression: Expression;
+    }
+
     /// A JSX expression of the form <TagName attrs>...</TagName>
     // @kind(SyntaxKind.JsxElement)
     export interface JsxElement extends PrimaryExpression {
@@ -2029,7 +2043,9 @@ namespace ts {
         exportsChecked?: boolean;           // True if exports of external module have been checked
         isDeclarationWithCollidingName?: boolean;    // True if symbol is block scoped redeclaration
         bindingElement?: BindingElement;    // Binding element associated with property symbol
-        exportsSomeValue?: boolean;         // true if module exports some value (not just types)
+        exportsSomeValue?: boolean;         // True if module exports some value (not just types)
+        firstAssignmentChecked?: boolean;   // True if first assignment node has been computed
+        firstAssignment?: Node;             // First assignment node (undefined if no assignments)
     }
 
     /* @internal */
@@ -2072,7 +2088,7 @@ namespace ts {
         isVisible?: boolean;              // Is this node visible
         generatedName?: string;           // Generated name for module, enum, or import declaration
         generatedNames?: Map<string>;     // Generated names table for source file
-        assignmentChecks?: Map<boolean>;  // Cache of assignment checks
+        assignmentMap?: Map<boolean>;     // Cached map of references assigned within this node
         hasReportedStatementInAmbientContext?: boolean;  // Cache boolean if we report statements in ambient context
         importOnRightSide?: Symbol;       // for import declarations - import that appear on the right side
         jsxFlags?: JsxFlags;              // flags for knowing what kind of element/attributes we're dealing with
@@ -2106,7 +2122,7 @@ namespace ts {
         /* @internal */
         FreshObjectLiteral      = 0x00100000,  // Fresh object literal type
         /* @internal */
-        ContainsUndefinedOrNull = 0x00200000,  // Type is or contains Undefined or Null type
+        ContainsUndefinedOrNull = 0x00200000,  // Type is or contains undefined or null type
         /* @internal */
         ContainsObjectLiteral   = 0x00400000,  // Type is or contains object literal type
         /* @internal */
@@ -2115,6 +2131,8 @@ namespace ts {
         ThisType                = 0x02000000,  // This type
         ObjectLiteralPatternWithComputedProperties = 0x04000000,  // Object literal type implied by binding pattern has computed properties
 
+        /* @internal */
+        Nullable = Undefined | Null,
         /* @internal */
         Intrinsic = Any | String | Number | Boolean | ESSymbol | Void | Undefined | Null,
         /* @internal */
@@ -2439,6 +2457,7 @@ namespace ts {
         allowSyntheticDefaultImports?: boolean;
         allowJs?: boolean;
         noImplicitUseStrict?: boolean;
+        strictNullChecks?: boolean;
         lib?: string[];
         /* @internal */ stripInternal?: boolean;
 

src/compiler/utilities.ts

@@ -511,6 +511,7 @@ namespace ts {
             case SyntaxKind.StringKeyword:
             case SyntaxKind.BooleanKeyword:
             case SyntaxKind.SymbolKeyword:
+            case SyntaxKind.UndefinedKeyword:
                 return true;
             case SyntaxKind.VoidKeyword:
                 return node.parent.kind !== SyntaxKind.VoidExpression;
@@ -968,6 +969,7 @@ namespace ts {
             case SyntaxKind.TaggedTemplateExpression:
             case SyntaxKind.AsExpression:
             case SyntaxKind.TypeAssertionExpression:
+            case SyntaxKind.NonNullExpression:
             case SyntaxKind.ParenthesizedExpression:
             case SyntaxKind.FunctionExpression:
             case SyntaxKind.ClassExpression:
@@ -2406,6 +2408,7 @@ namespace ts {
                 case SyntaxKind.ElementAccessExpression:
                 case SyntaxKind.NewExpression:
                 case SyntaxKind.CallExpression:
+                case SyntaxKind.NonNullExpression:
                 case SyntaxKind.JsxElement:
                 case SyntaxKind.JsxSelfClosingElement:
                 case SyntaxKind.TaggedTemplateExpression:

tests/baselines/reference/arrayLiteralWidened.types

@@ -19,7 +19,7 @@ var a = [undefined, undefined];
 
 var b = [[], [null, null]]; // any[][]
 >b : any[][]
->[[], [null, null]] : null[][]
+>[[], [null, null]] : undefined[][]
 >[] : undefined[]
 >[null, null] : null[]
 >null : null