Merge pull request #6744 from Microsoft/removePredicateTypiness

Remove notion of predicates as types, move predicates back to signatures

Author: DanielRosenwasser

src/compiler/checker.ts

@@ -715,6 +715,10 @@
         "category": "Error",
         "code": 1227
     },
+    "A type predicate is only allowed in return type position for functions and methods.": {
+        "category": "Error",
+        "code": 1228
+    },
     "A type predicate cannot reference a rest parameter.": {
         "category": "Error",
         "code": 1229

src/compiler/diagnosticMessages.json

@@ -1940,7 +1940,7 @@ namespace ts {
             return finishNode(node);
         }
 
-        function parseTypePredicate(lhs: Identifier | ThisTypeNode): TypePredicateNode {
+        function parseThisTypePredicate(lhs: ThisTypeNode): TypePredicateNode {
             nextToken();
             const node = createNode(SyntaxKind.TypePredicate, lhs.pos) as TypePredicateNode;
             node.parameterName = lhs;
@@ -2399,7 +2399,7 @@ namespace ts {
                 case SyntaxKind.ThisKeyword: {
                     const thisKeyword = parseThisTypeNode();
                     if (token === SyntaxKind.IsKeyword && !scanner.hasPrecedingLineBreak()) {
-                        return parseTypePredicate(thisKeyword);
+                        return parseThisTypePredicate(thisKeyword);
                     }
                     else {
                         return thisKeyword;

src/compiler/parser.ts

@@ -1777,7 +1777,8 @@ namespace ts {
         buildSignatureDisplay(signatures: Signature, writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags, kind?: SignatureKind): void;
         buildParameterDisplay(parameter: Symbol, writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags): void;
         buildTypeParameterDisplay(tp: TypeParameter, writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags): void;
-        buildTypeParameterDisplayFromSymbol(symbol: Symbol, writer: SymbolWriter, enclosingDeclaraiton?: Node, flags?: TypeFormatFlags): void;
+        buildTypePredicateDisplay(predicate: TypePredicate, writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags): void;
+        buildTypeParameterDisplayFromSymbol(symbol: Symbol, writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags): void;
         buildDisplayForParametersAndDelimiters(parameters: Symbol[], writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags): void;
         buildDisplayForTypeParametersAndDelimiters(typeParameters: TypeParameter[], writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags): void;
         buildReturnTypeDisplay(signature: Signature, writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags): void;
@@ -1842,22 +1843,24 @@ namespace ts {
         Identifier
     }
 
-    export interface TypePredicate {
+    export interface TypePredicateBase {
         kind: TypePredicateKind;
         type: Type;
     }
 
     // @kind (TypePredicateKind.This)
-    export interface ThisTypePredicate extends TypePredicate {
+    export interface ThisTypePredicate extends TypePredicateBase {
         _thisTypePredicateBrand: any;
     }
 
     // @kind (TypePredicateKind.Identifier)
-    export interface IdentifierTypePredicate extends TypePredicate {
+    export interface IdentifierTypePredicate extends TypePredicateBase {
         parameterName: string;
         parameterIndex: number;
     }
 
+    export type TypePredicate = IdentifierTypePredicate | ThisTypePredicate;
+
     /* @internal */
     export type AnyImportSyntax = ImportDeclaration | ImportEqualsDeclaration;
 
@@ -2125,7 +2128,6 @@ namespace ts {
         ESSymbol                = 0x01000000,  // Type of symbol primitive introduced in ES6
         ThisType                = 0x02000000,  // This type
         ObjectLiteralPatternWithComputedProperties = 0x04000000,  // Object literal type implied by binding pattern has computed properties
-        PredicateType           = 0x08000000,  // Predicate types are also Boolean types, but should not be considered Intrinsics - there's no way to capture this with flags
 
         /* @internal */
         Intrinsic = Any | String | Number | Boolean | ESSymbol | Void | Undefined | Null,
@@ -2137,7 +2139,7 @@ namespace ts {
         UnionOrIntersection = Union | Intersection,
         StructuredType = ObjectType | Union | Intersection,
         /* @internal */
-        RequiresWidening = ContainsUndefinedOrNull | ContainsObjectLiteral | PredicateType,
+        RequiresWidening = ContainsUndefinedOrNull | ContainsObjectLiteral,
         /* @internal */
         PropagatingFlags = ContainsUndefinedOrNull | ContainsObjectLiteral | ContainsAnyFunctionType
     }
@@ -2158,11 +2160,6 @@ namespace ts {
         intrinsicName: string;  // Name of intrinsic type
     }
 
-    // Predicate types (TypeFlags.Predicate)
-    export interface PredicateType extends Type {
-        predicate: ThisTypePredicate | IdentifierTypePredicate;
-    }
-
     // String literal types (TypeFlags.StringLiteral)
     export interface StringLiteralType extends Type {
         text: string;  // Text of string literal
@@ -2297,6 +2294,8 @@ namespace ts {
         erasedSignatureCache?: Signature;   // Erased version of signature (deferred)
         /* @internal */
         isolatedSignatureType?: ObjectType; // A manufactured type that just contains the signature for purposes of signature comparison
+        /* @internal */
+        typePredicate?: TypePredicate;
     }
 
     export const enum IndexKind {

src/compiler/types.ts

@@ -746,6 +746,10 @@ namespace ts {
         return predicate && predicate.kind === TypePredicateKind.Identifier;
     }
 
+    export function isThisTypePredicate(predicate: TypePredicate): predicate is ThisTypePredicate {
+        return predicate && predicate.kind === TypePredicateKind.This;
+    }
+
     export function getContainingFunction(node: Node): FunctionLikeDeclaration {
         while (true) {
             node = node.parent;

src/compiler/utilities.ts

@@ -4,7 +4,7 @@ var obj: Object;
 >Object : Object
 
 if (ArrayBuffer.isView(obj)) {
->ArrayBuffer.isView(obj) : arg is ArrayBufferView
+>ArrayBuffer.isView(obj) : boolean
 >ArrayBuffer.isView : (arg: any) => arg is ArrayBufferView
 >ArrayBuffer : ArrayBufferConstructor
 >isView : (arg: any) => arg is ArrayBufferView

tests/baselines/reference/arrayBufferIsViewNarrowsType.types

@@ -0,0 +1,16 @@
+//// [declarationEmitIdentifierPredicates01.ts]
+
+export function f(x: any): x is number {
+    return typeof x === "number";
+}
+
+//// [declarationEmitIdentifierPredicates01.js]
+"use strict";
+function f(x) {
+    return typeof x === "number";
+}
+exports.f = f;
+
+
+//// [declarationEmitIdentifierPredicates01.d.ts]
+export declare function f(x: any): x is number;

tests/baselines/reference/declarationEmitIdentifierPredicates01.js

@@ -0,0 +1,10 @@
+=== tests/cases/conformance/declarationEmit/typePredicates/declarationEmitIdentifierPredicates01.ts ===
+
+export function f(x: any): x is number {
+>f : Symbol(f, Decl(declarationEmitIdentifierPredicates01.ts, 0, 0))
+>x : Symbol(x, Decl(declarationEmitIdentifierPredicates01.ts, 1, 18))
+>x : Symbol(x, Decl(declarationEmitIdentifierPredicates01.ts, 1, 18))
+
+    return typeof x === "number";
+>x : Symbol(x, Decl(declarationEmitIdentifierPredicates01.ts, 1, 18))
+}

tests/baselines/reference/declarationEmitIdentifierPredicates01.symbols

@@ -0,0 +1,13 @@
+=== tests/cases/conformance/declarationEmit/typePredicates/declarationEmitIdentifierPredicates01.ts ===
+
+export function f(x: any): x is number {
+>f : (x: any) => x is number
+>x : any
+>x : any
+
+    return typeof x === "number";
+>typeof x === "number" : boolean
+>typeof x : string
+>x : any
+>"number" : string
+}

tests/baselines/reference/declarationEmitIdentifierPredicates01.types

@@ -0,0 +1,14 @@
+tests/cases/conformance/declarationEmit/typePredicates/declarationEmitIdentifierPredicatesWithPrivateName01.ts(6,33): error TS4060: Return type of exported function has or is using private name 'I'.
+
+
+==== tests/cases/conformance/declarationEmit/typePredicates/declarationEmitIdentifierPredicatesWithPrivateName01.ts (1 errors) ====
+    
+    interface I {
+        a: number;
+    }
+    
+    export function f(x: any): x is I {
+                                    ~
+!!! error TS4060: Return type of exported function has or is using private name 'I'.
+        return typeof x.a === "number";
+    }