Allow indexing generics with unique symbols

src/compiler/checker.ts

@@ -3725,8 +3725,8 @@ namespace ts {
                         return "(Anonymous function)";
                 }
             }
-            if ((symbol as TransientSymbol).syntheticLiteralTypeOrigin) {
-                const stringValue = (symbol as TransientSymbol).syntheticLiteralTypeOrigin.value;
+            if ((symbol as TransientSymbol).nameType && (symbol as TransientSymbol).nameType.flags & TypeFlags.StringLiteral) {
+                const stringValue = ((symbol as TransientSymbol).nameType as StringLiteralType).value;
                 if (!isIdentifierText(stringValue, compilerOptions.target)) {
                     return `"${escapeString(stringValue, CharacterCodes.doubleQuote)}"`;
                 }
@@ -5460,6 +5460,12 @@ namespace ts {
                         lateSymbol = createSymbol(SymbolFlags.None, memberName, CheckFlags.Late);
                     }
 
+                    const symbolLinks = getSymbolLinks(lateSymbol);
+                    if (!symbolLinks.nameType) {
+                        // Retain link to name type so that it can be reused later
+                        symbolLinks.nameType = type;
+                    }
+
                     addDeclarationToLateBoundSymbol(lateSymbol, decl, symbolFlags);
                     if (lateSymbol.parent) {
                         Debug.assert(lateSymbol.parent === parent, "Existing symbol parent should match new one");
@@ -5948,7 +5954,7 @@ namespace ts {
                 // If the current iteration type constituent is a string literal type, create a property.
                 // Otherwise, for type string create a string index signature.
                 if (t.flags & TypeFlags.StringLiteral) {
-                    const propName = escapeLeadingUnderscores((<StringLiteralType>t).value);
+                    const propName = getLateBoundNameFromType(t as LiteralType | UniqueESSymbolType);
                     const modifiersProp = getPropertyOfType(modifiersType, propName);
                     const isOptional = !!(templateModifiers & MappedTypeModifiers.IncludeOptional ||
                         !(templateModifiers & MappedTypeModifiers.ExcludeOptional) && modifiersProp && modifiersProp.flags & SymbolFlags.Optional);
@@ -5965,7 +5971,7 @@ namespace ts {
                         prop.syntheticOrigin = propertySymbol;
                         prop.declarations = propertySymbol.declarations;
                     }
-                    prop.syntheticLiteralTypeOrigin = t as StringLiteralType;
+                    prop.nameType = t;
                     members.set(propName, prop);
                 }
                 else if (t.flags & (TypeFlags.Any | TypeFlags.String)) {
@@ -7999,9 +8005,18 @@ namespace ts {
         }
 
         function getLiteralTypeFromPropertyName(prop: Symbol) {
-            return getDeclarationModifierFlagsFromSymbol(prop) & ModifierFlags.NonPublicAccessibilityModifier || isKnownSymbol(prop) ?
-                neverType :
-                getLiteralType(symbolName(prop));
+            const links = getSymbolLinks(prop);
+            if (!links.nameType) {
+                if (links.target && links.target.escapedName === prop.escapedName) {
+                    links.nameType = getLiteralTypeFromPropertyName(links.target);
+                }
+                else {
+                    links.nameType = getDeclarationModifierFlagsFromSymbol(prop) & ModifierFlags.NonPublicAccessibilityModifier || isKnownSymbol(prop) ?
+                        neverType :
+                        getLiteralType(symbolName(prop));
+                }
+            }
+            return links.nameType;
         }
 
         function getLiteralTypeFromPropertyNames(type: Type) {
@@ -11225,7 +11240,7 @@ namespace ts {
             result.type = undefinedType;
             const associatedKeyType = getLiteralType(unescapeLeadingUnderscores(name));
             if (associatedKeyType.flags & TypeFlags.StringLiteral) {
-                result.syntheticLiteralTypeOrigin = associatedKeyType as StringLiteralType;
+                result.nameType = associatedKeyType;
             }
             undefinedProperties.set(name, result);
             return result;
@@ -14998,10 +15013,15 @@ namespace ts {
                     typeFlags |= type.flags;
 
                     const nameType = hasLateBindableName(memberDecl) ? checkComputedPropertyName(memberDecl.name) : undefined;
-                    const prop = nameType && isTypeUsableAsLateBoundName(nameType)
-                        ? createSymbol(SymbolFlags.Property | member.flags, getLateBoundNameFromType(nameType), CheckFlags.Late)
+                    const hasLateBoundName = nameType && isTypeUsableAsLateBoundName(nameType);
+                    const prop = hasLateBoundName
+                        ? createSymbol(SymbolFlags.Property | member.flags, getLateBoundNameFromType(nameType as LiteralType | UniqueESSymbolType), CheckFlags.Late)
                         : createSymbol(SymbolFlags.Property | member.flags, literalName || member.escapedName);
 
+                    if (hasLateBoundName) {
+                        prop.nameType = nameType;
+                    }
+
                     if (inDestructuringPattern) {
                         // If object literal is an assignment pattern and if the assignment pattern specifies a default value
                         // for the property, make the property optional.

src/compiler/types.ts

@@ -3344,7 +3344,6 @@ namespace ts {
         leftSpread?: Symbol;                // Left source for synthetic spread property
         rightSpread?: Symbol;               // Right source for synthetic spread property
         syntheticOrigin?: Symbol;           // For a property on a mapped or spread type, points back to the original property
-        syntheticLiteralTypeOrigin?: StringLiteralType; // For a property on a mapped type, indicates the type whose text to use as the declaration name, instead of the symbol name
         isDiscriminantProperty?: boolean;   // True if discriminant synthetic property
         resolvedExports?: SymbolTable;      // Resolved exports of module or combined early- and late-bound static members of a class.
         resolvedMembers?: SymbolTable;      // Combined early- and late-bound members of a symbol
@@ -3356,6 +3355,7 @@ namespace ts {
         enumKind?: EnumKind;                // Enum declaration classification
         originatingImport?: ImportDeclaration | ImportCall; // Import declaration which produced the symbol, present if the symbol is marked as uncallable but had call signatures in `resolveESModuleSymbol`
         lateSymbol?: Symbol;                // Late-bound symbol for a computed property
+        nameType?: Type;                    // Type associate with a late-bound or mapped type property symbol's name
     }
 
     /* @internal */

tests/baselines/reference/lateBoundConstraintTypeChecksCorrectly.js

@@ -0,0 +1,33 @@
+//// [lateBoundConstraintTypeChecksCorrectly.ts]
+declare const fooProp: unique symbol;
+declare const barProp: unique symbol;
+
+type BothProps = typeof fooProp | typeof barProp;
+
+export interface Foo<T> {
+  [fooProp]: T;
+  [barProp]: string;
+}
+
+function f<T extends Foo<number>>(x: T) {
+    const abc = x[fooProp]; // expected: 'T[typeof fooProp]'
+
+    /**
+     * Expected: no error
+     */
+    const def: T[typeof fooProp] = x[fooProp];
+    const def2: T[typeof barProp] = x[barProp];
+}
+
+
+//// [lateBoundConstraintTypeChecksCorrectly.js]
+"use strict";
+exports.__esModule = true;
+function f(x) {
+    var abc = x[fooProp]; // expected: 'T[typeof fooProp]'
+    /**
+     * Expected: no error
+     */
+    var def = x[fooProp];
+    var def2 = x[barProp];
+}

tests/baselines/reference/lateBoundConstraintTypeChecksCorrectly.symbols

@@ -0,0 +1,56 @@
+=== tests/cases/compiler/lateBoundConstraintTypeChecksCorrectly.ts ===
+declare const fooProp: unique symbol;
+>fooProp : Symbol(fooProp, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 0, 13))
+
+declare const barProp: unique symbol;
+>barProp : Symbol(barProp, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 1, 13))
+
+type BothProps = typeof fooProp | typeof barProp;
+>BothProps : Symbol(BothProps, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 1, 37))
+>fooProp : Symbol(fooProp, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 0, 13))
+>barProp : Symbol(barProp, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 1, 13))
+
+export interface Foo<T> {
+>Foo : Symbol(Foo, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 3, 49))
+>T : Symbol(T, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 5, 21))
+
+  [fooProp]: T;
+>[fooProp] : Symbol(Foo[fooProp], Decl(lateBoundConstraintTypeChecksCorrectly.ts, 5, 25))
+>fooProp : Symbol(fooProp, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 0, 13))
+>T : Symbol(T, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 5, 21))
+
+  [barProp]: string;
+>[barProp] : Symbol(Foo[barProp], Decl(lateBoundConstraintTypeChecksCorrectly.ts, 6, 15))
+>barProp : Symbol(barProp, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 1, 13))
+}
+
+function f<T extends Foo<number>>(x: T) {
+>f : Symbol(f, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 8, 1))
+>T : Symbol(T, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 10, 11))
+>Foo : Symbol(Foo, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 3, 49))
+>x : Symbol(x, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 10, 34))
+>T : Symbol(T, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 10, 11))
+
+    const abc = x[fooProp]; // expected: 'T[typeof fooProp]'
+>abc : Symbol(abc, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 11, 9))
+>x : Symbol(x, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 10, 34))
+>fooProp : Symbol(fooProp, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 0, 13))
+
+    /**
+     * Expected: no error
+     */
+    const def: T[typeof fooProp] = x[fooProp];
+>def : Symbol(def, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 16, 9))
+>T : Symbol(T, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 10, 11))
+>fooProp : Symbol(fooProp, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 0, 13))
+>x : Symbol(x, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 10, 34))
+>fooProp : Symbol(fooProp, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 0, 13))
+
+    const def2: T[typeof barProp] = x[barProp];
+>def2 : Symbol(def2, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 17, 9))
+>T : Symbol(T, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 10, 11))
+>barProp : Symbol(barProp, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 1, 13))
+>x : Symbol(x, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 10, 34))
+>barProp : Symbol(barProp, Decl(lateBoundConstraintTypeChecksCorrectly.ts, 1, 13))
+}
+

tests/baselines/reference/lateBoundConstraintTypeChecksCorrectly.types

@@ -0,0 +1,59 @@
+=== tests/cases/compiler/lateBoundConstraintTypeChecksCorrectly.ts ===
+declare const fooProp: unique symbol;
+>fooProp : unique symbol
+
+declare const barProp: unique symbol;
+>barProp : unique symbol
+
+type BothProps = typeof fooProp | typeof barProp;
+>BothProps : unique symbol | unique symbol
+>fooProp : unique symbol
+>barProp : unique symbol
+
+export interface Foo<T> {
+>Foo : Foo<T>
+>T : T
+
+  [fooProp]: T;
+>[fooProp] : T
+>fooProp : unique symbol
+>T : T
+
+  [barProp]: string;
+>[barProp] : string
+>barProp : unique symbol
+}
+
+function f<T extends Foo<number>>(x: T) {
+>f : <T extends Foo<number>>(x: T) => void
+>T : T
+>Foo : Foo<T>
+>x : T
+>T : T
+
+    const abc = x[fooProp]; // expected: 'T[typeof fooProp]'
+>abc : number
+>x[fooProp] : number
+>x : T
+>fooProp : unique symbol
+
+    /**
+     * Expected: no error
+     */
+    const def: T[typeof fooProp] = x[fooProp];
+>def : T[unique symbol]
+>T : T
+>fooProp : unique symbol
+>x[fooProp] : number
+>x : T
+>fooProp : unique symbol
+
+    const def2: T[typeof barProp] = x[barProp];
+>def2 : T[unique symbol]
+>T : T
+>barProp : unique symbol
+>x[barProp] : string
+>x : T
+>barProp : unique symbol
+}
+

tests/cases/compiler/lateBoundConstraintTypeChecksCorrectly.ts

@@ -0,0 +1,19 @@
+declare const fooProp: unique symbol;
+declare const barProp: unique symbol;
+
+type BothProps = typeof fooProp | typeof barProp;
+
+export interface Foo<T> {
+  [fooProp]: T;
+  [barProp]: string;
+}
+
+function f<T extends Foo<number>>(x: T) {
+    const abc = x[fooProp]; // expected: 'T[typeof fooProp]'
+
+    /**
+     * Expected: no error
+     */
+    const def: T[typeof fooProp] = x[fooProp];
+    const def2: T[typeof barProp] = x[barProp];
+}