Allow Infinity and NaN to be used as an Enum property identifier

Author: fabiancook

src/compiler/checker.ts

@@ -10033,6 +10033,10 @@ namespace ts {
             return isTypeAny(type) || isTypeOfKind(type, kind);
         }
 
+        function isInfinityOrNaNString(name: string) : boolean {
+            return name === 'Infinity' || name === 'NaN';
+        }
+
         function isNumericLiteralName(name: string) {
             // The intent of numeric names is that
             //     - they are names with text in a numeric form, and that
@@ -16848,7 +16852,7 @@ namespace ts {
                     }
                     else {
                         const text = getTextOfPropertyName(<PropertyName>member.name);
-                        if (isNumericLiteralName(text)) {
+                        if (isNumericLiteralName(text) && !isInfinityOrNaNString(text)) {
                             error(member.name, Diagnostics.An_enum_member_cannot_have_a_numeric_name);
                         }
                     }

tests/baselines/reference/enumWithInfinityProperty.js

@@ -0,0 +1,11 @@
+//// [enumWithInfinityProperty.ts]
+enum A {
+    Infinity = 1
+}
+
+
+//// [enumWithInfinityProperty.js]
+var A;
+(function (A) {
+    A[A["Infinity"] = 1] = "Infinity";
+})(A || (A = {}));

tests/baselines/reference/enumWithInfinityProperty.symbols

@@ -0,0 +1,8 @@
+=== tests/cases/compiler/enumWithInfinityProperty.ts ===
+enum A {
+>A : Symbol(A, Decl(enumWithInfinityProperty.ts, 0, 0))
+
+    Infinity = 1
+>Infinity : Symbol(A.Infinity, Decl(enumWithInfinityProperty.ts, 0, 8))
+}
+

tests/baselines/reference/enumWithInfinityProperty.types

@@ -0,0 +1,9 @@
+=== tests/cases/compiler/enumWithInfinityProperty.ts ===
+enum A {
+>A : A
+
+    Infinity = 1
+>Infinity : A
+>1 : number
+}
+

tests/baselines/reference/enumWithNaNProperty.js

@@ -0,0 +1,11 @@
+//// [enumWithNaNProperty.ts]
+enum A {
+    NaN = 1
+}
+
+
+//// [enumWithNaNProperty.js]
+var A;
+(function (A) {
+    A[A["NaN"] = 1] = "NaN";
+})(A || (A = {}));

tests/baselines/reference/enumWithNaNProperty.symbols

@@ -0,0 +1,8 @@
+=== tests/cases/compiler/enumWithNaNProperty.ts ===
+enum A {
+>A : Symbol(A, Decl(enumWithNaNProperty.ts, 0, 0))
+
+    NaN = 1
+>NaN : Symbol(A.NaN, Decl(enumWithNaNProperty.ts, 0, 8))
+}
+

tests/baselines/reference/enumWithNaNProperty.types

@@ -0,0 +1,9 @@
+=== tests/cases/compiler/enumWithNaNProperty.ts ===
+enum A {
+>A : A
+
+    NaN = 1
+>NaN : A
+>1 : number
+}
+

tests/cases/compiler/enumWithInfinityProperty.ts

@@ -0,0 +1,3 @@
+enum A {
+    Infinity = 1
+}

tests/cases/compiler/enumWithNaNProperty.ts

@@ -0,0 +1,3 @@
+enum A {
+    NaN = 1
+}