Merge pull request #3969 from Microsoft/forwardRefsInEnumInitializers

Forward refs in enum initializers

src/compiler/checker.ts

@@ -12767,28 +12767,7 @@ namespace ts {
                     }
                     let initializer = member.initializer;
                     if (initializer) {
-                        autoValue = getConstantValueForEnumMemberInitializer(initializer);
-                        if (autoValue === undefined) {
-                            if (enumIsConst) {
-                                error(initializer, Diagnostics.In_const_enum_declarations_member_initializer_must_be_constant_expression);
-                            }
-                            else if (!ambient) {
-                                // Only here do we need to check that the initializer is assignable to the enum type.
-                                // If it is a constant value (not undefined), it is syntactically constrained to be a number.
-                                // Also, we do not need to check this for ambients because there is already
-                                // a syntax error if it is not a constant.
-                                checkTypeAssignableTo(checkExpression(initializer), enumType, initializer, /*headMessage*/ undefined);
-                            }
-                        }
-                        else if (enumIsConst) {
-                            if (isNaN(autoValue)) {
-                                error(initializer, Diagnostics.const_enum_member_initializer_was_evaluated_to_disallowed_value_NaN);
-                            }
-                            else if (!isFinite(autoValue)) {
-                                error(initializer, Diagnostics.const_enum_member_initializer_was_evaluated_to_a_non_finite_value);
-                            }
-                        }
-
+                        autoValue = computeConstantValueForEnumMemberInitializer(initializer, enumType, enumIsConst, ambient);
                     }
                     else if (ambient && !enumIsConst) {
                         autoValue = undefined;
@@ -12802,8 +12781,36 @@ namespace ts {
                 nodeLinks.flags |= NodeCheckFlags.EnumValuesComputed;
             }
 
-            function getConstantValueForEnumMemberInitializer(initializer: Expression): number {
-                return evalConstant(initializer);
+            function computeConstantValueForEnumMemberInitializer(initializer: Expression, enumType: Type, enumIsConst: boolean, ambient: boolean): number {
+                // Controls if error should be reported after evaluation of constant value is completed
+                // Can be false if another more precise error was already reported during evaluation.
+                let reportError = true;
+                let value = evalConstant(initializer);
+
+                if (reportError) {
+                    if (value === undefined) {
+                        if (enumIsConst) {
+                            error(initializer, Diagnostics.In_const_enum_declarations_member_initializer_must_be_constant_expression);
+                        }
+                        else if (!ambient) {
+                            // Only here do we need to check that the initializer is assignable to the enum type.
+                            // If it is a constant value (not undefined), it is syntactically constrained to be a number.
+                            // Also, we do not need to check this for ambients because there is already
+                            // a syntax error if it is not a constant.
+                            checkTypeAssignableTo(checkExpression(initializer), enumType, initializer, /*headMessage*/ undefined);
+                        }
+                    }
+                    else if (enumIsConst) {
+                        if (isNaN(value)) {
+                            error(initializer, Diagnostics.const_enum_member_initializer_was_evaluated_to_disallowed_value_NaN);
+                        }
+                        else if (!isFinite(value)) {
+                            error(initializer, Diagnostics.const_enum_member_initializer_was_evaluated_to_a_non_finite_value);
+                        }
+                    }
+                }
+
+                return value;
 
                 function evalConstant(e: Node): number {
                     switch (e.kind) {
@@ -12912,6 +12919,8 @@ namespace ts {
 
                             // illegal case: forward reference
                             if (!isDefinedBefore(propertyDecl, member)) {
+                                reportError = false;
+                                error(e, Diagnostics.A_member_initializer_in_a_const_enum_declaration_cannot_reference_members_declared_after_it_including_members_defined_in_other_const_enums);
                                 return undefined;
                             }
 

src/compiler/diagnosticInformationMap.generated.ts

@@ -425,7 +425,8 @@ namespace ts {
         JSX_element_class_does_not_support_attributes_because_it_does_not_have_a_0_property: { code: 2607, category: DiagnosticCategory.Error, key: "JSX element class does not support attributes because it does not have a '{0}' property" },
         The_global_type_JSX_0_may_not_have_more_than_one_property: { code: 2608, category: DiagnosticCategory.Error, key: "The global type 'JSX.{0}' may not have more than one property" },
         Cannot_emit_namespaced_JSX_elements_in_React: { code: 2650, category: DiagnosticCategory.Error, key: "Cannot emit namespaced JSX elements in React" },
-        Merged_declaration_0_cannot_include_a_default_export_declaration_Consider_adding_a_separate_export_default_0_declaration_instead: { code: 2651, category: DiagnosticCategory.Error, key: "Merged declaration '{0}' cannot include a default export declaration. Consider adding a separate 'export default {0}' declaration instead." },
+        A_member_initializer_in_a_const_enum_declaration_cannot_reference_members_declared_after_it_including_members_defined_in_other_const_enums: { code: 2651, category: DiagnosticCategory.Error, key: "A member initializer in a 'const' enum declaration cannot reference members declared after it, including members defined in other 'const' enums." },
+        Merged_declaration_0_cannot_include_a_default_export_declaration_Consider_adding_a_separate_export_default_0_declaration_instead: { code: 2652, category: DiagnosticCategory.Error, key: "Merged declaration '{0}' cannot include a default export declaration. Consider adding a separate 'export default {0}' declaration instead." },
         Import_declaration_0_is_using_private_name_1: { code: 4000, category: DiagnosticCategory.Error, key: "Import declaration '{0}' is using private name '{1}'." },
         Type_parameter_0_of_exported_class_has_or_is_using_private_name_1: { code: 4002, category: DiagnosticCategory.Error, key: "Type parameter '{0}' of exported class has or is using private name '{1}'." },
         Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1: { code: 4004, category: DiagnosticCategory.Error, key: "Type parameter '{0}' of exported interface has or is using private name '{1}'." },

src/compiler/diagnosticMessages.json

@@ -1689,9 +1689,13 @@
         "category": "Error",
         "code": 2650
     },
-    "Merged declaration '{0}' cannot include a default export declaration. Consider adding a separate 'export default {0}' declaration instead.": {
+    "A member initializer in a 'const' enum declaration cannot reference members declared after it, including members defined in other 'const' enums.": {
         "category": "Error",
         "code": 2651
+    },    
+    "Merged declaration '{0}' cannot include a default export declaration. Consider adding a separate 'export default {0}' declaration instead.": {
+        "category": "Error",
+        "code": 2652
     },
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",

tests/baselines/reference/constEnumErrors.errors.txt

@@ -1,6 +1,6 @@
 tests/cases/compiler/constEnumErrors.ts(1,12): error TS2300: Duplicate identifier 'E'.
 tests/cases/compiler/constEnumErrors.ts(5,8): error TS2300: Duplicate identifier 'E'.
-tests/cases/compiler/constEnumErrors.ts(12,9): error TS2474: In 'const' enum declarations member initializer must be constant expression.
+tests/cases/compiler/constEnumErrors.ts(12,9): error TS2651: A member initializer in a 'const' enum declaration cannot reference members declared after it, including members defined in other 'const' enums.
 tests/cases/compiler/constEnumErrors.ts(14,9): error TS2474: In 'const' enum declarations member initializer must be constant expression.
 tests/cases/compiler/constEnumErrors.ts(15,10): error TS2474: In 'const' enum declarations member initializer must be constant expression.
 tests/cases/compiler/constEnumErrors.ts(22,13): error TS2476: A const enum member can only be accessed using a string literal.
@@ -31,7 +31,7 @@ tests/cases/compiler/constEnumErrors.ts(42,9): error TS2478: 'const' enum member
         // forward reference to the element of the same enum
         X = Y, 
             ~
-!!! error TS2474: In 'const' enum declarations member initializer must be constant expression.
+!!! error TS2651: A member initializer in a 'const' enum declaration cannot reference members declared after it, including members defined in other 'const' enums.
         // forward reference to the element of the same enum
         Y = E1.Z,
             ~~~~

tests/baselines/reference/defaultExportsCannotMerge01.errors.txt

@@ -1,5 +1,5 @@
-tests/cases/conformance/es6/modules/m1.ts(2,25): error TS2651: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
-tests/cases/conformance/es6/modules/m1.ts(11,18): error TS2651: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+tests/cases/conformance/es6/modules/m1.ts(2,25): error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+tests/cases/conformance/es6/modules/m1.ts(11,18): error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
 tests/cases/conformance/es6/modules/m2.ts(5,8): error TS2304: Cannot find name 'Entity'.
 tests/cases/conformance/es6/modules/m2.ts(6,8): error TS2503: Cannot find namespace 'Entity'.
 tests/cases/conformance/es6/modules/m2.ts(8,8): error TS2339: Property 'x' does not exist on type '() => number'.
@@ -10,7 +10,7 @@ tests/cases/conformance/es6/modules/m2.ts(9,8): error TS2339: Property 'y' does
     
     export default function Decl() {
                             ~~~~
-!!! error TS2651: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+!!! error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
         return 0;
     }
     
@@ -21,7 +21,7 @@ tests/cases/conformance/es6/modules/m2.ts(9,8): error TS2339: Property 'y' does
     
     export namespace Decl {
                      ~~~~
-!!! error TS2651: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+!!! error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
         export var x = 10;
         export var y = 20;
     

tests/baselines/reference/defaultExportsCannotMerge02.errors.txt

@@ -1,5 +1,5 @@
-tests/cases/conformance/es6/modules/m1.ts(2,22): error TS2651: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
-tests/cases/conformance/es6/modules/m1.ts(5,18): error TS2651: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+tests/cases/conformance/es6/modules/m1.ts(2,22): error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+tests/cases/conformance/es6/modules/m1.ts(5,18): error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
 tests/cases/conformance/es6/modules/m2.ts(3,1): error TS2348: Value of type 'typeof Decl' is not callable. Did you mean to include 'new'?
 tests/cases/conformance/es6/modules/m2.ts(6,8): error TS2503: Cannot find namespace 'Entity'.
 tests/cases/conformance/es6/modules/m2.ts(8,13): error TS2339: Property 'p1' does not exist on type 'Decl'.
@@ -10,12 +10,12 @@ tests/cases/conformance/es6/modules/m2.ts(8,20): error TS2339: Property 'p2' doe
     
     export default class Decl {
                          ~~~~
-!!! error TS2651: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+!!! error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
     }
     
     export interface Decl {
                      ~~~~
-!!! error TS2651: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+!!! error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
         p1: number;
         p2: number;
     }

tests/baselines/reference/defaultExportsCannotMerge03.errors.txt

@@ -1,6 +1,6 @@
-tests/cases/conformance/es6/modules/m1.ts(2,22): error TS2651: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+tests/cases/conformance/es6/modules/m1.ts(2,22): error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
 tests/cases/conformance/es6/modules/m1.ts(5,11): error TS2518: Only an ambient class can be merged with an interface.
-tests/cases/conformance/es6/modules/m1.ts(5,11): error TS2651: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+tests/cases/conformance/es6/modules/m1.ts(5,11): error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
 tests/cases/conformance/es6/modules/m2.ts(3,1): error TS2348: Value of type 'typeof Decl' is not callable. Did you mean to include 'new'?
 tests/cases/conformance/es6/modules/m2.ts(6,8): error TS2503: Cannot find namespace 'Entity'.
 tests/cases/conformance/es6/modules/m2.ts(8,13): error TS2339: Property 'p1' does not exist on type 'Decl'.
@@ -11,14 +11,14 @@ tests/cases/conformance/es6/modules/m2.ts(8,20): error TS2339: Property 'p2' doe
     
     export default class Decl {
                          ~~~~
-!!! error TS2651: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+!!! error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
     }
     
     interface Decl {
               ~~~~
 !!! error TS2518: Only an ambient class can be merged with an interface.
               ~~~~
-!!! error TS2651: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+!!! error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
         p1: number;
         p2: number;
     }

tests/baselines/reference/defaultExportsCannotMerge04.errors.txt

@@ -1,5 +1,5 @@
-tests/cases/conformance/es6/modules/defaultExportsCannotMerge04.ts(2,25): error TS2651: Merged declaration 'Foo' cannot include a default export declaration. Consider adding a separate 'export default Foo' declaration instead.
-tests/cases/conformance/es6/modules/defaultExportsCannotMerge04.ts(5,11): error TS2651: Merged declaration 'Foo' cannot include a default export declaration. Consider adding a separate 'export default Foo' declaration instead.
+tests/cases/conformance/es6/modules/defaultExportsCannotMerge04.ts(2,25): error TS2652: Merged declaration 'Foo' cannot include a default export declaration. Consider adding a separate 'export default Foo' declaration instead.
+tests/cases/conformance/es6/modules/defaultExportsCannotMerge04.ts(5,11): error TS2652: Merged declaration 'Foo' cannot include a default export declaration. Consider adding a separate 'export default Foo' declaration instead.
 tests/cases/conformance/es6/modules/defaultExportsCannotMerge04.ts(9,11): error TS2395: Individual declarations in merged declaration 'Foo' must be all exported or all local.
 tests/cases/conformance/es6/modules/defaultExportsCannotMerge04.ts(12,18): error TS2395: Individual declarations in merged declaration 'Foo' must be all exported or all local.
 
@@ -8,12 +8,12 @@ tests/cases/conformance/es6/modules/defaultExportsCannotMerge04.ts(12,18): error
     
     export default function Foo() {
                             ~~~
-!!! error TS2651: Merged declaration 'Foo' cannot include a default export declaration. Consider adding a separate 'export default Foo' declaration instead.
+!!! error TS2652: Merged declaration 'Foo' cannot include a default export declaration. Consider adding a separate 'export default Foo' declaration instead.
     }
     
     namespace Foo {
               ~~~
-!!! error TS2651: Merged declaration 'Foo' cannot include a default export declaration. Consider adding a separate 'export default Foo' declaration instead.
+!!! error TS2652: Merged declaration 'Foo' cannot include a default export declaration. Consider adding a separate 'export default Foo' declaration instead.
         export var x;
     }