Merge pull request #10333 from jwbay/better-type-as-value-error

Add clearer error message when types are used as values

Author: mhegazy

src/compiler/checker.ts

@@ -877,7 +877,8 @@ namespace ts {
                 if (nameNotFoundMessage) {
                     if (!errorLocation ||
                         !checkAndReportErrorForMissingPrefix(errorLocation, name, nameArg) &&
-                        !checkAndReportErrorForExtendingInterface(errorLocation)) {
+                        !checkAndReportErrorForExtendingInterface(errorLocation) &&
+                        !checkAndReportErrorForUsingTypeAsValue(errorLocation, name, meaning)) {
                         error(errorLocation, nameNotFoundMessage, typeof nameArg === "string" ? nameArg : declarationNameToString(nameArg));
                     }
                 }
@@ -987,6 +988,16 @@ namespace ts {
             }
         }
 
+        function checkAndReportErrorForUsingTypeAsValue(errorLocation: Node, name: string, meaning: SymbolFlags): boolean {
+            if (meaning & (SymbolFlags.Value & ~SymbolFlags.NamespaceModule)) {
+                const symbol = resolveSymbol(resolveName(errorLocation, name, SymbolFlags.Type & ~SymbolFlags.Value, /*nameNotFoundMessage*/undefined, /*nameArg*/ undefined));
+                if (symbol && !(symbol.flags & SymbolFlags.NamespaceModule)) {
+                    error(errorLocation, Diagnostics._0_only_refers_to_a_type_but_is_being_used_as_a_value_here, name);
+                    return true;
+                }
+            }
+            return false;
+        }
 
         function checkResolvedBlockScopedVariable(result: Symbol, errorLocation: Node): void {
             Debug.assert((result.flags & SymbolFlags.BlockScopedVariable) !== 0);

src/compiler/diagnosticMessages.json

@@ -1947,6 +1947,10 @@
         "category": "Error",
         "code": 2692
     },
+    "'{0}' only refers to a type, but is being used as a value here.": {
+        "category": "Error",
+        "code": 2693
+    },
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
         "code": 4000

tests/baselines/reference/assignments.errors.txt

@@ -3,7 +3,7 @@ tests/cases/conformance/expressions/valuesAndReferences/assignments.ts(14,1): er
 tests/cases/conformance/expressions/valuesAndReferences/assignments.ts(17,1): error TS2364: Invalid left-hand side of assignment expression.
 tests/cases/conformance/expressions/valuesAndReferences/assignments.ts(18,1): error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
 tests/cases/conformance/expressions/valuesAndReferences/assignments.ts(21,1): error TS2364: Invalid left-hand side of assignment expression.
-tests/cases/conformance/expressions/valuesAndReferences/assignments.ts(31,1): error TS2304: Cannot find name 'I'.
+tests/cases/conformance/expressions/valuesAndReferences/assignments.ts(31,1): error TS2693: 'I' only refers to a type, but is being used as a value here.
 
 
 ==== tests/cases/conformance/expressions/valuesAndReferences/assignments.ts (6 errors) ====
@@ -49,4 +49,4 @@ tests/cases/conformance/expressions/valuesAndReferences/assignments.ts(31,1): er
     interface I { }
     I = null; // Error
     ~
-!!! error TS2304: Cannot find name 'I'.
+!!! error TS2693: 'I' only refers to a type, but is being used as a value here.

tests/baselines/reference/classExtendsInterfaceInExpression.errors.txt

@@ -1,4 +1,4 @@
-tests/cases/compiler/classExtendsInterfaceInExpression.ts(7,25): error TS2304: Cannot find name 'A'.
+tests/cases/compiler/classExtendsInterfaceInExpression.ts(7,25): error TS2693: 'A' only refers to a type, but is being used as a value here.
 
 
 ==== tests/cases/compiler/classExtendsInterfaceInExpression.ts (1 errors) ====
@@ -10,5 +10,5 @@ tests/cases/compiler/classExtendsInterfaceInExpression.ts(7,25): error TS2304: C
 
     class C extends factory(A) {}
                             ~
-!!! error TS2304: Cannot find name 'A'.
+!!! error TS2693: 'A' only refers to a type, but is being used as a value here.
 

tests/baselines/reference/errorsOnImportedSymbol.errors.txt

@@ -1,15 +1,15 @@
-tests/cases/compiler/errorsOnImportedSymbol_1.ts(2,13): error TS2304: Cannot find name 'Sammy'.
-tests/cases/compiler/errorsOnImportedSymbol_1.ts(3,9): error TS2304: Cannot find name 'Sammy'.
+tests/cases/compiler/errorsOnImportedSymbol_1.ts(2,13): error TS2693: 'Sammy' only refers to a type, but is being used as a value here.
+tests/cases/compiler/errorsOnImportedSymbol_1.ts(3,9): error TS2693: 'Sammy' only refers to a type, but is being used as a value here.
 
 
 ==== tests/cases/compiler/errorsOnImportedSymbol_1.ts (2 errors) ====
     import Sammy = require("./errorsOnImportedSymbol_0");
     var x = new Sammy.Sammy();
                 ~~~~~
-!!! error TS2304: Cannot find name 'Sammy'.
+!!! error TS2693: 'Sammy' only refers to a type, but is being used as a value here.
     var y = Sammy.Sammy(); 
             ~~~~~
-!!! error TS2304: Cannot find name 'Sammy'.
+!!! error TS2693: 'Sammy' only refers to a type, but is being used as a value here.
 
 
 ==== tests/cases/compiler/errorsOnImportedSymbol_0.ts (0 errors) ====

tests/baselines/reference/es6ExportEqualsInterop.errors.txt

@@ -1,4 +1,4 @@
-tests/cases/compiler/main.ts(15,1): error TS2304: Cannot find name 'z1'.
+tests/cases/compiler/main.ts(15,1): error TS2693: 'z1' only refers to a type, but is being used as a value here.
 tests/cases/compiler/main.ts(21,4): error TS2339: Property 'a' does not exist on type '() => any'.
 tests/cases/compiler/main.ts(23,4): error TS2339: Property 'a' does not exist on type 'typeof Foo'.
 tests/cases/compiler/main.ts(27,8): error TS1192: Module '"interface"' has no default export.
@@ -49,7 +49,7 @@ tests/cases/compiler/main.ts(106,15): error TS2498: Module '"class-module"' uses
 
     z1.a;
     ~~
-!!! error TS2304: Cannot find name 'z1'.
+!!! error TS2693: 'z1' only refers to a type, but is being used as a value here.
     z2.a;
     z3.a;
     z4.a;

tests/baselines/reference/exportAssignmentOfDeclaredExternalModule.errors.txt

@@ -1,16 +1,16 @@
-tests/cases/compiler/exportAssignmentOfDeclaredExternalModule_1.ts(3,13): error TS2304: Cannot find name 'Sammy'.
-tests/cases/compiler/exportAssignmentOfDeclaredExternalModule_1.ts(4,9): error TS2304: Cannot find name 'Sammy'.
+tests/cases/compiler/exportAssignmentOfDeclaredExternalModule_1.ts(3,13): error TS2693: 'Sammy' only refers to a type, but is being used as a value here.
+tests/cases/compiler/exportAssignmentOfDeclaredExternalModule_1.ts(4,9): error TS2693: 'Sammy' only refers to a type, but is being used as a value here.
 
 
 ==== tests/cases/compiler/exportAssignmentOfDeclaredExternalModule_1.ts (2 errors) ====
     ///<reference path='exportAssignmentOfDeclaredExternalModule_0.ts'/>
     import Sammy = require('./exportAssignmentOfDeclaredExternalModule_0');
     var x = new Sammy(); // error to use as constructor as there is not constructor symbol
                 ~~~~~
-!!! error TS2304: Cannot find name 'Sammy'.
+!!! error TS2693: 'Sammy' only refers to a type, but is being used as a value here.
     var y = Sammy(); // error to use interface name as call target
             ~~~~~
-!!! error TS2304: Cannot find name 'Sammy'.
+!!! error TS2693: 'Sammy' only refers to a type, but is being used as a value here.
     var z: Sammy; // no error - z is of type interface Sammy from module 'M'
     var a = new z(); // constructor - no error
     var b = z(); // call signature - no error

tests/baselines/reference/genericConstructInvocationWithNoTypeArg.errors.txt

@@ -1,4 +1,4 @@
-tests/cases/compiler/genericConstructInvocationWithNoTypeArg.ts(4,27): error TS2304: Cannot find name 'Foo'.
+tests/cases/compiler/genericConstructInvocationWithNoTypeArg.ts(4,27): error TS2693: 'Foo' only refers to a type, but is being used as a value here.
 
 
 ==== tests/cases/compiler/genericConstructInvocationWithNoTypeArg.ts (1 errors) ====
@@ -7,5 +7,5 @@ tests/cases/compiler/genericConstructInvocationWithNoTypeArg.ts(4,27): error TS2
     }
     var f2: Foo<number> = new Foo(3);
                               ~~~
-!!! error TS2304: Cannot find name 'Foo'.
+!!! error TS2693: 'Foo' only refers to a type, but is being used as a value here.
 

tests/baselines/reference/inheritFromGenericTypeParameter.errors.txt

@@ -1,11 +1,11 @@
-tests/cases/compiler/inheritFromGenericTypeParameter.ts(1,20): error TS2304: Cannot find name 'T'.
+tests/cases/compiler/inheritFromGenericTypeParameter.ts(1,20): error TS2693: 'T' only refers to a type, but is being used as a value here.
 tests/cases/compiler/inheritFromGenericTypeParameter.ts(2,24): error TS2312: An interface may only extend a class or another interface.
 
 
 ==== tests/cases/compiler/inheritFromGenericTypeParameter.ts (2 errors) ====
     class C<T> extends T { }
                        ~
-!!! error TS2304: Cannot find name 'T'.
+!!! error TS2693: 'T' only refers to a type, but is being used as a value here.
     interface I<T> extends T { }
                            ~
 !!! error TS2312: An interface may only extend a class or another interface.

tests/baselines/reference/intTypeCheck.errors.txt

@@ -10,7 +10,7 @@ tests/cases/compiler/intTypeCheck.ts(103,5): error TS2322: Type '() => void' is
   Property 'p' is missing in type '() => void'.
 tests/cases/compiler/intTypeCheck.ts(106,5): error TS2322: Type 'boolean' is not assignable to type 'i1'.
 tests/cases/compiler/intTypeCheck.ts(106,20): error TS1109: Expression expected.
-tests/cases/compiler/intTypeCheck.ts(106,21): error TS2304: Cannot find name 'i1'.
+tests/cases/compiler/intTypeCheck.ts(106,21): error TS2693: 'i1' only refers to a type, but is being used as a value here.
 tests/cases/compiler/intTypeCheck.ts(107,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
 tests/cases/compiler/intTypeCheck.ts(112,5): error TS2322: Type '{}' is not assignable to type 'i2'.
   Type '{}' provides no match for the signature '(): any'
@@ -21,7 +21,7 @@ tests/cases/compiler/intTypeCheck.ts(115,5): error TS2322: Type 'Base' is not as
   Type 'Base' provides no match for the signature '(): any'
 tests/cases/compiler/intTypeCheck.ts(120,5): error TS2322: Type 'boolean' is not assignable to type 'i2'.
 tests/cases/compiler/intTypeCheck.ts(120,21): error TS1109: Expression expected.
-tests/cases/compiler/intTypeCheck.ts(120,22): error TS2304: Cannot find name 'i2'.
+tests/cases/compiler/intTypeCheck.ts(120,22): error TS2693: 'i2' only refers to a type, but is being used as a value here.
 tests/cases/compiler/intTypeCheck.ts(121,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
 tests/cases/compiler/intTypeCheck.ts(126,5): error TS2322: Type '{}' is not assignable to type 'i3'.
   Type '{}' provides no match for the signature 'new (): any'
@@ -33,12 +33,12 @@ tests/cases/compiler/intTypeCheck.ts(131,5): error TS2322: Type '() => void' is
   Type '() => void' provides no match for the signature 'new (): any'
 tests/cases/compiler/intTypeCheck.ts(134,5): error TS2322: Type 'boolean' is not assignable to type 'i3'.
 tests/cases/compiler/intTypeCheck.ts(134,21): error TS1109: Expression expected.
-tests/cases/compiler/intTypeCheck.ts(134,22): error TS2304: Cannot find name 'i3'.
+tests/cases/compiler/intTypeCheck.ts(134,22): error TS2693: 'i3' only refers to a type, but is being used as a value here.
 tests/cases/compiler/intTypeCheck.ts(135,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
 tests/cases/compiler/intTypeCheck.ts(142,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
 tests/cases/compiler/intTypeCheck.ts(148,5): error TS2322: Type 'boolean' is not assignable to type 'i4'.
 tests/cases/compiler/intTypeCheck.ts(148,21): error TS1109: Expression expected.
-tests/cases/compiler/intTypeCheck.ts(148,22): error TS2304: Cannot find name 'i4'.
+tests/cases/compiler/intTypeCheck.ts(148,22): error TS2693: 'i4' only refers to a type, but is being used as a value here.
 tests/cases/compiler/intTypeCheck.ts(149,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
 tests/cases/compiler/intTypeCheck.ts(154,5): error TS2322: Type '{}' is not assignable to type 'i5'.
   Property 'p' is missing in type '{}'.
@@ -51,7 +51,7 @@ tests/cases/compiler/intTypeCheck.ts(159,5): error TS2322: Type '() => void' is
   Property 'p' is missing in type '() => void'.
 tests/cases/compiler/intTypeCheck.ts(162,5): error TS2322: Type 'boolean' is not assignable to type 'i5'.
 tests/cases/compiler/intTypeCheck.ts(162,21): error TS1109: Expression expected.
-tests/cases/compiler/intTypeCheck.ts(162,22): error TS2304: Cannot find name 'i5'.
+tests/cases/compiler/intTypeCheck.ts(162,22): error TS2693: 'i5' only refers to a type, but is being used as a value here.
 tests/cases/compiler/intTypeCheck.ts(163,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
 tests/cases/compiler/intTypeCheck.ts(168,5): error TS2322: Type '{}' is not assignable to type 'i6'.
   Type '{}' provides no match for the signature '(): any'
@@ -64,7 +64,7 @@ tests/cases/compiler/intTypeCheck.ts(173,5): error TS2322: Type '() => void' is
   Type 'void' is not assignable to type 'number'.
 tests/cases/compiler/intTypeCheck.ts(176,5): error TS2322: Type 'boolean' is not assignable to type 'i6'.
 tests/cases/compiler/intTypeCheck.ts(176,21): error TS1109: Expression expected.
-tests/cases/compiler/intTypeCheck.ts(176,22): error TS2304: Cannot find name 'i6'.
+tests/cases/compiler/intTypeCheck.ts(176,22): error TS2693: 'i6' only refers to a type, but is being used as a value here.
 tests/cases/compiler/intTypeCheck.ts(177,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
 tests/cases/compiler/intTypeCheck.ts(182,5): error TS2322: Type '{}' is not assignable to type 'i7'.
   Type '{}' provides no match for the signature 'new (): any'
@@ -76,12 +76,12 @@ tests/cases/compiler/intTypeCheck.ts(187,5): error TS2322: Type '() => void' is
   Type '() => void' provides no match for the signature 'new (): any'
 tests/cases/compiler/intTypeCheck.ts(190,5): error TS2322: Type 'boolean' is not assignable to type 'i7'.
 tests/cases/compiler/intTypeCheck.ts(190,21): error TS1109: Expression expected.
-tests/cases/compiler/intTypeCheck.ts(190,22): error TS2304: Cannot find name 'i7'.
+tests/cases/compiler/intTypeCheck.ts(190,22): error TS2693: 'i7' only refers to a type, but is being used as a value here.
 tests/cases/compiler/intTypeCheck.ts(191,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
 tests/cases/compiler/intTypeCheck.ts(198,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
 tests/cases/compiler/intTypeCheck.ts(204,5): error TS2322: Type 'boolean' is not assignable to type 'i8'.
 tests/cases/compiler/intTypeCheck.ts(204,21): error TS1109: Expression expected.
-tests/cases/compiler/intTypeCheck.ts(204,22): error TS2304: Cannot find name 'i8'.
+tests/cases/compiler/intTypeCheck.ts(204,22): error TS2693: 'i8' only refers to a type, but is being used as a value here.
 tests/cases/compiler/intTypeCheck.ts(205,17): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
 
 
@@ -214,7 +214,7 @@ tests/cases/compiler/intTypeCheck.ts(205,17): error TS2351: Cannot use 'new' wit
                        ~
 !!! error TS1109: Expression expected.
                         ~~
-!!! error TS2304: Cannot find name 'i1'.
+!!! error TS2693: 'i1' only refers to a type, but is being used as a value here.
     var obj10: i1 = new {};
                     ~~~~~~
 !!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
@@ -247,7 +247,7 @@ tests/cases/compiler/intTypeCheck.ts(205,17): error TS2351: Cannot use 'new' wit
                         ~
 !!! error TS1109: Expression expected.
                          ~~
-!!! error TS2304: Cannot find name 'i2'.
+!!! error TS2693: 'i2' only refers to a type, but is being used as a value here.
     var obj21: i2 = new {};
                     ~~~~~~
 !!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
@@ -281,7 +281,7 @@ tests/cases/compiler/intTypeCheck.ts(205,17): error TS2351: Cannot use 'new' wit
                         ~
 !!! error TS1109: Expression expected.
                          ~~
-!!! error TS2304: Cannot find name 'i3'.
+!!! error TS2693: 'i3' only refers to a type, but is being used as a value here.
     var obj32: i3 = new {};
                     ~~~~~~
 !!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
@@ -305,7 +305,7 @@ tests/cases/compiler/intTypeCheck.ts(205,17): error TS2351: Cannot use 'new' wit
                         ~
 !!! error TS1109: Expression expected.
                          ~~
-!!! error TS2304: Cannot find name 'i4'.
+!!! error TS2693: 'i4' only refers to a type, but is being used as a value here.
     var obj43: i4 = new {};
                     ~~~~~~
 !!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
@@ -341,7 +341,7 @@ tests/cases/compiler/intTypeCheck.ts(205,17): error TS2351: Cannot use 'new' wit
                         ~
 !!! error TS1109: Expression expected.
                          ~~
-!!! error TS2304: Cannot find name 'i5'.
+!!! error TS2693: 'i5' only refers to a type, but is being used as a value here.
     var obj54: i5 = new {};
                     ~~~~~~
 !!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
@@ -377,7 +377,7 @@ tests/cases/compiler/intTypeCheck.ts(205,17): error TS2351: Cannot use 'new' wit
                         ~
 !!! error TS1109: Expression expected.
                          ~~
-!!! error TS2304: Cannot find name 'i6'.
+!!! error TS2693: 'i6' only refers to a type, but is being used as a value here.
     var obj65: i6 = new {};
                     ~~~~~~
 !!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
@@ -411,7 +411,7 @@ tests/cases/compiler/intTypeCheck.ts(205,17): error TS2351: Cannot use 'new' wit
                         ~
 !!! error TS1109: Expression expected.
                          ~~
-!!! error TS2304: Cannot find name 'i7'.
+!!! error TS2693: 'i7' only refers to a type, but is being used as a value here.
     var obj76: i7 = new {};
                     ~~~~~~
 !!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
@@ -435,7 +435,7 @@ tests/cases/compiler/intTypeCheck.ts(205,17): error TS2351: Cannot use 'new' wit
                         ~
 !!! error TS1109: Expression expected.
                          ~~
-!!! error TS2304: Cannot find name 'i8'.
+!!! error TS2693: 'i8' only refers to a type, but is being used as a value here.
     var obj87: i8 = new {};
                     ~~~~~~
 !!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.