In TypeScript 0.8.1.1, a 'declare' is needed in front of the 'class Spinner', since without it the compiler attempts to compile it as an actual class definition, and fails with:
Message: Overload declaration lacks definition
Line number: 27
Column number: 5
Source error:
Line 26: class Spinner {
Line 27: constructor (options?: SpinnerOptions);
-------------^
Line 28: spin(target?: any);
The test in the typescript codebase that confirms this is intentional behavior is in tests/compiler/class.ts
http://typescript.codeplex.com/SourceControl/changeset/view/2bee84410e02#tests/compiler/class.ts
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describe('Testing function signatures inside classes', function () {
it('Regression test - was previously giving runtime error', function () {
var code = "class A { a(completed: () => any): void; }";
Harness.Compiler.compileString(code, 'fnsig-inside-classes', function (result) {
assert.compilerWarning(result, 1, 10, 'Overload declaration lacks definition');
assert.equal(result.errors.length, 1);
});
});
});
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The compiler code that implements the check is in src/compiler/signatures.ts
http://typescript.codeplex.com/SourceControl/changeset/view/2bee84410e02#src/compiler/signatures.ts
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if (!hasConstruct && !this.definitionSignature && this.signatures[i].declAST && this.signatures[i].declAST.isOverload && !hasFlag(this.signatures[i].declAST.fncFlags, FncFlags.Ambient)) {
checker.errorReporter.simpleError(this.signatures[i].declAST, "Overload declaration lacks definition");
}
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By adding the 'declare', we tell the TypeScript compiler that this is just intending to expose the API of the class, not the actual implementation.
This enables each definition to have a readme if necessary.
Also a .json metadata file to help with package managers.
And last, to have different versions of the definitions.
