createDiagnosticCollection should be @internal, or DiagnosticCollection should not be

[mihailik]

Generated definitions in bin/typescriptServices_internal.d.ts are invalid, causing compilation error if used:

typescriptServices_internal.d.ts 2304 @272:43 Cannot find name 'DiagnosticCollection'

declare module ts {
    // ...
    function createDiagnosticCollection(): DiagnosticCollection;

This is because DiagnosticCollection is defined with @internal flag in src/compiler/types.ts:

module ts {
    // ...

    // @internal
    export interface DiagnosticCollection {
        // Adds a diagnostic to this diagnostic collection.
        add(diagnostic: Diagnostic): void;

        // Gets all the diagnostics that aren't associated with a file.
        getGlobalDiagnostics(): Diagnostic[];

        // If fileName is provided, gets all the diagnostics associated with that file name.
        // Otherwise, returns all the diagnostics (global and file associated) in this colletion.
        getDiagnostics(fileName?: string): Diagnostic[];

        // Gets a count of how many times this collection has been modified.  This value changes
        // each time 'add' is called (regardless of whether or not an equivalent diagnostic was
        // already in the collection).  As such, it can be used as a simple way to tell if any
        // operation caused diagnostics to be returned by storing and comparing the return value 
        // of this method before/after the operation is performed.
        getModificationCount(): number;
    }

The interface looks internal enough, so I guess ts.createDiagnosticCollection() function should go under the internal flag together with the interface.

Also there need to be tests for the validity of all the generated d.ts files, shouldn't there?

[mihailik]

I've added a separate issue #2269 for generatedfiles.d.ts validity tests.

[mihailik]

The createDiagnosticCollection is defined in src/compiler/utilities.ts and used only in one place in src/compiler/program.ts:

    export function createProgram(rootNames: string[], options: CompilerOptions, host?: CompilerHost): Program {
        var program: Program;
        var files: SourceFile[] = [];
        var filesByName: Map<SourceFile> = {};
        var diagnostics = createDiagnosticCollection();  //  <--- here you go
        var seenNoDefaultLib = options.noLib;