More poor errors with value/type/namespace confusion

[mattmccutchen]

"Cannot find name" or "Namespace ... has no exported member", but I see it right there! Some of the more common cases came up in two recent Stack Overflow questions: 1, 2. Maybe we should just fix all the cases?

TypeScript Version: master (f6ca105)

Search Terms: value type namespace meaning error (and all the error messages below)

Code

const v = 42;
type t = number;
namespace n {}
const vt = 42;
type vt = number;
const vn = 42;
namespace vn {}
type tn = number;
namespace tn {}

namespace M { 
    export const v = 42;
    export type t = number;
    export namespace n {}
    export const vt = 42;
    export type vt = number;
    export const vn = 42;
    export namespace vn {}
    export type tn = number;
    export namespace tn {}    
}

// Actual is OK: 't' only refers to a type, but is being used as a value here.
const v1 = t;
// Actual: Property 't' does not exist on type 'typeof M'.
// Proposed: 't' only refers to a type, but is being used as a value here.
const v2 = M.t;
// Actual is OK: Cannot use namespace 'n' as a value.
const v3 = n;
// Actual: Property 'n' does not exist on type 'typeof M'.
// Proposed: Cannot use namespace 'n' as a value.
const v4 = M.n;
// Actual: Cannot use namespace 'tn' as a value.
// Proposed: 'tn' only refers to a type and a namespace, but is being used as a value here.
const v5 = tn;
// Actual: Property 'tn' does not exist on type 'typeof M'.
// Proposed: 'tn' only refers to a type and a namespace, but is being used as a value here.
const v6 = M.tn;

// Actual: Cannot find name 'v'.
// Proposed: 'v' only refers to a value, but is being used as a type here.
type t1 = v;
// Actual: Namespace 'M' has no exported member 'v'.
// Proposed: 'v' only refers to a value, but is being used as a type here.
type t2 = M.v;
// Actual is OK: Cannot use namespace 'n' as a type.
type t3 = n;
// Actual: Namespace 'M' has no exported member 'n'.
// Proposed: Cannot use namespace 'n' as a type.
type t4 = M.n;
// Actual: Cannot use namespace 'vn' as a type.
// Proposed: 'vn' only refers to a value and a namespace, but is being used as a type here.
type t5 = vn;
// Actual: Namespace 'M' has no exported member 'vn'.
// Proposed: 'vn' only refers to a value and a namespace, but is being used as a type here.
type t6 = M.vn;

// Actual: Cannot find namespace 'v'.
// Proposed: 'v' only refers to a value, but is being used as a namespace here.
type nt1 = v.oops;
// Actual: Namespace 'M' has no exported member 'v'.
// Proposed: 'v' only refers to a value, but is being used as a namespace here.
type nt2 = M.v.oops;
// Actual is OK: 't' only refers to a type, but is being used as a namespace here.
type nt3 = t.oops;
// Actual: Namespace 'M' has no exported member 't'.
// Proposed: 't' only refers to a type, but is being used as a namespace here.
type nt4 = M.t.oops;
// Actual: 'vt' only refers to a type, but is being used as a namespace here.
// Proposed: 'vt' only refers to a value and a type, but is being used as a namespace here.
type nt5 = vt.oops;
// Actual: Namespace 'M' has no exported member 'vt'.
// Proposed: 'vt' only refers to a value and a type, but is being used as a namespace here.
type nt6 = M.vt.oops;

Expected behavior: As indicated above

Actual behavior: As indicated above

Playground Link: link

Related Issues: #7900

[tibi77]

Can I work on this?