Rule 4.2

Chapter 4, Types Test

A type alias is another name for its target. An alias of a scalar, a vector, an array, or a struct must resolve wherever a type may stand, and an alias, an interface, or a class over an object type is one struct. A builtin type name must win over an alias of the same name, so type vec3 = f32 does not make vec3 a scalar.

The rule text and the parts under it are the compiler's own English, as the design document writes them.

Rationale

the first two clauses are what a type alias means in TypeScript and in WGSL alike. The third is a recorded divergence from WGSL, where a module-scope declaration hides the predeclared object of the same name. It is kept because a file that re-types a builtin name would make every later use of that name mean something no reader of the surface can see.

Derives from

Type Aliases for the resolution; surface §2 (roadmap 0.3 item T2) for the precedence, which reverses Declaration and Scope (“predeclared objects, and objects declared at module-scope, are in scope across the entire program source”, and the example “Shadowing predeclared objects”, where a module-scope fn min() hides the builtin).

How it is verified

Checked by a test. A test, a gate script or a CI workflow names this rule, and the traceability check fails when a file listed below stops naming it.

Where the rule says the compiler enforces it:

src/compiler/ts/type-alias.test.ts (resolution, and “an alias cannot shadow a builtin name”) and TS8023 DUPLICATE_SYMBOL for a second declaration of one struct name, whether or not anything uses the struct (#172), pinned by src/compiler/ts/type-structs.test.ts.

The files that verify it at commit 26de7be8, each at the first line that names the rule:

Explained in

The sections of the surface document that explain this rule, at commit 26de7be8:

§2 Value types — type, interface and class

Error codes that enforce it

The diagnostic codes the rule names under Enforced by, or whose registry text names the rule:

TS8023 DUPLICATE_SYMBOL: The same function, binding, module constant or struct name declared twice in one scope.

Source

The rule at commit 26de7be8:

docs/language-design.md:273 (the design document)
reqs/rules/RULE-0402.md (its traceability item)

Edit this page Report a problem