🔀 Merge chore/rename-primitive-union into main

CHANGELOG.md

@@ -8,6 +8,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 - add `getTaggedUnionMatcher` / `getTaggedUnionMatcherW` for discriminated unions
+- rename the primitive matcher to primitive-union: `getMatcher` /
+  `getMatcherW` → `getPrimitiveUnionMatcher` / `getPrimitiveUnionMatcherW`, and
+  `src/primitive.ts` / `src/primitive.test.ts` → `src/primitive-union.*`
 
 ## [0.5.0] - 2026-09-21
 

CONTRIBUTING.md

@@ -71,7 +71,7 @@ Every test pairs an `expectTypeOf(...)` with an `assert.*`; keep them together
 assertion on the value dispatch passed, not only the type it inferred (see
 [development/testing.md § Handler arguments](./development/testing.md#handler-arguments)).
 The autocomplete tests (`src/util/__tests__/lsp-completion.test.ts` for the
-helper, `src/primitive.test.ts` for the matcher's popup) are the
+helper, `src/primitive-union.test.ts` for the matcher's popup) are the
 exception —
 the language server, not the type system, is the oracle (see
 [development/testing.md § Autocomplete](./development/testing.md#autocomplete)).

backlog.tasks

@@ -24,7 +24,7 @@ v1.0:
     ☐ Document all exported types and functions
     ☐ Add JSDoc for public APIs
 ☐ Test coverage meets threshold
-    ☐ Achieve 100% branch coverage on `src/primitive.ts`
+    ☐ Achieve 100% branch coverage on `src/primitive-union.ts`
     ☐ Achieve 100% branch coverage on `src/index.ts`
 
 Testing:
@@ -42,7 +42,7 @@ Testing:
 ☐ Type hole when using broad types like string as a universe @high
     ☐ handlers cannot be exhaustive, yet it is possible to not have a fallback
     ☐ one test even exploits this, I think for a negative test
-    ☐ does the same type hole exist for tagged-union matchers or primitive matchers only?
+    ☐ does the same type hole exist for tagged-union matchers or primitive-union matchers only?
 
 Matcher:
 ✔ Clean up: adopt the 3-overload matcher (`src/prototype-ac2.ts`) and delete the prototypes @high @done
@@ -55,10 +55,11 @@ Matcher:
 ✔ Implement matcher with similar API like matcher from primitive.ts @high @done
     → `getTaggedUnionMatcher` / `getTaggedUnionMatcherW`, curried on the discriminant key
     → fallback is the second argument; `_` removed
-☐ Rename `primitive` to `primitive-union` and `getMatcher` to `getPrimitiveMatcher` @medium
+✔ Rename `primitive` to `primitive-union` and `getMatcher` to `getPrimitiveMatcher` @medium @done
     → `src/primitive.ts` / `src/primitive.test.ts` → `primitive-union.*`
     → `getMatcherW` → `getPrimitiveMatcherW` for symmetry with the tagged-union pair
     → update `src/index.ts`, `development/library.md` and any README references
+    → shipped as `getPrimitiveUnionMatcher` / `getPrimitiveUnionMatcherW`; kept `Union` for symmetry with the tagged-union pair
 ☐ when using a union type as a property, the current behavior of tagged union matcher is
     to pass never to handler parameters
     → new matcher function needed or can be fixed in tagged union matcher
@@ -72,7 +73,7 @@ Enhancements:
     ✔ Are there other primitive types that should be supported in union patterns? (e.g. `bigint`, `symbol`) @medium @done
         → added boolean, null and undefined; rejected `symbol` (compile-time brand, nothing at runtime) and `bigint` (not a property key)
 ☐ Allow boolean, null and undefined discriminant values in tagged-union patterns @medium
-    → needs the primitive matcher's `PatternKey` / `PatternParam` projection; see development/library.md § Tagged-union matcher
+    → needs the primitive-union matcher's `PatternKey` / `PatternParam` projection; see development/library.md § Tagged-union matcher
 
 Documentation:
 ☐ Bring README.md back to its previous form — synopsis and examples restored, in the correct place

development/library.md

@@ -3,8 +3,8 @@
 The type-level design of the public API and the limitations it carries. The
 user-facing reference is [README § API](../README.md#api).
 
-The matchers are implemented in `src/primitive.ts` (`getMatcher` /
+The matchers are implemented in `src/primitive-union.ts` (`getPrimitiveUnionMatcher` /
-`getMatcherW`) and `src/tagged-union.ts` (`getTaggedUnionMatcher` /
+`getPrimitiveUnionMatcherW`) and `src/tagged-union.ts` (`getTaggedUnionMatcher` /
 `getTaggedUnionMatcherW`), re-exported from `src/index.ts`; the rest of the
 library is placeholder code.
 
@@ -16,8 +16,8 @@ A factory takes the universe and returns a builder; the builder takes a handler
 map and an optional fallback:
 
 ```ts
-const matcher = getMatcher<"a" | "b">()({ a: (s) => …, b: (s) => … });
+const matcher = getPrimitiveUnionMatcher<"a" | "b">()({ a: (s) => …, b: (s) => … });
-const fallback = getMatcher<"a" | "b" | "c">()({ a: (s) => … }, (s) => …);
+const fallback = getPrimitiveUnionMatcher<"a" | "b" | "c">()({ a: (s) => … }, (s) => …);
 ```
 
 Exhaustive or fallback is decided **at the call site**, by whether the second
@@ -25,8 +25,8 @@ argument is present. The fallback's parameter is the remainder
 `Exclude<T, keyof Handled>`. Only the return-strictness axis remains, so there
 are two factories:
 
-- `getMatcher` — one common `R`; the fallback must fit it;
+- `getPrimitiveUnionMatcher` — one common `R`; the fallback must fit it;
-- `getMatcherW` — the union `PatternReturns<Handled> | R`.
+- `getPrimitiveUnionMatcherW` — the union `PatternReturns<Handled> | R`.
 
 Each factory is two overloads whose order is load-bearing:
 
@@ -118,7 +118,7 @@ use: `UnaryFn`, `PatternReturns`, `RedundantFallback`, `HandlerMap`.
 
 #### Decision (2026-09)
 
-`getTaggedUnionMatcher` / `getTaggedUnionMatcherW` mirror the primitive pair
+`getTaggedUnionMatcher` / `getTaggedUnionMatcherW` mirror the primitive-union pair
 with one extra curried step for the discriminant key:
 
 ```ts
@@ -142,14 +142,14 @@ The key is a separate call because `K` is inferred from its literal argument and
 
 #### Why
 
-- **Same fallback/remainder machinery as the primitive matcher.** `HandledMembers`
+- **Same fallback/remainder machinery as the primitive-union matcher.** `HandledMembers`
   maps the handled tags to their members and `Exclude<T, …>` is the fallback's
   parameter; the redundant-fallback guard is the same F-bounded constraint. Only
   the "universe" changes — `T`'s members instead of primitive values.
 - **`T extends object`, not `Record<PropertyKey, unknown>`.** An `interface` has
   no implicit index signature, so the `Record` constraint would reject
   interface-based unions. The runtime reads the tag off `object` with one
-  assertion, the tagged twin of the primitive dispatch's `shape as string | number`.
+  assertion, the tagged twin of the primitive-union dispatch's `shape as string | number`.
 - **`MapTaggedUnion` distributes with `Extract`.** A duplicated tag yields a
   union of members instead of dropping one.
 
@@ -158,7 +158,7 @@ The key is a separate call because `K` is inferred from its literal argument and
 - Tags are `string | number` only. A `boolean` / `null` / `undefined`
   discriminant (`{ ok: true } | { ok: false }`) is rejected by `Discriminated`,
   because those values are not property keys; supporting them needs the
-  primitive matcher's `PatternKey` / `PatternParam` projection.
+  primitive-union matcher's `PatternKey` / `PatternParam` projection.
 - A member's tag must be unique across the union; two members with the same tag
   collapse to a union under one handler.
 

development/testing.md

@@ -28,7 +28,7 @@ before the implementation.
 - Runtime-first (classic red/green): it verifies the value, not the contract,
   and the contract is the product.
 - Testing the type only: it would not catch handler dispatch or the `_`
-  fallback (see `src/primitive.test.ts`).
+  fallback (see `src/primitive-union.test.ts`).
 
 The runner is `node --test --strip-types "src/**/*.test.ts"` and the tiers are
 in
@@ -167,7 +167,7 @@ The script prints the labels the server offers at a `/*COMPLETE*/` marker inside
 `<file>` (the marker is stripped before the document is sent). Its `LspSession`
 is imported by `src/util/__tests__/lsp-completion.test.ts` — which tests the
 helper itself against inline documents, never the library's code — and by
-`src/primitive.test.ts`, where the same probe asserts the matcher's popup;
+`src/primitive-union.test.ts`, where the same probe asserts the matcher's popup;
 the CLI is for manual inspection.
 
 #### Why

development/tooling.md

@@ -107,7 +107,7 @@ Type-aware oxlint is enabled via `options.typeAware: true` in `.oxlintrc.json`
 #### Decision (2026-09)
 
 A type-aware rule that false-positives **at one site** is silenced with a
-source-level `oxlint-disable` directive (see `src/primitive.ts`). A rule that is
+source-level `oxlint-disable` directive (see `src/primitive-union.ts`). A rule that is
 wrong for a whole **file class** is turned off in a `.oxlintrc.json` `overrides`
 entry instead — e.g. `typescript/no-floating-promises` (synchronous
 `expectTypeOf` reads as an unhandled promise) and `unicorn/no-null` (intentional

src/index.ts

@@ -1,4 +1,7 @@
-export { getMatcher, getMatcherW } from "./primitive.ts";
+export {
+    getPrimitiveUnionMatcher,
+    getPrimitiveUnionMatcherW,
+} from "./primitive-union.ts";
 export {
     getTaggedUnionMatcher,
     getTaggedUnionMatcherW,

src/matcher-shared.ts

@@ -1,6 +1,6 @@
 import type { ValueOf } from "type-fest";
 
-// The primitive and tagged-union matchers differ in their universe, but the
+// The primitive-union and tagged-union matchers differ in their universe, but the
 // handler/fallback plumbing is identical; these are the shared pieces. The
 // boundary is deliberate: `Handlers`, `Fallback` and `MustBePartial` stay with
 // each matcher because they are built from its universe. See development/library.md.

src/primitive-union.test.ts

@@ -9,15 +9,18 @@ import {
     LspSession,
 } from "#test-utils/lsp-completion.ts";
 
-import { getMatcher, getMatcherW } from "./primitive.ts";
+import {
+    getPrimitiveUnionMatcher,
+    getPrimitiveUnionMatcherW,
+} from "./primitive-union.ts";
 
 // ============================================================================
-// API: getMatcher — ✔️ Exhaustive / ✔️ ReturnsStrict
+// API: getPrimitiveUnionMatcher — ✔️ Exhaustive / ✔️ ReturnsStrict
 // ============================================================================
 
-test("getMatcher: exhaustive pattern infers one common return type", () => {
+test("getPrimitiveUnionMatcher: exhaustive pattern infers one common return type", () => {
     // Arrange
-    const factory = getMatcher<"a" | "b">();
+    const factory = getPrimitiveUnionMatcher<"a" | "b">();
 
     // Act
     const matcher = factory({
@@ -42,9 +45,9 @@ test("getMatcher: exhaustive pattern infers one common return type", () => {
     assert.equal(matcher("b"), 2);
 });
 
-test("getMatcher: dispatches on numeric literal keys", () => {
+test("getPrimitiveUnionMatcher: dispatches on numeric literal keys", () => {
     // Arrange
-    const factory = getMatcher<1 | 2>();
+    const factory = getPrimitiveUnionMatcher<1 | 2>();
 
     // Act
     const matcher = factory({
@@ -67,9 +70,9 @@ test("getMatcher: dispatches on numeric literal keys", () => {
     assert.equal(matcher(2), 20);
 });
 
-test("getMatcher: dispatches on mixed string and numeric keys", () => {
+test("getPrimitiveUnionMatcher: dispatches on mixed string and numeric keys", () => {
     // Arrange
-    const factory = getMatcher<"a" | "b" | 1 | 2>();
+    const factory = getPrimitiveUnionMatcher<"a" | "b" | 1 | 2>();
 
     // Act
     const matcher = factory({
@@ -103,9 +106,9 @@ test("getMatcher: dispatches on mixed string and numeric keys", () => {
     assert.equal(matcher(2), 20);
 });
 
-test("getMatcher: dispatches on boolean literals", () => {
+test("getPrimitiveUnionMatcher: dispatches on boolean literals", () => {
     // Arrange
-    const factory = getMatcher<boolean>();
+    const factory = getPrimitiveUnionMatcher<boolean>();
 
     // Act
     const matcher = factory({
@@ -129,9 +132,9 @@ test("getMatcher: dispatches on boolean literals", () => {
     assert.equal(matcher(false), 2);
 });
 
-test("getMatcher: dispatches on null and undefined", () => {
+test("getPrimitiveUnionMatcher: dispatches on null and undefined", () => {
     // Arrange
-    const factory = getMatcher<null | undefined>();
+    const factory = getPrimitiveUnionMatcher<null | undefined>();
 
     // Act
     const matcher = factory({
@@ -154,12 +157,12 @@ test("getMatcher: dispatches on null and undefined", () => {
 });
 
 // ============================================================================
-// API: getMatcher — ❌ Exhaustive (fallback) / ✔️ ReturnsStrict
+// API: getPrimitiveUnionMatcher — ❌ Exhaustive (fallback) / ✔️ ReturnsStrict
 // ============================================================================
 
-test("getMatcher: a `_` fallback receives the unhandled keys", () => {
+test("getPrimitiveUnionMatcher: a `_` fallback receives the unhandled keys", () => {
     // Arrange
-    const factory = getMatcher<"a" | "b" | "c">();
+    const factory = getPrimitiveUnionMatcher<"a" | "b" | "c">();
 
     // Act
     const matcher = factory(
@@ -187,9 +190,9 @@ test("getMatcher: a `_` fallback receives the unhandled keys", () => {
     assert.equal(matcher("c"), 2);
 });
 
-test("getMatcher: a `_` fallback routes mixed string and numeric gaps", () => {
+test("getPrimitiveUnionMatcher: a `_` fallback routes mixed string and numeric gaps", () => {
     // Arrange
-    const factory = getMatcher<"a" | "b" | 1 | 2>();
+    const factory = getPrimitiveUnionMatcher<"a" | "b" | 1 | 2>();
 
     // Act
     const matcher = factory(
@@ -222,9 +225,11 @@ test("getMatcher: a `_` fallback routes mixed string and numeric gaps", () => {
     assert.equal(matcher(2), "fallback");
 });
 
-test("getMatcher: a `_` fallback receives unhandled boolean and nullish keys", () => {
+test("getPrimitiveUnionMatcher: a `_` fallback receives unhandled boolean and nullish keys", () => {
     // Arrange
-    const factory = getMatcher<"a" | true | false | null | undefined>();
+    const factory = getPrimitiveUnionMatcher<
+        "a" | true | false | null | undefined
+    >();
 
     // Act
     const matcher = factory(
@@ -261,12 +266,12 @@ test("getMatcher: a `_` fallback receives unhandled boolean and nullish keys", (
 });
 
 // ============================================================================
-// API: getMatcherW — ✔️ Exhaustive / ❌ ReturnsStrict
+// API: getPrimitiveUnionMatcherW — ✔️ Exhaustive / ❌ ReturnsStrict
 // ============================================================================
 
-test("getMatcherW: exhaustive pattern widens to the union of handler returns", () => {
+test("getPrimitiveUnionMatcherW: exhaustive pattern widens to the union of handler returns", () => {
     // Arrange
-    const factory = getMatcherW<"x" | "y">();
+    const factory = getPrimitiveUnionMatcherW<"x" | "y">();
 
     // Act
     const matcher = factory({
@@ -291,9 +296,9 @@ test("getMatcherW: exhaustive pattern widens to the union of handler returns", (
     assert.equal(matcher("y"), "two");
 });
 
-test("getMatcherW: dispatches on mixed string and numeric keys", () => {
+test("getPrimitiveUnionMatcherW: dispatches on mixed string and numeric keys", () => {
     // Arrange
-    const factory = getMatcherW<"a" | "b" | 1 | 2>();
+    const factory = getPrimitiveUnionMatcherW<"a" | "b" | 1 | 2>();
 
     // Act
     const matcher = factory({
@@ -329,9 +334,9 @@ test("getMatcherW: dispatches on mixed string and numeric keys", () => {
     assert.equal(matcher(2), 20);
 });
 
-test("getMatcherW: exhaustive boolean and nullish widen to the union", () => {
+test("getPrimitiveUnionMatcherW: exhaustive boolean and nullish widen to the union", () => {
     // Arrange
-    const factory = getMatcherW<boolean | null | undefined>();
+    const factory = getPrimitiveUnionMatcherW<boolean | null | undefined>();
 
     // Act
     const matcher = factory({
@@ -368,12 +373,12 @@ test("getMatcherW: exhaustive boolean and nullish widen to the union", () => {
 });
 
 // ============================================================================
-// API: getMatcherW — ❌ Exhaustive (fallback) / ❌ ReturnsStrict
+// API: getPrimitiveUnionMatcherW — ❌ Exhaustive (fallback) / ❌ ReturnsStrict
 // ============================================================================
 
-test("getMatcherW: a `_` fallback widens gaps into the union", () => {
+test("getPrimitiveUnionMatcherW: a `_` fallback widens gaps into the union", () => {
     // Arrange
-    const factory = getMatcherW<"x" | "y" | "z">();
+    const factory = getPrimitiveUnionMatcherW<"x" | "y" | "z">();
 
     // Act
     const matcher = factory(
@@ -404,9 +409,9 @@ test("getMatcherW: a `_` fallback widens gaps into the union", () => {
     assert.equal(matcher("z"), "z");
 });
 
-test("getMatcherW: a `_` fallback widens mixed string and numeric returns", () => {
+test("getPrimitiveUnionMatcherW: a `_` fallback widens mixed string and numeric returns", () => {
     // Arrange
-    const factory = getMatcherW<"a" | "b" | 1 | 2>();
+    const factory = getPrimitiveUnionMatcherW<"a" | "b" | 1 | 2>();
 
     // Act
     const matcher = factory(
@@ -447,9 +452,9 @@ test("getMatcherW: a `_` fallback widens mixed string and numeric returns", () =
 // Factory contracts — calls that must not compile
 // ============================================================================
 
-test("getMatcher factory rejects patterns outside its contract", () => {
+test("getPrimitiveUnionMatcher factory rejects patterns outside its contract", () => {
     // Arrange
-    const factory = getMatcher<"a" | "b">();
+    const factory = getPrimitiveUnionMatcher<"a" | "b">();
 
     // Act / Assert — the calls below must not compile.
     // `Parameters<typeof factory>[0]` resolves only the *last* overload, so it
@@ -469,9 +474,9 @@ test("getMatcher factory rejects patterns outside its contract", () => {
     factory({ a: () => 1, b: () => 2 }, () => 0);
 });
 
-test("getMatcher factory rejects non-exhaustive boolean and nullish maps", () => {
+test("getPrimitiveUnionMatcher factory rejects non-exhaustive boolean and nullish maps", () => {
     // Arrange
-    const factory = getMatcher<boolean | null | undefined>();
+    const factory = getPrimitiveUnionMatcher<boolean | null | undefined>();
 
     // Act / Assert — the calls below must not compile
     // @ts-expect-error only `true` is handled; `false`, `null`, `undefined` are not
@@ -490,9 +495,9 @@ test("getMatcher factory rejects non-exhaustive boolean and nullish maps", () =>
     );
 });
 
-test("getMatcher: an open universe keeps the fallback's remainder open", () => {
+test("getPrimitiveUnionMatcher: an open universe keeps the fallback's remainder open", () => {
     // Arrange
-    const factory = getMatcher<string>();
+    const factory = getPrimitiveUnionMatcher<string>();
 
     // Act
     const matcher = factory({ a: () => 1 }, (s) => {
@@ -512,9 +517,9 @@ test("getMatcher: an open universe keeps the fallback's remainder open", () => {
     assert.equal(matcher("b"), 2);
 });
 
-test("getMatcherW factory rejects patterns outside its contract", () => {
+test("getPrimitiveUnionMatcherW factory rejects patterns outside its contract", () => {
     // Arrange
-    const factory = getMatcherW<"x" | "y">();
+    const factory = getPrimitiveUnionMatcherW<"x" | "y">();
 
     // Act / Assert — the calls below must not compile
     factory({
@@ -533,7 +538,7 @@ test("getMatcherW factory rejects patterns outside its contract", () => {
 // Dispatch — runtime behavior
 // ============================================================================
 
-test("getMatcher: an unhandled shape throws without a fallback", () => {
+test("getPrimitiveUnionMatcher: an unhandled shape throws without a fallback", () => {
     // Arrange — an open universe types its handler map as an index signature,
     // so the type system cannot prove the runtime map is exhaustive.
     const handlers: Record<string, (shape: unknown) => number> = {
@@ -543,14 +548,14 @@ test("getMatcher: an unhandled shape throws without a fallback", () => {
             return 1;
         },
     };
-    const matcher = getMatcher<string>()(handlers);
+    const matcher = getPrimitiveUnionMatcher<string>()(handlers);
 
     // Act / Assert
     assert.equal(matcher("a"), 1);
     assert.throws(() => matcher("b"), /Unhandled shape: b/);
 });
 
-test("getMatcher: an unhandled boolean shape throws without a fallback", () => {
+test("getPrimitiveUnionMatcher: an unhandled boolean shape throws without a fallback", () => {
     // Arrange — an `string | boolean` universe widens its handler map to an
     // index signature, so the runtime map's exhaustiveness is not provable.
     const handlers: Record<string, (shape: unknown) => number> = {
@@ -561,7 +566,7 @@ test("getMatcher: an unhandled boolean shape throws without a fallback", () => {
             return 1;
         },
     };
-    const matcher = getMatcher<string | boolean>()(handlers);
+    const matcher = getPrimitiveUnionMatcher<string | boolean>()(handlers);
 
     // Act / Assert
     assert.equal(matcher(true), 1);
@@ -584,7 +589,7 @@ const UNIVERSE = `"a" | "b" | "c"`;
 // documents, project membership), so they pass in any order.
 interface LabelsProbe {
     readonly name: string;
-    readonly factory: "getMatcher" | "getMatcherW";
+    readonly factory: "getPrimitiveUnionMatcher" | "getPrimitiveUnionMatcherW";
     readonly body: string;
     readonly universe?: string;
     readonly tail?: string;
@@ -616,12 +621,12 @@ const labelsFor = ({
 
 test("autocomplete: an exhaustive pattern requires the universe", () => {
     // Arrange
-    const name = "getMatcher_fresh";
+    const name = "getPrimitiveUnionMatcher_fresh";
 
     // Act
     const labels = labelsFor({
         name,
-        factory: "getMatcher",
+        factory: "getPrimitiveUnionMatcher",
         body: "    /*COMPLETE*/",
     });
 
@@ -633,12 +638,12 @@ test("autocomplete: an exhaustive pattern requires the universe", () => {
 
 test("autocomplete: handled keys drop out of the popup", () => {
     // Arrange
-    const name = "getMatcher_after_key";
+    const name = "getPrimitiveUnionMatcher_after_key";
 
     // Act
     const labels = labelsFor({
         name,
-        factory: "getMatcher",
+        factory: "getPrimitiveUnionMatcher",
         body: "    a: () => 1,\n    /*COMPLETE*/",
     });
 
@@ -650,12 +655,12 @@ test("autocomplete: handled keys drop out of the popup", () => {
 
 test("autocomplete: a fallback makes the remaining keys optional", () => {
     // Arrange
-    const name = "getMatcher_with_fallback";
+    const name = "getPrimitiveUnionMatcher_with_fallback";
 
     // Act
     const labels = labelsFor({
         name,
-        factory: "getMatcher",
+        factory: "getPrimitiveUnionMatcher",
         body: "    /*COMPLETE*/",
         tail: ", () => 0",
     });
@@ -668,12 +673,12 @@ test("autocomplete: a fallback makes the remaining keys optional", () => {
 
 test("autocomplete: with a fallback, handled keys stay optional", () => {
     // Arrange
-    const name = "getMatcher_with_fallback_after_key";
+    const name = "getPrimitiveUnionMatcher_with_fallback_after_key";
 
     // Act
     const labels = labelsFor({
         name,
-        factory: "getMatcher",
+        factory: "getPrimitiveUnionMatcher",
         body: "    a: () => 1,\n    /*COMPLETE*/",
         tail: ", () => 0",
     });
@@ -684,14 +689,14 @@ test("autocomplete: with a fallback, handled keys stay optional", () => {
     });
 });
 
-test("autocomplete: `getMatcherW` offers the same popup as `getMatcher`", () => {
+test("autocomplete: `getPrimitiveUnionMatcherW` offers the same popup as `getPrimitiveUnionMatcher`", () => {
     // Arrange
-    const name = "getMatcherW_fresh";
+    const name = "getPrimitiveUnionMatcherW_fresh";
 
     // Act
     const labels = labelsFor({
         name,
-        factory: "getMatcherW",
+        factory: "getPrimitiveUnionMatcherW",
         body: "    /*COMPLETE*/",
     });
 
@@ -701,14 +706,14 @@ test("autocomplete: `getMatcherW` offers the same popup as `getMatcher`", () =>
     });
 });
 
-test("autocomplete: `getMatcherW` also offers optional keys with a fallback", () => {
+test("autocomplete: `getPrimitiveUnionMatcherW` also offers optional keys with a fallback", () => {
     // Arrange
-    const name = "getMatcherW_with_fallback";
+    const name = "getPrimitiveUnionMatcherW_with_fallback";
 
     // Act
     const labels = labelsFor({
         name,
-        factory: "getMatcherW",
+        factory: "getPrimitiveUnionMatcherW",
         body: "    /*COMPLETE*/",
         tail: ", () => 0",
     });
@@ -721,12 +726,12 @@ test("autocomplete: `getMatcherW` also offers optional keys with a fallback", ()
 
 test("autocomplete: boolean and nullish keys are offered by name", () => {
     // Arrange
-    const name = "getMatcher_boolean_nullish";
+    const name = "getPrimitiveUnionMatcher_boolean_nullish";
 
     // Act
     const labels = labelsFor({
         name,
-        factory: "getMatcher",
+        factory: "getPrimitiveUnionMatcher",
         universe: "boolean | null | undefined",
         body: "    /*COMPLETE*/",
     });
@@ -739,12 +744,12 @@ test("autocomplete: boolean and nullish keys are offered by name", () => {
 
 test("autocomplete: a handled boolean literal drops out of the popup", () => {
     // Arrange
-    const name = "getMatcher_boolean_after_key";
+    const name = "getPrimitiveUnionMatcher_boolean_after_key";
 
     // Act
     const labels = labelsFor({
         name,
-        factory: "getMatcher",
+        factory: "getPrimitiveUnionMatcher",
         universe: "boolean | null | undefined",
         body: "    true: () => 1,\n    /*COMPLETE*/",
     });

src/primitive-union.ts

@@ -123,6 +123,9 @@ const dispatch =
             shape as never,
         );
 
-export const getMatcher = <T extends Matchable>(): MatcherStrict<T> => dispatch;
+export const getPrimitiveUnionMatcher = <
-export const getMatcherW = <T extends Matchable>(): MatcherWidening<T> =>
+    T extends Matchable,
-    dispatch;
+>(): MatcherStrict<T> => dispatch;
+export const getPrimitiveUnionMatcherW = <
+    T extends Matchable,
+>(): MatcherWidening<T> => dispatch;

src/tagged-union.ts

@@ -36,7 +36,7 @@ type Handlers<T extends object, K extends keyof T, R> = {
 // The members `Handled` covers. Mapping over `Tags` keeps every index within
 // `MapTaggedUnion`'s keys, and the conditional drops a stray key outside `T` so
 // it cannot widen the remainder. The remainder is `Exclude<T, …>`, mirroring
-// the primitive matcher's `Exclude<T, PatternParam<keyof Handled>>`.
+// the primitive-union matcher's `Exclude<T, PatternParam<keyof Handled>>`.
 type HandledMembers<T extends object, K extends keyof T, Handled> = {
     [V in Tags<T, K>]: V extends keyof Handled
         ? MapTaggedUnion<T, K>[V]
@@ -52,7 +52,7 @@ type Fallback<T extends object, K extends keyof T, Handled, R> = UnaryFn<
 
 // A fallback is redundant once the handler map covers every tag of `T`. Folded
 // into `Handled`'s own (self-referential) constraint so it is checked *after*
-// inference; see the primitive matcher for why a conditional in the fallback's
+// inference; see the primitive-union matcher for why a conditional in the fallback's
 // parameter is evaluated too early.
 type MustBePartial<T extends object, K extends keyof T, Handled> =
     Tags<T, K> extends keyof Handled ? RedundantFallback : unknown;