test: Check for undefined types, as a means to detect typos in type names

src/core/PocomathInstance.mjs

@@ -16,7 +16,9 @@ export default class PocomathInstance {
       'install',
       'installType',
       'name',
-      'Types'])
+      'Types',
+      'undefinedTypes'
+   ])
 
    constructor(name) {
       this.name = name
@@ -25,6 +27,7 @@ export default class PocomathInstance {
       this._typed = typed.create()
       this._typed.clear()
       this.Types = {any: anySpec} // dummy entry to track the default 'any' type
+      this._usedTypes = new Set() // all types that have occurred in a signature
       this._doomed = new Set() // for detecting circular reference
       this._config = {predictable: false}
       const self = this
@@ -226,6 +229,13 @@ export default class PocomathInstance {
       this._invalidateDependents(':' + type)
    }
 
+   /* Returns a list of all types that have been mentioned in the
+    * signatures of operations, but which have not actually been installed:
+    */
+   undefinedTypes() {
+      return Array.from(this._usedTypes).filter(t => !(t in this.Types))
+   }
+
    /* Used internally by install, see the documentation there */
    _installFunctions(functions) {
       for (const [name, spec] of Object.entries(functions)) {
@@ -246,6 +256,7 @@ export default class PocomathInstance {
                   this._addAffect(depname, name)
                }
                for (const type of typesOfSignature(signature)) {
+                  this._usedTypes.add(type)
                   this._addAffect(':' + type, name)
                }
             }

test/_pocomath.mjs

@@ -2,6 +2,14 @@ import assert from 'assert'
 import math from '../src/pocomath.mjs'
 
 describe('The default full pocomath instance "math"', () => {
+   it('has no undefined types', () => {
+      const undef = math.undefinedTypes()
+      if (undef.length) {
+         console.log('Probable typo: found undefined types', undef)
+      }
+      assert.strictEqual(undef.length, 0)
+   })
+
    it('can subtract numbers', () => {
       assert.strictEqual(math.subtract(12, 5), 7)
    })
@@ -35,6 +43,9 @@ describe('The default full pocomath instance "math"', () => {
       assert.deepStrictEqual(math.complex(2,3), norm13)
       assert.deepStrictEqual(math.complex(2), math.complex(2,0))
       assert.deepStrictEqual(math.add(2, math.complex(0,3)), norm13)
+      assert.deepStrictEqual(
+         math.subtract(math.complex(1,1), math.complex(2,-2)),
+         math.complex(-1,3))
       assert.deepStrictEqual(
          math.subtract(16, math.add(3, math.complex(0,4), 2)),
          math.complex(11, -4))