src/core/PocomathInstance.mjs

@@ -164,7 +164,7 @@ export default class PocomathInstance {
     *    instantiation can be accomplished by prefixin the signature with an
     *    exclamation point.
     */
-   install(ops) {
+   install = Returns('void', function(ops) {
       if (ops instanceof PocomathInstance) {
          return _installInstance(ops)
       }
@@ -197,7 +197,7 @@ export default class PocomathInstance {
          }
       }
       this._installFunctions(stdFunctions)
-   }
+   })
 
    /* Merge any number of PocomathInstances or modules:  */
    static merge(name, ...pieces) {
@@ -209,7 +209,7 @@ export default class PocomathInstance {
    }
 
    /* Determine the return type of an operation given an input signature */
-   returnTypeOf(operation, signature) {
+   returnTypeOf = Returns('string', function(operation, signature) {
       for (const type of typeListOfSignature(signature)) {
          this._maybeInstantiate(type)
       }
@@ -217,13 +217,20 @@ export default class PocomathInstance {
          operation = operation.name
       }
       const details = this._pocoFindSignature(operation, signature)
-      return returnTypeOf(details.fn, signature, this)
-   }
+      if (details) {
+         return returnTypeOf(details.fn, signature, this)
+      }
+      console.log('Checking return type of', operation)
+      return returnTypeOf(this[operation], signature, this)
+   })
 
    /* Return a chain object for this instance with a given value: */
-   chain(value) {
-      return makeChain(value, this, this._chainRepository)
-   }
+   chain = Returns(
+      sig => `Chain<${sig}>`,
+      function(value) {
+         return makeChain(value, this, this._chainRepository)
+      }
+   )
 
    _installInstance(other) {
       for (const [type, spec] of Object.entries(other.Types)) {
@@ -272,9 +279,9 @@ export default class PocomathInstance {
          for (const name of requiredSet) {
             for (const type of typeSet) {
                try {
-                  const modName = `../${type}/${name}.mjs`
-                  const mod = await import(modName)
-                  this.install(mod)
+                  const moduleName = `../${type}/${name}.mjs`
+                  const module = await import(moduleName)
+                  this.install(module)
                } catch (err) {
                   if (!(err.message.includes('find'))) {
                      // Not just a error because module doesn't exist
@@ -315,7 +322,7 @@ export default class PocomathInstance {
     * Implementation note: unlike _installFunctions below, we can make
     * the corresponding changes to the _typed object immediately
     */
-   installType(type, spec) {
+   installType = Returns('void', function(type, spec) {
       const parts = type.split(/[<,>]/)
       if (this._templateParam(parts[0])) {
          throw new SyntaxError(
@@ -415,7 +422,7 @@ export default class PocomathInstance {
       const imp = {}
       imp[type] = {uses: new Set(), does: () => Returns('string', () => type)}
       this._installFunctions({typeOf: imp})
-   }
+   })
 
    _addSubtypeTo(sup, sub) {
       if (this.isSubtypeOf(sub, sup)) return
@@ -428,47 +435,48 @@ export default class PocomathInstance {
    }
 
    /* Returns true if typeA is a subtype of type B */
-   isSubtypeOf(typeA, typeB) {
+   isSubtypeOf = Returns('boolean', function(typeA, typeB) {
       return this._subtypes[typeB].includes(typeA)
-   }
+   })
 
    /* Returns true if typeA is a subtype of or converts to type B */
-   isPriorTo(typeA, typeB) {
+   isPriorTo = Returns('boolean', function(typeA, typeB) {
       if (!(typeB in this._priorTypes)) return false
       return this._priorTypes[typeB].has(typeA)
-   }
+   })
 
-   /* Returns a list of the subtypes of a given type, in topological sorted
-    * order (i.e, no type on the list contains one that comes after it).
+   /* Returns a list of the strict ubtypes of a given type, in topological
+    * sorted order (i.e, no type on the list contains one that comes after it).
     */
-   subtypesOf(type) {
+   subtypesOf = Returns('Array<string>', function(type) {
       return this._subtypes[type] // should we clone?
-   }
+   })
 
    /* Returns a list of the supertypes of a given type, starting with itself,
     * in topological order
     */
-   supertypesOf(type) {
+   supertypesOf = Returns('Array<string>', function(type) {
       const supList = []
       while (type) {
          supList.push(type)
          type = this.Types[type].refines
       }
       return supList
-   }
+   })
 
    /* Returns the most refined type containing all the types in the array,
     * with '' standing for the empty type for convenience. If the second
     * argument `convert` is true, a convertible type is considered a
     * a subtype (defaults to false).
     */
-   joinTypes(types, convert) {
+   joinTypes = Returns('string', function(types, convert) {
       let join = ''
       for (const type of types) {
          join = this._joinTypes(join, type, convert)
       }
       return join
-   }
+   })
+
    /* helper for above */
    _joinTypes(typeA, typeB, convert) {
       if (!typeA) return typeB
@@ -500,9 +508,9 @@ export default class PocomathInstance {
    /* Returns a list of all types that have been mentioned in the
     * signatures of operations, but which have not actually been installed:
     */
-   undefinedTypes() {
+   undefinedTypes = Returns('Array<string>', function() {
       return Array.from(this._seenTypes).filter(t => !(t in this.Types))
-   }
+   })
 
    /* Used internally to install a template type */
    _installTemplateType(type, spec) {
@@ -1137,7 +1145,7 @@ export default class PocomathInstance {
     * Returns the name of the type if added, false if it was already there,
     * and undefined if the type is declined (because of being nested too deep).
     */
-   instantiateTemplate(base, instantiator) {
+   instantiateTemplate = Returns('void', function(base, instantiator) {
       const depth = instantiator.split('<').length
       if (depth > this._maxDepthSeen ) {
          // don't bother with types much deeper thant we have seen
@@ -1204,7 +1212,7 @@ export default class PocomathInstance {
       }
       this.installType(wantsType, newTypeSpec)
       return wantsType
-   }
+   })
 
    _findSubtypeImpl(name, imps, neededSig) {
       if (neededSig in imps) return neededSig

test/_pocomath.mjs

@@ -34,6 +34,10 @@ describe('The default full pocomath instance "math"', () => {
          math.add(3, math.complex(2.5, 1)), math.complex(5.5, 1))
       assert.strictEqual(
          math.returnTypeOf('add', 'Complex<number>,NumInt'), 'Complex<number>')
+      assert.strictEqual(
+         math.returnTypeOf('chain', 'bigint'), 'Chain<bigint>')
+      assert.strictEqual(
+         math.returnTypeOf('returnTypeOf', 'string,string'), 'string')
    })
 
    it('can subtract numbers', () => {