refactor: Convert resolution to two-tier system

Typed-function's sort order/matching algorithm was interfering with
  template resolution. This commit solves the difficulty by moving the
  "catchall" implementations that implement generation of new template
  instances into a separate "fallback" typed-function universe, so that
  Pocomath can control exactly when that is searched.

  Removes a couple of the matching anomalies already noted in the tests.

  Also extends return types to somewhat more functions.

src/complex/Types/Complex.mjs

@@ -2,15 +2,13 @@ import {Returns, returnTypeOf} from '../../core/Returns.mjs'
 import PocomathInstance from '../../core/PocomathInstance.mjs'
 
 const Complex = new PocomathInstance('Complex')
-// Base type that should generally not be used directly
-Complex.installType('Complex', {
-   test: z => z && typeof z === 'object' && 're' in z && 'im' in z
-})
 // Now the template type: Complex numbers are actually always homogeneous
-// in their component types.
+// in their component types. For an explanation of the meanings of the
+// properties, see ../../tuple/Types/Tuple.mjs
 Complex.installType('Complex<T>', {
-   infer: ({typeOf, joinTypes}) => z => joinTypes([typeOf(z.re), typeOf(z.im)]),
+   base: z => z && typeof z === 'object' && 're' in z && 'im' in z,
    test: testT => z => testT(z.re) && testT(z.im),
+   infer: ({typeOf, joinTypes}) => z => joinTypes([typeOf(z.re), typeOf(z.im)]),
    from: {
       T: t => ({re: t, im: t-t}), // hack: maybe need a way to call zero(T)
       U: convert => u => {

src/complex/abs.mjs

@@ -3,6 +3,7 @@ export * from './Types/Complex.mjs'
 
 export const abs = {
    'Complex<T>': ({
+      T,
       sqrt, // Unfortunately no notation yet for the needed signature
       'absquare(T)': baseabsq,
       'absquare(Complex<T>)': absq

src/complex/associate.mjs

@@ -1,3 +1,4 @@
+import Returns from '../core/Returns.mjs'
 export * from './Types/Complex.mjs'
 
 /* Returns true if w is z multiplied by a complex unit */
@@ -9,9 +10,9 @@ export const associate = {
         'one(T)': uno,
         'complex(T,T)': cplx,
         'negate(Complex<T>)': neg
-    }) => (w,z) => {
+    }) => Returns('boolean', (w,z) => {
         if (eq(w,z) || eq(w,neg(z))) return true
         const ti = times(z, cplx(zr(z.re), uno(z.im)))
         return eq(w,ti) || eq(w,neg(ti))
-    }
+    })
 }

src/complex/multiply.mjs

@@ -6,13 +6,15 @@ export const multiply = {
       T,
       'complex(T,T)': cplx,
       'add(T,T)': plus,
-      'subtract(T,T)': sub,
+      'subtract(T,T)': subt,
       'self(T,T)': me,
       'conjugate(T)': conj // makes quaternion multiplication work
    }) => Returns(
       `Complex<${T}>`,
-      (w,z) => cplx(
-         sub(me(w.re, z.re), me(conj(w.im), z.im)),
-         plus(me(conj(w.re), z.im), me(w.im, z.re)))
+      (w,z) => {
+         const realpart = subt(me(     w.re,  z.re), me(conj(w.im), z.im))
+         const imagpart = plus(me(conj(w.re), z.im), me(     w.im,  z.re))
+         return cplx(realpart, imagpart)
+      }
    )
 }

src/core/PocomathInstance.mjs

@@ -9,6 +9,7 @@ const anySpec = {} // fixed dummy specification of 'any' type
 
 const theTemplateParam = 'T' // First pass: only allow this one exact parameter
 const restTemplateParam = `...${theTemplateParam}`
+const templateCall = `<${theTemplateParam}>`
 const templateFromParam = 'U' // For defining covariant conversions
 
 /* Returns a new signature just like sig but with the parameter replaced by
@@ -21,6 +22,8 @@ function substituteInSignature(signature, parameter, type) {
    return sig.replaceAll(pattern, type)
 }
 
+let lastWhatToDo = null // used in an infinite descent check
+
 export default class PocomathInstance {
    /* Disallowed names for ops; beware, this is slightly non-DRY
     * in that if a new top-level PocomathInstance method is added, its name
@@ -55,24 +58,39 @@ export default class PocomathInstance {
       this._affects = {}
       this._typed = typed.create()
       this._typed.clear()
-      this._typed.addTypes([{name: 'ground', test: () => true}])
+      // The following is an additional typed-function universe for resolving
+      // uninstantiated template instances. It is linked to the main one in
+      // its onMismatch function, below:
+      this._metaTyped = typed.create()
+      this._metaTyped.clear()
+      // And these are the meta bindings: (I think we don't need separate
+      // invalidation for them as they are only accessed through a main call.)
+      this._meta = {} // The resulting typed-functions
+      this._metaTFimps = {} // and their implementations
       const me = this
       const myTyped = this._typed
       this._typed.onMismatch = (name, args, sigs) => {
          if (me._invalid.has(name)) {
-            return me[name](...args) // rebuild implementation and try again
+            // rebuild implementation and try again
+            return me[name](...args)
          }
-         myTyped.throwMismatchError(name, args, sigs)
+         const metaversion = me._meta[name]
+         if (metaversion) {
+            return me._meta[name](...args)
+         }
+         me._typed.throwMismatchError(name, args, sigs)
       }
-      /* List of types installed in the instance. We start with just dummies
-       * for the 'any' type and for type parameters:
-       */
+      // List of types installed in the instance: (We start with just dummies
+      // for the 'any' type and for type parameters.)
       this.Types = {any: anySpec}
       this.Types[theTemplateParam] = anySpec
-      this.Types.ground = anySpec
-      // All the template types that have been defined
+      // Types that have been moved into the metaverse:
+      this._metafiedTypes = new Set()
+      // All the template types that have been defined:
       this.Templates = {}
-      // The actual type testing functions
+      // And their instantiations:
+      this._instantiationsOf = {}
+      // The actual type testing functions:
       this._typeTests = {}
       // For each type, gives all of its (in)direct subtypes in topo order:
       this._subtypes = {}
@@ -87,27 +105,19 @@ export default class PocomathInstance {
       this._maxDepthSeen = 1 // deepest template nesting we've actually encountered
       this._invalid = new Set() // methods that are currently invalid
       this._config = {predictable: false, epsilon: 1e-12}
-      const self = this
       this.config = new Proxy(this._config, {
          get: (target, property) => target[property],
          set: (target, property, value) => {
             if (value !== target[property]) {
                target[property] = value
-               self._invalidateDependents('config')
+               me._invalidateDependents('config')
             }
             return true // successful
          }
       })
       this._plainFunctions = new Set() // the names of the plain functions
       this._chainRepository = {} // place to store chainified functions
-
-      this._installFunctions({
-         typeOf: {
-            ground: {uses: new Set(), does: () => Returns('string', () => 'any')}
-         }
-      })
-
-      this.joinTypes = this.joinTypes.bind(this)
+      this.joinTypes = this.joinTypes.bind(me)
    }
 
    /**
@@ -330,9 +340,10 @@ export default class PocomathInstance {
             `Type name '${type}' reserved for template parameter`)
       }
       if (parts.some(this._templateParam.bind(this))) {
-         // It's a template, deal with it separately
+         // It's an uninstantiated template, deal with it separately
          return this._installTemplateType(type, spec)
       }
+      const base = parts[0]
       if (type in this.Types) {
          if (spec !== this.Types[type]) {
             throw new SyntaxError(`Conflicting definitions of type ${type}`)
@@ -345,7 +356,7 @@ export default class PocomathInstance {
       }
       let beforeType = spec.refines
       if (!beforeType) {
-         beforeType = 'ground'
+         beforeType = 'any'
          for (const other of spec.before || []) {
             if (other in this.Types) {
                beforeType = other
@@ -387,6 +398,21 @@ export default class PocomathInstance {
                for (const subtype of this._subtypes[from]) {
                   this._priorTypes[nextSuper].add(subtype)
                }
+
+               /* Add the conversion in the metaverse if need be: */
+               const toParts = nextSuper.split('<', 2)
+               if (toParts.length > 1) {
+                  const fromParts = from.split('<', 2)
+                  if (fromParts.length === 1 || fromParts[0] !== toParts[0]) {
+                     this._metafy(from)
+                     try {
+                        this._metaTyped.addConversion(
+                           {from, to: toParts[0], convert: spec.from[from]})
+                     } catch {
+                     }
+                  }
+               }
+
                nextSuper = this.Types[nextSuper].refines
             }
          }
@@ -411,6 +437,16 @@ export default class PocomathInstance {
                         convert: this.Types[to].from[fromtype]
                      })
                      this._invalidateDependents(':' + nextSuper)
+                     /* Add the conversion in the metaverse if need be: */
+                     const toParts = nextSuper.split('<', 2)
+                     if (toParts.length > 1 && base !== toParts[0]) {
+                        this._metafy(type)
+                        this._metaTyped.addConversion({
+                           from: type,
+                           to: toParts[0],
+                           convert: this.Types[to].from[fromtype]
+                        })
+                     }
                   } catch {
                   }
                   this._priorTypes[nextSuper].add(type)
@@ -425,6 +461,12 @@ export default class PocomathInstance {
       this._installFunctions({typeOf: imp})
    })
 
+   _metafy(type) {
+      if (this._metafiedTypes.has(type)) return
+      this._metaTyped.addTypes([{name: type, test: this._typeTests[type]}])
+      this._metafiedTypes.add(type)
+   }
+
    _addSubtypeTo(sup, sub) {
       if (this.isSubtypeOf(sub, sup)) return
       const supSubs = this._subtypes[sup]
@@ -435,8 +477,10 @@ export default class PocomathInstance {
       supSubs.splice(i, 0, sub)
    }
 
-   /* Returns true if typeA is a subtype of type B */
+   /* Returns true if typeA is a strict subtype of type B */
    isSubtypeOf = Returns('boolean', function(typeA, typeB) {
+      // Currently not considering types to be a subtype of 'any'
+      if (typeB === 'any' || typeA === 'any') return false
       return this._subtypes[typeB].includes(typeA)
    })
 
@@ -483,7 +527,6 @@ export default class PocomathInstance {
       if (!typeA) return typeB
       if (!typeB) return typeA
       if (typeA === 'any' || typeB === 'any') return 'any'
-      if (typeA === 'ground' || typeB === 'ground') return 'ground'
       if (typeA === typeB) return typeA
       const subber = convert ? this._priorTypes : this._subtypes
       const pick = convert ? 'has' : 'includes'
@@ -510,7 +553,8 @@ export default class PocomathInstance {
     * signatures of operations, but which have not actually been installed:
     */
    undefinedTypes = Returns('Array<string>', function() {
-      return Array.from(this._seenTypes).filter(t => !(t in this.Types))
+      return Array.from(this._seenTypes).filter(
+         t => !(t in this.Types || t in this.Templates))
    })
 
    /* Used internally to install a template type */
@@ -526,6 +570,18 @@ export default class PocomathInstance {
          }
          return
       }
+
+      // install the "base type" in the meta universe:
+      let beforeType = 'any'
+      for (const other of spec.before || []) {
+         if (other in this.templates) {
+            beforeType = other
+            break
+         }
+      }
+      this._metaTyped.addTypes([{name: base, test: spec.base}], beforeType)
+      this._instantiationsOf[base] = new Set()
+
       // update the typeOf function
       const imp = {}
       imp[type] = {
@@ -534,6 +590,9 @@ export default class PocomathInstance {
       }
       this._installFunctions({typeOf: imp})
 
+      // Invalidate any functions that reference this template type:
+      this._invalidateDependents(':' + base)
+
       // Nothing else actually happens until we match a template parameter
       this.Templates[base] = {type, spec}
    }
@@ -578,12 +637,11 @@ export default class PocomathInstance {
                }
                opImps[signature] = {
                   explicit,
+                  resolved: false,
                   uses: behavior.uses,
                   does: behavior.does
                }
-               if (explicit) {
-                  opImps[signature].resolved = false
-               } else {
+               if (!explicit) {
                   opImps[signature].hasInstantiations = {}
                   opImps[signature].needsInstantiations = new Set()
                }
@@ -628,6 +686,8 @@ export default class PocomathInstance {
    _invalidate(name, reason) {
       if (!(name in this._imps)) {
          this._imps[name] = {}
+         this._TFimps[name] = {}
+         this._metaTFimps[name] = {}
       }
       if (reason) {
          // Make sure no TF imps that depend on reason remain:
@@ -692,10 +752,8 @@ export default class PocomathInstance {
       if (!imps) {
          throw new SyntaxError(`No implementations for ${name}`)
       }
-      if (!(this._TFimps[name])) {
-         this._TFimps[name] = {}
-      }
       const tf_imps = this._TFimps[name]
+      const meta_imps = this._metaTFimps[name]
       /* Collect the entries we know the types for */
       const usableEntries = []
       for (const entry of Object.entries(imps)) {
@@ -751,6 +809,79 @@ export default class PocomathInstance {
             }
          }
 
+         /* Prevent other existing signatures from blocking use of top-level
+          * templates via conversions:
+          */
+         let baseSignature = rawSignature.replaceAll(templateCall, '')
+         /* Any remaining template params are top-level */
+         const signature = substituteInSignature(
+            baseSignature, theTemplateParam, 'any')
+         const hasTopLevel = (signature !== baseSignature)
+         if (!ubType && hasTopLevel) {
+            // collect upper-bound types
+            const ubTypes = new Set()
+            for (const othersig in imps) {
+               const thisUB = upperBounds.exec(othersig)
+               if (thisUB) ubTypes.add(thisUB[2])
+               let basesig = othersig.replaceAll(templateCall, '')
+               if (basesig !== othersig) {
+                  // A template
+                  const testsig = substituteInSignature(
+                     basesig, theTemplateParam, '')
+                  if (testsig === basesig) {
+                     // that is not also top-level
+                     for (const templateType of typeListOfSignature(basesig)) {
+                        if (templateType.slice(0,3) === '...') {
+                           templateType = templateType.slice(3)
+                        }
+                        ubTypes.add(templateType)
+                     }
+                  }
+               }
+            }
+            for (const othersig in imps) {
+               let basesig = othersig.replaceAll(templateCall, '')
+               const testsig = substituteInSignature(
+                  basesig, theTemplateParam, '')
+               if (testsig !== basesig) continue // a top-level template
+               for (let othertype of typeListOfSignature(othersig)) {
+                  if (othertype.slice(0,3) === '...') {
+                     othertype = othertype.slice(3)
+                  }
+                  if (this.Types[othertype] === anySpec) continue
+                  const testType = substituteInSignature(
+                     othertype, theTemplateParam, '')
+                  let otherTypeCollection = [othertype]
+                  if (testType !== othertype) {
+                     const base = othertype.split('<',1)[0]
+                     otherTypeCollection = this._instantiationsOf[base]
+                  }
+                  for (const possibility of otherTypeCollection) {
+                     for (const convtype of this._priorTypes[possibility]) {
+                        if (this.isSubtypeOf(convtype, possibility)) continue
+                        if (ubTypes.has(convtype)) continue
+                        let belowUB = false
+                        for (const anUB of ubTypes) {
+                           if (anUB in this.Templates) {
+                              if (convtype.slice(0, anUB.length) === anUB) {
+                                 belowUB = true
+                                 break
+                              }
+                           } else {
+                              if (this.isSubtypeOf(convtype, anUB)) {
+                                 belowUB = true
+                                 break
+                              }
+                           }
+                        }
+                        if (belowUB) continue
+                        instantiationSet.add(convtype)
+                     }
+                  }
+               }
+            }
+         }
+
          for (const instType of instantiationSet) {
             if (!(instType in this.Types)) continue
             if (this.Types[instType] === anySpec) continue
@@ -785,8 +916,7 @@ export default class PocomathInstance {
                }
                return behavior.does(innerRefs)
             }
-            this._addTFimplementation(
-               tf_imps, signature, {uses, does: patch})
+            this._addTFimplementation(tf_imps, signature, {uses, does: patch})
             tf_imps[signature]._pocoSignature = rawSignature
             tf_imps[signature]._pocoInstance = instType
             behavior.hasInstantiations[instType] = signature
@@ -794,13 +924,7 @@ export default class PocomathInstance {
          /* Now add the catchall signature */
          /* (Not needed if if it's a bounded template) */
          if (ubType) continue
-         if ('_catchall_' in behavior.hasInstantiations) continue
-         let templateCall = `<${theTemplateParam}>`
-         /* Relying here that the base of 'Foo<T>' is 'Foo': */
-         let baseSignature = rawSignature.replaceAll(templateCall, '')
-         /* Any remaining template params are top-level */
-         const signature = substituteInSignature(
-            baseSignature, theTemplateParam, 'ground')
+         if (behavior.resolved) continue
          /* The catchall signature has to detect the actual type of the call
           * and add the new instantiations.
           * First, prepare the type inference data:
@@ -840,150 +964,124 @@ export default class PocomathInstance {
          /* For return type annotation, we may have to fix this to
             propagate the return type. At the moment we are just bagging
          */
-         const patch = (refs) => (...args) => {
-            /* We unbundle the rest arg if there is one */
-            const regLength = args.length - 1
-            if (restParam) {
-               const restArgs = args.pop()
-               args = args.concat(restArgs)
-            }
-            /* Now infer the type we actually should have been called for */
-            let i = -1
-            let j = -1
-            /* collect the arg types */
-            const argTypes = []
-            for (const arg of args) {
-               ++j
-               // in case of rest parameter, reuse last parameter type:
-               if (i < inferences.length - 1) ++i
-               if (inferences[i]) {
-                  const argType = inferences[i](arg)
-                  if (!argType) {
-                     throw TypeError(
-                        `Type inference failed for argument ${j} of ${name}`)
-                  }
-                  if (argType === 'any') {
-                     throw TypeError(
-                        `In call to ${name}, incompatible template arguments: `
-                        // + args.map(a => JSON.stringify(a)).join(', ')
-                        // unfortunately barfs on bigints. Need a better formatter
-                        // wish we could just use the one that console.log uses;
-                        // is that accessible somehow?
-                           + args.map(a => a.toString()).join(', ')
-                           + ' of types ' + argTypes.join(', ') + argType)
-                  }
-                  argTypes.push(argType)
+         const patch = () => {
+            const patchFunc = (...tfBundledArgs) => {
+               /* We unbundle the rest arg if there is one */
+               let args = Array.from(tfBundledArgs)
+               const regLength = args.length - 1
+               if (restParam) {
+                  const restArgs = args.pop()
+                  args = args.concat(restArgs)
                }
-            }
-            if (argTypes.length === 0) {
-               throw TypeError('Type inference failed for' + name)
-            }
-            let usedConversions = false
-            let instantiateFor = self.joinTypes(argTypes)
-            if (instantiateFor === 'any') {
-               usedConversions = true
-               instantiateFor = self.joinTypes(argTypes, usedConversions)
+               /* Now infer the type we actually should have been called for */
+               let i = -1
+               let j = -1
+               /* collect the arg types */
+               const argTypes = []
+               for (const arg of args) {
+                  ++j
+                  // in case of rest parameter, reuse last parameter type:
+                  if (i < inferences.length - 1) ++i
+                  if (inferences[i]) {
+                     const argType = inferences[i](arg)
+                     if (!argType) {
+                        throw TypeError(
+                           `Type inference failed for argument ${j} of ${name}`)
+                     }
+                     if (argType === 'any') {
+                        throw TypeError(
+                           `In call to ${name}, `
+                              + 'incompatible template arguments:'
+                           // + args.map(a => JSON.stringify(a)).join(', ')
+                           // unfortunately barfs on bigints. Need a better
+                           // formatter. I wish we could just use the one that
+                           // console.log uses; is that accessible somehow?
+                              + args.map(a => a.toString()).join(', ')
+                              + ' of types ' + argTypes.join(', ') + argType)
+                     }
+                     argTypes.push(argType)
+                  }
+               }
+               if (argTypes.length === 0) {
+                  throw TypeError('Type inference failed for' + name)
+               }
+               let usedConversions = false
+               let instantiateFor = self.joinTypes(argTypes)
                if (instantiateFor === 'any') {
-                  throw TypeError(
-                     `In call to ${name}, no type unifies arguments `
-                        + args.toString() + '; of types ' + argTypes.toString()
-                        + '; note each consecutive pair must unify to a '
-                        + 'supertype of at least one of them')
-               }
-            }
-            const depth = instantiateFor.split('<').length
-            if (depth > self._maxDepthSeen) {
-               self._maxDepthSeen = depth
-            }
-            /* Generate the list of actual wanted types */
-            const wantTypes = parTypes.map(type => substituteInSignature(
-               type, theTemplateParam, instantiateFor))
-            const wantSig = wantTypes.join(',')
-            /* Now we have to add any actual types that are relevant
-             * to this invocation. Namely, that would be every formal parameter
-             * type in the invocation, with the parameter template instantiated
-             * by instantiateFor, and for all of instantiateFor's "prior types"
-             */
-            for (j = 0; j < parTypes.length; ++j) {
-               if (wantTypes[j] !== parTypes[j] && parTypes[j].includes('<')) {
-                  // actually used the param and is a template
-                  self._ensureTemplateTypes(parTypes[j], instantiateFor)
-               }
-            }
-            /* Transform the arguments if we used any conversions: */
-            if (usedConversions) {
-               i = - 1
-               for (j = 0; j < args.length; ++j) {
-                  if (i < parTypes.length - 1) ++i
-                  let wantType = parTypes[i]
-                  if (wantType.slice(0,3) === '...') {
-                     wantType = wantType.slice(3)
-                  }
-                  wantType = substituteInSignature(
-                     wantType, theTemplateParam, instantiateFor)
-                  if (wantType !== parTypes[i]) {
-                     args[j] = self._typed.convert(args[j], wantType)
+                  usedConversions = true
+                  instantiateFor = self.joinTypes(argTypes, usedConversions)
+                  if (instantiateFor === 'any') {
+                     throw TypeError(
+                        `In call to ${name}, no type unifies arguments `
+                           + args.toString() + '; of types ' + argTypes.toString()
+                           + '; note each consecutive pair must unify to a '
+                           + 'supertype of at least one of them')
                   }
                }
-            }
-            /* Finally reassemble the rest args if there were any */
-            if (restParam) {
-               const restArgs = args.slice(regLength)
-               args = args.slice(0,regLength)
-               args.push(restArgs)
-            }
-            /* Arrange that the desired instantiation will be there next
-             * time so we don't have to go through that again for this type
-             */
-            behavior.needsInstantiations.add(instantiateFor)
-            self._invalidate(name)
-            // And update refs because we now know the type we're instantiating
-            // for:
-            refs[theTemplateParam] = instantiateFor
-            const innerRefs = {}
-            for (const dep in simplifiedUses) {
-               const simplifiedDep = simplifiedUses[dep]
-               if (dep === simplifiedDep) {
-                  innerRefs[dep] = refs[dep]
-               } else {
-                  let [func, needsig] = dep.split(/[()]/)
-                  if (self._typed.isTypedFunction(refs[simplifiedDep])) {
-                     const subsig = substituteInSignature(
-                        needsig, theTemplateParam, instantiateFor)
-                     let resname = simplifiedDep
-                     if (resname == 'self') resname = name
-                     innerRefs[dep] = self.resolve(
-                        resname, subsig, refs[simplifiedDep])
-                  } else {
-                     innerRefs[dep] = refs[simplifiedDep]
+               const depth = instantiateFor.split('<').length
+               if (depth > self._maxDepthSeen) {
+                  self._maxDepthSeen = depth
+               }
+               /* Generate the list of actual wanted types */
+               const wantTypes = parTypes.map(type => substituteInSignature(
+                  type, theTemplateParam, instantiateFor))
+               const wantSig = wantTypes.join(',')
+               /* Now we have to add any actual types that are relevant
+                * to this invocation. Namely, that would be every formal
+                * parameter type in the invocation, with the parameter
+                * template instantiated by instantiateFor, and for all of
+                * instantiateFor's "prior types"
+                */
+               for (j = 0; j < parTypes.length; ++j) {
+                  if (wantTypes[j] !== parTypes[j] && parTypes[j].includes('<')) {
+                     // actually used the param and is a template
+                     self._ensureTemplateTypes(parTypes[j], instantiateFor)
                   }
                }
-            }
-            // Finally ready to make the call.
-            const implementation = behavior.does(innerRefs)
-            // We can access return type information here
-            // And in particular, if it might be a template, we should try to
-            // instantiate it:
-            const returnType = returnTypeOf(implementation, wantSig, self)
-            for (const possibility of returnType.split('|')) {
-               const instantiated = self._maybeInstantiate(possibility)
-               if (instantiated) {
-                  const tempBase = instantiated.split('<',1)[0]
-                  self._invalidateDependents(':' + tempBase)
+
+               /* Request the desired instantiation: */
+               // But possibly since this resolution was grabbed, the proper
+               // instantiation has been added (like if there are multiple
+               // uses in the implementation of another method.
+               if (!(behavior.needsInstantiations.has(instantiateFor))) {
+                  behavior.needsInstantiations.add(instantiateFor)
+                  self._invalidate(name)
                }
+               const brandNewMe = self[name]
+               const whatToDo = self._typed.resolve(brandNewMe, args)
+               // We can access return type information here
+               // And in particular, if it might be a template, we should try to
+               // instantiate it:
+               const returnType = returnTypeOf(whatToDo.fn, wantSig, self)
+               for (const possibility of returnType.split('|')) {
+                  const instantiated = self._maybeInstantiate(possibility)
+                  if (instantiated) {
+                     const tempBase = instantiated.split('<',1)[0]
+                     self._invalidateDependents(':' + tempBase)
+                  }
+               }
+               if (whatToDo === lastWhatToDo) {
+                  throw new Error(
+                     `Infinite recursion in resolving $name called on`
+                        + args.map(x => x.toString()).join(','))
+               }
+               lastWhatToDo = whatToDo
+               const retval = whatToDo.implementation(...args)
+               lastWhatToDo = null
+               return retval
             }
-            return implementation(...args)
+            Object.defineProperty(
+               patchFunc, 'name', {value: `${name}(${signature})`})
+            return patchFunc
          }
-         Object.defineProperty(patch, 'name', {value: `${name}(${signature})`})
-         // TODO: Decorate patch with a function that calculates the
+         Object.defineProperty(
+            patch, 'name', {value: `generate[${name}(${signature})]`})
+         // TODO?: Decorate patch with a function that calculates the
          // correct return type a priori. Deferring because unclear what
          // aspects will be merged into typed-function.
-         //
-         // The actual uses value needs to be a set:
-         const outerUses = new Set(Object.values(simplifiedUses))
          this._addTFimplementation(
-            tf_imps, signature, {uses: outerUses, does: patch})
-         behavior.hasInstantiations._catchall_ = rawSignature
+            meta_imps, signature, {uses: new Set(), does: patch})
+         behavior.resolved = true
       }
       this._correctPartialSelfRefs(name, tf_imps)
       // Make sure we have all of the needed (template) types; and if they
@@ -1007,8 +1105,19 @@ export default class PocomathInstance {
             delete fromBehavior.hasInstantiations[imp._pocoInstance]
          }
       }
-      const tf = this._typed(name, tf_imps)
-      Object.defineProperty(tf, 'fromInstance', {value: this})
+      let tf
+      if (Object.keys(tf_imps).length > 0) {
+         tf = this._typed(name, tf_imps)
+         Object.defineProperty(tf, 'fromInstance', {value: this})
+      }
+      let metaTF
+      if (Object.keys(meta_imps).length > 0) {
+         metaTF = this._metaTyped(name, meta_imps)
+         Object.defineProperty(metaTF, 'fromInstance', {value: this})
+      }
+      this._meta[name] = metaTF
+
+      tf = tf || metaTF
       Object.defineProperty(this, name, {configurable: true, value: tf})
       return tf
    }
@@ -1077,7 +1186,10 @@ export default class PocomathInstance {
                         'typed-function does not support mixed full and '
                            + 'partial self-reference')
                   }
-                  if (subsetOfKeys(typesOfSignature(needsig), this.Types)) {
+                  const needTypes = typesOfSignature(needsig)
+                  const mergedTypes = Object.assign(
+                     {}, this.Types, this.Templates)
+                  if (subsetOfKeys(needTypes, mergedTypes)) {
                      part_self_references.push(needsig)
                   }
                }
@@ -1097,10 +1209,19 @@ export default class PocomathInstance {
                 * accumulating:
                 */
                if (needsig) {
-                  const tempTF = this._typed('dummy_' + func, this._TFimps[func])
+                  let typedUniverse
+                  let tempTF
+                  if (Object.keys(this._TFimps[func]).length > 0) {
+                     typedUniverse = this._typed
+                     tempTF = typedUniverse('dummy_' + func, this._TFimps[func])
+                  } else {
+                     typedUniverse = this._metaTyped
+                     tempTF = typedUniverse(
+                        'dummy_' + func, this._metaTFimps[func])
+                  }
                   let result = undefined
                   try {
-                     result = this._typed.find(tempTF, needsig, {exact: true})
+                     result = typedUniverse.find(tempTF, needsig, {exact: true})
                   } catch {}
                   if (result) {
                      refs[dep] = result
@@ -1158,7 +1279,7 @@ export default class PocomathInstance {
          return
       }
       const implementation = does(refs)
-      // could do something with return type information here
+      // could do something with return type information here?
       imps[signature] = implementation
    }
 
@@ -1168,38 +1289,53 @@ export default class PocomathInstance {
          const deferral = imps[aSignature]
          const part_self_references = deferral.psr
          const corrected_self_references = []
+         const remaining_self_references = []
+         const refs = deferral.builtRefs
          for (const neededSig of part_self_references) {
             // Have to find a match for neededSig among the other signatures
             // of this function. That's a job for typed-function, but we will
             // try here:
             if (neededSig in imps) { // the easy case
                corrected_self_references.push(neededSig)
+               remaining_self_references.push(neededSig)
                continue
             }
             // No exact match, try to get one that matches with
             // subtypes since the whole conversion thing in typed-function
             // is too complicated to reproduce
-            const foundSig = this._findSubtypeImpl(name, imps, neededSig)
+            let foundSig = this._findSubtypeImpl(name, imps, neededSig)
             if (foundSig) {
                corrected_self_references.push(foundSig)
+               remaining_self_references.push(neededSig)
             } else {
-               throw new Error(
-                  'Implement inexact self-reference in typed-function for '
-                     + `${name}(${neededSig})`)
+               // Maybe it's a template instance we don't yet have
+               foundSig = this._findSubtypeImpl(
+                  name, this._imps[name], neededSig)
+               if (foundSig) {
+                  const match = this._pocoFindSignature(name, neededSig)
+                  refs[`self(${neededSig})`] = match.implementation
+               } else {
+                  throw new Error(
+                     'Implement inexact self-reference in typed-function for '
+                        + `${name}(${neededSig})`)
+               }
             }
          }
-         const refs = deferral.builtRefs
          const does = deferral.sigDoes
-         imps[aSignature] = this._typed.referTo(
-            ...corrected_self_references, (...impls) => {
-               for (let i = 0; i < part_self_references.length; ++i) {
-                  refs[`self(${part_self_references[i]})`] = impls[i]
+         if (remaining_self_references.length > 0) {
+            imps[aSignature] = this._typed.referTo(
+               ...corrected_self_references, (...impls) => {
+                  for (let i = 0; i < remaining_self_references.length; ++i) {
+                     refs[`self(${remaining_self_references[i]})`] = impls[i]
+                  }
+                  const implementation = does(refs)
+                  // What will we do with the return type info in here?
+                  return implementation
                }
-               const implementation = does(refs)
-               // What will we do with the return type info in here?
-               return implementation
-            }
-         )
+            )
+         } else {
+            imps[aSignature] = does(refs)
+         }
          imps[aSignature]._pocoSignature = deferral._pocoSignature
          imps[aSignature]._pocoInstance = deferral._pocoInstance
       }
@@ -1247,7 +1383,7 @@ export default class PocomathInstance {
       if (wantsType in this.Types) return false
       // OK, need to generate the type from the template
       // Set up refines, before, test, and from
-      const newTypeSpec = {refines: base}
+      const newTypeSpec = {}
       const maybeFrom = {}
       const template = this.Templates[base].spec
       if (!template) {
@@ -1255,6 +1391,11 @@ export default class PocomathInstance {
             `Implementor error in instantiateTemplate(${base}, ${instantiator})`)
       }
       const instantiatorSpec = this.Types[instantiator]
+      if (instantiatorSpec.refines) {
+         this.instantiateTemplate(base, instantiatorSpec.refines)
+         // Assuming our templates are covariant, I guess
+         newTypeSpec.refines = `${base}<${instantiatorSpec.refines}>`
+      }
       let beforeTypes = []
       if (instantiatorSpec.before) {
          beforeTypes = instantiatorSpec.before.map(type => `${base}<${type}>`)
@@ -1268,18 +1409,15 @@ export default class PocomathInstance {
       if (beforeTypes.length > 0) {
          newTypeSpec.before = beforeTypes
       }
-      newTypeSpec.test = template.test(this._typeTests[instantiator])
+      const templateTest = template.test(this._typeTests[instantiator])
+      newTypeSpec.test = x => (template.base(x) && templateTest(x))
       if (template.from) {
          for (let source in template.from) {
             const instSource = substituteInSignature(
                source, theTemplateParam, instantiator)
-            let usesFromParam = false
-            for (const word of instSource.split(/[<>]/)) {
-               if (word === templateFromParam) {
-                  usesFromParam = true
-                  break
-               }
-            }
+            const testSource = substituteInSignature(
+               instSource, templateFromParam, instantiator)
+            const usesFromParam = (testSource !== instSource)
             if (usesFromParam) {
                for (const iFrom in instantiatorSpec.from) {
                   const finalSource = substituteInSignature(
@@ -1287,11 +1425,13 @@ export default class PocomathInstance {
                   maybeFrom[finalSource] = template.from[source](
                      instantiatorSpec.from[iFrom])
                }
-               // Assuming all templates are covariant here, I guess...
-               for (const subType of this._subtypes[instantiator]) {
-                  const finalSource = substituteInSignature(
-                     instSource, templateFromParam, subType)
-                  maybeFrom[finalSource] = template.from[source](x => x)
+               if (testSource !== wantsType) { // subtypes handled with refines
+                  // Assuming all templates are covariant here, I guess...
+                  for (const subType of this._subtypes[instantiator]) {
+                     const finalSource = substituteInSignature(
+                        instSource, templateFromParam, subType)
+                     maybeFrom[finalSource] = template.from[source](x => x)
+                  }
                }
             } else {
                maybeFrom[instSource] = template.from[source]
@@ -1303,6 +1443,7 @@ export default class PocomathInstance {
          newTypeSpec.from = maybeFrom
       }
       this.installType(wantsType, newTypeSpec)
+      this._instantiationsOf[base].add(wantsType)
       return wantsType
    })
 
@@ -1314,7 +1455,7 @@ export default class PocomathInstance {
          const otherTypeList = typeListOfSignature(otherSig)
          if (typeList.length !== otherTypeList.length) continue
          let allMatch = true
-         let paramBound = 'ground'
+         let paramBound = 'any'
          for (let k = 0; k < typeList.length; ++k) {
             let myType = typeList[k]
             let otherType = otherTypeList[k]
@@ -1326,8 +1467,7 @@ export default class PocomathInstance {
                otherTypeList[k] = `...${paramBound}`
                otherType = paramBound
             }
-            const adjustedOtherType = otherType.replaceAll(
-               `<${theTemplateParam}>`, '')
+            const adjustedOtherType = otherType.replaceAll(templateCall, '')
             if (adjustedOtherType !== otherType) {
                otherTypeList[k] = adjustedOtherType
                otherType = adjustedOtherType
@@ -1342,22 +1482,21 @@ export default class PocomathInstance {
                   theTemplateParam, paramBound)
             }
             if (otherType === 'any') continue
-            if (otherType === 'ground') continue
-            if (!(otherType in this.Types)) {
-               allMatch = false
-               break
-            }
-            if (myType === otherType
-                || this.isSubtypeOf(myType, otherType)) {
-               continue
-            }
+            if (myType === otherType) continue
             if (otherType in this.Templates) {
+               const myBase = myType.split('<',1)[0]
+               if (myBase === otherType) continue
                if (this.instantiateTemplate(otherType, myType)) {
                   let dummy
                   dummy = this[name] // for side effects
                   return this._findSubtypeImpl(name, this._imps[name], neededSig)
                }
             }
+            if (!(otherType in this.Types)) {
+               allMatch = false
+               break
+            }
+            if (this.isSubtypeOf(myType, otherType)) continue
             allMatch = false
             break
          }
@@ -1373,19 +1512,42 @@ export default class PocomathInstance {
       if (!this._typed.isTypedFunction(typedFunction)) {
          typedFunction = this[name]
       }
-      let result = undefined
       const haveTF = this._typed.isTypedFunction(typedFunction)
       if (haveTF) {
+         // First try a direct match
+         let result
          try {
             result = this._typed.findSignature(typedFunction, sig, {exact: true})
          } catch {
          }
+         if (result) return result
+         // Next, look ourselves but with subtypes:
+         const wantTypes = typeListOfSignature(sig)
+         for (const [implSig, details]
+              of typedFunction._typedFunctionData.signatureMap) {
+            let allMatched = true
+            const implTypes = typeListOfSignature(implSig)
+            for (let i = 0; i < wantTypes.length; ++i) {
+               if (wantTypes[i] == implTypes[i]
+                   || this.isSubtypeOf(wantTypes[i], implTypes[i])) continue
+               allMatched = false
+               break
+            }
+            if (allMatched) return details
+         }
       }
-      if (result || !(this._imps[name])) return result
+      if (!(this._imps[name])) return undefined
       const foundsig = this._findSubtypeImpl(name, this._imps[name], sig)
       if (foundsig) {
          if (haveTF) {
-            return this._typed.findSignature(typedFunction, foundsig)
+            try {
+               return this._typed.findSignature(typedFunction, foundsig)
+            } catch {
+            }
+         }
+         try {
+            return this._metaTyped.findSignature(this._meta[name], foundsig)
+         } catch {
          }
          // We have an implementation but not a typed function. Do the best
          // we can:
@@ -1398,20 +1560,8 @@ export default class PocomathInstance {
          const pseudoImpl = foundImpl.does(needs)
          return {fn: pseudoImpl, implementation: pseudoImpl}
       }
-      const wantTypes = typeListOfSignature(sig)
-      for (const [implSig, details]
-           of typedFunction._typedFunctionData.signatureMap) {
-         let allMatched = true
-         const implTypes = typeListOfSignature(implSig)
-         for (let i = 0; i < wantTypes.length; ++i) {
-            if (wantTypes[i] == implTypes[i]
-                || this.isSubtypeOf(wantTypes[i], implTypes[i])) continue
-            allMatched = false
-            break
-         }
-         if (allMatched) return details
-      }
       // Hmm, no luck. Make sure bundle is up-to-date and retry:
+      let result = undefined
       typedFunction = this[name]
       try {
          result = this._typed.findSignature(typedFunction, sig)

src/generic/abs.mjs

@@ -1,7 +1,9 @@
+import Returns from '../core/Returns.mjs'
 export const abs = {
    T: ({
+      T,
       'smaller(T,T)': lt,
       'negate(T)': neg,
       'zero(T)': zr
-   }) => t => (smaller(t, zr(t)) ? neg(t) : t)
+   }) => Returns(T, t => (smaller(t, zr(t)) ? neg(t) : t))
 }

src/number/abs.mjs

@@ -1,3 +1,4 @@
+import Returns from '../core/Returns.mjs'
 export * from './Types/number.mjs'
 
-export const abs = {number: () => n => Math.abs(n)}
+export const abs = {'T:number': ({T}) => Returns(T, n => Math.abs(n))}

src/tuple/Types/Tuple.mjs

@@ -2,24 +2,22 @@
 import PocomathInstance from '../../core/PocomathInstance.mjs'
 
 const Tuple = new PocomathInstance('Tuple')
-// First a base type that will generally not be used directly
-Tuple.installType('Tuple', {
-   test: t => t && typeof t === 'object' && 'elts' in t && Array.isArray(t.elts)
-})
-// Now the template type that is the primary use of this
+
 Tuple.installType('Tuple<T>', {
-   // We are assuming that any 'Type<T>' refines 'Type', so this is
-   // not necessary:
-   // refines: 'Tuple',
-   // But we need there to be a way to determine the type of a tuple:
-   infer: ({typeOf, joinTypes}) => t => joinTypes(t.elts.map(typeOf)),
-   // For the test, we can assume that t is already a base tuple,
-   // and we get the test for T as an input and we have to return
-   // the test for Tuple<T>
+   // A test that "defines" the "base type", which is not really a type
+   // (only fully instantiated types are added to the universe)
+   base: t => t && typeof t === 'object' && 'elts' in t && Array.isArray(t.elts),
+   // The template portion of the test; it takes the test for T as
+   // input and returns the test for an entity _that already passes
+   // the base test_ to be a Tuple<T>:
    test: testT => t => t.elts.every(testT),
-   // These are only invoked for types U such that there is already
-   // a conversion from U to T, and that conversion is passed as an input
-   // and we have to return the conversion to Tuple<T>:
+   // And we need there to be a way to determine the (instantiation)
+   // type of an tuple (that has already passed the base test):
+   infer: ({typeOf, joinTypes}) => t => joinTypes(t.elts.map(typeOf)),
+   // Conversions. Parametrized conversions are only invoked for types
+   // U such that there is already a conversion from U to T, and that
+   // conversion is passed as an input, and we have to return the conversion
+   // function from the indicated template in terms of U to Tuple<T>:
    from: {
       'Tuple<U>': convert => tu => ({elts: tu.elts.map(convert)}),
       // Here since there is no U it's a straight conversion:

src/tuple/length.mjs

@@ -1,3 +1,4 @@
+import Returns from '../core/Returns.mjs'
 export {Tuple} from './Types/Tuple.mjs'
 
-export const length = {Tuple: () => t => t.elts.length}
+export const length = {'Tuple<T>': () => Returns('NumInt', t => t.elts.length)}