fix: canonicalize generic field objects for struct hashing

Use `types.Var.Origin()` when mapping and hashing struct fields so selector and
declaration sites share the same canonical field identity. This fixes build
failures for generic aliases and named types over those aliases.

Fixes #924

debugdir.go

@@ -142,25 +142,25 @@ func debugDirNeedsRebuild() (bool, error) {
 		return false, err
 	}
 	sawBuildInputs := false
+	missingArtifacts := false
 	for _, lpkg := range sharedCache.ListedPackages {
 		if len(lpkg.GarbleActionID) == 0 {
 			continue
 		}
 		if len(lpkg.CompiledGoFiles) > 0 {
 			sawBuildInputs = true
-			if debugArtifactsExistForPkg(fsCache, lpkg, debugCacheKindCompile) {
-				return false, nil
+			if !debugArtifactsExistForPkg(fsCache, lpkg, debugCacheKindCompile) {
+				missingArtifacts = true
 			}
 		}
 		if len(lpkg.SFiles) > 0 {
 			sawBuildInputs = true
-			if debugArtifactsExistForPkg(fsCache, lpkg, debugCacheKindAsm) {
-				return false, nil
+			if !debugArtifactsExistForPkg(fsCache, lpkg, debugCacheKindAsm) {
+				missingArtifacts = true
 			}
 		}
 	}
-	// If no debug artifacts exist yet, force one full rebuild to warm cache.
-	// Once at least one cache entry exists, incremental builds can repopulate
-	// from cache + newly rebuilt packages without forcing -a.
-	return sawBuildInputs, nil
+	// For -debugdir to be complete, we either need artifacts in cache for every
+	// package input, or we need to force one full rebuild with -a.
+	return sawBuildInputs && missingArtifacts, nil
 }

reverse.go

@@ -103,11 +103,15 @@ One can reverse a captured panic stack trace as follows:
 						if obj == nil || !obj.IsField() {
 							continue
 						}
-						strct := fieldToStruct[obj]
+						originObj := obj.Origin()
+						strct := fieldToStruct[originObj]
+						if strct == nil {
+							strct = fieldToStruct[obj]
+						}
 						if strct == nil {
 							panic("could not find struct for field " + name.Name)
 						}
-						replaces = append(replaces, hashWithStruct(strct, obj), name.Name)
+						replaces = append(replaces, hashWithStruct(strct, originObj), name.Name)
 					}
 
 				case *ast.CallExpr:

testdata/script/typeparams.txtar

@@ -16,6 +16,11 @@ func main() {
 
 	g2 := GenericGraph[*[]byte]{Content: new([]byte)}
 	g2.Edges = make([]GenericGraph[*[]byte], 1)
+
+	var ga genericAlias
+	ga.list = nil
+	var gan genericAliasNamed
+	gan.list = nil
 }
 
 func GenericFunc[GenericParamA, B any](x GenericParamA, y B) {}
@@ -66,3 +71,10 @@ func (w *AsyncResult[oldT, newT]) AsResult() Result[newT] {
 }
 
 func (w *AsyncResult[oldT, newT]) Redirect(struct {ret newT}) {}
+
+type genericAlias = generic[int]
+type generic[T any] struct {
+	list *T
+}
+
+type genericAliasNamed genericAlias

transformer.go

@@ -166,10 +166,11 @@ func recordType(used, origin types.Type, done map[*types.Named]bool, fieldToStru
 		origin := origin.(*types.Struct)
 		for i := range used.NumFields() {
 			field := used.Field(i)
-			fieldToStruct[field] = origin
+			fieldToStruct[field.Origin()] = origin
 
 			if field.Embedded() {
-				recordType(field.Type(), origin.Field(i).Type(), done, fieldToStruct)
+				originField := origin.Field(i)
+				recordType(field.Type(), originField.Type(), done, fieldToStruct)
 			}
 		}
 	}
@@ -1237,11 +1238,12 @@ func (tf *transformer) transformGoFile(file *ast.File) *ast.File {
 			// any field is unexported. If that is done, add a test
 			// that ensures unexported fields from different
 			// packages result in different obfuscated names.
-			strct := tf.fieldToStruct[obj]
+			originObj := obj.Origin()
+			strct := tf.fieldToStruct[originObj]
 			if strct == nil {
 				panic("could not find struct for field " + name)
 			}
-			node.Name = hashWithStruct(strct, obj)
+			node.Name = hashWithStruct(strct, originObj)
 			if flagDebug { // TODO(mvdan): remove once https://go.dev/issue/53465 if fixed
 				log.Printf("%s %q hashed with struct fields to %q", debugName, name, node.Name)
 			}