proposal: ignore interfaces that contains type constraints

mockgen/generic_go118.go

@@ -11,8 +11,10 @@
 package main
 
 import (
+	"errors"
 	"fmt"
 	"go/ast"
+	"go/token"
 	"strings"
 
 	"go.uber.org/mock/mockgen/model"
@@ -98,6 +100,16 @@ func (p *fileParser) parseGenericMethod(field *ast.Field, it *namedInterface, if
 	case *ast.IndexListExpr:
 		indices = v.Indices
 		typ = v.X
+	case *ast.UnaryExpr:
+		if v.Op == token.TILDE {
+			return nil, errIgnore
+		}
+		return nil, fmt.Errorf("~T may only appear as constraint for %T", field.Type)
+	case *ast.BinaryExpr:
+		if v.Op == token.OR {
+			return nil, errIgnore
+		}
+		return nil, fmt.Errorf("A|B may only appear as constraint for %T", field.Type)
 	default:
 		return nil, fmt.Errorf("don't know how to mock method of type %T", field.Type)
 	}
@@ -114,3 +126,5 @@ func (p *fileParser) parseGenericMethod(field *ast.Field, it *namedInterface, if
 
 	return p.parseMethod(nf, it, iface, pkg, tps)
 }
+
+var errIgnore = errors.New("parser decided to ignore the interface for constraints")

mockgen/internal/tests/generics/generics.go

@@ -57,3 +57,11 @@ type SolarSystem[T constraints.Ordered] interface {
 type Earth[R any] interface {
 	Water(R) []R
 }
+
+type Water[R any, C UnsignedInteger] interface {
+	Fish(R) []C
+}
+
+type UnsignedInteger interface {
+	~uint | ~uint32 | ~uint64
+}

mockgen/parse.go

@@ -232,6 +232,9 @@ func (p *fileParser) parseFile(importPath string, file *ast.File) (*model.Packag
 			continue
 		}
 		i, err := p.parseInterface(ni.name.String(), importPath, ni)
+		if err == errIgnore {
+			continue
+		}
 		if err != nil {
 			return nil, err
 		}