fix: error when enum and useUnderlyingTypeMethods conflict

builder/enum.go

@@ -14,6 +14,10 @@ type Enum struct{}
 
 // Matches returns true, if the builder can create handle the given types.
 func (*Enum) Matches(ctx *MethodContext, source, target *xtype.Type) bool {
+	return isEnum(ctx, source, target)
+}
+
+func isEnum(ctx *MethodContext, source, target *xtype.Type) bool {
 	return ctx.Conf.Enum.Enabled &&
 		source.Enum(&ctx.Conf.Enum).OK &&
 		target.Enum(&ctx.Conf.Enum).OK

builder/underlying.go

@@ -1,6 +1,8 @@
 package builder
 
 import (
+	"fmt"
+
 	"github.com/dave/jennifer/jen"
 	"github.com/jmattheis/goverter/xtype"
 )
@@ -20,6 +22,15 @@ func (*UseUnderlyingTypeMethods) Matches(ctx *MethodContext, source, target *xty
 
 // Build creates conversion source code for the given source and target type.
 func (*UseUnderlyingTypeMethods) Build(gen Generator, ctx *MethodContext, sourceID *xtype.JenID, source, target *xtype.Type, errPath ErrorPath) ([]jen.Code, *xtype.JenID, *Error) {
+	if isEnum(ctx, source, target) {
+		return nil, nil, NewError(fmt.Sprintf(`The conversion between the types
+    %s
+    %s
+
+does qualify for enum conversion but also match an extend method via useUnderlyingTypeMethods.
+You have to disable enum or useUnderlyingTypeMethods to resolve the setting conflict.`, source.String, target.String))
+	}
+
 	sourceUnderlying, targetUnderlying := findUnderlyingExtendMapping(ctx, source, target)
 
 	innerSource := source

docs/changelog.md

@@ -4,6 +4,12 @@ import GH from './GH.vue';
 
 # Changelog
 
+## unreleased
+
+- Error when the settings [`enum`](reference/enum.md) and
+  [`useUnderlyingTypeMethods`](reference/useUnderlyingTypeMethods.md) conflict.
+  <GH issue="141" pr="142"/>
+
 ## v1.4.0
 
 - Add [Enum Support](guide/enum.md) <GH issue="61" pr="136"/>. Can be disabled

scenario/enum_underlying_conflict.md

@@ -0,0 +1,37 @@
+input:
+    input.go: |
+        package example
+
+        // goverter:converter
+        // goverter:extend ConvertUnderlying
+        type Converter interface {
+            // goverter:useUnderlyingTypeMethods
+            Convert(SqlColor) Color
+        }
+
+        func ConvertUnderlying(s string) string {
+            return ""
+        }
+
+        type SqlColor string
+        const SqlColorDefault SqlColor = "default"
+
+        type Color string
+        const ColorDefault Color = "default"
+error: |-
+    Error while creating converter method:
+        func (github.com/jmattheis/goverter/execution.Converter).Convert(github.com/jmattheis/goverter/execution.SqlColor) github.com/jmattheis/goverter/execution.Color
+
+    | github.com/jmattheis/goverter/execution.SqlColor
+    |
+    source
+    target
+    |
+    | github.com/jmattheis/goverter/execution.Color
+
+    The conversion between the types
+        github.com/jmattheis/goverter/execution.SqlColor
+        github.com/jmattheis/goverter/execution.Color
+
+    does qualify for enum conversion but also match an extend method via useUnderlyingTypeMethods.
+    You have to disable enum or useUnderlyingTypeMethods to resolve the setting conflict.