fix(genapi): scope method-param enums per method, dedupe case-colliding enum consts

Bot API update added RichBlockListItem.type values (a/A/i/I/1) that
Pascal-case to identical const idents, and answerGuestQuery's non-enum
'result' param picked up answerChatJoinRequestQuery's Result enum via
the shared parent="" enum-plan key.

- key method params as method:<name> in the enum plan byField map
- enumDecl.ConstName resolves case collisions with Lower/Upper prefix
- regenerate api/ from 2026-06-11 snapshot

cmd/genapi/emitter.go

@@ -420,7 +420,7 @@ func funcs(plan *enumPlan) template.FuncMap {
 			return goField(plan, parent, f)
 		},
 		"goFieldP": func(methodName string, f spec.Field) string {
-			return goFieldX(plan, "", title(methodName)+"Params", f)
+			return goFieldX(plan, methodEnumParent(methodName), title(methodName)+"Params", f)
 		},
 		"docComment":  docComment,
 		"isOptional":  func(f spec.Field) bool { return !f.Required },
@@ -432,7 +432,7 @@ func funcs(plan *enumPlan) template.FuncMap {
 			return multipartFieldEntry(plan, parent, f)
 		},
 		"multipartFieldEntryP": func(methodName string, f spec.Field) string {
-			return multipartFieldEntryX(plan, "", title(methodName)+"Params", f)
+			return multipartFieldEntryX(plan, methodEnumParent(methodName), title(methodName)+"Params", f)
 		},
 		"multipartFileEntry": multipartFileEntry,
 		"returnGoType":       returnGoType,
@@ -915,15 +915,15 @@ func buildUnionTypeSet(api *spec.API) map[string]bool {
 // used in generated test param literals. plan supplies typed-enum names
 // so a method-param sentinel for a ParseMode field becomes a typed
 // constant rather than a magic string.
-func makeSentinelValue(unionTypes map[string]bool, plan *enumPlan) func(spec.Field) string {
-	return func(f spec.Field) string {
-		return sentinelForField(f, unionTypes, plan)
+func makeSentinelValue(unionTypes map[string]bool, plan *enumPlan) func(string, spec.Field) string {
+	return func(methodName string, f spec.Field) string {
+		return sentinelForField(methodName, f, unionTypes, plan)
 	}
 }
 
-func sentinelForField(f spec.Field, unionTypes map[string]bool, plan *enumPlan) string {
-	if name := plan.FieldEnum("", f.Name); name != "" && len(f.EnumValues) > 0 {
-		return constName(name, f.EnumValues[0])
+func sentinelForField(methodName string, f spec.Field, unionTypes map[string]bool, plan *enumPlan) string {
+	if name := plan.FieldEnum(methodEnumParent(methodName), f.Name); name != "" && len(f.EnumValues) > 0 {
+		return plan.ConstFor(name, f.EnumValues[0])
 	}
 	tr := f.Type
 	switch tr.Kind {

cmd/genapi/enums.go

@@ -26,15 +26,21 @@ type enumPlan struct {
 }
 
 // enumKey identifies a single Field occurrence so the emitter can look
-// up the enum name later. Parent is "" for method params (the method
-// doesn't share a Go type with the field).
+// up the enum name later. Parent is the type name for struct fields and
+// methodEnumParent(name) for method params, so two methods sharing a
+// param name never alias each other's enum (or non-enum) fields.
 func enumKey(parent, fieldName string) string { return parent + "::" + fieldName }
 
+// methodEnumParent is the enum-plan key parent for a method's params.
+// The "method:" prefix keeps it disjoint from type names.
+func methodEnumParent(methodName string) string { return "method:" + methodName }
+
 // planEnums walks the IR, decides on enum names, deduplicates, and
 // returns an enumPlan. All scraper-marked enum fields are covered.
 func planEnums(api *spec.API) *enumPlan {
 	type ref struct {
-		parent    string
+		parent    string // naming parent ("" for method params)
+		keyParent string // byField key parent (methodEnumParent(...) for method params)
 		fieldName string
 		jsonName  string
 		values    []string
@@ -52,7 +58,7 @@ func planEnums(api *spec.API) *enumPlan {
 	}
 
 	var refs []ref
-	collect := func(parent string, fields []spec.Field) {
+	collect := func(parent, keyParent string, fields []spec.Field) {
 		for _, f := range fields {
 			if len(f.EnumValues) == 0 {
 				continue
@@ -62,6 +68,7 @@ func planEnums(api *spec.API) *enumPlan {
 			}
 			refs = append(refs, ref{
 				parent:    parent,
+				keyParent: keyParent,
 				fieldName: f.Name,
 				jsonName:  f.JSONName,
 				values:    f.EnumValues,
@@ -70,13 +77,15 @@ func planEnums(api *spec.API) *enumPlan {
 		}
 	}
 	for _, t := range api.Types {
-		collect(t.Name, t.Fields)
+		collect(t.Name, t.Name, t.Fields)
 	}
 	for _, m := range api.Methods {
-		// Method params have no shared Go parent type, so we pass "" as
-		// the parent. The default-name heuristic still produces the
-		// right answer for ParseMode-style enums.
-		collect("", m.Params)
+		// Method params have no shared Go parent type, so the naming
+		// parent is "" (the default-name heuristic still produces the
+		// right answer for ParseMode-style enums), but the byField key
+		// is method-scoped so a same-named non-enum param on another
+		// method can never pick up this enum.
+		collect("", methodEnumParent(m.Name), m.Params)
 	}
 
 	// candidate name per ref (before collision resolution)
@@ -196,7 +205,7 @@ func planEnums(api *spec.API) *enumPlan {
 	}
 	for i, r := range refs {
 		name := groups[r.valueKey].name
-		plan.byField[enumKey(r.parent, r.fieldName)] = name
+		plan.byField[enumKey(r.keyParent, r.fieldName)] = name
 		_ = i
 	}
 	for vk, g := range groups {
@@ -389,6 +398,18 @@ func (p *enumPlan) FieldEnum(parent, fieldName string) string {
 	return p.byField[enumKey(parent, fieldName)]
 }
 
+// ConstFor returns the collision-resolved constant identifier for value
+// within the named enum declaration. Falls back to the plain constName
+// when the declaration is unknown (unit tests with partial plans).
+func (p *enumPlan) ConstFor(enumName, value string) string {
+	if p != nil {
+		if d, ok := p.decls[enumName]; ok {
+			return d.ConstName(value)
+		}
+	}
+	return constName(enumName, value)
+}
+
 // defaultEnumName picks an initial Go enum name for a field. parse_mode
 // fields collapse to the canonical "ParseMode"; otherwise the name is
 // parent + PascalCase(jsonName).
@@ -406,6 +427,48 @@ func constName(enumName, value string) string {
 	return enumName + valuePascal(value)
 }
 
+// ConstName returns the constant identifier for value within this enum,
+// resolving case-collisions between values that Pascal-case to the same
+// identifier (e.g. RichBlockListItem.type values "a" and "A"). Colliding
+// values get a Lower/Upper prefix on the value part based on the case of
+// the value's first letter; any residual collision gets a numeric suffix.
+func (e enumDecl) ConstName(value string) string {
+	counts := map[string]int{}
+	for _, v := range e.Values {
+		counts[constName(e.Name, v)]++
+	}
+	plain := constName(e.Name, value)
+	if counts[plain] <= 1 {
+		return plain
+	}
+	cased := e.Name + casePrefix(value) + valuePascal(value)
+	// Residual collision (same value text repeated, or Lower/Upper still
+	// ambiguous): append the value's 1-based position for determinism.
+	casedCounts := map[string]int{}
+	pos := 0
+	for i, v := range e.Values {
+		if counts[constName(e.Name, v)] > 1 {
+			casedCounts[e.Name+casePrefix(v)+valuePascal(v)]++
+		}
+		if v == value {
+			pos = i + 1
+		}
+	}
+	if casedCounts[cased] > 1 {
+		return cased + itoa(pos)
+	}
+	return cased
+}
+
+// casePrefix distinguishes case-colliding enum values: "Lower" when the
+// value starts with a lowercase letter, "Upper" otherwise.
+func casePrefix(v string) string {
+	if v != "" && v[0] >= 'a' && v[0] <= 'z' {
+		return "Lower"
+	}
+	return "Upper"
+}
+
 func valuePascal(v string) string {
 	// "image/jpeg" → "ImageOfJpeg"
 	parts := strings.Split(v, "/")

cmd/genapi/enums.tmpl

@@ -8,6 +8,6 @@ package api
 type {{$e.Name}} string
 
 const (
-{{range $v := $e.Values}}	{{enumConstName $e.Name $v}} {{$e.Name}} = {{printf "%q" $v}}
+{{range $v := $e.Values}}	{{$e.ConstName $v}} {{$e.Name}} = {{printf "%q" $v}}
 {{end}})
 {{end}}

cmd/genapi/enums_collision_test.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/lukaszraczylo/go-telegram/internal/spec"
+	"github.com/stretchr/testify/require"
+)
+
+// Regression: Bot API 9.x RichBlockListItem.type enumerates "a"/"A"/"i"/"I"/"1",
+// which Pascal-case to the same identifier. ConstName must disambiguate.
+func TestEnumDecl_ConstName_CaseCollision(t *testing.T) {
+	d := enumDecl{Name: "RichBlockListItemType", Values: []string{"a", "A", "i", "I", "1"}}
+	got := map[string]bool{}
+	for _, v := range d.Values {
+		n := d.ConstName(v)
+		require.False(t, got[n], "duplicate const ident %q for value %q", n, v)
+		got[n] = true
+	}
+	require.Equal(t, "RichBlockListItemTypeLowerA", d.ConstName("a"))
+	require.Equal(t, "RichBlockListItemTypeUpperA", d.ConstName("A"))
+	// Non-colliding values keep the plain name.
+	require.Equal(t, "RichBlockListItemType1", d.ConstName("1"))
+}
+
+// Regression: answerChatJoinRequestQuery has an enum param named "result";
+// answerGuestQuery has a NON-enum param also named "result". The enum plan
+// must scope method params per method so the enum never leaks onto the
+// other method's field.
+func TestPlanEnums_MethodParamsScopedPerMethod(t *testing.T) {
+	api := &spec.API{
+		Methods: []spec.MethodDecl{
+			{
+				Name: "answerChatJoinRequestQuery",
+				Params: []spec.Field{{
+					Name: "Result", JSONName: "result", Required: true,
+					Type:       spec.TypeRef{Kind: spec.KindPrimitive, Name: "string"},
+					EnumValues: []string{"approve", "decline", "queue"},
+				}},
+			},
+			{
+				Name: "answerGuestQuery",
+				Params: []spec.Field{{
+					Name: "Result", JSONName: "result", Required: true,
+					Type: spec.TypeRef{Kind: spec.KindNamed, Name: "InlineQueryResult"},
+				}},
+			},
+		},
+	}
+	plan := planEnums(api)
+	require.Equal(t, "Result",
+		plan.FieldEnum(methodEnumParent("answerChatJoinRequestQuery"), "Result"))
+	require.Empty(t,
+		plan.FieldEnum(methodEnumParent("answerGuestQuery"), "Result"),
+		"non-enum param must not inherit another method's enum")
+}

cmd/genapi/extra_test.go

@@ -574,7 +574,7 @@ func TestSentinelForField(t *testing.T) {
 	}
 	for _, c := range cases {
 		t.Run(c.name, func(t *testing.T) {
-			got := sentinelForField(c.field, unionTypes, nil)
+			got := sentinelForField("testMethod", c.field, unionTypes, nil)
 			require.Contains(t, got, c.contains, "sentinelForField for %q", c.name)
 		})
 	}

cmd/genapi/tests.tmpl

@@ -48,7 +48,7 @@ func Test_{{$mName}}_Success(t *testing.T) {
 	{{- if .Params}}
 	params := &{{$mName}}Params{
 		{{- range .Params}}{{if .Required}}
-		{{.Name}}: {{sentinelValue .}},{{end}}
+		{{.Name}}: {{sentinelValue $m.Name .}},{{end}}
 		{{- end}}
 	}
 	_, err := {{$mName}}(context.Background(), bot, params)
@@ -67,7 +67,7 @@ func Test_{{$mName}}_APIError(t *testing.T) {
 	{{- if .Params}}
 	params := &{{$mName}}Params{
 		{{- range .Params}}{{if .Required}}
-		{{.Name}}: {{sentinelValue .}},{{end}}
+		{{.Name}}: {{sentinelValue $m.Name .}},{{end}}
 		{{- end}}
 	}
 	_, err := {{$mName}}(context.Background(), bot, params)
@@ -89,7 +89,7 @@ func Test_{{$mName}}_NetworkError(t *testing.T) {
 	{{- if .Params}}
 	params := &{{$mName}}Params{
 		{{- range .Params}}{{if .Required}}
-		{{.Name}}: {{sentinelValue .}},{{end}}
+		{{.Name}}: {{sentinelValue $m.Name .}},{{end}}
 		{{- end}}
 	}
 	_, err := {{$mName}}(context.Background(), bot, params)
@@ -109,7 +109,7 @@ func Test_{{$mName}}_ParseError(t *testing.T) {
 	{{- if .Params}}
 	params := &{{$mName}}Params{
 		{{- range .Params}}{{if .Required}}
-		{{.Name}}: {{sentinelValue .}},{{end}}
+		{{.Name}}: {{sentinelValue $m.Name .}},{{end}}
 		{{- end}}
 	}
 	_, err := {{$mName}}(context.Background(), bot, params)
@@ -132,7 +132,7 @@ func Test_{{$mName}}_ContextCanceled(t *testing.T) {
 	{{- if .Params}}
 	params := &{{$mName}}Params{
 		{{- range .Params}}{{if .Required}}
-		{{.Name}}: {{sentinelValue .}},{{end}}
+		{{.Name}}: {{sentinelValue $m.Name .}},{{end}}
 		{{- end}}
 	}
 	_, err := {{$mName}}(ctx, bot, params)
@@ -177,7 +177,7 @@ func Test_{{$mName}}_Forbidden(t *testing.T) {
 	{{- if .Params}}
 	params := &{{$mName}}Params{
 		{{- range .Params}}{{if .Required}}
-		{{.Name}}: {{sentinelValue .}},{{end}}
+		{{.Name}}: {{sentinelValue $m.Name .}},{{end}}
 		{{- end}}
 	}
 	_, err := {{$mName}}(context.Background(), bot, params)
@@ -203,7 +203,7 @@ func Test_{{$mName}}_ServerError(t *testing.T) {
 	{{- if .Params}}
 	params := &{{$mName}}Params{
 		{{- range .Params}}{{if .Required}}
-		{{.Name}}: {{sentinelValue .}},{{end}}
+		{{.Name}}: {{sentinelValue $m.Name .}},{{end}}
 		{{- end}}
 	}
 	_, err := {{$mName}}(context.Background(), bot, params)