go/types,cmd/compile/internal/types2: add String methods

This change adds String methods to the types TypeList, TypeParamList
and Instance. The format is unspecified and is provided merely as
a debugging aid.

Fixes #79287

Change-Id: Ic283ea57bac6465b47b8b81b1fa4590641b639cb
Reviewed-on: https://go-review.googlesource.com/c/go/+/780581
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Auto-Submit: Alan Donovan <adonovan@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>

api/next/79287.txt

@@ -0,0 +1,3 @@
+pkg go/types, method (*TypeList) String() string #79287
+pkg go/types, method (*TypeParamList) String() string #79287
+pkg go/types, method (Instance) String() string #79287

doc/next/6-stdlib/99-minor/go/types/79287.md

@@ -0,0 +1 @@
+<!-- nothing to see here but some String methods -->

src/cmd/compile/internal/types2/api.go

@@ -437,6 +437,10 @@ type Instance struct {
 	Type     Type
 }
 
+func (inst Instance) String() string {
+	return fmt.Sprintf("%s%s", inst.TypeArgs, inst.Type)
+}
+
 // An Initializer describes a package-level variable, or a list of variables in case
 // of a multi-valued initialization expression, and the corresponding initialization
 // expression.

src/cmd/compile/internal/types2/typelists.go

@@ -4,6 +4,8 @@
 
 package types2
 
+import "bytes"
+
 // TypeParamList holds a list of type parameters.
 type TypeParamList struct{ tparams []*TypeParam }
 
@@ -24,6 +26,19 @@ func (l *TypeParamList) list() []*TypeParam {
 	return l.tparams
 }
 
+func (l *TypeParamList) String() string {
+	var buf bytes.Buffer
+	buf.WriteByte('[')
+	for i, tparam := range l.tparams {
+		if i > 0 {
+			buf.WriteString(", ")
+		}
+		WriteType(&buf, tparam, nil)
+	}
+	buf.WriteByte(']')
+	return buf.String()
+}
+
 // TypeList holds a list of types.
 type TypeList struct{ types []Type }
 
@@ -52,6 +67,19 @@ func (l *TypeList) list() []Type {
 	return l.types
 }
 
+func (l *TypeList) String() string {
+	var buf bytes.Buffer
+	buf.WriteByte('[')
+	for i, t := range l.types {
+		if i > 0 {
+			buf.WriteString(", ")
+		}
+		WriteType(&buf, t, nil)
+	}
+	buf.WriteByte(']')
+	return buf.String()
+}
+
 // ----------------------------------------------------------------------------
 // Implementation
 

src/go/types/api.go

@@ -445,6 +445,10 @@ type Instance struct {
 	Type     Type
 }
 
+func (inst Instance) String() string {
+	return fmt.Sprintf("%s%s", inst.TypeArgs, inst.Type)
+}
+
 // An Initializer describes a package-level variable, or a list of variables in case
 // of a multi-valued initialization expression, and the corresponding initialization
 // expression.

src/go/types/typelists.go

@@ -7,6 +7,8 @@
 
 package types
 
+import "bytes"
+
 // TypeParamList holds a list of type parameters.
 type TypeParamList struct{ tparams []*TypeParam }
 
@@ -27,6 +29,19 @@ func (l *TypeParamList) list() []*TypeParam {
 	return l.tparams
 }
 
+func (l *TypeParamList) String() string {
+	var buf bytes.Buffer
+	buf.WriteByte('[')
+	for i, tparam := range l.tparams {
+		if i > 0 {
+			buf.WriteString(", ")
+		}
+		WriteType(&buf, tparam, nil)
+	}
+	buf.WriteByte(']')
+	return buf.String()
+}
+
 // TypeList holds a list of types.
 type TypeList struct{ types []Type }
 
@@ -55,6 +70,19 @@ func (l *TypeList) list() []Type {
 	return l.types
 }
 
+func (l *TypeList) String() string {
+	var buf bytes.Buffer
+	buf.WriteByte('[')
+	for i, t := range l.types {
+		if i > 0 {
+			buf.WriteString(", ")
+		}
+		WriteType(&buf, t, nil)
+	}
+	buf.WriteByte(']')
+	return buf.String()
+}
+
 // ----------------------------------------------------------------------------
 // Implementation