cmd/compile/internal/types2: use TypeList in the Inferred struct

This is a port of CL 343934 from go/types with the necessary
adjustments to the compiler.

Change-Id: I810144e6e2eb2bc8fa0d34dc206403c993cbbe7a
Reviewed-on: https://go-review.googlesource.com/c/go/+/344616
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Dan Scales <danscales@google.com>

3 files changed, 7 insertions, 6 deletions

diff --git a/src/cmd/compile/internal/types2/api.go b/src/cmd/compile/internal/types2/api.go
index f268508825..b2938b84da 100644
--- a/src/cmd/compile/internal/types2/api.go
+++ b/src/cmd/compile/internal/types2/api.go
@@ -373,7 +373,7 @@ func (tv TypeAndValue) HasOk() bool {
 // Inferred reports the inferred type arguments and signature
 // for a parameterized function call that uses type inference.
 type Inferred struct {
-	TArgs []Type
+	TArgs *TypeList
 	Sig   *Signature
 }
 
diff --git a/src/cmd/compile/internal/types2/api_test.go b/src/cmd/compile/internal/types2/api_test.go
index 269b06f08a..039a6c0e5e 100644
--- a/src/cmd/compile/internal/types2/api_test.go
+++ b/src/cmd/compile/internal/types2/api_test.go
@@ -500,7 +500,7 @@ func TestInferredInfo(t *testing.T) {
 		}
 
 		// look for inferred type arguments and signature
-		var targs []Type
+		var targs *TypeList
 		var sig *Signature
 		for call, inf := range info.Inferred {
 			var fun syntax.Expr
@@ -524,11 +524,12 @@ func TestInferredInfo(t *testing.T) {
 		}
 
 		// check that type arguments are correct
-		if len(targs) != len(test.targs) {
-			t.Errorf("package %s: got %d type arguments; want %d", name, len(targs), len(test.targs))
+		if targs.Len() != len(test.targs) {
+			t.Errorf("package %s: got %d type arguments; want %d", name, targs.Len(), len(test.targs))
 			continue
 		}
-		for i, targ := range targs {
+		for i := 0; i < targs.Len(); i++ {
+			targ := targs.At(i)
 			if got := targ.String(); got != test.targs[i] {
 				t.Errorf("package %s, %d. type argument: got %s; want %s", name, i, got, test.targs[i])
 				continue
diff --git a/src/cmd/compile/internal/types2/check.go b/src/cmd/compile/internal/types2/check.go
index 6bc965c497..4226b4de82 100644
--- a/src/cmd/compile/internal/types2/check.go
+++ b/src/cmd/compile/internal/types2/check.go
@@ -416,7 +416,7 @@ func (check *Checker) recordInferred(call syntax.Expr, targs []Type, sig *Signat
 	assert(call != nil)
 	assert(sig != nil)
 	if m := check.Inferred; m != nil {
-		m[call] = Inferred{targs, sig}
+		m[call] = Inferred{NewTypeList(targs), sig}
 	}
 }