From 6c74ab7becad4a2a4bf7913da4c9cbd1f198c010 Mon Sep 17 00:00:00 2001
From: Marc Vertes <mvertes@free.fr>
Date: Mon, 13 Jun 2022 08:42:08 +0000
Subject: [PATCH] interp: allow conversions of untyped complex

For untyped numerical types, conversions to different numerical
types can be allowed if there is no overflow (not checked here).

Fixes #1402.
---
 interp/interp_eval_test.go | 5 ++++-
 interp/type.go             | 9 +++++++--
 interp/typecheck.go        | 4 ++--
 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/interp/interp_eval_test.go b/interp/interp_eval_test.go
index d7d98a500..903e7ded5 100644
--- a/interp/interp_eval_test.go
+++ b/interp/interp_eval_test.go
@@ -176,7 +176,7 @@ func TestEvalBuiltin(t *testing.T) {
 		{src: `m := complex(3, 2); real(m)`, res: "3"},
 		{src: `m := complex(3, 2); imag(m)`, res: "2"},
 		{src: `m := complex("test", 2)`, err: "1:33: invalid types string and int"},
-		{src: `imag("test")`, err: "1:33: cannot convert \"test\" to complex128"},
+		{src: `imag("test")`, err: "1:33: cannot convert untyped string to untyped complex"},
 		{src: `imag(a)`, err: "1:33: invalid argument type []int for imag"},
 		{src: `real(a)`, err: "1:33: invalid argument type []int for real"},
 		{src: `t := map[int]int{}; t[123]++; t`, res: "map[123:1]"},
@@ -184,6 +184,9 @@ func TestEvalBuiltin(t *testing.T) {
 		{src: `t := map[int]int{}; t[123] += 1; t`, res: "map[123:1]"},
 		{src: `t := map[int]int{}; t[123] -= 1; t`, res: "map[123:-1]"},
 		{src: `println("hello", _)`, err: "1:28: cannot use _ as value"},
+		{src: `f := func() complex64 { return complex(0, 0) }()`, res: "(0+0i)"},
+		{src: `f := func() float32 { return real(complex(2, 1)) }()`, res: "2"},
+		{src: `f := func() int8 { return imag(complex(2, 1)) }()`, res: "1"},
 	})
 }
 
diff --git a/interp/type.go b/interp/type.go
index c6955d41a..ecc390597 100644
--- a/interp/type.go
+++ b/interp/type.go
@@ -585,12 +585,12 @@ func nodeType2(interp *Interpreter, sc *scope, n *node, seen []*node) (t *itype,
 				}
 				if !t.incomplete {
 					switch k := t.TypeOf().Kind(); {
+					case t.untyped && isNumber(t.TypeOf()):
+						t = untypedFloat()
 					case k == reflect.Complex64:
 						t = sc.getType("float32")
 					case k == reflect.Complex128:
 						t = sc.getType("float64")
-					case t.untyped && isNumber(t.TypeOf()):
-						t = valueTOf(floatType, withUntyped(true), withScope(sc))
 					default:
 						err = n.cfgErrorf("invalid complex type %s", k)
 					}
@@ -1219,6 +1219,11 @@ func (t *itype) assignableTo(o *itype) bool {
 		return true
 	}
 
+	if t.untyped && isNumber(t.TypeOf()) && isNumber(o.TypeOf()) {
+		// Assignability depends on constant numeric value (overflow check), to be tested elsewhere.
+		return true
+	}
+
 	n := t.node
 	if n == nil || !n.rval.IsValid() {
 		return false
diff --git a/interp/typecheck.go b/interp/typecheck.go
index 0c3e9a4ab..7d30742a8 100644
--- a/interp/typecheck.go
+++ b/interp/typecheck.go
@@ -815,7 +815,7 @@ func (check typecheck) builtin(name string, n *node, child []*node, ellipsis boo
 		case !typ0.untyped && typ1.untyped:
 			err = check.convertUntyped(p1.nod, typ0)
 		case typ0.untyped && typ1.untyped:
-			fltType := check.scope.getType("float64")
+			fltType := untypedFloat()
 			err = check.convertUntyped(p0.nod, fltType)
 			if err != nil {
 				break
@@ -838,7 +838,7 @@ func (check typecheck) builtin(name string, n *node, child []*node, ellipsis boo
 		p := params[0]
 		typ := p.Type()
 		if typ.untyped {
-			if err := check.convertUntyped(p.nod, check.scope.getType("complex128")); err != nil {
+			if err := check.convertUntyped(p.nod, untypedComplex()); err != nil {
 				return err
 			}
 		}