diff --git a/src/cmd/compile/internal/types2/expr.go b/src/cmd/compile/internal/types2/expr.go
index b223387f18..d1cb27de16 100644
--- a/src/cmd/compile/internal/types2/expr.go
+++ b/src/cmd/compile/internal/types2/expr.go
@@ -972,14 +972,28 @@ func (check *Checker) binary(x *operand, e syntax.Expr, lhs, rhs syntax.Expr, op
 		return
 	}
 
-	check.convertUntyped(x, y.typ)
-	if x.mode == invalid {
-		return
+	canMix := func(x, y *operand) bool {
+		if IsInterface(x.typ) || IsInterface(y.typ) {
+			return true
+		}
+		if isBoolean(x.typ) != isBoolean(y.typ) {
+			return false
+		}
+		if isString(x.typ) != isString(y.typ) {
+			return false
+		}
+		return true
 	}
-	check.convertUntyped(&y, x.typ)
-	if y.mode == invalid {
-		x.mode = invalid
-		return
+	if canMix(x, &y) {
+		check.convertUntyped(x, y.typ)
+		if x.mode == invalid {
+			return
+		}
+		check.convertUntyped(&y, x.typ)
+		if y.mode == invalid {
+			x.mode = invalid
+			return
+		}
 	}
 
 	if isComparison(op) {
diff --git a/src/cmd/compile/internal/types2/testdata/check/const0.src b/src/cmd/compile/internal/types2/testdata/check/const0.src
index 5608b1549b..3cffdf904c 100644
--- a/src/cmd/compile/internal/types2/testdata/check/const0.src
+++ b/src/cmd/compile/internal/types2/testdata/check/const0.src
@@ -27,7 +27,7 @@ const (
 	ub1 = true
 	ub2 = 2 < 1
 	ub3 = ui1 == uf1
-	ub4 = true /* ERROR "cannot convert" */ == 0
+	ub4 = true /* ERROR "mismatched types untyped bool and untyped int" */ == 0
 
 	// integer values
 	ui0 = 0
diff --git a/src/cmd/compile/internal/types2/testdata/check/decls1.src b/src/cmd/compile/internal/types2/testdata/check/decls1.src
index e6beb78358..1167ced366 100644
--- a/src/cmd/compile/internal/types2/testdata/check/decls1.src
+++ b/src/cmd/compile/internal/types2/testdata/check/decls1.src
@@ -83,7 +83,7 @@ var (
 
 // Constant expression initializations
 var (
-	v1 = 1 /* ERROR "cannot convert" */ + "foo"
+	v1 = 1 /* ERROR "mismatched types untyped int and untyped string" */ + "foo"
 	v2 = c + 255
 	v3 = c + 256 /* ERROR "overflows" */
 	v4 = r + 2147483647
diff --git a/src/cmd/compile/internal/types2/testdata/check/expr1.src b/src/cmd/compile/internal/types2/testdata/check/expr1.src
index 4ead815158..85ad234bbb 100644
--- a/src/cmd/compile/internal/types2/testdata/check/expr1.src
+++ b/src/cmd/compile/internal/types2/testdata/check/expr1.src
@@ -111,10 +111,10 @@ type mystring string
 func _(x, y string, z mystring) {
 	x = x + "foo"
 	x = x /* ERROR not defined */ - "foo"
-	x = x + 1 // ERROR cannot convert
+	x = x + 1 // ERROR mismatched types string and untyped int
 	x = x + y
 	x = x /* ERROR not defined */ - y
-	x = x * 10 // ERROR cannot convert
+	x = x * 10 // ERROR mismatched types string and untyped int
 }
 
 func f() (a, b int) { return }
diff --git a/src/cmd/compile/internal/types2/testdata/check/expr2.src b/src/cmd/compile/internal/types2/testdata/check/expr2.src
index 0c959e8011..f9726b5de5 100644
--- a/src/cmd/compile/internal/types2/testdata/check/expr2.src
+++ b/src/cmd/compile/internal/types2/testdata/check/expr2.src
@@ -10,7 +10,7 @@ func _bool() {
 	const t = true == true
 	const f = true == false
 	_ = t /* ERROR "cannot compare" */ < f
-	_ = 0 /* ERROR "cannot convert" */ == t
+	_ = 0 /* ERROR "mismatched types untyped int and untyped bool" */ == t
 	var b bool
 	var x, y float32
 	b = x < y
diff --git a/src/cmd/compile/internal/types2/testdata/check/expr3.src b/src/cmd/compile/internal/types2/testdata/check/expr3.src
index eab3f72c4d..fd28421dc8 100644
--- a/src/cmd/compile/internal/types2/testdata/check/expr3.src
+++ b/src/cmd/compile/internal/types2/testdata/check/expr3.src
@@ -104,7 +104,7 @@ func indexes() {
 	var ok mybool
 	_, ok = m["bar"]
 	_ = ok
-	_ = m[0 /* ERROR "cannot use 0" */ ] + "foo" // ERROR "cannot convert"
+	_ = m[0 /* ERROR "cannot use 0" */ ] + "foo" // ERROR "mismatched types int and untyped string"
 
 	var t string
 	_ = t[- /* ERROR "negative" */ 1]
diff --git a/src/cmd/compile/internal/types2/testdata/check/stmt0.src b/src/cmd/compile/internal/types2/testdata/check/stmt0.src
index bedcbe5fce..d744f2ba81 100644
--- a/src/cmd/compile/internal/types2/testdata/check/stmt0.src
+++ b/src/cmd/compile/internal/types2/testdata/check/stmt0.src
@@ -49,18 +49,18 @@ func assignments1() {
 	b = true
 
 	i += 1
-	i += "foo" /* ERROR "cannot convert.*int" */
+	i += "foo" /* ERROR "mismatched types int and untyped string" */
 
 	f -= 1
 	f /= 0
 	f = float32(0)/0 /* ERROR "division by zero" */
-	f -= "foo" /* ERROR "cannot convert.*float64" */
+	f -= "foo" /* ERROR "mismatched types float64 and untyped string" */
 
 	c *= 1
 	c /= 0
 
 	s += "bar"
-	s += 1 /* ERROR "cannot convert.*string" */
+	s += 1 /* ERROR "mismatched types string and untyped int" */
 
 	var u64 uint64
 	u64 += 1<<u64
@@ -937,13 +937,13 @@ func issue6766b() {
 // errors reported).
 func issue10148() {
 	for y /* ERROR declared but not used */ := range "" {
-		_ = "" /* ERROR cannot convert */ + 1
+		_ = "" /* ERROR mismatched types untyped string and untyped int*/ + 1
 	}
 	for range 1 /* ERROR cannot range over 1 */ {
-		_ = "" /* ERROR cannot convert */ + 1
+		_ = "" /* ERROR mismatched types untyped string and untyped int*/ + 1
 	}
 	for y := range 1 /* ERROR cannot range over 1 */ {
-		_ = "" /* ERROR cannot convert */ + 1
+		_ = "" /* ERROR mismatched types untyped string and untyped int*/ + 1
 	}
 }
 
diff --git a/test/fixedbugs/issue41500.go b/test/fixedbugs/issue41500.go
index 3ec23a0dfe..b0ae7cfd59 100644
--- a/test/fixedbugs/issue41500.go
+++ b/test/fixedbugs/issue41500.go
@@ -13,8 +13,8 @@ type s struct {
 func f() {
 	var x *s
 
-	_ = x == nil || len(x.slice) // ERROR "invalid operation: .+ \(operator \|\| not defined on int\)|incompatible types|cannot convert"
-	_ = len(x.slice) || x == nil // ERROR "invalid operation: .+ \(operator \|\| not defined on int\)|incompatible types|cannot convert"
-	_ = x == nil && len(x.slice) // ERROR "invalid operation: .+ \(operator && not defined on int\)|incompatible types|cannot convert"
-	_ = len(x.slice) && x == nil // ERROR "invalid operation: .+ \(operator && not defined on int\)|incompatible types|cannot convert"
+	_ = x == nil || len(x.slice) // ERROR "invalid operation: .+ \(operator \|\| not defined on int\)|incompatible types|mismatched types untyped bool and int"
+	_ = len(x.slice) || x == nil // ERROR "invalid operation: .+ \(operator \|\| not defined on int\)|incompatible types|mismatched types int and untyped bool"
+	_ = x == nil && len(x.slice) // ERROR "invalid operation: .+ \(operator && not defined on int\)|incompatible types|mismatched types untyped bool and int"
+	_ = len(x.slice) && x == nil // ERROR "invalid operation: .+ \(operator && not defined on int\)|incompatible types|mismatched types int and untyped bool"
 }
diff --git a/test/fixedbugs/issue43762.go b/test/fixedbugs/issue43762.go
index 9f7682ad6a..bf950c8f52 100644
--- a/test/fixedbugs/issue43762.go
+++ b/test/fixedbugs/issue43762.go
@@ -6,6 +6,6 @@
 
 package p
 
-var _ = true == '\\' // ERROR "invalid operation: true == '\\\\'|cannot convert true"
-var _ = true == '\'' // ERROR "invalid operation: true == '\\''|cannot convert true"
-var _ = true == '\n' // ERROR "invalid operation: true == '\\n'|cannot convert true"
+var _ = true == '\\' // ERROR "invalid operation: (cannot compare true)|(true) == '\\\\' \(mismatched types untyped bool and untyped rune\)"
+var _ = true == '\'' // ERROR "invalid operation: (cannot compare true)|(true) == '\\'' \(mismatched types untyped bool and untyped rune\)"
+var _ = true == '\n' // ERROR "invalid operation: (cannot compare true)|(true) == '\\n' \(mismatched types untyped bool and untyped rune\)"
diff --git a/test/fixedbugs/issue46749.go b/test/fixedbugs/issue46749.go
index 63ed19795e..faf1f884a6 100644
--- a/test/fixedbugs/issue46749.go
+++ b/test/fixedbugs/issue46749.go
@@ -14,13 +14,13 @@ var iface interface{}
 var (
 	_ = "" + b   // ERROR "invalid operation.*mismatched types.*untyped string and bool"
 	_ = "" + i   // ERROR "invalid operation.*mismatched types.*untyped string and int"
-	_ = "" + nil // ERROR "invalid operation.*mismatched types.*untyped string and nil"
+	_ = "" + nil // ERROR "invalid operation.*mismatched types.*untyped string and nil|(untyped nil)"
 )
 
 var (
 	_ = s + false // ERROR "invalid operation.*mismatched types.*string and untyped bool"
 	_ = s + 1     // ERROR "invalid operation.*mismatched types.*string and untyped int"
-	_ = s + nil   // ERROR "invalid operation.*mismatched types.*string and nil"
+	_ = s + nil   // ERROR "invalid operation.*mismatched types.*string and nil|(untyped nil)"
 )
 
 var (
@@ -31,7 +31,7 @@ var (
 var (
 	_ = b + 1         // ERROR "invalid operation.*mismatched types.*bool and untyped int"
 	_ = i + false     // ERROR "invalid operation.*mismatched types.*int and untyped bool"
-	_ = iface + 1     // ERROR "invalid operation.*mismatched types.*interface {} and int"
-	_ = iface + 1.0   // ERROR "invalid operation.*mismatched types.*interface {} and float64"
-	_ = iface + false // ERROR "invalid operation.*mismatched types.*interface {} and bool"
+	_ = iface + 1     // ERROR "invalid operation.*mismatched types.*interface *{} and int"
+	_ = iface + 1.0   // ERROR "invalid operation.*mismatched types.*interface *{} and float64"
+	_ = iface + false // ERROR "invalid operation.*mismatched types.*interface *{} and bool"
 )
diff --git a/test/run.go b/test/run.go
index 1273b8edd6..656519e301 100644
--- a/test/run.go
+++ b/test/run.go
@@ -2089,7 +2089,6 @@ var excludedFiles = map[string]bool{
 	"fixedbugs/issue7525d.go":  true, // types2 reports init cycle error on different line - ok otherwise
 	"fixedbugs/issue7525e.go":  true, // types2 reports init cycle error on different line - ok otherwise
 	"fixedbugs/issue7525.go":   true, // types2 reports init cycle error on different line - ok otherwise
-	"fixedbugs/issue46749.go":  true, // types2 reports can not convert error instead of type mismatched
 	"fixedbugs/issue9691.go":   true, // "cannot assign to int(.autotmp_4)" (probably irgen's fault)
 
 	// tests that rely on -m diagnostics, which currently differ with -G=3