go/types: better error for assignment count mismatches

This matches the error message of cmd/compile (for assignments).

Change-Id: I42a428f5d72f034e7b7e97b090a929e317e812af
Reviewed-on: https://go-review.googlesource.com/38315
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>

src/go/types/assignments.go

@@ -219,7 +219,7 @@ func (check *Checker) initVars(lhs []*Var, rhs []ast.Expr, returnPos token.Pos)
 			check.errorf(returnPos, "wrong number of return values (want %d, got %d)", l, r)
 			return
 		}
-		check.errorf(rhs[0].Pos(), "assignment count mismatch (%d vs %d)", l, r)
+		check.errorf(rhs[0].Pos(), "cannot initialize %d variables with %d values", l, r)
 		return
 	}
 
@@ -253,7 +253,7 @@ func (check *Checker) assignVars(lhs, rhs []ast.Expr) {
 	}
 	if l != r {
 		check.useGetter(get, r)
-		check.errorf(rhs[0].Pos(), "assignment count mismatch (%d vs %d)", l, r)
+		check.errorf(rhs[0].Pos(), "cannot assign %d values to %d variables", r, l)
 		return
 	}
 

src/go/types/testdata/decls1.src

@@ -78,7 +78,7 @@ var (
 	u2 = iface.([]int)
 	u3 = iface.(a /* ERROR "not a type" */ )
 	u4, ok = iface.(int)
-	u5, ok2, ok3 = iface /* ERROR "assignment count mismatch" */ .(int)
+	u5, ok2, ok3 = iface /* ERROR "cannot initialize" */ .(int)
 )
 
 // Constant expression initializations

src/go/types/testdata/issues.src

@@ -98,8 +98,8 @@ func issue10979() {
 // issue11347
 // These should not crash.
 var a1, b1 /* ERROR cycle */ , c1 /* ERROR cycle */ b1 = 0 > 0<<""[""[c1]]>c1
-var a2, b2 /* ERROR cycle */ = 0 /* ERROR mismatch */ /* ERROR mismatch */ > 0<<""[b2]
-var a3, b3 /* ERROR cycle */ = int /* ERROR mismatch */ /* ERROR mismatch */ (1<<""[b3])
+var a2, b2 /* ERROR cycle */ = 0 /* ERROR cannot initialize */ /* ERROR cannot initialize */ > 0<<""[b2]
+var a3, b3 /* ERROR cycle */ = int /* ERROR cannot initialize */ /* ERROR cannot initialize */ (1<<""[b3])
 
 // issue10260
 // Check that error messages explain reason for interface assignment failures.

src/go/types/testdata/stmt0.src

@@ -15,19 +15,19 @@ func assignments0() (int, int) {
 	f3 := func() (int, int, int) { return 1, 2, 3 }
 
 	a, b, c = 1, 2, 3
-	a, b, c = 1 /* ERROR "assignment count mismatch" */ , 2
-	a, b, c = 1 /* ERROR "assignment count mismatch" */ , 2, 3, 4
+	a, b, c = 1 /* ERROR "cannot assign [1-9]+ values to [1-9]+ variables" */ , 2
+	a, b, c = 1 /* ERROR "cannot assign [1-9]+ values to [1-9]+ variables" */ , 2, 3, 4
 	_, _, _ = a, b, c
 
 	a = f0 /* ERROR "used as value" */ ()
 	a = f1()
-	a = f2 /* ERROR "assignment count mismatch" */ ()
+	a = f2 /* ERROR "cannot assign [1-9]+ values to [1-9]+ variables" */ ()
 	a, b = f2()
-	a, b, c = f2 /* ERROR "assignment count mismatch" */ ()
+	a, b, c = f2 /* ERROR "cannot assign [1-9]+ values to [1-9]+ variables" */ ()
 	a, b, c = f3()
-	a, b = f3 /* ERROR "assignment count mismatch" */ ()
+	a, b = f3 /* ERROR "cannot assign [1-9]+ values to [1-9]+ variables" */ ()
 
-	a, b, c = <- /* ERROR "assignment count mismatch" */ ch
+	a, b, c = <- /* ERROR "cannot assign [1-9]+ values to [1-9]+ variables" */ ch
 
 	return /* ERROR "wrong number of return values" */
 	return /* ERROR "wrong number of return values" */ 1
@@ -43,7 +43,7 @@ func assignments1() {
 	c = s /* ERROR "cannot use .* in assignment" */
 	s = b /* ERROR "cannot use .* in assignment" */
 
-	v0, v1, v2 := 1 /* ERROR "mismatch" */ , 2, 3, 4
+	v0, v1, v2 := 1 /* ERROR "cannot initialize" */ , 2, 3, 4
 	_, _, _ = v0, v1, v2
 
 	b = true
@@ -108,7 +108,7 @@ func assignments2() {
 	s, b = m["foo"]
 	_, d = m["bar"]
 	m["foo"] = nil
-	m["foo"] = nil /* ERROR assignment count mismatch */ , false
+	m["foo"] = nil /* ERROR cannot assign [1-9]+ values to [1-9]+ variables */ , false
 	_ = append(m["foo"])
 	_ = append(m["foo"], true)
 
@@ -116,12 +116,12 @@ func assignments2() {
 	_, b = <-c
 	_, d = <-c
 	<- /* ERROR cannot assign */ c = 0
-	<-c = 0 /* ERROR assignment count mismatch */ , false
+	<-c = 0 /* ERROR cannot assign [1-9]+ values to [1-9]+ variables */ , false
 
 	var x interface{}
 	_, b = x.(int)
 	x /* ERROR cannot assign */ .(int) = 0
-	x.(int) = 0 /* ERROR assignment count mismatch */ , false
+	x.(int) = 0 /* ERROR cannot assign [1-9]+ values to [1-9]+ variables */ , false
 
 	assignments2 /* ERROR used as value */ () = nil
 	int /* ERROR not an expression */ = 0

src/go/types/testdata/vardecl.src

@@ -28,39 +28,39 @@ var _ = f /* ERROR "used as value" */ ()
 // Identifier and expression arity must match.
 var _, _ = 1, 2
 var _ = 1, 2 /* ERROR "extra init expr 2" */
-var _, _ = 1 /* ERROR "assignment count mismatch" */
+var _, _ = 1 /* ERROR "cannot initialize [0-9]+ variables with [0-9]+ values" */
 var _, _, _ /* ERROR "missing init expr for _" */ = 1, 2
 
 var _ = g /* ERROR "2-valued g" */ ()
 var _, _ = g()
-var _, _, _ = g /* ERROR "assignment count mismatch" */ ()
+var _, _, _ = g /* ERROR "cannot initialize [0-9]+ variables with [0-9]+ values" */ ()
 
 var _ = m["foo"]
 var _, _ = m["foo"]
-var _, _, _ = m  /* ERROR "assignment count mismatch" */ ["foo"]
+var _, _, _ = m  /* ERROR "cannot initialize [0-9]+ variables with [0-9]+ values" */ ["foo"]
 
 var _, _ int = 1, 2
 var _ int = 1, 2 /* ERROR "extra init expr 2" */
-var _, _ int = 1 /* ERROR "assignment count mismatch" */
+var _, _ int = 1 /* ERROR "cannot initialize [0-9]+ variables with [0-9]+ values" */
 var _, _, _ /* ERROR "missing init expr for _" */ int = 1, 2
 
 var (
 	_, _ = 1, 2
 	_ = 1, 2 /* ERROR "extra init expr 2" */
-	_, _ = 1 /* ERROR "assignment count mismatch" */
+	_, _ = 1 /* ERROR "cannot initialize [0-9]+ variables with [0-9]+ values" */
 	_, _, _ /* ERROR "missing init expr for _" */ = 1, 2
 
 	_ = g /* ERROR "2-valued g" */ ()
 	_, _ = g()
-	_, _, _ = g /* ERROR "assignment count mismatch" */ ()
+	_, _, _ = g /* ERROR "cannot initialize [0-9]+ variables with [0-9]+ values" */ ()
 
 	_ = m["foo"]
 	_, _ = m["foo"]
-	_, _, _ = m /* ERROR "assignment count mismatch" */ ["foo"]
+	_, _, _ = m /* ERROR "cannot initialize [0-9]+ variables with [0-9]+ values" */ ["foo"]
 
 	_, _ int = 1, 2
 	_ int = 1, 2 /* ERROR "extra init expr 2" */
-	_, _ int = 1 /* ERROR "assignment count mismatch" */
+	_, _ int = 1 /* ERROR "cannot initialize [0-9]+ variables with [0-9]+ values" */
 	_, _, _ /* ERROR "missing init expr for _" */ int = 1, 2
 )
 
@@ -155,7 +155,7 @@ func (r T) _(a, b, c int) (u, v, w int) {
 func _() {
 	var a, b, c int
 	var x, y int
-	x, y = a /* ERROR assignment count mismatch */ , b, c
+	x, y = a /* ERROR cannot assign [0-9]+ values to [0-9]+ variables */ , b, c
 	_ = x
 	_ = y
 }