go/types, types2: better error messages for invalid calls

Rather than reporting "non-function" for an invalid type parameter,
report which type in the type parameter's type set is not a function.

Change-Id: I8beec25cc337bae8e03d23e62d97aa82db46bab4
Reviewed-on: https://go-review.googlesource.com/c/go/+/654475
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

diff --git a/src/cmd/compile/internal/types2/call.go b/src/cmd/compile/internal/types2/call.go
index bfce23655567efdbaf7ef28de5f7d84849d9d3b4..e64d6b6adfb3dbf3796790654810d18dd96667c7 100644 (file)
--- a/src/cmd/compile/internal/types2/call.go
+++ b/src/cmd/compile/internal/types2/call.go
@@ -244,19 +244,19 @@ func (check *Checker) callExpr(x *operand, call *syntax.CallExpr) exprKind {
 
        // If the operand type is a type parameter, all types in its type set
        // must have a common underlying type, which must be a signature.
-       // TODO(gri) use commonUnder condition for better error message
-       u, err := commonUnder(x.typ, nil)
-       sig, _ := u.(*Signature)
-       if sig == nil {
-               if err != nil {
-                       check.errorf(x, InvalidCall, invalidOp+"cannot call %s: %s", x, err.format(check))
-               } else {
-                       check.errorf(x, InvalidCall, invalidOp+"cannot call non-function %s", x)
+       u, err := commonUnder(x.typ, func(t, u Type) *errorCause {
+               if _, ok := u.(*Signature); u != nil && !ok {
+                       return newErrorCause("%s is not a function", t)
                }
+               return nil
+       })
+       if err != nil {
+               check.errorf(x, InvalidCall, invalidOp+"cannot call %s: %s", x, err.format(check))
                x.mode = invalid
                x.expr = call
                return statement
        }
+       sig := u.(*Signature) // u must be a signature per the commonUnder condition
 
        // Capture wasGeneric before sig is potentially instantiated below.
        wasGeneric := sig.TypeParams().Len() > 0

diff --git a/src/go/types/call.go b/src/go/types/call.go
index 0d84a8dc677021b64bb7dd676ad1b0820dbcb767..33cb5fc9dbe944cc3c177b07d6353ad4994bcc59 100644 (file)
--- a/src/go/types/call.go
+++ b/src/go/types/call.go
@@ -246,19 +246,19 @@ func (check *Checker) callExpr(x *operand, call *ast.CallExpr) exprKind {
 
        // If the operand type is a type parameter, all types in its type set
        // must have a common underlying type, which must be a signature.
-       // TODO(gri) use commonUnder condition for better error message
-       u, err := commonUnder(x.typ, nil)
-       sig, _ := u.(*Signature)
-       if sig == nil {
-               if err != nil {
-                       check.errorf(x, InvalidCall, invalidOp+"cannot call %s: %s", x, err.format(check))
-               } else {
-                       check.errorf(x, InvalidCall, invalidOp+"cannot call non-function %s", x)
+       u, err := commonUnder(x.typ, func(t, u Type) *errorCause {
+               if _, ok := u.(*Signature); u != nil && !ok {
+                       return newErrorCause("%s is not a function", t)
                }
+               return nil
+       })
+       if err != nil {
+               check.errorf(x, InvalidCall, invalidOp+"cannot call %s: %s", x, err.format(check))
                x.mode = invalid
                x.expr = call
                return statement
        }
+       sig := u.(*Signature) // u must be a signature per the commonUnder condition
 
        // Capture wasGeneric before sig is potentially instantiated below.
        wasGeneric := sig.TypeParams().Len() > 0

diff --git a/src/internal/types/testdata/check/lookup1.go b/src/internal/types/testdata/check/lookup1.go
index d9f90ba46a0716e531a8bec2f4bc203d7344f73b..669767b27876dcaa3489dc4acfaa9bc5d4c15f95 100644 (file)
--- a/src/internal/types/testdata/check/lookup1.go
+++ b/src/internal/types/testdata/check/lookup1.go
@@ -11,7 +11,7 @@ func _() {
                x, aBc int
        }
        _ = s.x
-       _ = s /* ERROR "invalid operation: cannot call non-function s.x (variable of type int)" */ .x()
+       _ = s /* ERROR "invalid operation: cannot call s.x (variable of type int): int is not a function" */ .x()
        _ = s.X // ERROR "s.X undefined (type struct{x int; aBc int} has no field or method X, but does have field x)"
        _ = s.X /* ERROR "s.X undefined (type struct{x int; aBc int} has no field or method X, but does have field x)" */ ()
 
@@ -26,7 +26,7 @@ func _() {
        }
        var s S
        _ = s.x
-       _ = s /* ERROR "invalid operation: cannot call non-function s.x (variable of type int)" */ .x()
+       _ = s /* ERROR "invalid operation: cannot call s.x (variable of type int): int is not a function" */ .x()
        _ = s.X // ERROR "s.X undefined (type S has no field or method X, but does have field x)"
        _ = s.X /* ERROR "s.X undefined (type S has no field or method X, but does have field x)" */ ()
 }
@@ -77,9 +77,9 @@ func _[P any](x P) {
 }
 
 func _[P int](x P) {
-       x /* ERROR "cannot call non-function x (variable of type P constrained by int)" */ ()
+       x /* ERROR "cannot call x (variable of type P constrained by int): int is not a function" */ ()
 }
 
 func _[P int | string](x P) {
-       x /* ERROR "cannot call x (variable of type P constrained by int | string): int and string have different underlying types" */ ()
+       x /* ERROR "cannot call x (variable of type P constrained by int | string): int is not a function" */ ()
 }

diff --git a/src/internal/types/testdata/fixedbugs/issue49482.go b/src/internal/types/testdata/fixedbugs/issue49482.go
index 7139baebc0cb66abc6e5944717e6fca45158c218..bc6b60099cf5aee1919cccd5f1809c4a7c06c484 100644 (file)
--- a/src/internal/types/testdata/fixedbugs/issue49482.go
+++ b/src/internal/types/testdata/fixedbugs/issue49482.go
@@ -13,7 +13,7 @@ const P = 2 // declare P to avoid noisy 'undefined' errors below.
 
 // The following parse as invalid array types due to parsing ambiguitiues.
 type _ [P *int /* ERROR "int (type) is not an expression" */ ]int
-type _ [P /* ERROR "non-function P" */ (*int)]int
+type _ [P /* ERROR "cannot call P (untyped int constant 2): untyped int is not a function" */ (*int)]int
 
 // Adding a trailing comma or an enclosing interface resolves the ambiguity.
 type _[P *int,] int

diff --git a/test/fixedbugs/issue17038.go b/test/fixedbugs/issue17038.go
index 1b65ffc1f0eec68f2fdafe403bd64b4054368e15..32d3c9320b43d186284709df085cd8129011c5be 100644 (file)
--- a/test/fixedbugs/issue17038.go
+++ b/test/fixedbugs/issue17038.go
@@ -6,4 +6,4 @@
 
 package main
 
-const A = complex(0()) // ERROR "cannot call non-function"
+const A = complex(0()) // ERROR "cannot call .* not a function"

diff --git a/test/fixedbugs/issue22822.go b/test/fixedbugs/issue22822.go
index 9483c9cab0ab1c7b6b401531dea514cc18402bf9..c760a8b9edb653196630a710ce011e0d2582ff0d 100644 (file)
--- a/test/fixedbugs/issue22822.go
+++ b/test/fixedbugs/issue22822.go
@@ -13,7 +13,7 @@ func F() {
        slice := []int{1, 2, 3}
        _ = slice
        len := int(2)
-       println(len(slice)) // ERROR "cannot call non-function len .type int., declared at LINE-1|expected function|cannot call non-function len"
+       println(len(slice)) // ERROR "cannot call non-function len .type int., declared at LINE-1|expected function|cannot call len"
        const iota = 1
-       println(iota(slice)) // ERROR "cannot call non-function iota .type int., declared at LINE-1|expected function|cannot call non-function iota"
+       println(iota(slice)) // ERROR "cannot call non-function iota .type int., declared at LINE-1|expected function|cannot call iota"
 }

diff --git a/test/fixedbugs/issue27356.go b/test/fixedbugs/issue27356.go
index c3e686df339544ff8f7b6954a35420a5ca310120..8be5d04af732a6b7377941d99e9d2886fb60d24c 100644 (file)
--- a/test/fixedbugs/issue27356.go
+++ b/test/fixedbugs/issue27356.go
@@ -11,9 +11,9 @@ package p
 var a = []int{1,2,3}
 
 func _(len int) {
-       _ =  len(a) // ERROR "cannot call non-function|expected function"
+       _ =  len(a) // ERROR "cannot call|expected function"
 }
 
 var cap = false
-var _ = cap(a) // ERROR "cannot call non-function|expected function"
+var _ = cap(a) // ERROR "cannot call|expected function"