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go/types, types2: flip message contents for reverse type inference errors

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Add a new flag 'reverse' to control the formatting of type inference
error messages.

This change only impacts error messages.

Fixes #60747.

Change-Id: I81e13075e3157252ccc09f358bd29bd676c34499
Reviewed-on: https://go-review.googlesource.com/c/go/+/549055
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Robert Griesemer 2023-12-11 17:54:18 -08:00 committed by Gopher Robot
parent 2643a59172
commit 0ac1e3b245
7 changed files with 34 additions and 18 deletions
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6
src/cmd/compile/internal/types2/call.go
View File

@ -87,6 +87,7 @@ func (check *Checker) funcInst(T *target, pos syntax.Pos, x *operand, inst *synt
//
var args []*operand
var params []*Var
var reverse bool
if T != nil && sig.tparams != nil {
if !versionErr && !check.allowVersion(check.pkg, instErrPos, go1_21) {
if inst != nil {
@ -102,13 +103,14 @@ func (check *Checker) funcInst(T *target, pos syntax.Pos, x *operand, inst *synt
// that makes sense when reported in error messages from infer, below.
expr := syntax.NewName(x.Pos(), T.desc)
args = []*operand{{mode: value, expr: expr, typ: T.sig}}
reverse = true
}
// Rename type parameters to avoid problems with recursive instantiations.
// Note that NewTuple(params...) below is (*Tuple)(nil) if len(params) == 0, as desired.
tparams, params2 := check.renameTParams(pos, sig.TypeParams().list(), NewTuple(params...))
targs = check.infer(pos, tparams, targs, params2.(*Tuple), args)
targs = check.infer(pos, tparams, targs, params2.(*Tuple), args, reverse)
if targs == nil {
// error was already reported
x.mode = invalid
@ -608,7 +610,7 @@ func (check *Checker) arguments(call *syntax.CallExpr, sig *Signature, targs []T
// infer missing type arguments of callee and function arguments
if len(tparams) > 0 {
targs = check.infer(call.Pos(), tparams, targs, sigParams, args)
targs = check.infer(call.Pos(), tparams, targs, sigParams, args, false)
if targs == nil {
// TODO(gri) If infer inferred the first targs[:n], consider instantiating
// the call signature for better error messages/gopls behavior.

10
src/cmd/compile/internal/types2/infer.go
View File

@ -24,9 +24,11 @@ const enableReverseTypeInference = true // disable for debugging
// based on the given type parameters tparams, type arguments targs, function parameters params, and
// function arguments args, if any. There must be at least one type parameter, no more type arguments
// than type parameters, and params and args must match in number (incl. zero).
// If reverse is set, an error message's contents are reversed for a better error message for some
// errors related to reverse type inference (where the function call is synthetic).
// If successful, infer returns the complete list of given and inferred type arguments, one for each
// type parameter. Otherwise the result is nil and appropriate errors will be reported.
func (check *Checker) infer(pos syntax.Pos, tparams []*TypeParam, targs []Type, params *Tuple, args []*operand) (inferred []Type) {
func (check *Checker) infer(pos syntax.Pos, tparams []*TypeParam, targs []Type, params *Tuple, args []*operand, reverse bool) (inferred []Type) {
// Don't verify result conditions if there's no error handler installed:
// in that case, an error leads to an exit panic and the result value may
// be incorrect. But in that case it doesn't matter because callers won't
@ -137,7 +139,11 @@ func (check *Checker) infer(pos syntax.Pos, tparams []*TypeParam, targs []Type,
// InvalidTypeArg). We can't differentiate these cases, so fall back on
// the more general CannotInferTypeArgs.
if inferred != tpar {
check.errorf(arg, CannotInferTypeArgs, "type %s of %s does not match inferred type %s for %s", targ, arg.expr, inferred, tpar)
if reverse {
check.errorf(arg, CannotInferTypeArgs, "inferred type %s for %s does not match type %s of %s", inferred, tpar, targ, arg.expr)
} else {
check.errorf(arg, CannotInferTypeArgs, "type %s of %s does not match inferred type %s for %s", targ, arg.expr, inferred, tpar)
}
} else {
check.errorf(arg, CannotInferTypeArgs, "type %s of %s does not match %s", targ, arg.expr, tpar)
}

6
src/go/types/call.go
View File

@ -89,6 +89,7 @@ func (check *Checker) funcInst(T *target, pos token.Pos, x *operand, ix *typepar
//
var args []*operand
var params []*Var
var reverse bool
if T != nil && sig.tparams != nil {
if !versionErr && !check.allowVersion(check.pkg, instErrPos, go1_21) {
if ix != nil {
@ -105,13 +106,14 @@ func (check *Checker) funcInst(T *target, pos token.Pos, x *operand, ix *typepar
expr := ast.NewIdent(T.desc)
expr.NamePos = x.Pos() // correct position
args = []*operand{{mode: value, expr: expr, typ: T.sig}}
reverse = true
}
// Rename type parameters to avoid problems with recursive instantiations.
// Note that NewTuple(params...) below is (*Tuple)(nil) if len(params) == 0, as desired.
tparams, params2 := check.renameTParams(pos, sig.TypeParams().list(), NewTuple(params...))
targs = check.infer(atPos(pos), tparams, targs, params2.(*Tuple), args)
targs = check.infer(atPos(pos), tparams, targs, params2.(*Tuple), args, reverse)
if targs == nil {
// error was already reported
x.mode = invalid
@ -610,7 +612,7 @@ func (check *Checker) arguments(call *ast.CallExpr, sig *Signature, targs []Type
// infer missing type arguments of callee and function arguments
if len(tparams) > 0 {
targs = check.infer(call, tparams, targs, sigParams, args)
targs = check.infer(call, tparams, targs, sigParams, args, false)
if targs == nil {
// TODO(gri) If infer inferred the first targs[:n], consider instantiating
// the call signature for better error messages/gopls behavior.

10
src/go/types/infer.go
View File

@ -26,9 +26,11 @@ const enableReverseTypeInference = true // disable for debugging
// based on the given type parameters tparams, type arguments targs, function parameters params, and
// function arguments args, if any. There must be at least one type parameter, no more type arguments
// than type parameters, and params and args must match in number (incl. zero).
// If reverse is set, an error message's contents are reversed for a better error message for some
// errors related to reverse type inference (where the function call is synthetic).
// If successful, infer returns the complete list of given and inferred type arguments, one for each
// type parameter. Otherwise the result is nil and appropriate errors will be reported.
func (check *Checker) infer(posn positioner, tparams []*TypeParam, targs []Type, params *Tuple, args []*operand) (inferred []Type) {
func (check *Checker) infer(posn positioner, tparams []*TypeParam, targs []Type, params *Tuple, args []*operand, reverse bool) (inferred []Type) {
// Don't verify result conditions if there's no error handler installed:
// in that case, an error leads to an exit panic and the result value may
// be incorrect. But in that case it doesn't matter because callers won't
@ -139,7 +141,11 @@ func (check *Checker) infer(posn positioner, tparams []*TypeParam, targs []Type,
// InvalidTypeArg). We can't differentiate these cases, so fall back on
// the more general CannotInferTypeArgs.
if inferred != tpar {
check.errorf(arg, CannotInferTypeArgs, "type %s of %s does not match inferred type %s for %s", targ, arg.expr, inferred, tpar)
if reverse {
check.errorf(arg, CannotInferTypeArgs, "inferred type %s for %s does not match type %s of %s", inferred, tpar, targ, arg.expr)
} else {
check.errorf(arg, CannotInferTypeArgs, "type %s of %s does not match inferred type %s for %s", targ, arg.expr, inferred, tpar)
}
} else {
check.errorf(arg, CannotInferTypeArgs, "type %s of %s does not match %s", targ, arg.expr, tpar)
}

14
src/internal/types/testdata/examples/inference2.go vendored
View File

@ -27,9 +27,9 @@ var (
_ func(int) int = f3[int]
v6 func(int, int) = f4
v7 func(int, string) = f4 // ERROR "type func(int, string) of v7 does not match inferred type func(int, int) for func(P, P)"
v7 func(int, string) = f4 // ERROR "inferred type func(int, int) for func(P, P) does not match type func(int, string) of v7"
v8 func(int) []int = f5
v9 func(string) []int = f5 // ERROR "type func(string) []int of v9 does not match inferred type func(string) []string for func(P) []P"
v9 func(string) []int = f5 // ERROR "inferred type func(string) []string for func(P) []P does not match type func(string) []int of v9"
_, _ func(int) = f1, f1
_, _ func(int) = f1, f2 // ERROR "cannot infer P"
@ -49,13 +49,13 @@ func _() {
v5 = f3[int]
v6 = f4
v7 = f4 // ERROR "type func(int, string) of v7 does not match inferred type func(int, int) for func(P, P)"
v7 = f4 // ERROR "inferred type func(int, int) for func(P, P) does not match type func(int, string) of v7"
v8 = f5
v9 = f5 // ERROR "type func(string) []int of v9 does not match inferred type func(string) []string for func(P) []P"
v9 = f5 // ERROR "inferred type func(string) []string for func(P) []P does not match type func(string) []int of v9"
// non-trivial LHS
var a [2]func(string) []int
a[0] = f5 // ERROR "type func(string) []int of a[0] does not match inferred type func(string) []string for func(P) []P"
a[0] = f5 // ERROR "inferred type func(string) []string for func(P) []P does not match type func(string) []int of a[0]"
}
// Return statements
@ -66,11 +66,11 @@ func _() func(int) int { return f3[int] }
func _() func(int, int) { return f4 }
func _() func(int, string) {
return f4 /* ERROR "type func(int, string) of result variable does not match inferred type func(int, int) for func(P, P)" */
return f4 /* ERROR "inferred type func(int, int) for func(P, P) does not match type func(int, string) of result variable" */
}
func _() func(int) []int { return f5 }
func _() func(string) []int {
return f5 /* ERROR "type func(string) []int of result variable does not match inferred type func(string) []string for func(P) []P" */
return f5 /* ERROR "inferred type func(string) []string for func(P) []P does not match type func(string) []int of result variable" */
}
func _() (_, _ func(int)) { return f1, f1 }

2
src/internal/types/testdata/fixedbugs/issue60688.go vendored
View File

@ -13,4 +13,4 @@ func g[P any](P, string) {}
// be identical to match).
// The result is an error from type inference, rather than an
// error from an assignment mismatch.
var f func(int, String) = g // ERROR "type func(int, String) of f does not match inferred type func(int, string) for func(P, string)"
var f func(int, String) = g // ERROR "inferred type func(int, string) for func(P, string) does not match type func(int, String) of f"

4
src/internal/types/testdata/fixedbugs/issue60747.go vendored
View File

@ -6,8 +6,8 @@ package p
func f[P any](P) P { panic(0) }
var v func(string) int = f // ERROR "type func(string) int of v does not match inferred type func(string) string for func(P) P"
var v func(string) int = f // ERROR "inferred type func(string) string for func(P) P does not match type func(string) int of v"
func _() func(string) int {
return f // ERROR "type func(string) int of result variable does not match inferred type func(string) string for func(P) P"
return f // ERROR "inferred type func(string) string for func(P) P does not match type func(string) int of result variable"
}