From b004c739b525d354ea62f5caadd962de4569d96e Mon Sep 17 00:00:00 2001 From: Robert Griesemer Date: Tue, 21 Jun 2022 15:56:16 -0700 Subject: [PATCH] go/types, types2: fix parameter order dependence in type inference If we have more than two function arguments to a generic function, we may have arguments with named and unnamed types. If that is the case, permutate params and args such that the arguments with named types are first in the list. This way, independent of parameter ordering, the type inference will produce the same result. This extra step is not explicitly outlined in the spec yet but we all agree that (parameter) order independence is an invariant that we should uphold for type inference. As we move towards less operational and more descriptive rules for type inference, we will incorporate this property as well. The actual fix for this bug existed before 1.18 but was not enabled. This CL merely enables the fix (switches a flag) and adjusts some tests. Fixes #43056. Change-Id: Ie4e40cf8438dfd82fa94b78068e4f6f6f53f83e6 Reviewed-on: https://go-review.googlesource.com/c/go/+/413459 Reviewed-by: Ian Lance Taylor Reviewed-by: Robert Griesemer --- src/cmd/compile/internal/types2/infer.go | 7 ++----- .../compile/internal/types2/testdata/examples/functions.go | 2 +- .../internal/types2/testdata/fixedbugs/issue43056.go | 4 ++-- src/go/types/infer.go | 7 ++----- src/go/types/testdata/examples/functions.go | 2 +- src/go/types/testdata/fixedbugs/issue43056.go | 4 ++-- 6 files changed, 10 insertions(+), 16 deletions(-) diff --git a/src/cmd/compile/internal/types2/infer.go b/src/cmd/compile/internal/types2/infer.go index b0c6a4fcea..8425cd6034 100644 --- a/src/cmd/compile/internal/types2/infer.go +++ b/src/cmd/compile/internal/types2/infer.go @@ -128,11 +128,8 @@ func (check *Checker) infer(pos syntax.Pos, tparams []*TypeParam, targs []Type, // named and unnamed types are passed to parameters with identical type, different types // (named vs underlying) may be inferred depending on the order of the arguments. // By ensuring that named types are seen first, order dependence is avoided and unification - // succeeds where it can. - // - // This code is disabled for now pending decision whether we want to address cases like - // these and make the spec on type inference more complicated (see issue #43056). - const enableArgSorting = false + // succeeds where it can (issue #43056). + const enableArgSorting = true if m := len(args); m >= 2 && enableArgSorting { // Determine indices of arguments with named and unnamed types. var named, unnamed []int diff --git a/src/cmd/compile/internal/types2/testdata/examples/functions.go b/src/cmd/compile/internal/types2/testdata/examples/functions.go index ef8953cb43..d50f79d11f 100644 --- a/src/cmd/compile/internal/types2/testdata/examples/functions.go +++ b/src/cmd/compile/internal/types2/testdata/examples/functions.go @@ -182,7 +182,7 @@ func _() { type myString string var s1 string g3(nil, "1", myString("2"), "3") - g3(&s1, "1", myString /* ERROR does not match */ ("2"), "3") + g3(& /* ERROR does not match */ s1, "1", myString("2"), "3") _ = s1 type myStruct struct{x int} diff --git a/src/cmd/compile/internal/types2/testdata/fixedbugs/issue43056.go b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue43056.go index 35c7ef592d..8ff4e7f9b4 100644 --- a/src/cmd/compile/internal/types2/testdata/fixedbugs/issue43056.go +++ b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue43056.go @@ -14,7 +14,7 @@ func _() { var j func(F) f(i, j) - // f(j, i) // disabled for now + f(j, i) } // example from issue @@ -27,5 +27,5 @@ func _() { var j interface{ Equal(I) bool } g(i, j) - // g(j, i) // disabled for now + g(j, i) } diff --git a/src/go/types/infer.go b/src/go/types/infer.go index 1aa2612638..768efbf73b 100644 --- a/src/go/types/infer.go +++ b/src/go/types/infer.go @@ -128,11 +128,8 @@ func (check *Checker) infer(posn positioner, tparams []*TypeParam, targs []Type, // named and unnamed types are passed to parameters with identical type, different types // (named vs underlying) may be inferred depending on the order of the arguments. // By ensuring that named types are seen first, order dependence is avoided and unification - // succeeds where it can. - // - // This code is disabled for now pending decision whether we want to address cases like - // these and make the spec on type inference more complicated (see issue #43056). - const enableArgSorting = false + // succeeds where it can (issue #43056). + const enableArgSorting = true if m := len(args); m >= 2 && enableArgSorting { // Determine indices of arguments with named and unnamed types. var named, unnamed []int diff --git a/src/go/types/testdata/examples/functions.go b/src/go/types/testdata/examples/functions.go index 0af77267c5..1d30075c7c 100644 --- a/src/go/types/testdata/examples/functions.go +++ b/src/go/types/testdata/examples/functions.go @@ -182,7 +182,7 @@ func _() { type myString string var s1 string g3(nil, "1", myString("2"), "3") - g3(&s1, "1", myString /* ERROR does not match */ ("2"), "3") + g3(& /* ERROR does not match */ s1, "1", myString("2"), "3") type myStruct struct{x int} var s2 myStruct diff --git a/src/go/types/testdata/fixedbugs/issue43056.go b/src/go/types/testdata/fixedbugs/issue43056.go index 35c7ef592d..8ff4e7f9b4 100644 --- a/src/go/types/testdata/fixedbugs/issue43056.go +++ b/src/go/types/testdata/fixedbugs/issue43056.go @@ -14,7 +14,7 @@ func _() { var j func(F) f(i, j) - // f(j, i) // disabled for now + f(j, i) } // example from issue @@ -27,5 +27,5 @@ func _() { var j interface{ Equal(I) bool } g(i, j) - // g(j, i) // disabled for now + g(j, i) } -- 2.48.1