From: Robert Griesemer Date: Wed, 20 Oct 2021 01:09:30 +0000 (-0700) Subject: cmd/compile/internal/types2: more detailed error messages for generic conversions X-Git-Tag: go1.18beta1~798 X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=5d414d180bfb631d3835f819f7f524ec271f11eb;p=gostls13.git cmd/compile/internal/types2: more detailed error messages for generic conversions - slightly refactor convertibleTo and convertibleToImpl - provide ability to return a conversion failure cause - add detailed cause for generic conversions For #47150. Change-Id: Ie97d89be0234414ef4df22a6920e18acc944a102 Reviewed-on: https://go-review.googlesource.com/c/go/+/357249 Trust: Robert Griesemer Reviewed-by: Robert Findley --- diff --git a/src/cmd/compile/internal/types2/api.go b/src/cmd/compile/internal/types2/api.go index e6d28af3c8..f13fa95b62 100644 --- a/src/cmd/compile/internal/types2/api.go +++ b/src/cmd/compile/internal/types2/api.go @@ -438,7 +438,7 @@ func AssignableTo(V, T Type) bool { // ConvertibleTo reports whether a value of type V is convertible to a value of type T. func ConvertibleTo(V, T Type) bool { x := operand{mode: value, typ: V} - return x.convertibleTo(nil, T) // check not needed for non-constant x + return x.convertibleTo(nil, T, nil) // check not needed for non-constant x; if check == nil, cause can be nil } // Implements reports whether type V implements interface T. diff --git a/src/cmd/compile/internal/types2/conversions.go b/src/cmd/compile/internal/types2/conversions.go index 112d728188..a4fba28fce 100644 --- a/src/cmd/compile/internal/types2/conversions.go +++ b/src/cmd/compile/internal/types2/conversions.go @@ -17,6 +17,7 @@ func (check *Checker) conversion(x *operand, T Type) { constArg := x.mode == constant_ var ok bool + var cause string switch { case constArg && isConstType(T): // constant conversion @@ -31,17 +32,20 @@ func (check *Checker) conversion(x *operand, T Type) { x.val = constant.MakeString(string(codepoint)) ok = true } - case x.convertibleTo(check, T): + case x.convertibleTo(check, T, &cause): // non-constant conversion x.mode = value ok = true } if !ok { - if x.mode != invalid { - check.errorf(x, "cannot convert %s to %s", x, T) - x.mode = invalid + var err error_ + err.errorf(x, "cannot convert %s to %s", x, T) + if cause != "" { + err.errorf(nopos, cause) } + check.report(&err) + x.mode = invalid return } @@ -80,57 +84,74 @@ func (check *Checker) conversion(x *operand, T Type) { // is tricky because we'd have to run updateExprType on the argument first. // (Issue #21982.) -// convertibleTo reports whether T(x) is valid. +// convertibleTo reports whether T(x) is valid. In the failure case, *cause +// may be set to the cause for the failure. // The check parameter may be nil if convertibleTo is invoked through an // exported API call, i.e., when all methods have been type-checked. -func (x *operand) convertibleTo(check *Checker, T Type) bool { +func (x *operand) convertibleTo(check *Checker, T Type, cause *string) bool { // "x is assignable to T" - if ok, _ := x.assignableTo(check, T, nil); ok { + if ok, _ := x.assignableTo(check, T, cause); ok { return true } - // TODO(gri) consider passing under(x.typ), under(T) into convertibleToImpl (optimization) Vp, _ := under(x.typ).(*TypeParam) Tp, _ := under(T).(*TypeParam) + errorf := func(format string, args ...interface{}) { + if check != nil && cause != nil { + msg := check.sprintf(format, args...) + if *cause != "" { + msg += "\n\t" + *cause + } + *cause = msg + } + } + // generic cases // (generic operands cannot be constants, so we can ignore x.val) switch { case Vp != nil && Tp != nil: - x := *x // don't modify outer x return Vp.is(func(V *term) bool { - x.typ = V.typ return Tp.is(func(T *term) bool { - return x.convertibleToImpl(check, T.typ) + if !convertibleToImpl(check, V.typ, T.typ, cause) { + errorf("cannot convert %s (in %s) to %s (in %s)", V.typ, Vp, T.typ, Tp) + return false + } + return true }) }) case Vp != nil: - x := *x // don't modify outer x return Vp.is(func(V *term) bool { - x.typ = V.typ - return x.convertibleToImpl(check, T) + if !convertibleToImpl(check, V.typ, T, cause) { + errorf("cannot convert %s (in %s) to %s", V.typ, Vp, T) + return false + } + return true }) case Tp != nil: return Tp.is(func(T *term) bool { - return x.convertibleToImpl(check, T.typ) + if !convertibleToImpl(check, x.typ, T.typ, cause) { + errorf("cannot convert %s to %s (in %s)", x.typ, T.typ, Tp) + return false + } + return true }) } // non-generic case - return x.convertibleToImpl(check, T) + return convertibleToImpl(check, x.typ, T, cause) } // convertibleToImpl should only be called by convertibleTo -func (x *operand) convertibleToImpl(check *Checker, T Type) bool { - // "x's type and T have identical underlying types if tags are ignored" - V := x.typ +func convertibleToImpl(check *Checker, V, T Type, cause *string) bool { + // "V and T have identical underlying types if tags are ignored" Vu := under(V) Tu := under(T) if IdenticalIgnoreTags(Vu, Tu) { return true } - // "x's type and T are unnamed pointer types and their pointer base types + // "V and T are unnamed pointer types and their pointer base types // have identical underlying types if tags are ignored" if V, ok := V.(*Pointer); ok { if T, ok := T.(*Pointer); ok { @@ -140,22 +161,22 @@ func (x *operand) convertibleToImpl(check *Checker, T Type) bool { } } - // "x's type and T are both integer or floating point types" + // "V and T are both integer or floating point types" if isIntegerOrFloat(V) && isIntegerOrFloat(T) { return true } - // "x's type and T are both complex types" + // "V and T are both complex types" if isComplex(V) && isComplex(T) { return true } - // "x is an integer or a slice of bytes or runes and T is a string type" + // "V an integer or a slice of bytes or runes and T is a string type" if (isInteger(V) || isBytesOrRunes(Vu)) && isString(T) { return true } - // "x is a string and T is a slice of bytes or runes" + // "V a string and T is a slice of bytes or runes" if isString(V) && isBytesOrRunes(Tu) { return true } @@ -170,7 +191,7 @@ func (x *operand) convertibleToImpl(check *Checker, T Type) bool { return true } - // "x is a slice, T is a pointer-to-array type, + // "V a slice, T is a pointer-to-array type, // and the slice and array types have identical element types." if s := asSlice(V); s != nil { if p := asPointer(T); p != nil { @@ -180,12 +201,15 @@ func (x *operand) convertibleToImpl(check *Checker, T Type) bool { return true } // check != nil - if check.conf.CompilerErrorMessages { - check.error(x, "conversion of slices to array pointers only supported as of -lang=go1.17") - } else { - check.error(x, "conversion of slices to array pointers requires go1.17 or later") + if cause != nil { + if check.conf.CompilerErrorMessages { + // compiler error message assumes a -lang flag + *cause = "conversion of slices to array pointers only supported as of -lang=go1.17" + } else { + *cause = "conversion of slices to array pointers requires go1.17 or later" + } } - x.mode = invalid // avoid follow-up error + return false } } } diff --git a/src/cmd/compile/internal/types2/operand.go b/src/cmd/compile/internal/types2/operand.go index a5b2729451..5c8654dbf1 100644 --- a/src/cmd/compile/internal/types2/operand.go +++ b/src/cmd/compile/internal/types2/operand.go @@ -296,6 +296,7 @@ func (x *operand) assignableTo(check *Checker, T Type, reason *string) (bool, er if Ti, ok := Tu.(*Interface); ok { if m, wrongType := check.missingMethod(V, Ti, true); m != nil /* Implements(V, Ti) */ { if reason != nil { + // TODO(gri) the error messages here should follow the style in Checker.typeAssertion (factor!) if wrongType != nil { if Identical(m.typ, wrongType.typ) { *reason = fmt.Sprintf("missing method %s (%s has pointer receiver)", m.name, m.name) diff --git a/src/cmd/compile/internal/types2/testdata/examples/conversions.go2 b/src/cmd/compile/internal/types2/testdata/examples/conversions.go2 index 5c1b30a2b5..0acd2762a1 100644 --- a/src/cmd/compile/internal/types2/testdata/examples/conversions.go2 +++ b/src/cmd/compile/internal/types2/testdata/examples/conversions.go2 @@ -21,7 +21,7 @@ type Far struct{f float64 } func _[X Foo, T Bar](x X) T { return T(x) } func _[X Foo|Bar, T Bar](x X) T { return T(x) } func _[X Foo, T Foo|Bar](x X) T { return T(x) } -func _[X Foo, T Far](x X) T { return T(x /* ERROR cannot convert */ ) } +func _[X Foo, T Far](x X) T { return T(x /* ERROR cannot convert x \(variable of type X constrained by Foo\) to T\n\tcannot convert Foo \(in X\) to Far \(in T\) */ ) } // "x's type and T are unnamed pointer types and their pointer base types // have identical underlying types if tags are ignored" @@ -29,7 +29,7 @@ func _[X Foo, T Far](x X) T { return T(x /* ERROR cannot convert */ ) } func _[X ~*Foo, T ~*Bar](x X) T { return T(x) } func _[X ~*Foo|~*Bar, T ~*Bar](x X) T { return T(x) } func _[X ~*Foo, T ~*Foo|~*Bar](x X) T { return T(x) } -func _[X ~*Foo, T ~*Far](x X) T { return T(x /* ERROR cannot convert */ ) } +func _[X ~*Foo, T ~*Far](x X) T { return T(x /* ERROR cannot convert x \(variable of type X constrained by ~\*Foo\) to T\n\tcannot convert \*Foo \(in X\) to \*Far \(in T\) */ ) } // Verify that the defined types in constraints are considered for the rule above. @@ -60,12 +60,12 @@ func _[X Unsigned, T Float](x X) T { return T(x) } func _[X Float, T Float](x X) T { return T(x) } func _[X, T Integer|Unsigned|Float](x X) T { return T(x) } -func _[X, T Integer|~string](x X) T { return T(x /* ERROR cannot convert */ ) } +func _[X, T Integer|~string](x X) T { return T(x /* ERROR cannot convert x \(variable of type X constrained by Integer\|~string\) to T\n\tcannot convert string \(in X\) to int \(in T\) */ ) } // "x's type and T are both complex types" func _[X, T Complex](x X) T { return T(x) } -func _[X, T Float|Complex](x X) T { return T(x /* ERROR cannot convert */ ) } +func _[X, T Float|Complex](x X) T { return T(x /* ERROR cannot convert x \(variable of type X constrained by Float\|Complex\) to T\n\tcannot convert float32 \(in X\) to complex64 \(in T\) */ ) } // "x is an integer or a slice of bytes or runes and T is a string type" @@ -76,25 +76,25 @@ func _[T ~string](x int) T { return T(x) } func _[T ~string](x myInt) T { return T(x) } func _[X Integer](x X) string { return string(x) } func _[X Integer](x X) myString { return myString(x) } -func _[X Integer](x X) *string { return (*string)(x /* ERROR cannot convert */ ) } +func _[X Integer](x X) *string { return (*string)(x /* ERROR cannot convert x \(variable of type X constrained by Integer\) to \*string\n\tcannot convert int \(in X\) to \*string */ ) } func _[T ~string](x []byte) T { return T(x) } func _[T ~string](x []rune) T { return T(x) } func _[X ~[]byte, T ~string](x X) T { return T(x) } func _[X ~[]rune, T ~string](x X) T { return T(x) } func _[X Integer|~[]byte|~[]rune, T ~string](x X) T { return T(x) } -func _[X Integer|~[]byte|~[]rune, T ~*string](x X) T { return T(x /* ERROR cannot convert */ ) } +func _[X Integer|~[]byte|~[]rune, T ~*string](x X) T { return T(x /* ERROR cannot convert x \(variable of type X constrained by Integer\|~\[\]byte\|~\[\]rune\) to T\n\tcannot convert int \(in X\) to \*string \(in T\) */ ) } // "x is a string and T is a slice of bytes or runes" func _[T ~[]byte](x string) T { return T(x) } func _[T ~[]rune](x string) T { return T(x) } -func _[T ~[]rune](x *string) T { return T(x /* ERROR cannot convert */ ) } +func _[T ~[]rune](x *string) T { return T(x /* ERROR cannot convert x \(variable of type \*string\) to T\n\tcannot convert \*string to \[\]rune \(in T\) */ ) } func _[X ~string, T ~[]byte](x X) T { return T(x) } func _[X ~string, T ~[]rune](x X) T { return T(x) } func _[X ~string, T ~[]byte|~[]rune](x X) T { return T(x) } -func _[X ~*string, T ~[]byte|~[]rune](x X) T { return T(x /* ERROR cannot convert */ ) } +func _[X ~*string, T ~[]byte|~[]rune](x X) T { return T(x /* ERROR cannot convert x \(variable of type X constrained by ~\*string\) to T\n\tcannot convert \*string \(in X\) to \[\]byte \(in T\) */ ) } // package unsafe: // "any pointer or value of underlying type uintptr can be converted into a unsafe.Pointer" @@ -103,20 +103,20 @@ type myUintptr uintptr func _[X ~uintptr](x X) unsafe.Pointer { return unsafe.Pointer(x) } func _[T unsafe.Pointer](x myUintptr) T { return T(x) } -func _[T unsafe.Pointer](x int64) T { return T(x /* ERROR cannot convert */ ) } +func _[T unsafe.Pointer](x int64) T { return T(x /* ERROR cannot convert x \(variable of type int64\) to T\n\tcannot convert int64 to unsafe\.Pointer \(in T\) */ ) } // "and vice versa" func _[T ~uintptr](x unsafe.Pointer) T { return T(x) } func _[X unsafe.Pointer](x X) uintptr { return uintptr(x) } func _[X unsafe.Pointer](x X) myUintptr { return myUintptr(x) } -func _[X unsafe.Pointer](x X) int64 { return int64(x /* ERROR cannot convert */ ) } +func _[X unsafe.Pointer](x X) int64 { return int64(x /* ERROR cannot convert x \(variable of type X constrained by unsafe\.Pointer\) to int64\n\tcannot convert unsafe\.Pointer \(in X\) to int64 */ ) } // "x is a slice, T is a pointer-to-array type, // and the slice and array types have identical element types." func _[X ~[]E, T ~*[10]E, E any](x X) T { return T(x) } -func _[X ~[]E, T ~[10]E, E any](x X) T { return T(x /* ERROR cannot convert */ ) } +func _[X ~[]E, T ~[10]E, E any](x X) T { return T(x /* ERROR cannot convert x \(variable of type X constrained by ~\[\]E\) to T\n\tcannot convert \[\]E \(in X\) to \[10\]E \(in T\) */ ) } // ---------------------------------------------------------------------------- // The following declarations can be replaced by the exported types of the