cmd/compile/internal/types2: better error position for instantiation failure
- Thread type argument expressions (rather than posLists) through various
type-checker functions so we can provide a better error position.
- Adjust signatures that expect a syntax.Pos to accept a poser instead
to avoid gratuituous conversions from expressions to positions.
- Rename targsx to xlist so we use xlist consistently for expression
lists.
First step in providing a better error message for the issue below.
For #49179.
Change-Id: I8fc685a2ee4f5640f4abd35568ba32bcb34e9e84
Reviewed-on: https://go-review.googlesource.com/c/go/+/366757
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
diff --git a/src/cmd/compile/internal/types2/builtins.go b/src/cmd/compile/internal/types2/builtins.go
index 53d8345..fcf02a6 100644
--- a/src/cmd/compile/internal/types2/builtins.go
+++ b/src/cmd/compile/internal/types2/builtins.go
@@ -129,7 +129,7 @@
arg(&x, i)
xlist = append(xlist, &x)
}
- check.arguments(call, sig, nil, xlist) // discard result (we know the result type)
+ check.arguments(call, sig, nil, xlist, nil) // discard result (we know the result type)
// ok to continue even if check.arguments reported errors
x.mode = value
diff --git a/src/cmd/compile/internal/types2/call.go b/src/cmd/compile/internal/types2/call.go
index 91e2a8f..ed8b67c 100644
--- a/src/cmd/compile/internal/types2/call.go
+++ b/src/cmd/compile/internal/types2/call.go
@@ -50,14 +50,8 @@
}
assert(got == want)
- // determine argument positions (for error reporting)
- poslist := make([]syntax.Pos, len(xlist))
- for i, x := range xlist {
- poslist[i] = syntax.StartPos(x)
- }
-
// instantiate function signature
- res := check.instantiateSignature(x.Pos(), sig, targs, poslist)
+ res := check.instantiateSignature(x.Pos(), sig, targs, xlist)
assert(res.TypeParams().Len() == 0) // signature is not generic anymore
check.recordInstance(inst.X, targs, res)
x.typ = res
@@ -65,7 +59,7 @@
x.expr = inst
}
-func (check *Checker) instantiateSignature(pos syntax.Pos, typ *Signature, targs []Type, posList []syntax.Pos) (res *Signature) {
+func (check *Checker) instantiateSignature(pos syntax.Pos, typ *Signature, targs []Type, xlist []syntax.Expr) (res *Signature) {
assert(check != nil)
assert(len(targs) == typ.TypeParams().Len())
@@ -79,17 +73,17 @@
}
inst := check.instance(pos, typ, targs, check.bestContext(nil)).(*Signature)
- assert(len(posList) <= len(targs))
+ assert(len(xlist) <= len(targs))
tparams := typ.TypeParams().list()
if i, err := check.verify(pos, tparams, targs); err != nil {
// best position for error reporting
pos := pos
- if i < len(posList) {
- pos = posList[i]
+ if i < len(xlist) {
+ pos = syntax.StartPos(xlist[i])
}
- check.softErrorf(pos, err.Error())
+ check.softErrorf(pos, "%s", err)
} else {
- check.mono.recordInstance(check.pkg, pos, tparams, targs, posList)
+ check.mono.recordInstance(check.pkg, pos, tparams, targs, xlist)
}
return inst
@@ -179,9 +173,10 @@
}
// evaluate type arguments, if any
+ var xlist []syntax.Expr
var targs []Type
if inst != nil {
- xlist := unpackExpr(inst.Index)
+ xlist = unpackExpr(inst.Index)
targs = check.typeList(xlist)
if targs == nil {
check.use(call.ArgList...)
@@ -205,7 +200,7 @@
// evaluate arguments
args, _ := check.exprList(call.ArgList, false)
isGeneric := sig.TypeParams().Len() > 0
- sig = check.arguments(call, sig, targs, args)
+ sig = check.arguments(call, sig, targs, args, xlist)
if isGeneric && sig.TypeParams().Len() == 0 {
// update the recorded type of call.Fun to its instantiated type
@@ -279,7 +274,8 @@
return
}
-func (check *Checker) arguments(call *syntax.CallExpr, sig *Signature, targs []Type, args []*operand) (rsig *Signature) {
+// xlist is the list of type argument expressions supplied in the source code.
+func (check *Checker) arguments(call *syntax.CallExpr, sig *Signature, targs []Type, args []*operand, xlist []syntax.Expr) (rsig *Signature) {
rsig = sig
// TODO(gri) try to eliminate this extra verification loop
@@ -381,15 +377,13 @@
check.versionErrorf(call.Pos(), "go1.18", "implicit function instantiation")
}
}
- // TODO(gri) provide position information for targs so we can feed
- // it to the instantiate call for better error reporting
targs := check.infer(call.Pos(), sig.TypeParams().list(), targs, sigParams, args)
if targs == nil {
return // error already reported
}
// compute result signature
- rsig = check.instantiateSignature(call.Pos(), sig, targs, nil)
+ rsig = check.instantiateSignature(call.Pos(), sig, targs, xlist)
assert(rsig.TypeParams().Len() == 0) // signature is not generic anymore
check.recordInstance(call.Fun, targs, rsig)
diff --git a/src/cmd/compile/internal/types2/mono.go b/src/cmd/compile/internal/types2/mono.go
index 39c4d4f..7bd79f4 100644
--- a/src/cmd/compile/internal/types2/mono.go
+++ b/src/cmd/compile/internal/types2/mono.go
@@ -168,11 +168,11 @@
// recordInstance records that the given type parameters were
// instantiated with the corresponding type arguments.
-func (w *monoGraph) recordInstance(pkg *Package, pos syntax.Pos, tparams []*TypeParam, targs []Type, posList []syntax.Pos) {
+func (w *monoGraph) recordInstance(pkg *Package, pos syntax.Pos, tparams []*TypeParam, targs []Type, xlist []syntax.Expr) {
for i, tpar := range tparams {
pos := pos
- if i < len(posList) {
- pos = posList[i]
+ if i < len(xlist) {
+ pos = syntax.StartPos(xlist[i])
}
w.assign(pkg, pos, tpar, targs[i])
}
diff --git a/src/cmd/compile/internal/types2/testdata/fixedbugs/issue39754.go2 b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue39754.go2
index a88f4cf..9edd239 100644
--- a/src/cmd/compile/internal/types2/testdata/fixedbugs/issue39754.go2
+++ b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue39754.go2
@@ -17,7 +17,5 @@
func _() {
f[int, Optional[int], Optional[int]]()
_ = f[int, Optional[int], Optional /* ERROR does not implement Box */ [string]]
- // TODO(gri) Provide better position information here.
- // See TODO in call.go, Checker.arguments.
- f[int, Optional[int], Optional[string]]( /* ERROR does not implement Box */ )
+ _ = f[int, Optional[int], Optional /* ERROR Optional.* does not implement Box.* */ [string]]
}
diff --git a/src/cmd/compile/internal/types2/testdata/fixedbugs/issue49179.go2 b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue49179.go2
new file mode 100644
index 0000000..7cba52a
--- /dev/null
+++ b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue49179.go2
@@ -0,0 +1,19 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type SliceConstraint[T any] interface {
+ []T
+}
+
+func Map[S SliceConstraint[E], E any](s S, f func(E) E) S {
+ return s
+}
+
+type MySlice []int
+
+func f(s MySlice) {
+ Map[MySlice /* ERROR MySlice does not implement SliceConstraint\[int\] */, int](s, nil)
+}
diff --git a/src/cmd/compile/internal/types2/typexpr.go b/src/cmd/compile/internal/types2/typexpr.go
index 862a315..56a7dcd 100644
--- a/src/cmd/compile/internal/types2/typexpr.go
+++ b/src/cmd/compile/internal/types2/typexpr.go
@@ -402,9 +402,9 @@
return typ
}
-func (check *Checker) instantiatedType(x syntax.Expr, targsx []syntax.Expr, def *Named) (res Type) {
+func (check *Checker) instantiatedType(x syntax.Expr, xlist []syntax.Expr, def *Named) (res Type) {
if check.conf.Trace {
- check.trace(x.Pos(), "-- instantiating %s with %s", x, targsx)
+ check.trace(x.Pos(), "-- instantiating %s with %s", x, xlist)
check.indent++
defer func() {
check.indent--
@@ -424,18 +424,12 @@
}
// evaluate arguments
- targs := check.typeList(targsx)
+ targs := check.typeList(xlist)
if targs == nil {
def.setUnderlying(Typ[Invalid]) // avoid later errors due to lazy instantiation
return Typ[Invalid]
}
- // determine argument positions
- posList := make([]syntax.Pos, len(targs))
- for i, arg := range targsx {
- posList[i] = arg.Pos()
- }
-
// create the instance
ctxt := check.bestContext(nil)
h := ctxt.instanceHash(orig, targs)
@@ -484,12 +478,12 @@
if i, err := check.verify(x.Pos(), inst.tparams.list(), inst.targs.list()); err != nil {
// best position for error reporting
pos := x.Pos()
- if i < len(posList) {
- pos = posList[i]
+ if i < len(xlist) {
+ pos = syntax.StartPos(xlist[i])
}
- check.softErrorf(pos, err.Error())
+ check.softErrorf(pos, "%s", err)
} else {
- check.mono.recordInstance(check.pkg, x.Pos(), inst.tparams.list(), inst.targs.list(), posList)
+ check.mono.recordInstance(check.pkg, x.Pos(), inst.tparams.list(), inst.targs.list(), xlist)
}
}
