cmd/compile/internal/types2: report argument type for unsafe.OffsetOf

Before parameterized types, unsafe.OffsetOf was always evaluating to
a constant. With parameterized types, the result may be a run-time
value, and unsafe.OffsetOf(x.f) is a call that is recorded. Also
record the argument x.f.

Fixes #47895.

Change-Id: Ia3da25028d4865d7295ce7990c7216bffe9e7c72
Reviewed-on: https://go-review.googlesource.com/c/go/+/344252
Trust: Robert Griesemer <gri@golang.org>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>

diff --git a/src/cmd/compile/internal/types2/api_test.go b/src/cmd/compile/internal/types2/api_test.go
index d6a2eb4eb35e00ae87b06c27f2945cc5375d07ed..3ed2799a84746746086a1155a6959db2975980fb 100644 (file)
--- a/src/cmd/compile/internal/types2/api_test.go
+++ b/src/cmd/compile/internal/types2/api_test.go
@@ -346,6 +346,9 @@ func TestTypesInfo(t *testing.T) {
 
                // issue 45096
                {genericPkg + `issue45096; func _[T interface{ ~int8 | ~int16 | ~int32 }](x T) { _ = x < 0 }`, `0`, `generic_issue45096.T₁`},
+
+               // issue 47895
+               {`package p; import "unsafe"; type S struct { f int }; var s S; var _ = unsafe.Offsetof(s.f)`, `s.f`, `int`},
        }
 
        for _, test := range tests {

diff --git a/src/cmd/compile/internal/types2/builtins.go b/src/cmd/compile/internal/types2/builtins.go
index da2dcf54aa36537814f05015ea4db6f4f9a40949..87295fe0e709bc9580c74942348432fb4332ed84 100644 (file)
--- a/src/cmd/compile/internal/types2/builtins.go
+++ b/src/cmd/compile/internal/types2/builtins.go
@@ -662,6 +662,15 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
                // TODO(gri) Should we pass x.typ instead of base (and have indirect report if derefStructPtr indirected)?
                check.recordSelection(selx, FieldVal, base, obj, index, false)
 
+               // record the selector expression (was bug - issue #47895)
+               {
+                       mode := value
+                       if x.mode == variable || indirect {
+                               mode = variable
+                       }
+                       check.record(&operand{mode, selx, obj.Type(), nil, 0})
+               }
+
                // The field offset is considered a variable even if the field is declared before
                // the part of the struct which is variable-sized. This makes both the rules
                // simpler and also permits (or at least doesn't prevent) a compiler from re-