go/analysis/passes/printf: update logic now that type parameters are
interfaces
Now that the underlying of type parameters is their constraint
interface, a couple places in the printf analyzer need to be updated:
- We need to explicitly exclude type parameters when looking at
interfaces in isFormatter.
- We need to consider at the element type, not its underlying, when
looking at pointers to type parameters
Change-Id: I8c6843e001a98d45ff0f30df305e3536335f567e
Reviewed-on: https://go-review.googlesource.com/c/tools/+/364678
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
diff --git a/go/analysis/passes/printf/printf.go b/go/analysis/passes/printf/printf.go
index 0206073..dee37d7 100644
--- a/go/analysis/passes/printf/printf.go
+++ b/go/analysis/passes/printf/printf.go
@@ -25,6 +25,7 @@
"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
"golang.org/x/tools/go/ast/inspector"
"golang.org/x/tools/go/types/typeutil"
+ "golang.org/x/tools/internal/typeparams"
)
func init() {
@@ -520,7 +521,12 @@
func isFormatter(typ types.Type) bool {
// If the type is an interface, the value it holds might satisfy fmt.Formatter.
if _, ok := typ.Underlying().(*types.Interface); ok {
- return true
+ // Don't assume type parameters could be formatters. With the greater
+ // expressiveness of constraint interface syntax we expect more type safety
+ // when using type parameters.
+ if !typeparams.IsTypeParam(typ) {
+ return true
+ }
}
obj, _, _ := types.LookupFieldOrMethod(typ, false, nil, "Format")
fn, ok := obj.(*types.Func)
diff --git a/go/analysis/passes/printf/types.go b/go/analysis/passes/printf/types.go
index 81bf36e..270e917 100644
--- a/go/analysis/passes/printf/types.go
+++ b/go/analysis/passes/printf/types.go
@@ -178,10 +178,12 @@
return true
}
+ if typeparams.IsTypeParam(typ.Elem()) {
+ return true // We don't know whether the logic below applies. Give up.
+ }
+
under := typ.Elem().Underlying()
switch under.(type) {
- case *typeparams.TypeParam:
- return true // We don't know whether the logic below applies. Give up.
case *types.Struct: // see below
case *types.Array: // see below
case *types.Slice: // see below
diff --git a/internal/typeparams/common.go b/internal/typeparams/common.go
index 9fc6b4b..961d036 100644
--- a/internal/typeparams/common.go
+++ b/internal/typeparams/common.go
@@ -13,6 +13,7 @@
import (
"go/ast"
"go/token"
+ "go/types"
)
// A IndexExprData holds data from both ast.IndexExpr and the new
@@ -23,3 +24,9 @@
Indices []ast.Expr // index expressions
Rbrack token.Pos // position of "]"
}
+
+// IsTypeParam reports whether t is a type parameter.
+func IsTypeParam(t types.Type) bool {
+ _, ok := t.(*TypeParam)
+ return ok
+}
