go/analysis/passes/printf: add missing call to Func.Origin

A call to an instance of a generic printf wrapper should
be checked as a printf wrapper; but a missing call to
Func.Origin prevented that.

+ Test

Fixes golang/go#70572

Change-Id: I61de6dc42bfea9b152aabb895ea66962453cb0e4
Reviewed-on: https://go-review.googlesource.com/c/tools/+/631955
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Alan Donovan <adonovan@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>

Author: adonovan

go/analysis/passes/printf/printf.go

@@ -433,6 +433,9 @@ func printfNameAndKind(pass *analysis.Pass, call *ast.CallExpr) (fn *types.Func,
 		return nil, 0
 	}
 
+	// Facts are associated with generic declarations, not instantiations.
+	fn = fn.Origin()
+
 	_, ok := isPrint[fn.FullName()]
 	if !ok {
 		// Next look up just "printf", for use with -printf.funcs.

go/analysis/passes/printf/printf_test.go

@@ -16,6 +16,6 @@ func Test(t *testing.T) {
 	printf.Analyzer.Flags.Set("funcs", "Warn,Warnf")
 
 	analysistest.Run(t, testdata, printf.Analyzer,
-		"a", "b", "nofmt", "typeparams", "issue68744")
+		"a", "b", "nofmt", "typeparams", "issue68744", "issue70572")
 	analysistest.RunWithSuggestedFixes(t, testdata, printf.Analyzer, "fix")
 }

go/analysis/passes/printf/testdata/src/issue70572/issue70572.go

@@ -0,0 +1,25 @@
+package issue70572
+
+// Regression test for failure to detect that a call to B[bool].Printf
+// was printf-like, because of a missing call to types.Func.Origin.
+
+import "fmt"
+
+type A struct{}
+
+func (v A) Printf(format string, values ...any) { // want Printf:"printfWrapper"
+	fmt.Printf(format, values...)
+}
+
+type B[T any] struct{}
+
+func (v B[T]) Printf(format string, values ...any) { // want Printf:"printfWrapper"
+	fmt.Printf(format, values...)
+}
+
+func main() {
+	var a A
+	var b B[bool]
+	a.Printf("x", 1) // want "arguments but no formatting directives"
+	b.Printf("x", 1) // want "arguments but no formatting directives"
+}