database/sql: use reflect.TypeFor for known types

For #60088

Change-Id: Ib05ba3d456b22f7370459037b3d263c4b3ebe3b1
Reviewed-on: https://go-review.googlesource.com/c/go/+/514975
Reviewed-by: Daniel Theophanes <[email protected]>
Run-TryBot: Ian Lance Taylor <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Run-TryBot: Ian Lance Taylor <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>

Author: ianlancetaylor

src/database/sql/convert.go

@@ -529,7 +529,7 @@ func asBytes(buf []byte, rv reflect.Value) (b []byte, ok bool) {
 	return
 }
 
-var valuerReflectType = reflect.TypeOf((*driver.Valuer)(nil)).Elem()
+var valuerReflectType = reflect.TypeFor[driver.Valuer]()
 
 // callValuerValue returns vr.Value(), with one exception:
 // If vr.Value is an auto-generated method on a pointer type and the

src/database/sql/driver/types.go

@@ -211,7 +211,7 @@ type defaultConverter struct{}
 
 var _ ValueConverter = defaultConverter{}
 
-var valuerReflectType = reflect.TypeOf((*Valuer)(nil)).Elem()
+var valuerReflectType = reflect.TypeFor[Valuer]()
 
 // callValuerValue returns vr.Value(), with one exception:
 // If vr.Value is an auto-generated method on a pointer type and the

src/database/sql/fakedb_test.go

@@ -1251,33 +1251,33 @@ func converterForType(typ string) driver.ValueConverter {
 func colTypeToReflectType(typ string) reflect.Type {
 	switch typ {
 	case "bool":
-		return reflect.TypeOf(false)
+		return reflect.TypeFor[bool]()
 	case "nullbool":
-		return reflect.TypeOf(NullBool{})
+		return reflect.TypeFor[NullBool]()
 	case "int16":
-		return reflect.TypeOf(int16(0))
+		return reflect.TypeFor[int16]()
 	case "nullint16":
-		return reflect.TypeOf(NullInt16{})
+		return reflect.TypeFor[NullInt16]()
 	case "int32":
-		return reflect.TypeOf(int32(0))
+		return reflect.TypeFor[int32]()
 	case "nullint32":
-		return reflect.TypeOf(NullInt32{})
+		return reflect.TypeFor[NullInt32]()
 	case "string":
-		return reflect.TypeOf("")
+		return reflect.TypeFor[string]()
 	case "nullstring":
-		return reflect.TypeOf(NullString{})
+		return reflect.TypeFor[NullString]()
 	case "int64":
-		return reflect.TypeOf(int64(0))
+		return reflect.TypeFor[int64]()
 	case "nullint64":
-		return reflect.TypeOf(NullInt64{})
+		return reflect.TypeFor[NullInt64]()
 	case "float64":
-		return reflect.TypeOf(float64(0))
+		return reflect.TypeFor[float64]()
 	case "nullfloat64":
-		return reflect.TypeOf(NullFloat64{})
+		return reflect.TypeFor[NullFloat64]()
 	case "datetime":
-		return reflect.TypeOf(time.Time{})
+		return reflect.TypeFor[time.Time]()
 	case "any":
-		return reflect.TypeOf(new(any)).Elem()
+		return reflect.TypeFor[any]()
 	}
 	panic("invalid fakedb column type of " + typ)
 }

src/database/sql/sql.go

@@ -3244,7 +3244,7 @@ func rowsColumnInfoSetupConnLocked(rowsi driver.Rows) []*ColumnType {
 		if prop, ok := rowsi.(driver.RowsColumnTypeScanType); ok {
 			ci.scanType = prop.ColumnTypeScanType(i)
 		} else {
-			ci.scanType = reflect.TypeOf(new(any)).Elem()
+			ci.scanType = reflect.TypeFor[any]()
 		}
 		if prop, ok := rowsi.(driver.RowsColumnTypeDatabaseTypeName); ok {
 			ci.databaseType = prop.ColumnTypeDatabaseTypeName(i)