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// Copyright 2020 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 completion
import (
"context"
"go/ast"
"go/types"
)
// builtinArgKind determines the expected object kind for a builtin
// argument. It attempts to use the AST hints from builtin.go where
// possible.
func (c *completer) builtinArgKind(ctx context.Context, obj types.Object, call *ast.CallExpr) objKind {
builtin, err := c.snapshot.BuiltinPackage(ctx)
if err != nil {
return 0
}
exprIdx := exprAtPos(c.pos, call.Args)
builtinObj := builtin.Package.Scope.Lookup(obj.Name())
if builtinObj == nil {
return 0
}
decl, ok := builtinObj.Decl.(*ast.FuncDecl)
if !ok || exprIdx >= len(decl.Type.Params.List) {
return 0
}
switch ptyp := decl.Type.Params.List[exprIdx].Type.(type) {
case *ast.ChanType:
return kindChan
case *ast.ArrayType:
return kindSlice
case *ast.MapType:
return kindMap
case *ast.Ident:
switch ptyp.Name {
case "Type":
switch obj.Name() {
case "make":
return kindChan | kindSlice | kindMap
case "len":
return kindSlice | kindMap | kindArray | kindString | kindChan
case "cap":
return kindSlice | kindArray | kindChan
}
}
}
return 0
}
// builtinArgType infers the type of an argument to a builtin
// function. parentInf is the inferred type info for the builtin
// call's parent node.
func (c *completer) builtinArgType(obj types.Object, call *ast.CallExpr, parentInf candidateInference) candidateInference {
var (
exprIdx = exprAtPos(c.pos, call.Args)
// Propagate certain properties from our parent's inference.
inf = candidateInference{
typeName: parentInf.typeName,
modifiers: parentInf.modifiers,
}
)
switch obj.Name() {
case "append":
if parentInf.objType == nil {
break
}
inf.objType = parentInf.objType
if exprIdx <= 0 {
break
}
inf.objType = deslice(inf.objType)
// Check if we are completing the variadic append() param.
inf.variadic = exprIdx == 1 && len(call.Args) <= 2
// Penalize the first append() argument as a candidate. You
// don't normally append a slice to itself.
if sliceChain := objChain(c.pkg.GetTypesInfo(), call.Args[0]); len(sliceChain) > 0 {
inf.penalized = append(inf.penalized, penalizedObj{objChain: sliceChain, penalty: 0.9})
}
case "delete":
if exprIdx > 0 && len(call.Args) > 0 {
// Try to fill in expected type of map key.
firstArgType := c.pkg.GetTypesInfo().TypeOf(call.Args[0])
if firstArgType != nil {
if mt, ok := firstArgType.Underlying().(*types.Map); ok {
inf.objType = mt.Key()
}
}
}
case "copy":
var t1, t2 types.Type
if len(call.Args) > 0 {
t1 = c.pkg.GetTypesInfo().TypeOf(call.Args[0])
if len(call.Args) > 1 {
t2 = c.pkg.GetTypesInfo().TypeOf(call.Args[1])
}
}
// Fill in expected type of either arg if the other is already present.
if exprIdx == 1 && t1 != nil {
inf.objType = t1
} else if exprIdx == 0 && t2 != nil {
inf.objType = t2
}
case "new":
inf.typeName.wantTypeName = true
if parentInf.objType != nil {
// Expected type for "new" is the de-pointered parent type.
if ptr, ok := parentInf.objType.Underlying().(*types.Pointer); ok {
inf.objType = ptr.Elem()
}
}
case "make":
if exprIdx == 0 {
inf.typeName.wantTypeName = true
inf.objType = parentInf.objType
} else {
inf.objType = types.Typ[types.Int]
}
}
return inf
}
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