.gitignore added

[dotfiles/.git] / .config / coc / extensions / coc-go-data / tools / pkg / mod / golang.org / x / tools@v0.1.0 / go / analysis / passes / ifaceassert / ifaceassert.go

diff --git a/.config/coc/extensions/coc-go-data/tools/pkg/mod/golang.org/x/tools@v0.1.0/go/analysis/passes/ifaceassert/ifaceassert.go b/.config/coc/extensions/coc-go-data/tools/pkg/mod/golang.org/x/tools@v0.1.0/go/analysis/passes/ifaceassert/ifaceassert.go
new file mode 100644 (file)
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--- /dev/null
+++ b/.config/coc/extensions/coc-go-data/tools/pkg/mod/golang.org/x/tools@v0.1.0/go/analysis/passes/ifaceassert/ifaceassert.go
@@ -0,0 +1,105 @@
+// 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 ifaceassert defines an Analyzer that flags
+// impossible interface-interface type assertions.
+package ifaceassert
+
+import (
+       "go/ast"
+       "go/types"
+
+       "golang.org/x/tools/go/analysis"
+       "golang.org/x/tools/go/analysis/passes/inspect"
+       "golang.org/x/tools/go/ast/inspector"
+)
+
+const Doc = `detect impossible interface-to-interface type assertions
+
+This checker flags type assertions v.(T) and corresponding type-switch cases
+in which the static type V of v is an interface that cannot possibly implement
+the target interface T. This occurs when V and T contain methods with the same
+name but different signatures. Example:
+
+       var v interface {
+               Read()
+       }
+       _ = v.(io.Reader)
+
+The Read method in v has a different signature than the Read method in
+io.Reader, so this assertion cannot succeed.
+`
+
+var Analyzer = &analysis.Analyzer{
+       Name:     "ifaceassert",
+       Doc:      Doc,
+       Requires: []*analysis.Analyzer{inspect.Analyzer},
+       Run:      run,
+}
+
+// assertableTo checks whether interface v can be asserted into t. It returns
+// nil on success, or the first conflicting method on failure.
+func assertableTo(v, t types.Type) *types.Func {
+       if t == nil || v == nil {
+               // not assertable to, but there is no missing method
+               return nil
+       }
+       // ensure that v and t are interfaces
+       V, _ := v.Underlying().(*types.Interface)
+       T, _ := t.Underlying().(*types.Interface)
+       if V == nil || T == nil {
+               return nil
+       }
+       if f, wrongType := types.MissingMethod(V, T, false); wrongType {
+               return f
+       }
+       return nil
+}
+
+func run(pass *analysis.Pass) (interface{}, error) {
+       inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
+       nodeFilter := []ast.Node{
+               (*ast.TypeAssertExpr)(nil),
+               (*ast.TypeSwitchStmt)(nil),
+       }
+       inspect.Preorder(nodeFilter, func(n ast.Node) {
+               var (
+                       assert  *ast.TypeAssertExpr // v.(T) expression
+                       targets []ast.Expr          // interfaces T in v.(T)
+               )
+               switch n := n.(type) {
+               case *ast.TypeAssertExpr:
+                       // take care of v.(type) in *ast.TypeSwitchStmt
+                       if n.Type == nil {
+                               return
+                       }
+                       assert = n
+                       targets = append(targets, n.Type)
+               case *ast.TypeSwitchStmt:
+                       // retrieve type assertion from type switch's 'assign' field
+                       switch t := n.Assign.(type) {
+                       case *ast.ExprStmt:
+                               assert = t.X.(*ast.TypeAssertExpr)
+                       case *ast.AssignStmt:
+                               assert = t.Rhs[0].(*ast.TypeAssertExpr)
+                       }
+                       // gather target types from case clauses
+                       for _, c := range n.Body.List {
+                               targets = append(targets, c.(*ast.CaseClause).List...)
+                       }
+               }
+               V := pass.TypesInfo.TypeOf(assert.X)
+               for _, target := range targets {
+                       T := pass.TypesInfo.TypeOf(target)
+                       if f := assertableTo(V, T); f != nil {
+                               pass.Reportf(
+                                       target.Pos(),
+                                       "impossible type assertion: no type can implement both %v and %v (conflicting types for %v method)",
+                                       V, T, f.Name(),
+                               )
+                       }
+               }
+       })
+       return nil, nil
+}