243 lines
5.3 KiB
Go
243 lines
5.3 KiB
Go
package lang
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import (
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"fmt"
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"sync"
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"github.com/hashicorp/terraform/config/lang/ast"
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)
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// TypeCheck implements ast.Visitor for type checking an AST tree.
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// It requires some configuration to look up the type of nodes.
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//
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// It also optionally will not type error and will insert an implicit
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// type conversions for specific types if specified by the Implicit
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// field. Note that this is kind of organizationally weird to put into
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// this structure but we'd rather do that than duplicate the type checking
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// logic multiple times.
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type TypeCheck struct {
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Scope ast.Scope
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// Implicit is a map of implicit type conversions that we can do,
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// and that shouldn't error. The key of the first map is the from type,
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// the key of the second map is the to type, and the final string
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// value is the function to call (which must be registered in the Scope).
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Implicit map[ast.Type]map[ast.Type]string
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// Stack of types. This shouldn't be used directly except by implementations
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// of TypeCheckNode.
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Stack []ast.Type
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err error
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lock sync.Mutex
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}
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// TypeCheckNode is the interface that must be implemented by any
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// ast.Node that wants to support type-checking. If the type checker
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// encounters a node that doesn't implement this, it will error.
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type TypeCheckNode interface {
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TypeCheck(*TypeCheck) (ast.Node, error)
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}
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func (v *TypeCheck) Visit(root ast.Node) error {
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v.lock.Lock()
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defer v.lock.Unlock()
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defer v.reset()
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root.Accept(v.visit)
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return v.err
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}
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func (v *TypeCheck) visit(raw ast.Node) ast.Node {
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if v.err != nil {
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return raw
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}
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var result ast.Node
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var err error
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switch n := raw.(type) {
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case *ast.Call:
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tc := &typeCheckCall{n}
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result, err = tc.TypeCheck(v)
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case *ast.Concat:
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tc := &typeCheckConcat{n}
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result, err = tc.TypeCheck(v)
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case *ast.LiteralNode:
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tc := &typeCheckLiteral{n}
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result, err = tc.TypeCheck(v)
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case *ast.VariableAccess:
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tc := &typeCheckVariableAccess{n}
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result, err = tc.TypeCheck(v)
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default:
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tc, ok := raw.(TypeCheckNode)
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if !ok {
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err = fmt.Errorf("unknown node: %#v", raw)
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break
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}
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result, err = tc.TypeCheck(v)
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}
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if err != nil {
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pos := raw.Pos()
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v.err = fmt.Errorf("At column %d, line %d: %s",
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pos.Column, pos.Line, err)
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}
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return result
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}
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type typeCheckCall struct {
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n *ast.Call
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}
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func (tc *typeCheckCall) TypeCheck(v *TypeCheck) (ast.Node, error) {
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// Look up the function in the map
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function, ok := v.Scope.LookupFunc(tc.n.Func)
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if !ok {
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return nil, fmt.Errorf("unknown function called: %s", tc.n.Func)
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}
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// The arguments are on the stack in reverse order, so pop them off.
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args := make([]ast.Type, len(tc.n.Args))
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for i, _ := range tc.n.Args {
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args[len(tc.n.Args)-1-i] = v.StackPop()
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}
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// Verify the args
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for i, expected := range function.ArgTypes {
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if args[i] != expected {
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cn := v.ImplicitConversion(args[i], expected, tc.n.Args[i])
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if cn != nil {
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tc.n.Args[i] = cn
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continue
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}
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return nil, fmt.Errorf(
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"%s: argument %d should be %s, got %s",
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tc.n.Func, i+1, expected, args[i])
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}
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}
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// If we're variadic, then verify the types there
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if function.Variadic {
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args = args[len(function.ArgTypes):]
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for i, t := range args {
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if t != function.VariadicType {
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realI := i + len(function.ArgTypes)
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cn := v.ImplicitConversion(
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t, function.VariadicType, tc.n.Args[realI])
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if cn != nil {
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tc.n.Args[realI] = cn
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continue
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}
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return nil, fmt.Errorf(
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"%s: argument %d should be %s, got %s",
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tc.n.Func, realI,
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function.VariadicType, t)
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}
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}
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}
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// Return type
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v.StackPush(function.ReturnType)
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return tc.n, nil
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}
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type typeCheckConcat struct {
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n *ast.Concat
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}
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func (tc *typeCheckConcat) TypeCheck(v *TypeCheck) (ast.Node, error) {
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n := tc.n
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types := make([]ast.Type, len(n.Exprs))
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for i, _ := range n.Exprs {
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types[len(n.Exprs)-1-i] = v.StackPop()
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}
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// All concat args must be strings, so validate that
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for i, t := range types {
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if t != ast.TypeString {
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cn := v.ImplicitConversion(t, ast.TypeString, n.Exprs[i])
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if cn != nil {
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n.Exprs[i] = cn
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continue
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}
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return nil, fmt.Errorf(
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"argument %d must be a string", i+1)
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}
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}
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// This always results in type string
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v.StackPush(ast.TypeString)
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return n, nil
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}
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type typeCheckLiteral struct {
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n *ast.LiteralNode
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}
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func (tc *typeCheckLiteral) TypeCheck(v *TypeCheck) (ast.Node, error) {
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v.StackPush(tc.n.Typex)
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return tc.n, nil
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}
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type typeCheckVariableAccess struct {
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n *ast.VariableAccess
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}
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func (tc *typeCheckVariableAccess) TypeCheck(v *TypeCheck) (ast.Node, error) {
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// Look up the variable in the map
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variable, ok := v.Scope.LookupVar(tc.n.Name)
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if !ok {
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return nil, fmt.Errorf(
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"unknown variable accessed: %s", tc.n.Name)
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}
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// Add the type to the stack
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v.StackPush(variable.Type)
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return tc.n, nil
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}
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func (v *TypeCheck) ImplicitConversion(
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actual ast.Type, expected ast.Type, n ast.Node) ast.Node {
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if v.Implicit == nil {
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return nil
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}
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fromMap, ok := v.Implicit[actual]
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if !ok {
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return nil
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}
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toFunc, ok := fromMap[expected]
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if !ok {
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return nil
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}
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return &ast.Call{
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Func: toFunc,
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Args: []ast.Node{n},
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Posx: n.Pos(),
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}
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}
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func (v *TypeCheck) reset() {
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v.Stack = nil
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v.err = nil
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}
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func (v *TypeCheck) StackPush(t ast.Type) {
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v.Stack = append(v.Stack, t)
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}
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func (v *TypeCheck) StackPop() ast.Type {
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var x ast.Type
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x, v.Stack = v.Stack[len(v.Stack)-1], v.Stack[:len(v.Stack)-1]
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return x
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}
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