github.com/panjjo/go@v0.0.0-20161104043856-d62b31386338/src/runtime/error.go (about)

     1  // Copyright 2010 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package runtime
     6  
     7  // The Error interface identifies a run time error.
     8  type Error interface {
     9  	error
    10  
    11  	// RuntimeError is a no-op function but
    12  	// serves to distinguish types that are run time
    13  	// errors from ordinary errors: a type is a
    14  	// run time error if it has a RuntimeError method.
    15  	RuntimeError()
    16  }
    17  
    18  // A TypeAssertionError explains a failed type assertion.
    19  type TypeAssertionError struct {
    20  	interfaceString string
    21  	concreteString  string
    22  	assertedString  string
    23  	missingMethod   string // one method needed by Interface, missing from Concrete
    24  }
    25  
    26  func (*TypeAssertionError) RuntimeError() {}
    27  
    28  func (e *TypeAssertionError) Error() string {
    29  	inter := e.interfaceString
    30  	if inter == "" {
    31  		inter = "interface"
    32  	}
    33  	if e.concreteString == "" {
    34  		return "interface conversion: " + inter + " is nil, not " + e.assertedString
    35  	}
    36  	if e.missingMethod == "" {
    37  		return "interface conversion: " + inter + " is " + e.concreteString +
    38  			", not " + e.assertedString
    39  	}
    40  	return "interface conversion: " + e.concreteString + " is not " + e.assertedString +
    41  		": missing method " + e.missingMethod
    42  }
    43  
    44  // An errorString represents a runtime error described by a single string.
    45  type errorString string
    46  
    47  func (e errorString) RuntimeError() {}
    48  
    49  func (e errorString) Error() string {
    50  	return "runtime error: " + string(e)
    51  }
    52  
    53  // plainError represents a runtime error described a string without
    54  // the prefix "runtime error: " after invoking errorString.Error().
    55  // See Issue #14965.
    56  type plainError string
    57  
    58  func (e plainError) RuntimeError() {}
    59  
    60  func (e plainError) Error() string {
    61  	return string(e)
    62  }
    63  
    64  type stringer interface {
    65  	String() string
    66  }
    67  
    68  func typestring(x interface{}) string {
    69  	e := efaceOf(&x)
    70  	return e._type.string()
    71  }
    72  
    73  // For calling from C.
    74  // Prints an argument passed to panic.
    75  // There's room for arbitrary complexity here, but we keep it
    76  // simple and handle just a few important cases: int, string, and Stringer.
    77  func printany(i interface{}) {
    78  	switch v := i.(type) {
    79  	case nil:
    80  		print("nil")
    81  	case stringer:
    82  		print(v.String())
    83  	case error:
    84  		print(v.Error())
    85  	case int:
    86  		print(v)
    87  	case string:
    88  		print(v)
    89  	default:
    90  		print("(", typestring(i), ") ", i)
    91  	}
    92  }
    93  
    94  // called from generated code
    95  func panicwrap(pkg, typ, meth string) {
    96  	panic(plainError("value method " + pkg + "." + typ + "." + meth + " called using nil *" + typ + " pointer"))
    97  }