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compiler: fix handling of struct, array and interface values.
As outlined in #661, the compiler fails to generate code to copy a struct/array value for an assignment when the target's underlying type is an interface type, whether for explicit variable assignments, implicit function/method parameters etc. Instead, taking the example of explicit variable assignment, the interface variable is assigned a value that contains the same pointer to the source struct/array val (we're in Javascript world, so everything is a pointer). This means that changes to the struct/array value via the source variable are, incorrectly, visible via the target variable. #661 gives a simple example. There is a further issue when interface values are assigned to interface-typed variables: struct/array values are not copied when they should be. Fixes #661.
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,88 @@ | ||
package tests | ||
|
||
import ( | ||
"fmt" | ||
"testing" | ||
) | ||
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type Struct struct { | ||
Name string | ||
} | ||
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func (s Struct) SetName(n string) { | ||
s.Name = n | ||
} | ||
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type SetName interface { | ||
SetName(n string) | ||
} | ||
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func TestAssignStructValInterface(t *testing.T) { | ||
s := Struct{ | ||
Name: "Rob", | ||
} | ||
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var i1 interface{} = s | ||
var i2 interface{} = i1 | ||
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s.Name = "Pike" | ||
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ss := fmt.Sprintf("%#v", s) | ||
i1s := fmt.Sprintf("%#v", i1) | ||
i2s := fmt.Sprintf("%#v", i2) | ||
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if exp := "tests.Struct{Name:\"Pike\"}"; ss != exp { | ||
t.Fatalf("ss should have been %q; got %q", exp, ss) | ||
} | ||
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iexp := "tests.Struct{Name:\"Rob\"}" | ||
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if i1s != iexp { | ||
t.Fatalf("is should have been %q; got %q", iexp, i1s) | ||
} | ||
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if i2s != iexp { | ||
t.Fatalf("is should have been %q; got %q", iexp, i2s) | ||
} | ||
} | ||
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func TestStructValInterfaceMethodCall(t *testing.T) { | ||
var i SetName = Struct{ | ||
Name: "Rob", | ||
} | ||
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i.SetName("Pike") | ||
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is := fmt.Sprintf("%#v", i) | ||
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if exp := "tests.Struct{Name:\"Rob\"}"; is != exp { | ||
t.Fatalf("is should have been %q; got %q", exp, is) | ||
} | ||
} | ||
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func TestAssignArrayInterface(t *testing.T) { | ||
a := [2]int{1, 2} | ||
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var i1 interface{} = a | ||
var i2 interface{} = i1 | ||
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a[0] = 0 | ||
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as := fmt.Sprintf("%#v", a) | ||
i1s := fmt.Sprintf("%#v", i1) | ||
i2s := fmt.Sprintf("%#v", i2) | ||
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if exp := "[2]int{0, 2}"; as != exp { | ||
t.Fatalf("ss should have been %q; got %q", exp, as) | ||
} | ||
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iexp := "[2]int{1, 2}" | ||
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if i1s != iexp { | ||
t.Fatalf("is should have been %q; got %q", iexp, i1s) | ||
} | ||
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if i2s != iexp { | ||
t.Fatalf("is should have been %q; got %q", iexp, i2s) | ||
} | ||
} |