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spec: adjust type identity rules for type parameters
Change-Id: I5ffc7f26236487070447eaa0f6b14d1fab44c3c7 Reviewed-on: https://go-review.googlesource.com/c/go/+/366794 Trust: Robert Griesemer <gri@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
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@ -1750,7 +1750,7 @@ Two types are either <i>identical</i> or <i>different</i>.
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</p>
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<p>
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A <a href="#Type_definitions">defined type</a> is always different from any other type.
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A <a href="#Types">named type</a> is always different from any other type.
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Otherwise, two types are identical if their <a href="#Types">underlying</a> type literals are
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structurally equivalent; that is, they have the same literal structure and corresponding
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components have identical types. In detail:
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@ -1775,15 +1775,17 @@ components have identical types. In detail:
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identical, and either both functions are variadic or neither is.
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Parameter and result names are not required to match.</li>
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<li>Two interface types are identical if they have the same set of methods
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with the same names and identical function types.
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<a href="#Exported_identifiers">Non-exported</a> method names from different
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packages are always different. The order of the methods is irrelevant.</li>
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<li>Two interface types are identical if they define the same type set.
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</li>
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<li>Two map types are identical if they have identical key and element types.</li>
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<li>Two channel types are identical if they have identical element types and
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the same direction.</li>
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<li>Two <a href="#Instantiations">instantiated</a> types are identical if
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their defined types and all type arguments are identical.
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</li>
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</ul>
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<p>
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@ -1798,18 +1800,18 @@ type (
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A3 = int
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A4 = func(A3, float64) *A0
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A5 = func(x int, _ float64) *[]string
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)
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type (
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B0 A0
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B1 []string
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B2 struct{ a, b int }
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B3 struct{ a, c int }
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B4 func(int, float64) *B0
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B5 func(x int, y float64) *A1
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)
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type C0 = B0
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C0 = B0
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D0[P1, P2 any] struct{ x P1; y P2 }
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E0 = D0[int, string]
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)
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</pre>
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<p>
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@ -1823,6 +1825,7 @@ A3 and int
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A4, func(int, float64) *[]string, and A5
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B0 and C0
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D0[int, string] and E0
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[]int and []int
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struct{ a, b *T5 } and struct{ a, b *T5 }
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func(x int, y float64) *[]string, func(int, float64) (result *[]string), and A5
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@ -1832,7 +1835,13 @@ func(x int, y float64) *[]string, func(int, float64) (result *[]string), and A5
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<code>B0</code> and <code>B1</code> are different because they are new types
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created by distinct <a href="#Type_definitions">type definitions</a>;
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<code>func(int, float64) *B0</code> and <code>func(x int, y float64) *[]string</code>
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are different because <code>B0</code> is different from <code>[]string</code>.
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are different because <code>B0</code> is different from <code>[]string</code>;
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and <code>P1</code> and <code>P2</code> are different because they are different
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type parameters.
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<code>D0[int, string]</code> and <code>struct{ x int; y string }</code> are
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different because the former is an <a href="#Instantiations">instantiated</a>
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defined type while the latter is a type literal
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(but they are still <a href="#Assignability">assignable</a>).
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</p>
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<h3 id="Assignability">Assignability</h3>
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