mirror of
https://github.com/icsharpcode/ILSpy.git
synced 2026-10-12 02:15:58 +00:00
Christoph Wille
fe9f6db3ee
Shortening default(T) is the same problem as removing the redundant cast around a lambda whose delegate type the context already fixes, so it uses the same mechanism: ConvertTo makes the explicit type implicit when the conversion is an identity conversion and the caller allows an implicit one. The literal keeps the type it was shortened from, so any later conversion to a different type - or any context that requires an explicit type, such as an overload resolution recheck falling back to CastArguments - can spell default(T) out again. That keeps the value intact where the bare literal would change it, e.g. "object o = default(SomeStruct)", which boxes a non-null struct while "default" would be null. Because the shortened literal resolves to DefaultLiteralResolveResult, CallBuilder's existing overload resolution recheck sees a real default literal and rejects ambiguous calls on its own; no separate bookkeeping about which arguments may stay untyped is needed. Only the contexts that supply no target type at all restore the explicit form: an awaited expression, and arguments of operator methods, which later become operator or cast syntax rather than calls. Assisted-by: Claude:claude-opus-5[1m]:Claude Code
58 lines
2.3 KiB
C#
58 lines
2.3 KiB
C#
// Copyright (c) 2026 Siegfried Pammer
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy of this
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// software and associated documentation files (the "Software"), to deal in the Software
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// without restriction, including without limitation the rights to use, copy, modify, merge,
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// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
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// to whom the Software is furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all copies or
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// substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
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// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
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// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
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// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
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// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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// DEALINGS IN THE SOFTWARE.
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using ICSharpCode.Decompiler.TypeSystem;
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namespace ICSharpCode.Decompiler.Semantics
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{
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/// <summary>
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/// Represents a typeless default literal `default`, which is implicitly convertible
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/// to any type (C# standard 10.2.16 default literal conversions).
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/// </summary>
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class DefaultLiteralResolveResult : ResolveResult
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{
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/// <summary>
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/// The type of the "default(T)" expression the literal was shortened from; it is restored
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/// wherever the surrounding syntax stops supplying that very type.
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/// <see cref="SpecialType.UnknownType"/> if the literal does not stand for a shortened
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/// expression.
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/// </summary>
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public readonly IType ShortenedFrom;
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public DefaultLiteralResolveResult() : this(SpecialType.UnknownType)
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{
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}
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public DefaultLiteralResolveResult(IType shortenedFrom) : base(SpecialType.NoType)
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{
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this.ShortenedFrom = shortenedFrom;
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}
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// A default_value_expression is a constant expression (C# standard 12.8.21);
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// like the null literal, the typeless default literal is modeled as a constant
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// with value null (the target-typed value is only known after conversion).
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public override bool IsCompileTimeConstant {
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get { return true; }
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}
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public override object ConstantValue {
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get { return null; }
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}
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}
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}
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