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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System;
using System.Composition;
using System.Diagnostics.CodeAnalysis;
using System.Threading;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.InlineHints;
using Microsoft.CodeAnalysis.Text;
using Roslyn.Utilities;
namespace Microsoft.CodeAnalysis.CSharp.InlineHints;
[ExportLanguageService(typeof(IInlineTypeHintsService), LanguageNames.CSharp), Shared]
[method: ImportingConstructor]
[method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
internal sealed class CSharpInlineTypeHintsService() : AbstractInlineTypeHintsService
{
protected override TypeHint? TryGetTypeHint(
SemanticModel semanticModel,
SyntaxNode node,
bool displayAllOverride,
bool forImplicitVariableTypes,
bool forLambdaParameterTypes,
bool forImplicitObjectCreation,
bool forCollectionExpressions,
CancellationToken cancellationToken)
{
if (forImplicitVariableTypes || displayAllOverride)
{
if (node is VariableDeclarationSyntax { Type.IsVar: true } variableDeclaration &&
variableDeclaration.Variables.Count == 1 &&
!variableDeclaration.Variables[0].Identifier.IsMissing)
{
var type = semanticModel.GetTypeInfo(variableDeclaration.Type, cancellationToken).Type;
if (IsValidType(type))
return CreateTypeHint(type, variableDeclaration.Type, variableDeclaration.Variables[0].Identifier);
}
// We handle individual variables of ParenthesizedVariableDesignationSyntax separately.
// For example, in `var (x, y) = (0, "")`, we should `int` for `x` and `string` for `y`.
// It's redundant to show `(int, string)` for `var`
if (node is DeclarationExpressionSyntax { Type.IsVar: true, Designation: not ParenthesizedVariableDesignationSyntax } declarationExpression)
{
var type = semanticModel.GetTypeInfo(declarationExpression.Type, cancellationToken).Type;
if (IsValidType(type))
return CreateTypeHint(type, declarationExpression.Type, declarationExpression.Designation);
}
else if (node is SingleVariableDesignationSyntax { Parent: not DeclarationPatternSyntax and not DeclarationExpressionSyntax } variableDesignation)
{
var local = semanticModel.GetDeclaredSymbol(variableDesignation, cancellationToken) as ILocalSymbol;
var type = local?.Type;
if (IsValidType(type))
{
return node.Parent is VarPatternSyntax varPattern
? CreateTypeHint(type, varPattern.VarKeyword, variableDesignation.Identifier)
: new(type, new TextSpan(variableDesignation.Identifier.SpanStart, 0), textChange: null, trailingSpace: true);
}
}
else if (node is ForEachStatementSyntax { Type.IsVar: true } forEachStatement)
{
var info = semanticModel.GetForEachStatementInfo(forEachStatement);
var type = info.ElementType;
if (IsValidType(type))
return CreateTypeHint(type, forEachStatement.Type, forEachStatement.Identifier);
}
}
if (forLambdaParameterTypes || displayAllOverride)
{
if (node is ParameterSyntax { Type: null } parameterNode)
{
var span = new TextSpan(parameterNode.Identifier.SpanStart, 0);
var parameter = semanticModel.GetDeclaredSymbol(parameterNode, cancellationToken);
if (parameter?.ContainingSymbol is IMethodSymbol { MethodKind: MethodKind.AnonymousFunction } &&
IsValidType(parameter?.Type))
{
return parameterNode.Parent?.Parent?.Kind() is SyntaxKind.ParenthesizedLambdaExpression
? new TypeHint(parameter.Type, span, textChange: new TextChange(span, GetTypeDisplayString(parameter.Type) + " "), trailingSpace: true)
: new TypeHint(parameter.Type, span, textChange: null, trailingSpace: true);
}
}
}
if (forImplicitObjectCreation || displayAllOverride)
{
if (node is ImplicitObjectCreationExpressionSyntax implicitNew)
{
var type = semanticModel.GetTypeInfo(implicitNew, cancellationToken).Type;
if (IsValidType(type))
{
var span = new TextSpan(implicitNew.NewKeyword.Span.End, 0);
return new(type, span, new TextChange(span, " " + GetTypeDisplayString(type)), leadingSpace: true);
}
}
}
if (forCollectionExpressions || displayAllOverride)
{
if (node is CollectionExpressionSyntax collectionExpression)
{
var type = semanticModel.GetTypeInfo(collectionExpression, cancellationToken).ConvertedType;
if (IsValidType(type))
{
var span = new TextSpan(collectionExpression.OpenBracketToken.SpanStart, 0);
return new(type, span, new TextChange(span, GetTypeDisplayString(type)), leadingSpace: true);
}
}
}
return null;
string GetTypeDisplayString(ITypeSymbol type)
// ToMinimalDisplayString will produce the smallest name for this type that should compile at the specified
// location in this tree. We want that over ToDisplayString as that will produce the most readable name,
// which isn't necessarily something that will compile (for example, if needed namespaces are missing from
// the name).
=> type.ToMinimalDisplayString(semanticModel, node.SpanStart, s_minimalTypeStyle);
TypeHint CreateTypeHint(
ITypeSymbol type,
SyntaxNodeOrToken displayAllSpan,
SyntaxNodeOrToken normalSpan)
{
var span = GetSpan(displayAllOverride, forImplicitVariableTypes, displayAllSpan, normalSpan);
// if this is a hint that is placed in-situ (i.e. it's not overwriting text like 'var'), then place
// a space after it to make things feel less cramped.
var trailingSpace = span.Length == 0;
return new TypeHint(type, span, new TextChange(displayAllSpan.Span, GetTypeDisplayString(type)), trailingSpace: trailingSpace);
}
}
private static TextSpan GetSpan(
bool displayAllOverride,
bool normalOption,
SyntaxNodeOrToken displayAllSpan,
SyntaxNodeOrToken normalSpan)
{
// If we're showing this because the normal option is on, then place the hint prior to the node being marked.
if (normalOption)
return new TextSpan(normalSpan.SpanStart, 0);
// Otherwise, we're showing because the user explicitly asked to see all hints. In that case, overwrite the
// provided span (i.e. overwrite 'var' with 'int') as this provides a cleaner view while the user is in this
// mode.
Contract.ThrowIfFalse(displayAllOverride);
return displayAllSpan.Span;
}
private static bool IsValidType([NotNullWhen(true)] ITypeSymbol? type)
{
return type is not null or IErrorTypeSymbol && type.Name != "var";
}
}
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