Add check for if constraint indendation

README.md

@@ -140,6 +140,7 @@ Note that the "--skipTests" option is the equivalent of changing each
 * Redundant visibility attributes
 * Public declarations without a documented unittest. By default disabled.
 * Asserts without an explanatory message. By default disabled.
+* Indentation of if constraints
 
 #### Wishlist
 

src/dscanner/analysis/config.d

@@ -192,6 +192,9 @@ struct StaticAnalysisConfig
 	@INI("Check for asserts without an explanatory message")
 	string assert_without_msg = Check.disabled;
 
+	@INI("Check indent of if constraints")
+	string if_constraints_indent = Check.disabled;
+
 	@INI("Module-specific filters")
 	ModuleFilters filters;
 }

src/dscanner/analysis/if_constraints_indent.d

@@ -0,0 +1,233 @@
+// Distributed under the Boost Software License, Version 1.0.
+//	  (See accompanying file LICENSE_1_0.txt or copy at
+//			http://www.boost.org/LICENSE_1_0.txt)
+
+module dscanner.analysis.if_constraints_indent;
+
+import dparse.lexer;
+import dparse.ast;
+import dscanner.analysis.base : BaseAnalyzer, Message;
+import dsymbol.scope_ : Scope;
+
+import std.algorithm.iteration : filter;
+import std.range;
+
+/**
+Checks whether all if constraints have the same indention as their declaration.
+*/
+class IfConstraintsIndentCheck : BaseAnalyzer
+{
+	///
+	this(string fileName, const(Token)[] tokens, bool skipTests = false)
+	{
+		super(fileName, null, skipTests);
+
+		// libdparse columns start at 1
+		foreach (t; tokens)
+		{
+			while (firstSymbolAtLine.length < t.line - 1)
+				firstSymbolAtLine ~= Pos(1);
+
+			if (firstSymbolAtLine.length < t.line)
+				firstSymbolAtLine ~= Pos(t.column, t.type == tok!"if");
+		}
+	}
+
+	override void visit(const FunctionDeclaration decl)
+	{
+		if (decl.constraint !is null)
+			checkConstraintSpace(decl.constraint, decl.name);
+	}
+
+	override void visit(const InterfaceDeclaration decl)
+	{
+		if (decl.constraint !is null)
+			checkConstraintSpace(decl.constraint, decl.name);
+	}
+
+
+	override void visit(const ClassDeclaration decl)
+	{
+		if (decl.constraint !is null)
+			checkConstraintSpace(decl.constraint, decl.name);
+	}
+
+	override void visit(const TemplateDeclaration decl)
+	{
+		if (decl.constraint !is null)
+			checkConstraintSpace(decl.constraint, decl.name);
+	}
+
+	override void visit(const UnionDeclaration decl)
+	{
+		if (decl.constraint !is null)
+			checkConstraintSpace(decl.constraint, decl.name);
+	}
+
+	override void visit(const StructDeclaration decl)
+	{
+		if (decl.constraint !is null)
+			checkConstraintSpace(decl.constraint, decl.name);
+	}
+
+	override void visit(const Constructor decl)
+	{
+		if (decl.constraint !is null)
+			checkConstraintSpace(decl.constraint, decl.line);
+	}
+
+	alias visit = ASTVisitor.visit;
+
+private:
+
+	enum string KEY = "dscanner.style.if_constraints_indent";
+	enum string MESSAGE = "If constraints should have the same indentation as the function";
+
+	Pos[] firstSymbolAtLine;
+	static struct Pos
+	{
+		size_t column;
+		bool isIf;
+	}
+
+	/**
+	Check indentation of constraints
+	*/
+	void checkConstraintSpace(const Constraint constraint, const Token token)
+	{
+		checkConstraintSpace(constraint, token.line);
+	}
+
+	void checkConstraintSpace(const Constraint constraint, size_t line)
+	{
+		// dscanner lines start at 1
+		auto pDecl = firstSymbolAtLine[line - 1];
+
+		// search for constraint if (might not be on the same line as the expression)
+		auto r = firstSymbolAtLine[line .. constraint.expression.line].retro.filter!(s => s.isIf);
+
+		// no hit = constraint is on the same line
+		if (r.empty)
+			addErrorMessage(constraint.expression.line, constraint.expression.column, KEY, MESSAGE);
+		else if (pDecl.column != r.front.column)
+			addErrorMessage(constraint.expression.line, constraint.expression.column, KEY, MESSAGE);
+	}
+}
+
+unittest
+{
+	import dscanner.analysis.config : StaticAnalysisConfig, Check, disabledConfig;
+	import dscanner.analysis.helpers : assertAnalyzerWarnings;
+	import std.format : format;
+	import std.stdio : stderr;
+
+	StaticAnalysisConfig sac = disabledConfig();
+	sac.if_constraints_indent = Check.enabled;
+
+	assertAnalyzerWarnings(q{
+void foo(R)(R r)
+if (R == int)
+{}
+
+void foo(R)(R r)
+	if (R == int) // [warn]: %s
+{}
+	}c.format(
+		IfConstraintsIndentCheck.MESSAGE,
+	), sac);
+
+	assertAnalyzerWarnings(q{
+	void foo(R)(R r)
+	if (R == int)
+	{}
+
+	void foo(R)(R r)
+if (R == int) // [warn]: %s
+	{}
+
+	void foo(R)(R r)
+		if (R == int) // [warn]: %s
+	{}
+	}c.format(
+		IfConstraintsIndentCheck.MESSAGE,
+		IfConstraintsIndentCheck.MESSAGE,
+	), sac);
+
+	assertAnalyzerWarnings(q{
+	struct Foo(R)
+	if (R == int)
+	{}
+
+	struct Foo(R)
+if (R == int) // [warn]: %s
+	{}
+
+	struct Foo(R)
+		if (R == int) // [warn]: %s
+	{}
+	}c.format(
+		IfConstraintsIndentCheck.MESSAGE,
+		IfConstraintsIndentCheck.MESSAGE,
+	), sac);
+
+	// test example from Phobos
+	assertAnalyzerWarnings(q{
+Num abs(Num)(Num x) @safe pure nothrow
+if (is(typeof(Num.init >= 0)) && is(typeof(-Num.init)) &&
+    !(is(Num* : const(ifloat*)) || is(Num* : const(idouble*))
+    || is(Num* : const(ireal*))))
+{
+    static if (isFloatingPoint!(Num))
+        return fabs(x);
+    else
+        return x >= 0 ? x : -x;
+}
+	}, sac);
+
+	// weird constraint formatting
+	assertAnalyzerWarnings(q{
+	struct Foo(R)
+	if
+	(R == int)
+	{}
+
+	struct Foo(R)
+	if
+		(R == int)
+	{}
+
+	struct Foo(R)
+if
+	(R == int) // [warn]: %s
+	{}
+
+	struct Foo(R)
+	if (
+	R == int)
+	{}
+
+	struct Foo(R)
+	if (
+		R == int
+	)
+	{}
+
+	struct Foo(R)
+		if (
+		R == int // [warn]: %s
+	) {}
+	}c.format(
+		IfConstraintsIndentCheck.MESSAGE,
+		IfConstraintsIndentCheck.MESSAGE,
+	), sac);
+
+	// constraint on the same line
+	assertAnalyzerWarnings(q{
+	struct CRC(uint N, ulong P) if (N == 32 || N == 64) // [warn]: %s
+	{}
+	}c.format(
+		IfConstraintsIndentCheck.MESSAGE,
+	), sac);
+
+	stderr.writeln("Unittest for IfConstraintsIndentCheck passed.");
+}

src/dscanner/analysis/run.d

@@ -71,6 +71,7 @@ import dscanner.analysis.allman;
 import dscanner.analysis.redundant_attributes;
 import dscanner.analysis.has_public_example;
 import dscanner.analysis.assert_without_msg;
+import dscanner.analysis.if_constraints_indent;
 
 import dsymbol.string_interning : internString;
 import dsymbol.scope_;
@@ -506,6 +507,10 @@ MessageSet analyze(string fileName, const Module m, const StaticAnalysisConfig a
 		checks ~= new AssertWithoutMessageCheck(fileName, moduleScope,
 		analysisConfig.assert_without_msg == Check.skipTests && !ut);
 
+	if (moduleName.shouldRun!"if_constraints_indent"(analysisConfig))
+		checks ~= new IfConstraintsIndentCheck(fileName, tokens,
+		analysisConfig.if_constraints_indent == Check.skipTests && !ut);
+
 	version (none)
 		if (moduleName.shouldRun!"redundant_if_check"(analysisConfig))
 			checks ~= new IfStatementCheck(fileName, moduleScope,