improve related highlight performance

See #336

Author: WebFreak001

workspace-d/source/workspaced/com/dcdext.d

@@ -884,6 +884,15 @@ class DCDExtComponent : ComponentWrapper
 		if (token >= tokens.length || !tokens[token].isLikeIdentifier)
 			return null;
 
+		Module _parsed;
+		RollbackAllocator rba;
+		Module parsed()
+		{
+			if (_parsed)
+				return _parsed;
+			return _parsed = parseModule(tokens, "stdin", &rba);
+		}
+
 		Related[] ret;
 
 		switch (tokens[token].type)
@@ -908,8 +917,6 @@ class DCDExtComponent : ComponentWrapper
 			// if lister
 			auto finder = new IfFinder();
 			finder.target = tokens[token].index;
-			RollbackAllocator rba;
-			auto parsed = parseModule(tokens, "stdin", &rba);
 			finder.visit(parsed);
 			foreach (ifToken; finder.foundIf)
 				ret ~= Related(Related.Type.controlFlow, [ifToken.index, ifToken.index + ifToken.tokenText.length]);
@@ -929,8 +936,6 @@ class DCDExtComponent : ComponentWrapper
 			finder.isLoop = !(tokens[token].type == tok!"break" || tokens[token].type == tok!"continue");
 			if (token + 1 < tokens.length && tokens[token + 1].type == tok!"identifier")
 				finder.label = tokens[token + 1].text;
-			RollbackAllocator rba;
-			auto parsed = parseModule(tokens, "stdin", &rba);
 			finder.visit(parsed);
 
 			if (finder.isLoop && finder.foundBlock.length)
@@ -951,8 +956,6 @@ class DCDExtComponent : ComponentWrapper
 			// switch/case lister
 			auto finder = new SwitchFinder();
 			finder.target = tokens[token].index;
-			RollbackAllocator rba;
-			auto parsed = parseModule(tokens, "stdin", &rba);
 			finder.visit(parsed);
 			foreach (switchToken; finder.foundSwitch)
 				ret ~= Related(Related.Type.controlFlow, [switchToken.index, switchToken.index + switchToken.tokenText.length]);
@@ -961,8 +964,6 @@ class DCDExtComponent : ComponentWrapper
 			// return effect lister
 			auto finder = new ReturnFinder();
 			finder.target = tokens[token].index;
-			RollbackAllocator rba;
-			auto parsed = parseModule(tokens, "stdin", &rba);
 			finder.visit(parsed);
 			foreach (switchToken; finder.related)
 				ret ~= Related(Related.Type.controlFlow, [switchToken.index, switchToken.index + switchToken.tokenText.length]);
@@ -2149,6 +2150,9 @@ final class IfFinder : ASTVisitor
 
 	alias visit = ASTVisitor.visit;
 
+	mixin ASTSearchScopeLimit!("target", FunctionBody);
+	mixin ASTFinisher;
+
 	static foreach (If; AliasSeq!(IfStatement, ConditionalStatement))
 	override void visit(const If ifStatement)
 	{
@@ -2279,6 +2283,7 @@ final class IfFinder : ASTVisitor
 			if (v.index == target)
 			{
 				foundIf = currentIf;
+				exitVisitor = true;
 				return;
 			}
 	}
@@ -2340,6 +2345,9 @@ final class SwitchFinder : ASTVisitor
 
 	alias visit = ASTVisitor.visit;
 
+	mixin ASTSearchScopeLimit!("target", FunctionBody);
+	mixin ASTFinisher;
+
 	override void visit(const SwitchStatement stmt)
 	{
 		if (foundSwitch.length)
@@ -2404,6 +2412,7 @@ final class SwitchFinder : ASTVisitor
 			if (v.index == target)
 			{
 				foundSwitch = currentSwitch;
+				exitVisitor = true;
 				return;
 			}
 	}
@@ -2457,6 +2466,9 @@ final class BreakFinder : ASTVisitor
 
 	alias visit = ASTVisitor.visit;
 
+	mixin ASTSearchScopeLimit!("target", FunctionBody);
+	mixin ASTFinisher;
+
 	override void visit(const LabeledStatement stmt)
 	{
 		if (foundBlock.length)
@@ -2622,6 +2634,7 @@ final class BreakFinder : ASTVisitor
 			if (v.index == target)
 			{
 				foundBlock = currentBlock;
+				exitVisitor = true;
 				return;
 			}
 	}

workspace-d/source/workspaced/dparseext.d

@@ -434,3 +434,31 @@ C[] substr(C)(C[] s, size_t start, size_t end)
 		return s[start .. start];
 	return s[start .. end];
 }
+
+/// Overrides visit for each ASTScopes to only travese them when the ast node
+/// tokens contain a token at index `mixin(member)`
+mixin template ASTSearchScopeLimit(string member, ASTScopes...)
+{
+	static foreach (ASTScope; ASTScopes)
+		override void visit(const ASTScope n)
+		{
+			if (!n.tokens.length ||
+				(mixin(member) >= n.tokens[0].index && mixin(member) <= n.tokens[$ - 1].index + n.tokens[$ - 1].textLength))
+				super.visit(n);
+		}
+}
+
+/// Defines a `exitVisitor` method, when it's set to true, almost all traversing
+/// will be skipped. This is realized by overriding DeclarationOrStatement and
+/// just returning if it's true.
+mixin template ASTFinisher()
+{
+	bool exitVisitor;
+
+	override void visit(const DeclarationOrStatement decl)
+	{
+		if (exitVisitor)
+			return;
+		super.visit(decl);
+	}
+}