typeParameterOf(VAR) Live Template macro (IDEA-16499)

GitOrigin-RevId: abaa39f4d53740b076d6c00ea8bb9f4f7e23ab77

java/java-impl/src/META-INF/JavaPlugin.xml

@@ -1151,6 +1151,7 @@
     <liveTemplateMacro implementation="com.intellij.codeInsight.template.macro.CastToLeftSideTypeMacro"/>
     <liveTemplateMacro implementation="com.intellij.codeInsight.template.macro.IterableVariableMacro"/>
     <liveTemplateMacro implementation="com.intellij.codeInsight.template.macro.IterableComponentTypeMacro"/>
+    <liveTemplateMacro implementation="com.intellij.codeInsight.template.macro.TypeParameterOfMacro"/>
     <liveTemplateMacro implementation="com.intellij.codeInsight.template.macro.DescendantClassesEnumMacro"/>
     <liveTemplateMacro implementation="com.intellij.codeInsight.template.macro.SubtypesMacro"/>
     <liveTemplateMacro implementation="com.intellij.codeInsight.template.macro.TypeOfVariableMacro"/>

java/java-impl/src/com/intellij/codeInsight/template/macro/TypeParameterOfMacro.java

@@ -0,0 +1,88 @@
+// Copyright 2000-2022 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package com.intellij.codeInsight.template.macro;
+
+import com.intellij.codeInsight.template.*;
+import com.intellij.psi.*;
+import com.intellij.psi.util.PsiTypesUtil;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * @author Bas Leijdekkers
+ */
+public class TypeParameterOfMacro extends Macro {
+  @Override
+  public String getName() {
+    return "typeParameterOf";
+  }
+
+  @Override
+  public String getPresentableName() {
+    return getName() + "(VAR[,indexOrName])";
+  }
+
+  @Override
+  public @NotNull String getDefaultValue() {
+    return "A";
+  }
+
+  @Override
+  public @Nullable Result calculateResult(Expression @NotNull [] params, ExpressionContext context) {
+    if (params.length == 0) return null;
+    final Result result = params[0].calculateResult(context);
+    if (result == null) {
+      return null;
+    }
+
+    final PsiType type;
+    if (result instanceof PsiTypeResult typeResult) {
+      type = typeResult.getType();
+    }
+    else {
+      final PsiExpression expression = MacroUtil.resultToPsiExpression(result, context);
+      if (expression == null) {
+        return null;
+      }
+      type = expression.getType();
+    }
+    if (type instanceof PsiClassType) {
+      final PsiClassType classType = (PsiClassType)type;
+      final PsiType[] parameters = classType.getParameters();
+      if (params.length > 1) {
+        final Result result1 = params[1].calculateResult(context);
+        if (result1 == null) {
+          return null;
+        }
+        final String value = result1.toString();
+        try {
+          final int i = Integer.parseInt(value);
+          return new PsiTypeResult(parameters[i], context.getProject());
+        }
+        catch (ArrayIndexOutOfBoundsException e) {
+          return null;
+        }
+        catch (NumberFormatException e) {
+          final PsiClass aClass = PsiTypesUtil.getPsiClass(classType);
+          if (aClass == null) return null;
+          PsiTypeParameter @NotNull [] typeParameters = aClass.getTypeParameters();
+          for (int i = 0; i < typeParameters.length; i++) {
+            PsiTypeParameter parameter = typeParameters[i];
+            if (value.equals(parameter.getName())) {
+              return new PsiTypeResult(parameters[i], context.getProject());
+            }
+          }
+          return null;
+        }
+      }
+      else {
+        return new PsiTypeResult(parameters[0], context.getProject());
+      }
+    }
+    return null;
+  }
+
+  @Override
+  public boolean isAcceptableInContext(TemplateContextType context) {
+    return context instanceof JavaCodeContextType;
+  }
+}