Propose convert to string template as inspection more frequent

idea/src/org/jetbrains/kotlin/idea/intentions/ConvertToStringTemplateIntention.kt

@@ -51,9 +51,9 @@ open class ConvertToStringTemplateIntention : SelfTargetingOffsetIndependentInte
         fun shouldSuggestToConvert(expression: KtBinaryExpression): Boolean {
             val entries = buildReplacement(expression).entries
             return entries.none { it is KtBlockStringTemplateEntry }
-                   && !entries.all { it is KtLiteralStringTemplateEntry || it is KtEscapeStringTemplateEntry }
+                    && !entries.all { it is KtLiteralStringTemplateEntry || it is KtEscapeStringTemplateEntry }
-                   && entries.count { it is KtLiteralStringTemplateEntry } > 1
+                    && entries.count { it is KtLiteralStringTemplateEntry } >= 1
-                   && !expression.textContains('\n')
+                    && !expression.textContains('\n')
         }
 
         @JvmStatic

idea/testData/intentions/convertToStringTemplate/inspectionData/expected.xml

@@ -7,4 +7,44 @@
         <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Convert string concatenation to string template</problem_class>
         <description>Convert concatenation to template</description>
     </problem>
+    <problem>
+        <file>noBracesSimpleFollowedByDot.kt</file>
+        <line>3</line>
+        <module>light_idea_test_case</module>
+        <entry_point TYPE="file" FQNAME="noBracesSimpleFollowedByDot.kt" />
+        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">String concatenation that can be converted to string template</problem_class>
+        <description>Convert concatenation to template</description>
+    </problem>
+    <problem>
+        <file>specialCharsInCharLiteral.kt</file>
+        <line>2</line>
+        <module>light_idea_test_case</module>
+        <entry_point TYPE="file" FQNAME="specialCharsInCharLiteral.kt" />
+        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">String concatenation that can be converted to string template</problem_class>
+        <description>Convert concatenation to template</description>
+    </problem>
+    <problem>
+        <file>doesNotCorruptExistingTemplate.kt</file>
+        <line>4</line>
+        <module>light_idea_test_case</module>
+        <entry_point TYPE="file" FQNAME="doesNotCorruptExistingTemplate.kt" />
+        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">String concatenation that can be converted to string template</problem_class>
+        <description>Convert concatenation to template</description>
+    </problem>
+    <problem>
+        <file>unescapeSingleQuote.kt</file>
+        <line>2</line>
+        <module>light_idea_test_case</module>
+        <entry_point TYPE="file" FQNAME="unescapeSingleQuote.kt" />
+        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">String concatenation that can be converted to string template</problem_class>
+        <description>Convert concatenation to template</description>
+    </problem>
+    <problem>
+        <file>noBracesForLastSimpleExpression.kt</file>
+        <line>3</line>
+        <module>light_idea_test_case</module>
+        <entry_point TYPE="file" FQNAME="noBracesForLastSimpleExpression.kt" />
+        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">String concatenation that can be converted to string template</problem_class>
+        <description>Convert concatenation to template</description>
+    </problem>
 </problems>

j2k/testData/fileOrElement/assertStatement/withStringDetail2.kt

@@ -1 +1 @@
-assert(true) { "string details:" + x }
+assert(true) { "string details:$x" }

j2k/testData/fileOrElement/detectProperties/GetterWithSideEffect1.kt

@@ -11,6 +11,6 @@ class C {
         }
 
     internal fun foo() {
-        println("myX = " + myX)
+        println("myX = $myX")
     }
 }

j2k/testData/fileOrElement/detectProperties/GetterWithSideEffect2.kt

@@ -11,6 +11,6 @@ class C {
     }
 
     internal fun foo() {
-        println("x = " + x)
+        println("x = $x")
     }
 }

j2k/testData/fileOrElement/issues/kt-1074.java

@@ -2,13 +2,8 @@
 package demo;
 
 class Test {
-    static void subListRangeCheck(int fromIndex, int toIndex, int size) {
+    static void bar(int a) {
-        if (fromIndex < 0)
+        if (a < 0)
-            throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
+            throw new RuntimeException("a = " + a);
-        if (toIndex > size)
-            throw new IndexOutOfBoundsException("toIndex = " + toIndex);
-        if (fromIndex > toIndex)
-            throw new IllegalArgumentException("fromIndex(" + fromIndex
-                    + ") > toIndex(" + toIndex + ")");
     }
 }

j2k/testData/fileOrElement/issues/kt-1074.kt

@@ -1,13 +1,8 @@
 package demo
 
 internal object Test {
-    fun subListRangeCheck(fromIndex: Int, toIndex: Int, size: Int) {
+    fun bar(a: Int) {
-        if (fromIndex < 0)
+        if (a < 0)
-            throw IndexOutOfBoundsException("fromIndex = " + fromIndex)
+            throw RuntimeException("a = $a")
-        if (toIndex > size)
-            throw IndexOutOfBoundsException("toIndex = " + toIndex)
-        if (fromIndex > toIndex)
-            throw IllegalArgumentException("fromIndex(" + fromIndex
-                    + ") > toIndex(" + toIndex + ")")
     }
 }

j2k/testData/fileOrElement/methodCallExpression/stringMethods.kt

@@ -89,7 +89,7 @@ internal class A {
         val limit = 5
         useSplit(s.split("\\s+".toRegex(), limit.coerceAtLeast(0)).toTypedArray())
         s.trim { it <= ' ' }
-        s + " another"
+        "$s another"
 
         s.toByteArray()
         s.toByteArray(Charset.forName("utf-8"))

j2k/testData/fileOrElement/overloads/Annotations.kt

@@ -31,6 +31,6 @@ internal class A {
     }
 
     fun f(p: Int) {
-        println("p = " + p)
+        println("p = $p")
     }
 }

j2k/testData/fileOrElement/overloads/Override.kt

@@ -5,7 +5,7 @@ internal interface I {
 
 internal open class A : I {
     override fun foo(i: Int, c: Char, s: String) {
-        println("foo" + i + c + s)
+        println("foo$i$c$s")
     }
 
     fun foo(i: Int, c: Char) {

j2k/testData/fileOrElement/overloads/Simple.kt

@@ -1,7 +1,7 @@
 internal class A {
     @JvmOverloads
     fun foo(i: Int, c: Char = 'a', s: String = "") {
-        println("foo" + i + c + s)
+        println("foo$i$c$s")
     }
 
     @JvmOverloads