Fix IR generation for string templates containing single entry.

compiler/testData/ir/irText/expressions/stringTemplates.kt

@@ -1,4 +1,5 @@
 fun foo(): String = ""
+val x = 42
 
 val test1 = ""
 val test2 = "abc"
@@ -7,4 +8,8 @@ val test4 = """abc"""
 val test5 = """
 abc
 """
-val test6 = "$test1 ${foo()}"
+val test6 = "$test1 ${foo()}"
+
+val test7 = "$test1"
+val test8 = "${foo()}"
+val test9 = "$x"

compiler/testData/ir/irText/expressions/stringTemplates.txt

@@ -3,6 +3,14 @@ FILE /stringTemplates.kt
     BLOCK_BODY
       RETURN type=kotlin.Nothing from='foo(): String'
         CONST String type=kotlin.String value=''
+  PROPERTY public val x: kotlin.Int = 42
+    FIELD PROPERTY_BACKING_FIELD public val x: kotlin.Int = 42
+      EXPRESSION_BODY
+        CONST Int type=kotlin.Int value='42'
+    FUN DEFAULT_PROPERTY_ACCESSOR public fun <get-x>(): kotlin.Int
+      BLOCK_BODY
+        RETURN type=kotlin.Nothing from='<get-x>(): Int'
+          GET_FIELD 'x: Int' type=kotlin.Int origin=null
   PROPERTY public val test1: kotlin.String = ""
     FIELD PROPERTY_BACKING_FIELD public val test1: kotlin.String = ""
       EXPRESSION_BODY
@@ -63,3 +71,30 @@ abc
       BLOCK_BODY
         RETURN type=kotlin.Nothing from='<get-test6>(): String'
           GET_FIELD 'test6: String' type=kotlin.String origin=null
+  PROPERTY public val test7: kotlin.String = ""
+    FIELD PROPERTY_BACKING_FIELD public val test7: kotlin.String = ""
+      EXPRESSION_BODY
+        STRING_CONCATENATION type=kotlin.String
+          CALL '<get-test1>(): String' type=kotlin.String origin=GET_PROPERTY
+    FUN DEFAULT_PROPERTY_ACCESSOR public fun <get-test7>(): kotlin.String
+      BLOCK_BODY
+        RETURN type=kotlin.Nothing from='<get-test7>(): String'
+          GET_FIELD 'test7: String' type=kotlin.String origin=null
+  PROPERTY public val test8: kotlin.String
+    FIELD PROPERTY_BACKING_FIELD public val test8: kotlin.String
+      EXPRESSION_BODY
+        STRING_CONCATENATION type=kotlin.String
+          CALL 'foo(): String' type=kotlin.String origin=null
+    FUN DEFAULT_PROPERTY_ACCESSOR public fun <get-test8>(): kotlin.String
+      BLOCK_BODY
+        RETURN type=kotlin.Nothing from='<get-test8>(): String'
+          GET_FIELD 'test8: String' type=kotlin.String origin=null
+  PROPERTY public val test9: kotlin.String = "42"
+    FIELD PROPERTY_BACKING_FIELD public val test9: kotlin.String = "42"
+      EXPRESSION_BODY
+        STRING_CONCATENATION type=kotlin.String
+          CALL '<get-x>(): Int' type=kotlin.Int origin=GET_PROPERTY
+    FUN DEFAULT_PROPERTY_ACCESSOR public fun <get-test9>(): kotlin.String
+      BLOCK_BODY
+        RETURN type=kotlin.Nothing from='<get-test9>(): String'
+          GET_FIELD 'test9: String' type=kotlin.String origin=null