Extended string template

runtime/ast/elementtype.go

@@ -85,4 +85,5 @@ const (
 	ElementTypeForceExpression
 	ElementTypePathExpression
 	ElementTypeAttachExpression
+	ElementTypeStringTemplateExpression
 )

runtime/ast/expression.go

@@ -220,6 +220,64 @@ func (*StringExpression) precedence() precedence {
 	return precedenceLiteral
 }
 
+// StringTemplateExpression
+
+type StringTemplateExpression struct {
+	Values      []string
+	Expressions []Expression
+	Range
+}
+
+var _ Expression = &StringTemplateExpression{}
+
+func NewStringTemplateExpression(gauge common.MemoryGauge, values []string, exprs []Expression, exprRange Range) *StringTemplateExpression {
+	// STRINGTODO: change to be similar to array memory usage?
+	common.UseMemory(gauge, common.StringExpressionMemoryUsage)
+	return &StringTemplateExpression{
+		Values:      values,
+		Expressions: exprs,
+		Range:       exprRange,
+	}
+}
+
+var _ Element = &StringExpression{}
+var _ Expression = &StringExpression{}
+
+func (*StringTemplateExpression) ElementType() ElementType {
+	return ElementTypeStringTemplateExpression
+}
+
+func (*StringTemplateExpression) isExpression() {}
+
+func (*StringTemplateExpression) isIfStatementTest() {}
+
+func (*StringTemplateExpression) Walk(_ func(Element)) {
+	// NO-OP
+}
+
+func (e *StringTemplateExpression) String() string {
+	return Prettier(e)
+}
+
+func (e *StringTemplateExpression) Doc() prettier.Doc {
+	return prettier.Text(QuoteString("String template"))
+}
+
+func (e *StringTemplateExpression) MarshalJSON() ([]byte, error) {
+	type Alias StringTemplateExpression
+	return json.Marshal(&struct {
+		*Alias
+		Type string
+	}{
+		Type:  "StringTemplateExpression",
+		Alias: (*Alias)(e),
+	})
+}
+
+func (*StringTemplateExpression) precedence() precedence {
+	return precedenceLiteral
+}
+
 // IntegerExpression
 
 type IntegerExpression struct {

runtime/ast/expression_extractor.go

@@ -48,6 +48,10 @@ type StringExtractor interface {
 	ExtractString(extractor *ExpressionExtractor, expression *StringExpression) ExpressionExtraction
 }
 
+type StringTemplateExtractor interface {
+	ExtractStringTemplate(extractor *ExpressionExtractor, expression *StringTemplateExpression) ExpressionExtraction
+}
+
 type ArrayExtractor interface {
 	ExtractArray(extractor *ExpressionExtractor, expression *ArrayExpression) ExpressionExtraction
 }
@@ -117,31 +121,32 @@ type AttachExtractor interface {
 }
 
 type ExpressionExtractor struct {
-	IndexExtractor       IndexExtractor
-	ForceExtractor       ForceExtractor
-	BoolExtractor        BoolExtractor
-	NilExtractor         NilExtractor
-	IntExtractor         IntExtractor
-	FixedPointExtractor  FixedPointExtractor
-	StringExtractor      StringExtractor
-	ArrayExtractor       ArrayExtractor
-	DictionaryExtractor  DictionaryExtractor
-	IdentifierExtractor  IdentifierExtractor
-	AttachExtractor      AttachExtractor
-	MemoryGauge          common.MemoryGauge
-	VoidExtractor        VoidExtractor
-	UnaryExtractor       UnaryExtractor
-	ConditionalExtractor ConditionalExtractor
-	InvocationExtractor  InvocationExtractor
-	BinaryExtractor      BinaryExtractor
-	FunctionExtractor    FunctionExtractor
-	CastingExtractor     CastingExtractor
-	CreateExtractor      CreateExtractor
-	DestroyExtractor     DestroyExtractor
-	ReferenceExtractor   ReferenceExtractor
-	MemberExtractor      MemberExtractor
-	PathExtractor        PathExtractor
-	nextIdentifier       int
+	IndexExtractor          IndexExtractor
+	ForceExtractor          ForceExtractor
+	BoolExtractor           BoolExtractor
+	NilExtractor            NilExtractor
+	IntExtractor            IntExtractor
+	FixedPointExtractor     FixedPointExtractor
+	StringExtractor         StringExtractor
+	StringTemplateExtractor StringTemplateExtractor
+	ArrayExtractor          ArrayExtractor
+	DictionaryExtractor     DictionaryExtractor
+	IdentifierExtractor     IdentifierExtractor
+	AttachExtractor         AttachExtractor
+	MemoryGauge             common.MemoryGauge
+	VoidExtractor           VoidExtractor
+	UnaryExtractor          UnaryExtractor
+	ConditionalExtractor    ConditionalExtractor
+	InvocationExtractor     InvocationExtractor
+	BinaryExtractor         BinaryExtractor
+	FunctionExtractor       FunctionExtractor
+	CastingExtractor        CastingExtractor
+	CreateExtractor         CreateExtractor
+	DestroyExtractor        DestroyExtractor
+	ReferenceExtractor      ReferenceExtractor
+	MemberExtractor         MemberExtractor
+	PathExtractor           PathExtractor
+	nextIdentifier          int
 }
 
 var _ ExpressionVisitor[ExpressionExtraction] = &ExpressionExtractor{}
@@ -271,6 +276,35 @@ func (extractor *ExpressionExtractor) ExtractString(expression *StringExpression
 	return rewriteExpressionAsIs(expression)
 }
 
+func (extractor *ExpressionExtractor) VisitStringTemplateExpression(expression *StringTemplateExpression) ExpressionExtraction {
+
+	// delegate to child extractor, if any,
+	// or call default implementation
+
+	if extractor.StringTemplateExtractor != nil {
+		return extractor.StringTemplateExtractor.ExtractStringTemplate(extractor, expression)
+	}
+	return extractor.ExtractStringTemplate(expression)
+}
+
+func (extractor *ExpressionExtractor) ExtractStringTemplate(expression *StringTemplateExpression) ExpressionExtraction {
+
+	// copy the expression
+	newExpression := *expression
+
+	// rewrite all value expressions
+
+	rewrittenExpressions, extractedExpressions :=
+		extractor.VisitExpressions(expression.Expressions)
+
+	newExpression.Expressions = rewrittenExpressions
+
+	return ExpressionExtraction{
+		RewrittenExpression:  &newExpression,
+		ExtractedExpressions: extractedExpressions,
+	}
+}
+
 func (extractor *ExpressionExtractor) VisitArrayExpression(expression *ArrayExpression) ExpressionExtraction {
 
 	// delegate to child extractor, if any,

runtime/ast/precedence.go

@@ -83,6 +83,7 @@ const (
 	// - BoolExpression
 	// - NilExpression
 	// - StringExpression
+	// - StringTemplateExpression
 	// - IntegerExpression
 	// - FixedPointExpression
 	// - ArrayExpression

runtime/ast/visitor.go

@@ -183,6 +183,7 @@ type ExpressionVisitor[T any] interface {
 	VisitNilExpression(*NilExpression) T
 	VisitBoolExpression(*BoolExpression) T
 	VisitStringExpression(*StringExpression) T
+	VisitStringTemplateExpression(*StringTemplateExpression) T
 	VisitIntegerExpression(*IntegerExpression) T
 	VisitFixedPointExpression(*FixedPointExpression) T
 	VisitDictionaryExpression(*DictionaryExpression) T
@@ -219,6 +220,9 @@ func AcceptExpression[T any](expression Expression, visitor ExpressionVisitor[T]
 	case ElementTypeStringExpression:
 		return visitor.VisitStringExpression(expression.(*StringExpression))
 
+	case ElementTypeStringTemplateExpression:
+		return visitor.VisitStringTemplateExpression(expression.(*StringTemplateExpression))
+
 	case ElementTypeIntegerExpression:
 		return visitor.VisitIntegerExpression(expression.(*IntegerExpression))
 

runtime/compiler/compiler.go

@@ -246,6 +246,11 @@ func (compiler *Compiler) VisitFunctionExpression(_ *ast.FunctionExpression) ir.
 	panic(errors.NewUnreachableError())
 }
 
+func (compiler *Compiler) VisitStringTemplateExpression(e *ast.StringTemplateExpression) ir.Expr {
+	// TODO
+	panic(errors.NewUnreachableError())
+}
+
 func (compiler *Compiler) VisitStringExpression(e *ast.StringExpression) ir.Expr {
 	return &ir.Const{
 		Constant: ir.String{

runtime/interpreter/interpreter_expression.go

@@ -20,6 +20,7 @@ package interpreter
 
 import (
 	"math/big"
+	"strings"
 	"time"
 
 	"github.com/onflow/atree"
@@ -957,6 +958,33 @@ func (interpreter *Interpreter) VisitStringExpression(expression *ast.StringExpr
 	return NewUnmeteredStringValue(expression.Value)
 }
 
+func (interpreter *Interpreter) VisitStringTemplateExpression(expression *ast.StringTemplateExpression) Value {
+	values := interpreter.visitExpressionsNonCopying(expression.Expressions)
+
+	templatesType := interpreter.Program.Elaboration.StringTemplateExpressionTypes(expression)
+	argumentTypes := templatesType.ArgumentTypes
+
+	var builder strings.Builder
+	for i, str := range expression.Values {
+		builder.WriteString(str)
+		if i < len(values) {
+			// STRINGTODO: is this how the conversion should happen?
+			s := values[i].String()
+			switch argumentTypes[i] {
+			case sema.StringType:
+				// remove quotations
+				s = s[1 : len(s)-1]
+				builder.WriteString(s)
+			default:
+				builder.WriteString(s)
+			}
+		}
+	}
+
+	// STRINGTODO: already metered as a string constant in parser?
+	return NewUnmeteredStringValue(builder.String())
+}
+
 func (interpreter *Interpreter) VisitArrayExpression(expression *ast.ArrayExpression) Value {
 	values := interpreter.visitExpressionsNonCopying(expression.Values)