tfdiags: Helper to construct SourceRange from hcl.Range

HCL will be the most frequent origin of a source range, so this helper
should make it easier to translate these between the two worlds so we
can more easily use them in native Terraform diagnostics and other
messaging.

tfdiags/hcl.go

@@ -30,34 +30,48 @@ func (d hclDiagnostic) Description() Description {
 func (d hclDiagnostic) Source() Source {
 	var ret Source
 	if d.diag.Subject != nil {
-		ret.Subject = &SourceRange{
-			Filename: d.diag.Subject.Filename,
-			Start: SourcePos{
-				Line:   d.diag.Subject.Start.Line,
-				Column: d.diag.Subject.Start.Column,
-				Byte:   d.diag.Subject.Start.Byte,
-			},
-			End: SourcePos{
-				Line:   d.diag.Subject.End.Line,
-				Column: d.diag.Subject.End.Column,
-				Byte:   d.diag.Subject.End.Byte,
-			},
-		}
+		rng := SourceRangeFromHCL(*d.diag.Subject)
+		ret.Subject = &rng
 	}
 	if d.diag.Context != nil {
-		ret.Context = &SourceRange{
-			Filename: d.diag.Context.Filename,
-			Start: SourcePos{
-				Line:   d.diag.Context.Start.Line,
-				Column: d.diag.Context.Start.Column,
-				Byte:   d.diag.Context.Start.Byte,
-			},
-			End: SourcePos{
-				Line:   d.diag.Context.End.Line,
-				Column: d.diag.Context.End.Column,
-				Byte:   d.diag.Context.End.Byte,
-			},
-		}
+		rng := SourceRangeFromHCL(*d.diag.Context)
+		ret.Context = &rng
 	}
 	return ret
 }
+
+// SourceRangeFromHCL constructs a SourceRange from the corresponding range
+// type within the HCL package.
+func SourceRangeFromHCL(hclRange hcl.Range) SourceRange {
+	return SourceRange{
+		Filename: hclRange.Filename,
+		Start: SourcePos{
+			Line:   hclRange.Start.Line,
+			Column: hclRange.Start.Column,
+			Byte:   hclRange.Start.Byte,
+		},
+		End: SourcePos{
+			Line:   hclRange.End.Line,
+			Column: hclRange.End.Column,
+			Byte:   hclRange.End.Byte,
+		},
+	}
+}
+
+// ToHCL constructs a HCL Range from the receiving SourceRange. This is the
+// opposite of SourceRangeFromHCL.
+func (r SourceRange) ToHCL() hcl.Range {
+	return hcl.Range{
+		Filename: r.Filename,
+		Start: hcl.Pos{
+			Line:   r.Start.Line,
+			Column: r.Start.Column,
+			Byte:   r.Start.Byte,
+		},
+		End: hcl.Pos{
+			Line:   r.End.Line,
+			Column: r.End.Column,
+			Byte:   r.End.Byte,
+		},
+	}
+}