hclsyntax: Additional tests for template sequence escapes

In previous versions we had some bugs around template sequence escapes.
These tests show that they no longer seem to be present, and should
hopefully avoid them regressing in future.

hclsyntax/expression_template_test.go

@@ -84,6 +84,12 @@ hello world
 			cty.StringVal("hello $$nonescape"),
 			0,
 		},
+		{
+			`hello %${"world"}`,
+			nil,
+			cty.StringVal("hello %world"),
+			0,
+		},
 		{
 			`${true}`,
 			nil,
@@ -253,6 +259,30 @@ trim`,
 			cty.StringVal("%%"),
 			0,
 		},
+		{
+			`hello %%{ if true }world%%{ endif }`,
+			nil,
+			cty.StringVal(`hello %{ if true }world%{ endif }`),
+			0,
+		},
+		{
+			`hello $%{ if true }world%{ endif }`,
+			nil,
+			cty.StringVal("hello $world"),
+			0,
+		},
+		{
+			`%{ endif }`,
+			nil,
+			cty.UnknownVal(cty.String),
+			1, // Unexpected endif directive
+		},
+		{
+			`%{ endfor }`,
+			nil,
+			cty.UnknownVal(cty.String),
+			1, // Unexpected endfor directive
+		},
 	}
 
 	for _, test := range tests {