if-expression requires parentheses within string interpolation

[danielkroeni]

When using an if-expression within string interpolation an error gets reported. But the error mentions that the token 'if' belongs to the expected tokens.

Steps to Reproduce

Evaluate the following string:
"\{ if True then "a" else "b" }"

Expected Behavior

I would expect that it evaluates to "a"
or a parse error that says that if is not allowed in this position.

Observed Behavior

Main> "\{ if True then "a" else "b" }"
Couldn't parse any alternatives:
1: Expected 'case', 'if', 'do', application or operator expression.
(Interactive):1:5--1:7
 1 | "\{ if True then "a" else "b" }"
         ^^

It works as expected when the if-expression is surrounded with parentheses.

Main> "\{ (if True then "a" else "b") }"
"a"

Idris2 Version

Version 0.4.0-5f3480120

[andylokandy]

I printed the token for examples:

"\{ (if True then "a" else "b") }"
[multiline string begin, string interp begin, symbol (, if, identifier True, then, multiline string begin, string "a", string end, else, multiline string begin, string "b", string end, symbol ), string interp end, string end, end of input]

"\{ if True then "a" else "b" }"
[multiline string begin, string interp begin, if, identifier True, then, multiline string begin, string "a", string end, else, multiline string begin, string "b", string end, string interp end, string end, end of input]

seems that all strings are identified as multiline strings.

[andrevidela]

that's incorrect but that shouldn't cause the problem that we see here, mhhhh

[andrevidela]

@andylokandy I quickly tried adding commit after parsing the if keyword but no change. It looks like it's stuck at simpleExpr.

[andrevidela]

I think I've figured it out. An if statement was not considering InterpEnd as a valid closing token for a block. Adding this in and running the tests, fingers crossed. The fix should also help with do notation etc

[andylokandy]

@andrevidela that's amazing! Anyway I'll investigate the weird multiline string a bit.

[andylokandy]

I've figured it out! It was a silly printing problem, the flag indicating whether the string is multiline is showed in the opposite:

Idris2/src/Parser/Lexer/Source.idr

Lines 58 to 59 in 34167d5

	show (StringBegin True) = "string begin"
	show (StringBegin False) = "multiline string begin"

Idris2/src/Parser/Lexer/Source.idr

Lines 87 to 88 in 34167d5

	pretty (StringBegin True) = reflow "string begin"
	pretty (StringBegin False) = reflow "multiline string begin"

[andrevidela]

Those booleans are evil…